Chapter 5 Discussion
5.5 Conclusions
We developed a series of statistical methods to elucidate the process of non-referral and to quantify its impact on colonoscopy in terms of CRC mortality and advanced CRC and further evaluate the efficacy of colonoscopy with 100% compliance under the context of Taiwan nationwide colorectal cancer screening programme. Through our analysis, we demonstrated that a full compliance is a goal to be pursued to reach the efficacy of 48% mortality reduction by colonoscopy under the context of service
screening for CRC.
List of Tables
Table 2.1 The main randomized control trials of guaiac fecal occult blood test No. of CRC deaths Mortality rate
RCTs Screen Control Screen Control Mortality
reduction Nottingham
(Hardcastle JD, 1996)
593/76466 684/76384 0.70/1000py 0.81/1000py 13%
Funen (Kronborg O, 1996)
362/30967 431/30966 0.84/1000py 1.00/1000py 16%
Goteborg (Kewenter J, 1994)
252/34144 300/34164 0.53/1000py 0.64/1000py 16%
Minnesota-A (Mandel JS, 1993)
121/15570 177/15384 0.67/1000py 1.00/1000py 33%
Minnesota-B (Mandel JS, 2000)
148/15587 - 0.79/1000py - 21%
Abbreviation: CRC, colorectal cancer; RCT, randomized control trial
Table 2.2 Summary of effect of fecal immunochemical test versus guaiac fecal occult blood test and flexible sigmoidoscopy
Journal(Author, year)
Study
site/population
Study design/aim Remark Gut
Detection rate of advanced neoplasia:
FIT vs gFOBT: 2.4% vs 1.1%(OR, 2.0; CI, 1.3 to 3.1) FS vs gFOBT: 8.0% vs 1.1% (OR, 7.0; CI, 4.6 to 10.7) Diagnostic yield of advanced neoplasia per 100 invitees screening: positivity rates of cancer and/or significant adenoma of
gFOBT and FIT
Cancer (n=24):
FIT: 87.5% (significantly more) vs. gFOBT: 54.2%
Significant adenomas (n=61):
FIT: 42.6% (significantly more) vs gFOBT: 23.0%
Journal(Author, year)
Study
site/population
Study design/aim Remark diagnostic for the detection of ACRN or CRC in average-risk people undergoing
screening colonoscopy
The sensitivity and specificity of the gFOBT for detecting advanced adenomas, cancer, and ACRNs were 13.6 % / 92.4
% , 30.8 % / 92.4 % ,and 16.7 % / 92.9 %, respectively.
Using the 100 ng / ml cut point and three-sample qFIT results, the
sensitivity and specifi city of the qFIT for detecting
advanced adenomas, cancer, and ACRNs were 33.9 % / 90.6
% , 84.6 % / 89.8 % , and 43.7 % / 91.9 % , respectively.
Abbreviations: RCT, randomized control trial; gFOBT, guaiac fecal occult blood test; FIT, fecal immunochemical test; FS, flexible
sigmoidoscopy; ACRN, advanced colorectal neoplasia; CRC, colorectal cancer
Table 3.1 Information on the derivation of CRC mortality for FIT-positive subject under untreated scenario
Information Overall
population FIT-negative FIT positive
Proportion 1 0.93 0.07 (A)
CRC mortality 0.50 per 1000 0.24* per 1000 (B) - CRC mortality with
increasing incidence
0.53 per 1000 (C) - 2.28 per 1000 (= ( × )×
× )
*CRC mortality of FIT negative was based on Chen et al (2013, BMJ Open).
Table 4.1.1 Colorectal cancer mortality rate by characteristics of subjects with positive fecal immunochemical test, the KCIS cohort
Variable Person-year
Table 4.1.2 Advanced stage of colorectal cancer incidence rate by characteristics of subjects with positive fecal immunochemical test, the KCIS cohort
Variable Person-year Advanced CRC Incidence
Abbreviations: FHbC, fecal hemoglobin concentration.
Table 4.1.3 Characteristics of referral and non-referral subjects and referral rate,
Variable Frequency Referral rate
Abbreviations: BW, body weight; CRC, colorectal cancer.
Table 4.1.4 Estimated results of crude and adjusted hazard ratio for colorectal cancer death, the KCIS cohort
Variable Hazard ratio
Abbreviations: CRC, colorectal cancer; FHbC, fecal hemoglobin concentration, CI, confidence interval.
Table 4.1.5 Estimated results of crude and adjusted hazard ratio for advanced stage of colorectal cancer, the KCIS cohort
Variable Hazard ratio
Abbreviations: CRC, colorecatal cancer; FHbC, fecal hemoglobin concentration, CI, confidence interval.
Table 4.1.6 The effect of factors on referral rate, the KCIS cohort
Variable aOR 95% CI
Abbreviations: BW, body weight; CRC, colorectal cancer; CI, confidence interval.
Table 4.1.7 The estimated efficacy of colonoscopy on colorectal cancer mortality and advanced colorectal cancer incidence by adjusting with propensity score, the KCIS cohort
CRC mortality Advanced stage of CRC incidence
Odds ratio (95% CI) P value Odds ratio (95% CI) P value Referral (No vs Yes) 1.82 (1.22-2.70) 0.003 1.49 (1.05-2.13) 0.024 Propensity score 0.78 (0.48-1.29) 0.340 0.84 (0.54-1.32) 0.427 Abbreviations: CRC, colorecatal cancer; CI, confidence interval.
Table 4.1.8 Characteristics of referral and non-referral subjects in data matched by propensity score, the KCIS cohort
Variable Frequency
Elementary school 379 373
Illiterate 167 167
Variable Frequency
Referred Non-referred P
Sometimes 677 676
Often 109 110
Sea food No 435 437 0.987
Sometimes 217 214
Often 371 372
Bean/Egg No 390 391 0.981
Sometimes 245 248
Often 388 384
Fruit No 584 593 0.757
Sometimes 192 179
Often 247 251
Milk No 364 379 0.767
Sometimes 221 212
Often 438 432
Soft drinks No 435 437 0.987
Sometimes 217 214
Often 371 372
Coffee/tea No 314 316 0.893
Sometimes 105 111
Often 604 596
Abbreviations: BW, body weight.
Table 4.1.9 Estimated results of the effect of referral on colorectal cancer mortality by using matched data set, the KCIS cohort
Hazard ratio
Crude HR 95% CI aHR 95% CI
Referral No 2.04 1.30 3.23 2.08 1.32 3.23
Yes 1.00 1.00
FHbC
20-49 - - - 1.00
50-99 - - - 1.21 0.60 2.46
100-149 - - - 1.54 0.63 3.77
150-249 - - - 3.00 1.51 5.98
250-449 - - - 3.74 2.02 6.93
>=450 - - - 4.02 1.92 8.41
Abbreviations: aHR, adjusted hazard ratio; CI, confidence interval.
Table 4.1.10 Estimated results of the effect of referral on advanced colorectal cancer by using matched data set, the KCIS cohort
Hazard ratio
Crude HR 95% CI aHR 95% CI
Referral No 1.67 1.11 2.50 1.61 1.08 2.44
Yes 1.00 1.00
FHbC
20-49 - - - 1.00
50-99 - - - 0.86 0.42 1.75
100-149 - - - 1.14 0.45 2.95
150-249 - - - 4.16 2.35 7.36
250-449 - - - 3.66 2.03 6.63
>=450 - - - 7.02 3.95 12.48
Abbreviations: aHR, adjusted hazard ratio; CI, confidence interval
Table 4.2.1 Numbers of colorectal cancer deaths and advanced cancer by characteristics of study subjects with positive FIT, Taiwanese nationwide CRC screening program*
Characteristics CRC Death Advanced CRC
No Yes % No Yes % Type of screening units
Hospital 6622 75 1.12 6326 270 4.09
*There were 669 cases with missing stage information
Table 4.2.2 Referral rate and median waiting time for confirmatory exam among subjects with positive FIT, Taiwanese nationwide CRC screening program
Characteristics Referral Waiting time
No Yes % Median Q1 Q3 Type of screening units
Hospital 2232 4465 66.67 36 24 59
Table 4.2.3 Estimated results on the risk of colorectal cancer mortality by using Cox regression model, Taiwanese nationwide CRC screening program
(a) Referral for colonoscopy
HR 95% CI aHR 95% CI HR: hazard ratio, aHR: adjusted hazard ratio
(b) Referral for all confirmatory examinations
Screening round (vs Subsequent)
Prevalent 1.38 1.10 1.73 1.26 1.00 1.59
F-Hb concentration (vs 20-49)
50-99 1.90 1.39 2.61 1.96 1.43 2.69
100-149 1.50 1.04 2.18 1.52 1.04 2.21
150-249 3.94 2.95 5.26 4.04 3.02 5.39
250-449 4.23 3.17 5.64 4.28 3.20 5.72
>=450 5.29 4.02 6.97 5.49 4.15 7.26
Table 4.2.4 Estimated results on the risk of advanced colorectal cancer by using Cox regression model, Taiwanese nationwide CRC screening program
(a) Referral for colonoscopy
HR 95% CI aHR 95% CI
HR: hazard ratio, aHR: adjusted hazard ratio
(b) Referral for all confirmatory examinations
Screening round (vs Subsequent)
Prevalent 1.43 1.25 1.63 1.33 1.17 1.52 F-Hb concentration (vs 20-49)
50-99 1.34 1.12 1.61 1.39 1.16 1.68
100-149 1.47 1.20 1.80 1.54 1.26 1.89
150-249 3.19 2.72 3.76 3.37 2.86 3.98
250-449 3.85 3.28 4.52 3.98 3.39 4.67
>=450 4.45 3.81 5.19 4.79 4.09 5.60
Table 4.2.5 Estimated results on the risk scores for noncompliance and waiting time by characteristics of study population based on Hurdle Poisson regression model, Taiwanese nationwide CRC screening program
Characteristics Coefficient
Score of noncompliance1 Score of waiting time2 Gender
Northern -0.3086 0.1754
Middle -0.1176 0.2401
Southern -0.2028 0.2104
Eastern/offshore islands -0.4811# -4.1044#
Type of screening units
Hospital 0.1558 -0.0219
Public health centers -0.8247 0.2795
Local clinics -0.4811# -4.1044#
Screening round
Prevalent -0.4811# -4.1044#
Subsequent -0.6542 0.0639
1: Based on the hurdle part of Hurdle regression model with logistic regression model
2: Based on the count (non-hurdle) part of Hurdle regression model with truncated Poisson regression model (given those compliers)
# represents intercept
Table 4.2.6 Propensity score adjusted analysis on risk of colorectal cancer mortality by three kinds of model, Taiwanese nationwide CRC screening program
(a) Referral for colonoscopy
Non-compliance Score Non-compliance Score and Poisson WT
Non-compliance Score and Coxian WT
aHR 95%CI aHR 95%CI aHR 95%CI
Nonreferral (vs Referral) 1.59 1.32 1.92 1.59 1.32 1.96 1.61 1.32 1.96
Score of nonreferral
$1.15 0.94 1.42 1.31 0.94 1.84 1.15 0.93 1.41
Waiting time
Score of waiting time
&(Hurdle-Poisson approach)
- - - 0.57 0.18 1.76 - - -
Delay for colonoscopy
(Hurdle-Coxian approach)
- - - - - - 1.26 0.39 4.03
F-Hb concentration (vs 20-49)
50-99 1.91 1.36 2.70 1.90 1.35 2.68 1.91 1.36 2.70
100-149 1.39 0.92 2.11 1.37 0.90 2.08 1.40 0.92 2.12
150-249 3.72 2.71 5.12 3.66 2.66 5.04 3.73 2.71 5.12
250-449 4.35 3.18 5.95 4.29 3.14 5.88 4.35 3.18 5.95
>=450 5.72 4.25 7.69 5.58 4.13 7.54 5.72 4.25 7.70
$
The greater the score, the more likely as non-referral
&
The greater the score, the longer the waiting time
aHR: adjusted hazard ratio
(b) Referral for all confirmatory examinations
Non-compliance Score Non-compliance Score and Poisson WT
Non-compliance Score and Coxian WT
aHR 95%CI aHR 95%CI aHR 95%CI
Nonreferral (vs Referral) 1.46 1.21 1.77 1.46 1.21 1.76 1.47 1.21 1.78
Score of nonreferral
$1.26 1.03 1.53 1.03 0.76 1.41 1.26 1.03 1.53
Waiting time
Score of waiting time
&(Hurdle-Poisson approach) - - - 2.24 0.83 6.02 - - -
Delay for colonoscopy
(Hurdle-Coxian approach) - - - - - - 1.18 0.41 3.40
F-Hb concentration (vs 20-49)
50-99 1.94 1.42 2.66 1.96 1.43 2.68 1.94 1.42 2.66
100-149 1.50 1.04 2.18 1.55 1.07 2.25 1.50 1.04 2.18
150-249 3.96 2.97 5.28 4.07 3.05 5.44 3.96 2.97 5.28
250-449 4.21 3.16 5.63 4.31 3.22 5.76 4.22 3.16 5.63
>=450 5.33 4.05 7.02 5.54 4.19 7.33 5.33 4.05 7.03
Table 4.2.7 Propensity score adjusted analysis on risk of advanced colorectal cancer by three kinds of model, Taiwanese nationwide CRC screening program
(a) Referral for colonoscopy
Non-compliance Score Non-compliance Score and
Poisson WT Non-compliance score and Coxian WT
aHR 95%CI aHR 95%CI aHR 95%CI
Nonreferral (vs Referral) 1.23 1.10 1.39 1.23 1.10 1.39 1.25 1.11 1.41
Score of nonreferral
$1.49 1.32 1.67 1.48 1.22 1.81 1.48 1.31 1.67
Waiting time
Score of waiting time
&(Hurdle approach) - - - 1.01 0.53 1.94 - - -
Delay for colonoscopy
(Hurdle-Coxian approach) - - - - - - 1.63 0.90 2.98
F-Hb concentration (vs 20-49)
50-99 1.34 1.10 1.63 1.34 1.10 1.63 1.34 1.10 1.63
100-149 1.55 1.25 1.92 1.55 1.25 1.93 1.55 1.25 1.93
150-249 3.24 2.72 3.87 3.25 2.72 3.87 3.25 2.73 3.87
250-449 3.91 3.29 4.64 3.91 3.29 4.65 3.91 3.29 4.64
>=450 4.52 3.82 5.34 4.52 3.82 5.35 4.52 3.83 5.34
$
The greater the score, the more likely as non-referral
&
The greater the score, the longer the waiting time
aHR: adjusted hazard ratio
(b) Referral for all confirmatory examinations
Non-compliance Score Non-compliance Score and Poisson WT
Non-compliance score and Coxian WT
aHR 95%CI aHR 95%CI aHR 95%CI
Nonreferral (vs Referral) 1.19 1.06 1.34 1.19 1.06 1.33 1.21 1.07 1.36
Score of nonreferral
$1.48 1.32 1.65 1.18 0.98 1.41 1.47 1.31 1.64
Waiting time
Score of waiting time
&(Hurdle approach)
- - - 2.47 1.38 4.42 - - -
Delay for colonoscopy
(Hurdle-Coxian approach) - - - - - - 1.59 0.92 2.77
F-Hb concentration (vs 20-49)
50-99 1.37 1.14 1.65 1.38 1.15 1.66 1.37 1.14 1.65
100-149 1.48 1.21 1.81 1.53 1.25 1.88 1.48 1.21 1.81
150-249 3.23 2.74 3.80 3.34 2.83 3.93 3.23 2.75 3.80
250-449 3.85 3.28 4.51 3.95 3.36 4.63 3.85 3.28 4.52
>=450 4.49 3.85 5.24 4.68 4.00 5.48 4.50 3.85 5.24
Table 4.2.8 Propensity score matching analysis on risk of colorectal cancer mortality by three kinds of model, Taiwanese nationwide CRC screening program
(a) Referral for colonoscopy
Non-compliance Score Non-compliance Score and Poisson WT
Non-compliance Score and Coxian WT
aHR 95%CI aHR 95%CI aHR 95%CI
Nonreferral (vs Referral) 1.49 1.15 1.92 1.49 1.15 1.92 1.52 1.16 1.96
Waiting time
Score of waiting time
&(Hurdle-Poisson approach)
- - - 1.24 0.52 2.97 - - -
Delay for colonoscopy
(Hurdle-Coxian approach)
- - - - - - 1.74 0.24 12.65
F-Hb concentration (vs 20-49)
50-99 1.43 0.89 2.31 1.44 0.89 2.32 1.43 0.89 2.31
100-149 0.98 0.55 1.75 0.99 0.55 1.78 0.98 0.55 1.75
150-249 2.46 1.59 3.82 2.50 1.61 3.89 2.47 1.59 3.83
250-449 3.23 2.13 4.90 3.26 2.15 4.95 3.23 2.13 4.90
>=450 4.29 2.90 6.34 4.36 2.93 6.48 4.29 2.90 6.35
$
The greater the score, the more likely as non-referral
&
The greater the score, the longer the waiting time
aHR: adjusted hazard ratio
(b) Referral for all confirmatory examinations
Non-compliance Score Non-compliance Score and Poisson WT
Non-compliance score and Coxian WT
aHR 95%CI aHR 95%CI aHR 95%CI
Nonreferral (vs Referral) 1.40 1.09 1.81 1.41 1.09 1.81 1.42 1.10 1.85
Waiting time
Score of waiting time
&(Hurdle approach) - - - 1.67 0.72 3.91 - - -
Delay for colonoscopy
(Hurdle-Coxian approach) - - - - - - 1.60 0.21 11.96
F-Hb concentration (vs 20-49)
50-99 1.35 0.84 2.19 1.37 0.85 2.22 1.36 0.84 2.19
100-149 0.94 0.53 1.68 0.98 0.55 1.75 0.95 0.53 1.69
150-249 2.78 1.83 4.22 2.87 1.88 4.38 2.78 1.83 4.23
250-449 3.11 2.06 4.70 3.19 2.10 4.83 3.11 2.06 4.70
>=450 4.13 2.80 6.09 4.30 2.90 6.38 4.14 2.81 6.11
Table 4.2.9 Propensity score matching analysis on risk of advanced colorectal cancer by three kinds of model.
(a)
Referral for colonoscopy
Non-compliance Score Non-compliance Score and Poisson WT
Non-compliance score and Coxian WT
aHR 95%CI aHR 95%CI aHR 95%CI
Nonreferral (vs Referral) 1.22 1.04 1.43 1.22 1.05 1.43 1.28 1.09 1.49
Waiting time
Score of waiting time
&(Hurdle approach) - - - 2.58 1.55 4.29
Delay for colonoscopy
(Hurdle-Coxian approach) 4.02 1.71 9.46
F-Hb concentration (vs 20-49)
50-99 1.23 0.92 1.63 1.26 0.94 1.68 1.23 0.89 2.31
100-149 1.29 0.95 1.76 1.37 1.00 1.87 1.30 0.55 1.75
150-249 2.56 1.98 3.31 2.72 2.10 3.51 2.58 1.59 3.83
250-449 3.21 2.51 4.10 3.35 2.62 4.29 3.21 2.13 4.90
>=450 3.46 2.72 4.40 3.72 2.91 4.74 3.48 2.90 6.35
$The greater the score, the more likely as non-referral
&The greater the score, the longer the waiting time
aHR: adjusted hazard ratio
(b) Referral for all confirmatory examinations
Non-compliance Score Non-compliance Score and Poisson WT
Non-compliance score and Coxian WT
aHR 95%CI aHR 95%CI aHR 95%CI
Nonreferral (vs Referral) 1.15 0.99 1.34 1.16 0.99 1.34 1.20 1.03 1.41
Waiting time
Score of waiting time
&(Hurdle approach) - - - 3.56 2.17 5.85
Delay for colonoscopy
(Hurdle-Coxian approach) 3.70 1.55 8.86
F-Hb concentration (vs 20-49)
50-99 1.07 0.79 1.43 1.11 0.82 1.48 1.07 0.80 1.44
100-149 1.22 0.89 1.65 1.32 0.97 1.80 1.22 0.90 1.66
150-249 2.69 2.10 3.43 2.91 2.28 3.73 2.70 2.11 3.45
250-449 3.05 2.40 3.89 3.25 2.55 4.14 3.06 2.40 3.89
>=450 3.46 2.74 4.37 3.81 3.00 4.83 3.48 2.76 4.40
Table 4.3.1 Number of CRC death and CRC mortality by areas and adenoma detection rates (ADR) among compliers with colonoscopy exam
Northern Middle Southern Eastern/Offshore Overall
CRC
Table 4.3.2 Estimated results on the risk of colorectal cancer mortality by using Cox regression model
(a) Referral for colonoscopy
Adjusting for area
Adjusting for area and adenoma detection rate
aHR 95% CI aHR 95% CI
Nonreferral (vs Referral) 1.68 1.38 2.03 1.68 1.39 2.04 Geographic area
(vs Northern)
Middle 1.08 0.86 1.35 1.05 0.83 1.32
Southern 1.43 1.16 1.77 1.41 1.13 1.74 Eastern/offshore islands 1.58 1.01 2.47 1.59 1.02 2.48
(b) Referral for all confirmatory examinations Adjusting for
area
Adjusting for area and adenoma detection rate
aHR 95% CI aHR 95% CI
Nonreferral (vs Referral) 1.55 1.29 1.87 1.59 1.32 1.92 Geographic area
(vs Northern)
Middle 1.00 0.81 1.23 0.98 0.79 1.21 Southern 1.31 1.08 1.59 1.28 1.05 1.56 Eastern/offshore islands 1.45 0.96 2.17 1.42 0.95 2.14 aHR: adjusted hazard ratio
Table 4.3.3 Estimated results of risk of CRC death with intention-to-untreat adjustment
(a) Referral for colonoscopy
Estimate
aRR (95% CI) aRR* (95% CI) Adjusting for area
Nonreferral (vs. Referral) 1.58 (1.39,1.78) 1.65 (1.44,1.86) Adjusting for area, and adenoma detection rate
Nonreferral (vs. Referral) 1.59 (1.40,1.78) 1.66 (1.46,1.87)
(b) Referral for all confirmatory examinations
Estimate
aRR (95% CI) aRR* (95% CI) Adjusting for area
Nonreferral (vs. Referral) 1.49 (1.32,1.66) 1.56 (1.38,1.75) Adjusting for area, and adenoma detection rate
Nonreferral (vs. Referral) 1.51 (1.35,1.69) 1.59 (1.41,1.79)
*adjustment for increasing incidence Model A: adjustment for areas
Model B: adjustment for areas, and adenoma detection rates
Table 4.3.4 Estimated results of risk of CRC death with adjustment for non-compliance
(a) Referral for colonoscopy
Estimate
Adjusting for area, and adenoma detection rates Referral increase to
100% 0.55 (0.47,0.63) 0.52(0.44,0.61)
(b) Referral for all confirmatory examinations
Estimate
Adjusting for area, and adenoma detection rates Referral increase to
100% 0.59 (0.50,0.67) 0.55 (0.47,0.63)
*adjustment for increasing incidence Model A: adjustment for areas
Model B: adjustment for areas, and adenoma detection rates
Table 5.1 Summary on the estimated results on the impact of referral on colonoscopy based in KCIS data
Mortality Advanced CRC
aHR 95% CI aHR 95% CI
Conventional Cox regression model 1.69 1.14 2.56 1.12 0.79 1.61
Propensity score adjustment 1.82 1.22 2.7 1.49 1.05 2.13
Propensity score matching 2.08 1.32 3.23 1.61 1.08 2.44
Table 5.2 Summary on the estimated results on the impact of referral on colonoscopy based in Taiwanese nationwide colorectal cancer screening data
Mortality Advanced CRC
aHR 95% CI aHR 95% CI
Referral for colonoscopy
Conventional Cox regression model 1.59 1.32 1.92 1.23 1.10 1.39 Referral for all confirmatory examinations
Conventional Cox regression model 1.46 1.21 1.77 1.19 1.06 1.34
List of Figures
Figure 4.1.1 Cumulative colorectal cancer mortality by referral status
Non-referral
Referral
Figure 4.1.2 Cumulative incidence rate of advanced stage of colorectal cancer mortality by referral status
Non-referral
Referral
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