Demography

4.1.1 Patient characteristics

Sixty-four dogs met the inclusion criteria between January 2010 and February 2018 and was enrolled in the present study. 42 dogs received the 25-week protocol as their initial treatment; 22 dogs were treated with the 15-week protocol. There were 18 (28%) mixed breed dogs, 16 (25%) Golden retrievers, 6 (9%) Welsh corgis, 4 (6%) Schnauzers, 3 (5%) Beagles, 3 (5%) Malteses, 3 (5%) Shi-tzu, 2 (3%) West highland white terriers, 2 (3%) Poodles, and the rest included 1 Dachshund, 1 Labrador, 1 Husky, 1 Cavalier King Charles Spaniel, 1 Sheltie, 1 Shiba inu and 1 Yorkshire. The most common breeds in two groups both were mixed breed dogs and Golden Retrievers (Table 5). Median age was 7.8 (range 2-13 years) in the 25-week group and 9.5 (range 4-12 years) in 15-week group. Median body weight was 16.15 kg (range 5.06-54.4 kg) in 25-week group and 15.95 (range 1.46-40 kg) in the 15-week group. There were 17 spayed females, 5 intact females, 14 castrated males and 6 intact males in the 25-week group; 8 spayed females, 4 intact females, 9 castrated males and 1 intact male in the 15-week group. There was no significant difference in the distribution of patient characteristics between two groups. Detailed information was summarized in Table 5.

4.1.2 Clinical stage

Fifty-six dogs had sufficient information for staging, with 8 dogs in the 25-week

both abdominal radiography and ultrasonography were available for evaluation in 9 dogs; only abdominal radiography or ultrasonography were available for 7 dogs and 12 dogs, respectively. In the 15-week group, only 1 dog had information of both abdominal radiography and ultrasonography. The rest were staged via abdominal ultrasonography for determination of stage IV. No dogs in either group performed a splenic or hepatic cytology. The thoracic image for pulmonary infiltration and intrathoracic lymph node evaluation was available in 27 (64.3%) dogs of the 25-week group and 20 (90%) dogs of 15 weeks. In 25-week group, 10 dogs had abnormal change in thoracic radiography, including pulmonary infiltration in 7 dogs; enlargement of sternal and tracheobronchial lymph node both in 6 dogs and widen cranial mediastinum in 4 dogs. In the 15-week group, 9 dogs were identified with abnormal findings, including 2 dogs with pulmonary infiltration, 3 dogs with enlarged sternal lymph node, 4 dogs with enlarged tracheobronchial lymph node and 3 dogs with widening cranial mediastinum.

Overall, among the 34 dogs available for complete staging in 25-week group, there were 1 dog (2.9%) in stage I, 8 (23.5%) dogs in stage III, 16 (47.1%) dogs in stage IV, and 9 (26.5%) dogs in stage V. The remaining 8 dogs without sufficient information were in either stage III or IV. In 15-week group, 2 (9.1%) dogs were in stage III, 14 (63.6%) dogs were in stage IV and 6 (37.3%) dogs were in stage V. No significant difference in stage allocation between two groups (P=0.408) (Table 5).

For substage, in the 25-week group 23 (54.8%) dogs and 19 (45.2%) dogs were classified as substage a and b, respectively. In the 15-week group, 12 (54.5%) dogs were substage a and 10 (45.5%) dogs were substage b. Most common clinical signs presented in dogs with substage b were lethargy, anorexia and panting. Other less frequent signs included ecchymosis, vomiting, diarrhea and vision impairment. No significant difference in substage distribution between two groups (P=0.987) (Table 5).

4.1.3 Immunophenotype

Examination for immunophenotype was performed in 51 dogs. All dogs but 2 dogs from the 25-week group who were defined by immunohistochemistry were analyzed by flow cytometry. In 32 dogs available for immunophenotype from 25-week group, 28 (87.5%) dogs were B-cell; 1 (3.1%) dog was T-cell; 3 (9.4%) dogs were null type. In 19 dogs with available information from the 15-week group, 14 dogs (73.7%) were classified as B-cell; 2 (10.5%) dogs were T-cell; 3 (15.8%) dogs were null type. No significant difference in the distribution of immunophenotype between two groups (P=0.406) (Table 5).

4.1.4 Laboratory findings

More than half dogs from either group had no specific findings in laboratory examinations. Hypercalcemia as a possible paraneoplastic syndrome was only noted in 1 dog from the 25-week group among the whole population. Abnormal hematologic laboratory findings possibly associated with poor prognosis (e.g. thrombocytopenia and anemia) were not overrepresented in either group, for there was no significance recognized in the distribution of these factors between two groups (Table 5). Detailed features for two groups were listed in Table 6.

4.2 Chemotherapy protocol

Twenty-seven (64.3%) dogs from the 25-week group and 18 (81.8%) dogs from 15-week group were treated with the protocol on the same day of diagnosis. 5 (11.9%)

between diagnosis and treatment and numbers of population pretreated with steroid before chemotherapy between two groups (Table 5).

Particularly, the 1^st dose adjustment for prevention of ATLS was more significantly presented in the 15-week group (4.8% in 25-week group versus 40.9% in the 15-week group, P=0.000) (Table 9).

4.2.1 Treatment of the 25-week group

Forty-two dogs were treated by the 25-week protocol. In respect of the construct of 25-week protocol, CHOP was used in 32 (76.2%) dogs and CMOP protocol was used in 7 (16.6%) dogs. 2 (4.8%) dogs were given 3 cycles of CMOP followed by 1 cycle of CHOP; 1 (2.4%) dog was given 3 cycles of CHOP and then 1 cycle of CMOP.

Thirty (71.4%) dogs completed the 25-week protocol. Among the 12 dogs who didn’t finish the treatment, 4 dogs failed to retain complete remission through the current protocol and 8 dogs relapsed during treatment. Available information regarding rescue protocol for the 39 dogs who eventually relapsed included continuous incorporation of L-asparaginase into CHOP-based protocol (n=23), CCNU (n=2) and Dactinomycin (n=1).

Seven (16.7%) dogs were given L-asparaginase in the protocol. All dogs, except for 1 dog who was given 3 doses, received only 1 dose of L-asparaginase (10,000 IU/m², intramuscularly or subcutaneously). All doses were administered during treatment based on the judgement of the attending clinician, with none at the initiation of treatment as part of chemotherapy induction. The number of patients administered with L-asparaginase was not significantly different between two groups (Table 5).

Apart from the dose reduction for prevention of ATLS at initiation of chemotherapy, 13 (31%) dogs experienced a total of 20 dose reductions during treatment. Of these 13

dogs, 9 dogs required one dose reduction, 2 dogs experienced dose reduction for twice;

1 dog for 3 times and 1 dog for 4 times. 16 (80%) events were due to neutropenia. As for preventive dose reduction for ATLS, 2 (4.8%) dogs whose large tumor burden recognized as a risk factor of developing ATLS received dose reduction of vincristine (0.5 mg/m²) at treatment initiation.

Twenty-nine (69%) dogs experienced a total of 62 dose delays during treatment. 8 dogs required one dose delay, 12 dogs required two dose delays, 7 dogs required 3 dose delays, 1 dog required 4 dose delays and 1 dog required 5 dose delay. 43 (69.4%) episodes were due to neutropenia. 7 (11.3%) times were due to gastrointestinal toxicity.

3 (4.8%) episodes were due to elevated liver indexes. Other miscellaneous causes were such as leukocytosis, foreign body digestion before visit or owner’s request. Median and mean dose delay were both 1.5 times (range: 0-5).

4.2.2 Treatment of the 15-week group

Twenty-two dogs were treated with 15-week protocol. Most dogs received the construct of CHOP, except for 1 dogs who was initially given mitoxantrone for the first 2 cycles in consideration of cardiac toxicity by the attending clinician according to the finding of heart murmur but then switched to Adriamycin after evaluation by a cardiologist and it turned out no previous concern. 16 (72.7%) dogs completed the protocol. Of the 6 dogs failing to complete, 1 was unable to reach complete remission, 2 were due to development of progressive disease during treatment and 3 were due to owner’s financial concern. Available information regarding rescue protocol for the 13 dogs who eventually developed progressive disease included continuous incorporation

Two dogs were given L-asparaginase during treatment. One dog was given 1 dose and the other dog was given 2 doses due to multiple wounds on skin over the body and was therefore given L-asparaginase due to contradiction to chemotherapy. All doses were administered during treatment, rather than the treatment initiation.

Nine (40.9%) dogs experienced dose reduction during treatment. 5 dogs required 1 dose reduction, 3 dogs required 2 dose reductions and 1 dog required 4 dose reductions.

As in 25-week group, most dogs were due to neutropenia. Other causes included gastrointestinal side effect (n=1), elevated liver indexes (n=1), or both (n=1). For prevention of ATLS, 9 (40.9%) dogs received dose reduction for 1^st vincristine (0.5-0.6 mg/m²) at treatment initiation.

A total of 30 episodes of dose delay were presented in 15 (68.2%) dogs. 8 dogs experienced 1 dose delay; 3 dogs required 2 dose delays; 2 dogs required 3 dose delays;

1 dog needed 4 dose delays and 1 dog needed 6 dose delays. 19 (63.3%) episodes were due to neutropenia; 5 (16.7%) were due to elevated liver indexes; 4 (13.3%) were due to gastrointestinal toxicity. The median and mean time of dose delay were 1 and 1.36, respectively (range: 0-6)