Japanese Lung Cancer Research Trends and Performance
in Science Citation Index
Yuh-Shan Ho
1,2, Hiroaki Satoh
3and Shih-Yuan Lin
3Abstract
Objective This study was undertaken to explore a bibliometric approach to quantitatively assess current
re-search trends in lung cancer in Japan, using the related literature in the Science Citation Index (SCI) database from 1991 to 2008.
Materials and Methods Articles were analyzed by the scientific output and research performances of
indi-viduals, institutes, and collaborative countries with Japan. Distribution of words in the article title, author keywords, and KeyWords Plus in different periods was applied to evaluate research trends by the frequency of keywords used.
Results Keyword analysis indicated that there has been a strategy to connect molecular biology with
clini-cal practice. Researchers in Japan have published high impact articles related to non-small cell and small cell lung cancer.
Conclusion Finally, this study highlights the topics in lung cancer research that are becoming popular in
Japan.
Key words: lung cancer, scientometrics, web of science, Japan (Inter Med 49: 2219-2228, 2010)
(DOI: 10.2169/internalmedicine.49.3687)
Introduction
Lung cancer has long been investigated. In earlier years, information on primary lung cancer (1) and radical surgery for primary lung carcinoma (2) were presented. In Japan, an earlier published article discussed unusual intraluminal proc-esses of capillaries in a case of undifferentiated lung can-cer (3). In 1981, Hirayama reported that wives of heavy smokers had a higher risk of developing lung cancer (4). Naruke et al (5) evaluated a new Tumor, Node, Metastasis (TNM) staging system for lung cancer. In subsequent years, high impact studies related to small-cell lung cancer (6) and non-small-cell lung cancer (7, 8) were reported. Epidermal growth factor receptor (EGFR) mutations in lung cancer (9) and clinical and biological features associated with EGFR gene mutations in lung cancers (10) were reported in Japan.
Lung cancer is one of the leading causes of cancer-related death among men and women in the civilized world.
Al-though the long-term outlook for lung cancer patients has not changed significantly (11), there have been steady im-provements over the recent decades in surgical tech-niques (12) and in the role of chemotherapy (13) and radio-therapy (14) in the treatment of lung cancer. Lung cancer re-search is and will be one of the forefront and hotspot sub-jects of clinical medical sciences. The 7 major industrial countries (G7: USA, Japan, Germany, Italy, UK, France, and Canada) with USA leading the top, held the top 7 spots of total world production in the field of lung cancer research, along with the domination pattern in the publication in most scientific fields. In this research field, however, Japan ranked second in the recent decade.
The present study was designed to determine the Japanese share of published research in the field of lung cancer from 1991 to 2008. A bibliometric method was used to analyze lung cancer research trends and performances including in-ternational collaboration, distribution of institutes and author publications.
１Trend Research Centre, Asia University, Taichung, Taiwan,２Department of Public Health, China Medical University, Taichung, Taiwan and ３Division of Respiratory Medicine, Institute of Clinical Medicine, University of Tsukuba, Tsukuba
Received for publication March 23, 2010; Accepted for publication July 2, 2010 Correspondence to Dr. Yuh-Shan Ho, ysho@asia.edu.tw
Methodology
The data were from the online version of the Science Ci-tation Index (SCI), Web of Science, Philadelphia, PA, USA. According to Journal Citation Reports (JCR), it indexed 6,620 major journals with citation references across 173 sci-entific disciplines in 2008. All documents from 1991 to 2008 with “Japan” in the address field and which had the following keywords were downloaded: “lung cancer”, “lung carcinoma”, “lung malignancy”, and “lung metastasis”. In total, 10,052 publications met the selection criteria. These publications were check to determine whether they were published by Japan; eighteen publications were excluded which used “Japan” in the address for example, China-Japan Friendship Hospital in China; China-Japan Union Hospital of Jilin University at China; Kuakini Medical Center, and Japan-Hawaii Cancer Study in USA.
Document information included names of authors, titles, years of publication, source journals, contact addresses, and subject categories of journals. The records were downloaded using Microsoft Excel software, and additional coding was manually performed for the number of authors, origin coun-tries and institutes of the collaborators, and impact factors of the source journals. Impact factors were taken from the Journal Citation Report (JCR) published in 2008. Contribu-tions of different institutes and countries were estimated by the affiliation of at least one author to the article. Articles originating from England, Scotland, Northern Ireland, and Wales were reclassified as from the United Kingdom (UK). Articles from Hong Kong were not included in China. Col-laboration type was determined by the addresses of the authors, where the term “Japan independent article” was as-signed if the researchers’ addresses were all from Japan. The term “internationally collaborative article” was designated to those articles that were coauthored by researchers from mul-tiple countries. The term “institute independent article” was assigned if the researchers’ addresses were from the same institute in Japan. The term “inter-institutionally collabora-tive article” was assigned if authors were from different in-stitutes. The emphasis of the following discussion was to determine the scientific performances and research activity trends which consisted of categories, journals, institutes and countries distributions; and the trends in research topics were addressed.
Results and Discussion
Document type and language of publicationThe distribution of the document type identified by the Institute for Scientific Information (ISI) was analyzed. Eleven document types were found in the total 10,034 publi-cations during the 18-year study period. Article (8,373) was the most-frequently used document type comprising 83% of the total publications, followed distantly by meeting
ab-stracts (661; 6.6%), proceedings papers (661; 3.5%), and re-views (283; 2.8%). The others showing less significance were letters (169), notes (122), editorial materials (72), dis-cussions (3), corrections (2), new item (1), and addition cor-rection (1). As journal articles represented the majority of document types that also included whole research. Only 8,373 articles were used for further analysis. Almost all of these articles (8,251) were published in English. Three other languages also appeared, including Japanese with 20 articles and one for Korean and Russian.
Trend of articles
The total of Japanese articles in SCI including the search words “lung cancer”, “lung carcinoma”, “lung malignancy”, and “lung metastasis” during the last 36 years was counted (Fig. 1). A development trend was found for all documents and articles, searched by titles, keywords, and abstracts, which increased from 3 in 1973 to 777 publications in 2008 and 3 in 1973 to 646 articles in 2008. According to a limita-tion of the SCI database, since 1991, abstract informalimita-tion has been included in it. However, the topic search can trace the related information in titles, abstracts, and keywords at one time. Thus searching keywords in titles only is neces-sary to obtain a reasonable base for the years before 1991. A similar trend also appeared for all documents and articles, searched by titles only, which increased from 3 in 1973 to 310 publications in 2008 and 2 in 1973 to 237 articles in 2008. In the last 18 years, the number of articles devoted to lung cancer research increased more than four-fold, from 191 in 1991 to 696 in 2006. It is clear that a decreasing trend was found during last three years. Same trend was ob-served with articles published in impact factor (IF!3) jour-nals. Along with the Japanese development of SCI articles, lung cancer research continually grew in this period, which started to increase significantly in the 1980s and rocketed after 1990. Japan had important contributions in lung cancer research during 1991 to 2008. For example, Dr. Y. Fujii at Nagoya City University Medical School, published the most cited paper “EGFR mutations in lung cancer: correlation with clinical response to Gefitinib therapy” and Dr. M. Fukuoka at Kinki University with an international team pub-lished “multi-institutional randomized phase II trial of Gefit-inib for previously treated patients with advanced non-small-cell lung cancer”. In 1984, the Japanese government started the 3rd 10-year project for cancer. In 1990, the Japan Clini-cal Oncology Group (JCOG), a collaboration group of many institutions, facilitated by public research funds subsidized by Ministry of Health, Labor and Welfare cancer research grants and public welfare labor science research funds, was established. JCOG taught appropriate research methodology to physicians through a well-designed curriculum (15). In addition a high impact article related to small-cell lung can-cer was published by the Japan Clinical Oncology Group (16). Several lung cancer study groups such as the West Japan Oncology Group were established subsequently. Recently, systematic education of medical oncology
includ-Figure 1.NumberofJapanesepublicationsin SCIreferring to keywords“lung cancer”,“lung carcinoma”,“lung malignancy”,and “lung metastasis” during last36 years.
0 100 200 300 400 500 600 700 800 900 1000 1970 1975 1980 1985 1990 1995 2000 2005 2010 Number of Japan SCI papers Year All documents Article only
All documents (searched by title only) Article only (searched by title only)
ing the systematic training program of “clinical research methodology” at the undergraduate level has been started at many academic teaching institutions. Such efforts have ef-fectively promoted the development of Japan lung cancer re-search. Lung cancer research in Japan is still developing, al-though some research has attained the international level.
Distribution of output in subject categories and journals
Based on the classification of subject categories in JCR 2008, the article output data was grouped into 106 SCI sub-ject categories. The annual articles of the top 5 productive subject categories were analyzed and are shown in Fig. 2. The number of scientific articles per category exhibited con-stant growth during this period, which indicated that Japa-nese lung cancer research had been steadily developing in various categories. The distribution of subject categories showed that Japanese lung cancer research covered not only clinical but also basic science research. Oncology held the primary position all through the study period as it was a typical field for lung cancer research. The following study area showing an increasing trend was respiratory system.
In total, 8,373 articles were published in 854 journals. Lung Cancer published the most articles with 376 articles comprising 4.5% of all the articles, followed by Anticancer Research (4.1%), Cancer Research (3.6%), Oncology Re-ports (3.1%), and Japanese Journal of Cancer Research (3.1%).
International collaboration
The collaboration with different countries was estimated by the location of the affiliation of at least one author of the published papers. Of all the 8,373 articles with author ad-dresses, 7,194 (86%) were Japan independent articles and 1,179 (14%) were internationally collaborative articles. The results demonstrated Japanese strong independent research ability and less desire to collaborate with other institutes in lung cancer research. Similarly a high percentage of interna-tionally collaborative articles (20%) was also found in stroke-related research in Taiwan (17). Table 1 lists the top 10 internationally collaborative countries ranked by the number of articles with Japan, and the number of tionally collaborative articles, the rank of the total interna-tionally collaborative articles, together with the number and rank of first author articles and corresponding author arti-cles. Domination in collaborative country was the USA fol-lowed by China. South Korea had more first and corre-sponding author articles with Japan. It may be interpreted that such studies were joint research with a country of peo-ple who had a similar social background to Japan and a similar genetic background. An increasing trend was found for articles which were published with China (Fig. 3). The most high impact collaborative articles were collaboratively published with the USA (6, 8, 9, 18).
Institutional comparisons
The contributions of Japanese different institutes were es-timated by the affiliation of at least one author. The
remain-Figure 2.Comparison ofthegrowth trendsofthetop fiveproductivesubjectcategories. 0 50 100 150 200 250 300 350 400 450 0 20 40 60 80 100 120 140 1991 1992 1993 1994 1995 1996 1997 1998 1999 2000 2001 2002 2003 2004 2005 2006 2007 2008 Number of articles in oncology Number of articles Year Oncology Respiratory System Surgery
Radiology, Nuclear Medicine & Medical Imaging Biochemistry & Molecular Biology
Table 1.Top 10 MostInternationally CollaborativeCountries
Country R (CP) R (FA) R (RP) USA 1 (772) 1 (361) 1 (328) China 2 (102) 3 (25) 5 (23) UK 3 (69) 6 (17) 6 (15) France 4 (67) 3 (25) 4 (24) Germany 5 (65) 5 (20) 3 (26) South Korea 6 (61) 2 (28) 2 (27) Italy 7 (38) 8 (12) 8 (12) Sweden 8 (37) 11 (8) 10 (8) Canada 9 (35) 7 (13) 7 (13) Australia 10 (33) 17 (4) 13 (6)
R, rank; CP, internationally collaborative articles; FA, first author articles; RP, corresponding author articles.
ing 8,373 articles were published by 2,266 Japanese insti-tutes that collaborated with 995 overseas instiinsti-tutes. Of the 8,373 articles with Japan author addresses, 3,525 (42%) were independent articles and 4,848 (58%) were inter-institutionally collaborations of two or more institutes. The top 20 institutes were ranked by the number of articles, in-cluding the number and percentage of single institute arti-cles and inter-institutionally collaborative artiarti-cles, as well as first and corresponding author articles (Table 2). The Na-tional Cancer Center had the most total articles with 710 ar-ticles, followed by Kyushu University with 400 arar-ticles, The University of Tokyo with 339 articles, Okayama University with 310 articles, and Kyoto University with 304 articles. The National Cancer Center published not only the most
to-tal articles, it also completed the most independent and inter-institutionally collaborative articles. Moreover, the first author and corresponding author of articles from The Na-tional Cancer Center ranked the highest. It was important that the budget of the project invested in these institutions, and researchers who tried to promote the project gathered there. Among the top 20 institutes, 3 were not universities including The National Cancer Center, Aichi Cancer Center, and The National Cancer Center Hospital East. In terms of lung cancer-related research, universities performed very well in Japan. While the University of Tokyo and Aichi Cancer Center have higher total articles and percentage of inter-institutionally collaborative articles in total institute ar-ticles (C%), they may have extensive research networks and
Figure 3.Top six mostcollaborativecountries. 0 10 20 30 40 50 60 70 80 90 0 2 4 6 8 10 12 14 16 18 20 1991 1992 1993 1994 1995 1996 1997 1998 1999 2000 2001 2002 2003 2004 2005 2006 2007 2008 Number of USA articles Number of articles Year USA China UK France Germany South Korea
many collaborators (17). However, the University of Tokushima is more inclined or able to conduct research in-dependently with 56% of collaborative articles in total arti-cles. The ratio of inter-institutionally collaborative articles’ to total articles of institutes was higher than 50%, which in-dicated that lung cancer research in Japan called for team-work and collaboration among different institutes. Further-more, articles published in high impact factor (IF!3) jour-nals were also analyzed and are listed in Table 2. The Na-tional Cancer Center still led the top in all indicators in the high impact factor journals. Aichi Cancer Center (68% of all articles published in the institute) and University of Tokyo (63%) had a higher percentage of the high impact factor journal articles, however Okayama University had a lower percentage (40%) of high impact factor journal articles.
Distribution of authors
The average number of authors per article, from 1991 to 2008, was 7.6 with 66 as the largest number of authors. The 8,373 published articles were coauthored by 15,650 authors, of which 8,461 authors (54%) contributed to only 1 article, 2,436 (16%) 2 articles, 1,207 (7.7%) 3 articles, and 666 (4.3%) 4 articles. Lotka (1926) (19) reported a relationship
xn
y=c, (1)
where x is the number of articles, y is the number of authors publishing x articles, n is an exponent which was normally in a value between 1 and 2, and c, a constant depending on the specific field is the number of authors who published only one article. Higher n means a higher distribution of authors who published more articles in a research topic. Lotka law was applied to describe the relationship between
the number of articles in Japan lung cancer research and the number of authors making the specified number of articles. Determined by a trial-and-error procedure for the non-linear method using the solver add-in with Microsoft’s spread-sheet, Microsoft Excel, the constants c and n in Eq. (1) could be determined from the first 20 points, which were found to be 10,834 and 1.90. Thus, the general Lotka model for the relation was found to exist between the frequency y of researchers making x articles published in Japan lung cancer research field in 1991 to 2008, which can be written as: x1.90 y=10,834 (2) or x=133y-0.526 (3)
Figure 4 shows a significant correlation between the num-ber of articles in Japanese lung cancer research and the number of authors making the specified number of articles with the Lotka model. Furthermore, for the special case of the Lotka law whereby n=2, the inverse square law of scien-tific productivity is also presented in Fig. 4 for a reason of comparison. The relationship of authors to articles for dental science literature was reported to be 1/n1.95
.
In general, the most support of profession and funding for a paper is from the corresponding author. An analysis of the corresponding authors (reprint authors), institutes, and the countries was undertaken for the articles. A total of 7,668 articles with records of reprint authors in the ISI were ana-lyzed. Ninety-three percent (7,118) of total reprint author ar-ticles were published by Japan. Only one article per Japan investigator was published by 59% (1,565) of corresponding authors, whereas 16% (427) of corresponding authors had
Table 2.TheTop 20 MostProductiveJapan Instituteson Lung CancerResearch
Institute TP TP3 (R) TPR (%) IPR (%) CPR (%) FPR (%) RPR (%) C%
TP TP3 IP IP3 CP CP3 FP FP3 RP RP3
National Cancer Center 710 394 (55) 1 (8.5) 1 (11) 1 (4.5) 1 (5.4) 1 (11) 1 (14) 1 (5.9) 1 (7.4) 1 (5.0) 1 (6.4) 77 Kyushu University 400 191 (48) 2 (4.8) 3 (5.4) 2 (3.7) 2 (4.9) 3 (5.6) 7 (5.6) 2 (3.0) 2 (3.5) 2 (2.9) 2 (3.3) 68 University of Tokyo 339 214 (63) 3 (4.0) 2 (6.0) 23 (1.1) 12 (1.6) 2 (6.2) 2 (8.2) 12 (1.7) 5 (2.5) 13 (1.6) 4 (2.5) 89 Okayama University 310 123 (40) 4 (3.7) 11 (3.5) 3 (2.8) 17 (1.2) 9 (4.4) 9 (4.6) 3 (2.5) 8 (2.2) 3 (2.7) 6 (2.4) 68 Kyoto University 304 178 (59) 5 (3.6) 4 (5.0) 9 (1.9) 4 (3.1) 4 (4.9) 5 (5.9) 4 (2.1) 3 (3.0) 7 (1.9) 3 (2.6) 78 Osaka University 297 176 (59) 6 (3.5) 5 (5.0) 10 (1.8) 6 (2.8) 6 (4.8) 4 (6.0) 10 (1.8) 4 (2.5) 9 (1.8) 5 (2.5) 78 Nagoya University 291 170 (58) 7 (3.5) 6 (4.8) 12 (1.8) 7 (2.7) 7 (4.7) 6 (5.8) 7 (1.9) 6 (2.4) 10 (1.7) 8 (2.3) 79 Hokkaido University 280 139 (50) 8 (3.3) 8 (3.9) 11 (1.8) 11 (1.8) 8 (4.5) 8 (4.9) 5 (2.0) 9 (2.2) 4 (2.0) 8 (2.3) 77 Tohoku University 269 131 (49) 9 (3.2) 9 (3.7) 7 (2.2) 10 (2.1) 10 (3.9) 10 (4.5) 8 (1.9) 10 (1.9) 6 (1.9) 10 (2.0) 71 Chiba University 256 124 (48) 10 (3.1) 10 (3.5) 4 (2.7) 3 (4.0) 11 (3.3) 14 (3.3) 6 (2.0) 7 (2.2) 5 (1.9) 7 (2.3) 63 Aichi Cancer Center 245 166 (68) 11 (2.9) 7 (4.7) 89 (0.26) 92 (0.17) 4 (4.9) 3 (6.9) 18 (1.2) 11 (1.9) 20 (1.0) 14 (1.6) 96 Kanazawa University 237 110 (46) 12 (2.8) 12 (3.1) 5 (2.5) 9 (2.2) 13 (3.1) 11 (3.6) 11 (1.7) 13 (1.5) 7 (1.9) 13 (1.7) 63 Gunma University 206 85 (41) 13 (2.5) 16 (2.4) 13 (1.7) 14 (1.5) 14 (3.0) 15 (2.8) 15 (1.3) 19 (0.87) 15 (1.3) 18 (0.93) 70 University of Tokushima 197 87 (44) 14 (2.4) 15 (2.5) 6 (2.5) 5 (2.9) 18 (2.3) 21 (2.2) 9 (1.9) 11 (1.9) 11 (1.7) 11 (1.8) 56 University of Occupational and
Environmental Health
189 89 (47) 15 (2.3) 14 (2.5) 8 (2.0) 8 (2.2) 17 (2.5) 19 (2.6) 13 (1.4) 14 (1.3) 12 (1.6) 12 (1.7) 63
National Cancer Center Hospital 184 98 (53) 16 (2.2) 13 (2.8) 25 (1.0) 15 (1.3) 12 (3.1) 12 (3.5) 20 (1.1) 15 (1.2) 19 (1.0) 15 (1.2) 82 East
Hiroshima University 178 74 (42) 17 (2.1) 19 (2.1) 16 (1.5) 33 (0.86) 15 (2.6) 18 (2.7) 16 (1.3) 20 (0.85) 16 (1.3) 19 (0.87) 70 Nagasaki University 155 55 (35) 18 (1.9) 25 (1.6) 17 (1.4) 17 (1.2) 19 (2.2) 27 (1.7) 17 (1.2) 16 (1.0) 17 (1.1) 16 (1.0) 68 University of Tsukuba 152 52 (34) 19 (1.8) 27 (1.5) 14 (1.6) 40 (0.69) 23 (2.0) 24 (1.8) 14 (1.3) 22 (0.82) 14 (1.4) 19 (0.87) 63 Nagoya City University 146 59 (40) 20 (1.7) 22 (1.7) 15 (1.6) 15 (1.3) 25 (1.9) 24 (1.8) 19 (1.1) 32 (0.70) 17 (1.1) 30 (0.75) 62 TP, total articles; TP3, total articles (impact factor ≥ 3); R, percentage of total articles (impact factor ≥ 3) in a institute; TPR, total article rank; IP, independent articles; IP3, independent articles (impact factor ≥ 3); IPR, independent article rank; CP, inter-institutionally collaborative articles; CP3, inter-institutionally collaborative articles (impact factor ≥ 3); CP, inter-institutionally collaborative articles; CP3, inter-institutionally collaborative articles (impact factor ≥ 3); CPR, inter-institutionally collaborative article rank; FP, first author articles; FP3, first author articles (impact factor ≥ 3); FPR, first author article rank; RP, corresponding author articles; RP3, corresponding author articles (impact factor ≥ 3); RPR, corresponding author article rank; % share in total articles; C% percentage of inter-institutionally collaborative articles in total institute articles.
contributed two articles. There were 7,118 articles from 2,674 Japanese corresponding authors who were from 814 Japanese institutes. Of the 814 institutes that published cles on lung cancer, 474 (58%) institutes had only one arti-cle with corresponding authors. Furthermore, Table 2 shows that 386 corresponding author articles were addressed in the National Cancer Center followed by Kyushu University (224) and the University of Tokyo (204).
Research emphasis: words in title, author-chosen keywords, and KeyWords Plus
The title of an article always includes the information which the authors would most like to express to their read-ers, because it would be seen by all readers first. Author keywords analysis offers the information of research trends as viewed by researchers (21). KeyWords Plus provides search terms extracted from the titles of papers cited in the article according to the ISI database (21). In recent years, using the results of distributions of words in the title, author keywords, and KeyWords Plus in different periods have been presented to evaluate research treads (22, 23). All of
the single words in the titles of Japanese lung cancer research-related articles were statistically analyzed. As a re-sult, 20 of the most frequently used substantives in titles are shown in Table 3 in 3 six-year periods. Some words are of no use for the analysis of research trends such as preposi-tions, articles, and conjuncpreposi-tions, which were discarded in this analysis. Therefore, other than the terms “lung”, “can-cer”, “carcinoma”, and “lung-cancer” which were searching words, “cell”, “human”, “patients”, and “expression” were the most frequently used single words in titles. “Phase”, “non-small”, “small”, “receptor”, “prognostic”, and “growth” in titles showed a notable increasing trend. However, the terms “p53”, “chemotherapy”, and “human” in titles showed a decreasing trend during the study period.
The analysis of author keywords revealed that 11,058 author keywords were used in 6,125 articles from 1991 to 2008. Table 4 shows the 20 most frequently used author keywords with their rankings and percentages. The three most frequently used author keywords were “non-small cell lung cancer”, “prognosis”, and “immunohistochemistry”. It is clear that authors used both “non-small cell lung cancer”
Figure 4.Relationship between thenumberofarticlesand thenumberofauthorspublishing the specified numberofarticles. 0 5 10 15 20 25 0 1000 2000 3000 4000 5000 6000 7000 8000 9000 Number of articles
Number of authors making the specified number of articles
Data
Lotka model (n = 2.12) Lotka model (n = 2)
and “non-small-cell lung cancer” as keywords. “Non-small cell lung cancer” was used the most and became popular. “Lung”, “cancer”, “metastasis”, “p53”, “adenocarcinoma”, and “chemotherapy” were also listed as frequently used words in titles (Table 4). “EGFR”, “mutation”, “irinotecan”, “apoptosis”, “paclitaxel”, and “non-small cell lung cancer” had higher increasing rates in the ranking of frequency.
The KeyWords Plus in the Science Citation Index (SCI) and Social Science Citation Index (SSCI) database is “an in-ventive application of the unique power of citation index-ing” (21). KeyWords Plus are words or phrases that may be present for articles that have no author keywords or may in-clude important terms not listed among the titles. In recent years, KeyWords Plus were separated into different year pe-riods to analyze the variations of trends on research topics of pentachlorophenol (24), aerosol (22), and stem cell (23). KeyWords Plus were analyzed to substantially augment author-keyword and title-word indexing. Except for “cell lung-cancer”, “survival”, “breast-cancer”, “tumors”, “ther-apy”, “mutations”, “identification”, “in-vivo”, “activation”, “trial”, “lines”, “gene-expression”, “inhibition”, “carcino-mas”, “in-vitro”, and “colorectal-cancer” all other 14 words listed in the top 30 of KeyWords Plus also appeared in the top 30 of author keywords and words in titles. Again, “in-vitro”, “in-vivo”, “angiogenesis”, “apoptosis”, “colorectal-cancer”, “trial”, and “gene-expression” exhibited a rapidly growing pace in Japan lung cancer research. In addition, “metastasis”, “adenocarcinoma”, and “chemotherapy” ap-peared in the top 30 of words in titles, author keywords, and KeyWords Plus.
From the analysis of three types of the above keywords, research emphasis and trends could be roughly found. Con-sidering Japanese lung cancer-related research articles, after analyzing the distribution of the three types of the key-words, we summed up the research hotspots into 12 topics: “non-small cell and small cell lung cancers”, “metastasis”, “chemotherapy”, “prognosis”, “apoptosis”, “Gefitinib”, “sur-gery”, “cisplatin”, “immunohistochemistry”, “p53”, “angio-genesis”, and “irinotecan” related research. Articles concern-ing these keywords were analyzed and the distribution of these articles is shown in Fig. 5, 6. The hotspots could be reflected by some highly cited articles. Taking “EGFR” and “Gefitinib” related research for instance, in 2004, “EGFR mutations in lung cancer: correlation with clinical response to Gefitinib therapy” was reported (9). After 2004, a sharply increasing trend appeared. Topics related to non-small-cell lung cancer were introduced in studies such as, “phase III study of concurrent versus sequential thoracic radiotherapy in combination with mitomycin, vindesine, and cisplatin in unresectable stage III non-small-cell lung cancer” (7) and “multi-institutional randomized phase II trial of Gefitinib for previously treated patients with advanced non-small-cell lung cancer” (8). Itoh et al (25), reported “reduced angio-genesis and tumor progression in gelatinase A-deficient mice”.
Conclusions
In this study dealing with lung cancer SCI journal papers, we obtained some significant points on Japanese lung cancer
Table 3.Top 20 MostFrequency Substantivesin SourceTitlesduring 1991-2008 and 3 Six-yearPeriods Words in title TP 91-08 R (%) 91-96 R (%) 97-02 R (%) 03-08 R (%) Lung 3,669 1 (44) 3 (20) 1 (51) 1 (48) Cancer 3,348 2 (40) 4 (13) 2 (45) 2 (47) Cell 2,032 3 (24) 6 (10) 3 (27) 3 (28) Human 1,257 4 (15) 2 (22) 4 (17) 9 (11) Patients 1,166 5 (14) 5 (11) 7 (14) 4 (15) Carcinoma 1,007 6 (12) 10 (7.1) 5 (14) 6 (12) Expression 992 7 (12) 8 (7.8) 6 (14) 7 (12) Cells 864 8 (10) 12 (5.7) 8 (11) 8 (11) Non-small 808 9 (9.7) 72 (1.7) 10 (10) 5 (13) Gene 770 10 (9.2) 9 (7.3) 9 (10) 10 (9.1) Tumor 573 11 (6.8) 15 (4.7) 11 (7.5) 12 (7.2) Growth 558 12 (6.7) 46 (2.2) 13 (6.7) 11 (8.4) Study 540 13 (6.4) 13 (5.4) 15 (6.2) 14 (7.1) Factor 528 14 (6.3) 19 (4.0) 14 (6.4) 13 (7.2) Metastasis 506 15 (6.0) 14 (5.3) 12 (7.1) 15 (5.5) Lung-cancer 455 16 (5.4) 1 (29) 889 (0.17) 2203 (0.052) Pulmonary 416 17 (5.0) 25 (3.3) 17 (5.3) 17 (5.4) Protein 349 18 (4.2) 23 (3.7) 18 (4.7) 22 (4.0) P53 346 19 (4.1) 11 (6.7) 16 (5.5) 68 (2.0) Small 340 20 (4.1) 65 (1.8) 18 (4.7) 18 (4.5) TP: the number of total articles; R (%): the rank and percentage of words in titles in total articles.
Table 4.Top 20 Frequency ofKey WordsUsed
Key words TP 91-08 R (%) 91-96 R (%) 97-02 R (%) 03-08 R (%) Lung cancer 1,454 1 (24) 1 (25) 1 (24) 1 (23) Non-small cell lung cancer 363 2 (5.9) 30 (1.1) 2 (5.8) 2 (7.7) Prognosis 262 3 (4.3) 8 (3.1) 3 (4.7) 3 (4.3) Immunohistochemistry 242 4 (4.0) 4 (4.6) 5 (4.0) 7 (3.7) Chemotherapy 229 5 (3.7) 6 (3.5) 6 (3.9) 6 (3.7) Metastasis 213 6 (3.5) 2 (4.9) 7 (3.8) 8 (2.7) P53 208 7 (3.4) 6 (3.5) 4 (4.5) 10 (2.5) Apoptosis 207 8 (3.4) 98 (0.41) 9 (3.5) 5 (4.3) Cisplatin 194 9 (3.2) 5 (3.6) 8 (3.7) 9 (2.6) Non-small-cell lung cancer 134 10 (2.2) 9 (2.5) 11 (2.0) 12 (2.3) Small cell lung cancer 129 11 (2.1) 3 (4.7) 14 (1.9) 24 (1.4)
Gefitinib 124 12 (2.0) N/A N/A 4 (4.3)
Angiogenesis 110 13 (1.8) 60 (0.62) 10 (2.4) 19 (1.7) Lung carcinoma 109 14 (1.8) 10 (2.3) 11 (2.0) 23 (1.5) Adenocarcinoma 103 15 (1.7) 20 (1.4) 18 (1.4) 13 (2.0) Lung metastasis 99 16 (1.6) 15 (1.6) 11 (2.0) 28 (1.3) Irinotecan 94 17 (1.5) 234 (0.21) 15 (1.8) 18 (1.8) Gastric cancer 88 18 (1.4) 38 (0.93) 16 (1.5) 21 (1.6) Surgery 87 19 (1.4) 17 (1.5) 25 (1.1) 20 (1.6) Cancer 86 20 (1.4) 30 (1.1) 43 (0.79) 13 (2.0) Carboplatin 86 20 (1.4) 17 (1.5) 16 (1.5) 28 (1.3) TP: articles in the study period; R (%): the rank and percentage of the author keyword; N/A: not available
research trends and performances from 1991 to 2008. This study provided a systematically structural picture, as well as clues to the impact of various lung cancer research topics. There was a total of 854 journals listed in the 106 SCI sub-ject categories. The highest number of articles was in Lung Cancer and in the subject category of oncology. The USA
ranked first in internationally collaborative articles with Ja-pan. The National Cancer Center was the flagship in lung cancer research in Japan, distinctly followed by Kyushu University. Japan has strongly independent research ability. Research collaborative papers shifted from national inter-institutional to international collaboration. Lung cancer
re-Figure 5.Growth trendsofhotspotsin lung cancerrelated articles,including non-smallcelland smallcelllung cancer,metastasis,chemotherapy,prognosis,apoptosis,and Gefitinib.
0 50 100 150 200 250 1990 1991 1992 1993 1994 1995 1996 1997 1998 1999 2000 2001 2002 2003 2004 2005 2006 2007 2008 2009 Number of articles Year non-small cell and small cell lung cancer metastasis
chemotherapy prognosis apoptosis Gefitinib
Figure 6.Growth trendsofhotspotsin lung cancerrelated articles,including EGFR,surgery,cis platin,immunohistochemistry,p53,and angiogenesis.
0 10 20 30 40 50 60 70 80 90 1990 1991 1992 1993 1994 1995 1996 1997 1998 1999 2000 2001 2002 2003 2004 2005 2006 2007 2008 2009 Number of articles Year EGFR surgery cisplatin immunohistochemistry p53 angiogenesis
search in Japan is still developing, although some research has attained an international level. Participation in the joint clinical studies between many countries is the next issue. Keyword analysis showed that there has been a strategy to
connect molecular biology with clinical practice. “Metasta-sis”, “adenocarcinoma”, and “chemotherapy” were the most popular terms used by Japanese authors. Japan published high impact articles related to non-small cell and small cell
lung cancer. Apoptosis and Gefitinib have been the new re-search topics in recent years. The findings of this study may be of interest for medical staff who are currently undertak-ing studies and for those who will be performundertak-ing research and studying lung cancer medicine for Japanese.
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