Various protocols are described in the literature. Three examples are provided below.

Note that oral cytotoxic drugs cannot be split or divided and should not be crushed. It is also important that patients are not overdosed with cytotoxic medications. Ideally, for these reasons a compounding / reformulating pharmacy should be used to match patient requirements exactly; there are now companies (e.g. ChemoPet) who will prepare single per patient doses of chemotherapy to allow accurate dosing and save potential wastage due to bulk compounding. If this is not possible, then patients should be underdosed rather than overdosed based on the available tablet sizes. Extended dosing frequency or alternating administered dose on different days can occasionally be used to average out to the required dose. Refer to specialist texts or seek advice from a veterinary oncologist for further information regarding protocols.

When administering chemotherapy, appropriate personal protective equipment must be worn. Closed administration systems are recommended. The ‘ACVIM Small Animal Consensus Statement on Safe Use of Cytotoxic Chemotherapeutics in Veterinary Practice’ (Smith et al. (2018) Journal of Veterinary Internal Medicine) is a useful resource.

Protocol 1: Combination cytotoxic therapy COP (low dose)

Induction:

Cyclophosphamide: 50 mg/m2 p.o. on alternate days or 50 mg/m2 p.o. for the first 4 days of each week

Vincristine: 0.5 mg/m2 i.v. q7d

Prednisolone: 2 mg/kg p.o. q24h (week 1), 1.5 mg/kg p.o. q24h (week 2), 1 mg/kg p.o. q24h (week 3), 1 mg/kg p.o. q48h thereafter.

Maintenance after a minimum of 2 months:

Cyclophosphamide: 50 mg/m2 p.o. on alternate days or 50 mg/m2 p.o. for the first 4 days of each second week (alternate-week therapy)

Vincristine: 0.5 mg/m2 i.v. q14d

Prednisolone: 1 mg/kg p.o. q48h.

Maintenance after 6 months (if disease in remission):

Cyclophosphamide: 50 mg/m2 p.o. q48h (one week in three) or 50 mg/m2 p.o. for the first 4 days of each third week (one week in three)

Vincristine: 0.5 mg/m2 i.v. q21d

Prednisolone: 1 mg/kg p.o. q48h.

After 12 months:

Stop and monitor for relapse (see below for options at recurrence/relapse)

General notes:

• Catheters should be placed in all cases and only catheters placed by ‘first-stick’ should be used for chemotherapy.

• GI protectants are recommended for first 14 days. Omeprazole (1 mg/kg q24h or q12h) is often used by oncologists. Ranitidine with sucralfate is an alternative approach. Cimetidine is avoided due to its effect on the hepatic cytochrome P450 enzyme pathway and the potential for altering metabolism of chemotherapeutics.

• Certain breeds (generally Collie type) are very sensitive to vincristine due to the MDR1 mutation; a commercial test is available.

• Co-administration of 1 mg/kg of furosemide q12h on each cyclophosphamide treatment day reduces the frequency of sterile haemorrhagic cystitis.

• Chlorambucil (5 mg/m2 p.o. on alternate days) may be given as an alternative for cyclophosphamide if haemorrhagic cystitis develops.

• Most oncologists prefer a CHOP type or the high dose COP protocol.

Recommended monitoring:

• Haematology should be checked prior to each vincristine treatment.

• Biochemistry is checked prior to the first treatment and then a minimum of every 6 months.

• Check free-catch urine by dipstick prior to and then each week that the patient receives cyclophosphamide. If blood is noted, suspend cyclophosphamide and culture urine. If urine culture is negative, start chlorambucil as described above.

Contraindications and adverse effects

Myelosuppression, haemorrhagic cystitis (cyclophosphamide only) or GI effects may occur. Vincristine is a vesicant, therefore catheters should be placed in all cases and only catheters placed by ‘first-stick’ should be used. Discontinue cyclophosphamide therapy if the neutrophil count decreases to <2 × 109/l; check count weekly and do not resume treatment until neutrophil count is >3 × 109/l. If neutropenia recurs following reinstitution of therapy, decrease dose by 10-25%.

Protocol 2: Combination cytotoxic therapy COP (high dose)

Induction:

Cyclophosphamide: 250 mg/m2 p.o. q21d

Vincristine: 0.70 mg/m2 i.v. q7d for 4 weeks then 0.70 mg/m2 i.v. q21d on same day as cyclophosphamide

Prednisolone: 2 mg/kg p.o. q24h (week 1), 1.5 mg/kg p.o. q24h (week 2), 1 mg/kg p.o. q24h (week 3), 1 mg/kg p.o. q48h thereafter

Furosemide: 1 mg/kg p.o. q12h for 48h (i.e. 4 doses), administration with cyclophosphamide.

Maintenance after 6 months:

Cyclophosphamide: 250 mg/m2 p.o. q28d

Vincristine: 0.70 mg/m2 i.v. q28d with cyclophosphamide

Prednisolone: 1 mg/kg p.o. q48h

Furosemide: 1 mg/kg p.o. q12h for 48h (i.e. 4 doses), administration with cyclophosphamide.

After 12 months:

Stop and monitor for relapse (see below for options at recurrence/relapse).

General notes:

• Catheters should be placed in all cases and only catheters placed by ‘first-stick’ should be used for chemotherapy.

• GI protectants are recommended for the first 21 days. Omeprazole (1 mg/kg q24h or q12h) is often used by oncologists. Ranitidine with sucralfate is an alternative approach. Cimetidine is avoided due to its effect on the hepatic cytochrome P450 enzyme pathway and the potential for altering metabolism of chemotherapeutics.

• Certain breeds (generally Collie type) are very sensitive to vincristine due to the MDR1 mutation; a commercial test is available.

• Chlorambucil (20 mg/m2 p.o.) may be given as an alternative for cyclophosphamide if haemorrhagic cystitis develops.

• Most oncologists prefer a CHOP type, but high dose COP is a useful and relatively straightforward protocol for use in a non-specialist setting.

Recommended monitoring:

• Haematology should be checked prior to each vincristine treatment.

• Biochemistry is checked prior to the first treatment and then a minimum of every 6 months.

• Check free-catch urine by dipstick prior to each cyclophosphamide administration. If blood is noted, suspend cyclophosphamide and culture urine. If urine culture is negative, start chlorambucil as above.

Contraindications and adverse effects

Myelosuppression, haemorrhagic cystitis (cyclophosphamide only) or GI effects are relatively common. Vincristine is a vesicant, therefore catheters should be placed in all cases and only catheters placed by ‘first-stick’ should be used. Should an extravasation occur, contact an oncologist. Treatment can be given if the neutrophil count is > 3 × 109/l and platelet count > 100 x109/l. If the neutrophil count is < 3 × 109/l, then suspend treatment and recheck in 5 - 7 days. If neutrophil count is < 1 × 109/l, prescribe prophylactic antibiotics (until neutrophil count is > 1 × 109/l). If neutrophil count is < 1 × 109/l and the patient is pyrexic or unwell, administer i.v. antibiotics and contact an oncologist for advice. If a neutrophil count of < 1 x 109/l is noted, decrease dose of one chemotherapy drug by 10% at the next administration; if recurrent, contact an oncologist for advice.

Protocol 3: 25-week CHOP / CEOP protocol

Week 1

Vincristine: 0.7 mg/m2 i.v. once

Prednisolone: 2 mg/kg p.o. q24h

Week 2

Cyclophosphamide: 250 mg/m2 p.o. once

Prednisolone: 1.5 mg/kg p.o. q24h

Furosemide: 1 mg/kg p.o. q12h for 48h (i.e. 4 doses), administration with cyclophosphamide

Week 3

Vincristine: 0.7 mg/m2 i.v. once

Prednisolone: 1 mg/kg p.o. q24h

Week 4

Doxorubicin or epirubicin: 30 mg/m2 i.v. once (in 0.9% NaCl (not Hartmann’s)) given over 20 minutes. For patients < 15 kg, use 1 mg/kg.

Maropitant: 1 mg/kg s.c. once ais given before doxorubicin/epirubicin

Prednisolone: 0.5 mg/kg p.o. q24h for one week

Week 5

No medication (prednisolone is stopped)

Week 6

Vincristine: 0.7 mg/m2 i.v. once

Week 7

Cyclophosphamide: 250 mg/m2 p.o., i.v.

Furosemide: 1 mg/kg p.o. q12h for 48h (i.e. 4 doses), administration with cyclophosphamide.

Week 8

Vincristine: 0.7 mg/m2 i.v. once

Week 9

Doxorubicin or epirubicin: 30 mg/m2 i.v. once (in 0.9% NaCl (not Hartmann’s)) given over 20 minutes. For patients <15 kg, use 1 mg/kg.

Maropitant: 1 mg/kg s.c. once is given before doxorubicin/epirubicin

Week 10

No medication

Week 11

Vincristine: 0.7 mg/m2 i.v. once

Week 12

No medication

Week 13

Cyclophosphamide: 250 mg/m2 p.o., i.v. once

Furosemide: 1 mg/kg p.o. q12h for 48h (i.e. 4 doses), administration with cyclophosphamide.

Week 14

No medication

Week 15

Vincristine: 0.7 mg/m2 i.v. once

Week 16

No medication

Week 17

Doxorubicin or epirubicin: 30 mg/m2 i.v. once (in 0.9% NaCl (not Hartmann’s)) given over 20 minutes. For patients < 15 kg, use 1 mg/kg.

Maropitant: 1 mg/kg s.c. once is given before doxorubicin/epirubicin

Week 18

No medication

Week 19

Vincristine: 0.7 mg/m2 i.v. once

Week 20

No medication

Week 21

Cyclophosphamide: 250 mg/m2 p.o., i.v. once

Furosemide: 1 mg/kg p.o. q12h for 48h (i.e. 4 doses), administration with cyclophosphamide.

Week 22

No medication

Week 23

Vincristine: 0.7 mg/m2 i.v. once

Week 24

No medication

Week 25

Doxorubicin or epirubicin: 30 mg/m2 i.v. once (in 0.9% NaCl (not Hartmann’s)) given over 20 minutes. For patients < 15 k, use 1 mg/kg.

Maropitant: 1 mg/kg s.c. once is given before doxorubicin/epirubicin

Week 26 and thereafter

Stop chemotherapy and monitor for relapse (see below for options at recurrence/relapse).

General notes

• Catheters should be placed in all cases and only catheters placed by ‘first-stick’ should be used for chemotherapy.

• GI protectants are recommended for the first 21 days. Omeprazole (1mg/kg q24h or q12h) is often used by oncologists. Ranitidine with sucralfate is an alternative approach. Cimetidine is avoided due to its effect on the hepatic cytochrome P450 enzyme pathway and the potential for altering metabolism of chemotherapeutics.

• Certain breeds (generally Collie type) are very sensitive to vincristine and doxorubicin / epirubicin due to the MDR1 mutation; a commercial test is available.

• Chlorambucil (20 mg/m2 p.o.) may be given as an alternative for cyclophosphamide if haemorrhagic cystitis develops.

• In case of cardiac dysfunction, mitoxantrone 5.5 mg/m2 over 10 minutes can be considered as an alternative to doxorubicin/epirubicin.

• After initial 6 months, all medication is stopped until a relapse occurs.

Suggested monitoring:

• Haematology is checked prior to each treatment.

• A nadir neutrophil count should be assessed 7 days after the first doxorubicin treatment.

• Check free-catch urine by dipstick prior to each cyclophosphamide administration. If blood is noted, suspend cyclophosphamide and culture urine. If urine culture is negative, start chlorambucil as above.

• Biochemistry is checked prior to the first treatment and then a minimum of every 6 months.

• Baseline echocardiography can be considered in all patients and should be done before giving doxorubicin / epirubicin if evidence of pre-existing heart disease.

Contraindications and adverse effects

Myelosuppression, haemorrhagic cystitis (cyclophosphamide only) or GI effects may occur. Vincristine is a vesicant and doxorubicin/epirubicin are severe vesicants, therefore catheters should be placed in all cases and only catheters placed by ‘first-stick’ should be used. Should an extravasation occur, contact an oncologist. Doxorubicin/epirubicin can cause cardiotoxicity (arrythmia if given too quickly or systolic dysfunction at high cumulative doses (>180 mg/m2)).

Treatment can be given if the neutrophil count is > 3 × 109/l and platelet count > 100 x109/l. If the neutrophil count is < 3 × 109/l, then suspend treatment and recheck in 5-7 days. If neutrophil count is < 1 × 109/l, prescribe prophylactic antibiotics (until neutrophil count is > 1 × 109/l). If neutrophil count is < 1 × 109/l and the patient is pyrexic or unwell, administer i.v. antibiotics and contact an oncologist for advice. If the neutrophil count is < 1 x 109/l, decrease dose of the causative chemotherapy drug by 10%; if recurrent, contact an oncologist for advice.

Disease monitoring and relapse

Restaging: Ideally, restaging should be performed at the end of the induction phase (after week 4) and at treatment cessation.

Remission: Attaining complete remission is an important prognostic indicator (especially in cats). Complete remission is defined as the lack of identifiable disease (for example, the lymph nodes should be normal on palpation and a cytological assessment should not yield evidence of tumour cells).

Relapse: If a patient completes treatment in remission, they should be monitored monthly. Most canine multicentric lymphoma patients relapse after 1-3 months. Many patients that relapse after cessation of treatment can reattain remission by reintroduction of the original chemotherapy protocol. For patients who relapse during treatment or fail to respond to reintroduction of treatment, rescue therapy is indicated; commonly used rescue protocols in dogs include L-asparaginase (single agent), LOPP and DMAC (or single agent doxorubicin if COP used originally). Rescue therapy in cats is less successful than in dogs.