Canine B-Cell Lymphoma CHOP Protocol

Excellent work getting the immunophenotype. Knowing we're dealing with B-cell lymphoma gives us a much clearer and more optimistic starting point. For an owner committed to aggressive treatment, a multi-agent CHOP-based protocol is absolutely the gold standard.

Here is the plan I would recommend for this patient.

Gold Standard CHOP Protocol (25-week)

The goal here is to induce a complete and durable remission. For B-cell lymphoma, we expect a first remission rate of 85-90%, with a median survival time (MST) of 12-14 months. The key is that most dogs feel excellent while on protocol.

Induction Phase (First 4-week cycle):
* Week 1: Vincristine 0.7 mg/m² IV. Start Prednisone 2 mg/kg/day PO.
* Week 2: Cyclophosphamide 250 mg/m² PO. Administer with furosemide (1-2 mg/kg PO) to mitigate risk of sterile hemorrhagic cystitis. Give this dose in the morning to encourage urination throughout the day.
* Week 3: Vincristine 0.7 mg/m² IV.
* Week 4: Doxorubicin 30 mg/m² IV, given as a slow infusion over 20-30 minutes.

This 4-week block is one cycle. We repeat this for a total of 6 cycles (24 weeks total), followed by a final vincristine dose at week 25. The prednisone is tapered down and discontinued after the first cycle.

Monitoring & Supportive Care

* Pre-Chemo: Before every single treatment, a CBC is mandatory to ensure the absolute neutrophil count (ANC) is >1,500/µL and platelets are >75,000/µL.
* Cardiac Screen: Before the first dose of Doxorubicin, I strongly recommend a baseline echocardiogram. While Goldens are not the highest-risk breed for DCM, doxorubicin carries a risk of cumulative cardiotoxicity, and a baseline is crucial.
* Nadir Checks: Initially, check a CBC 7 days after the first doxorubicin and cyclophosphamide doses to assess the patient's nadir. This helps guide potential dose reductions.
* Side Effects: Counsel the owner on GI upset (usually 2-3 days post-treatment), managed with maropitant and a bland diet. Febrile neutropenia (fever >103.5°F with an ANC <1,000) is an emergency requiring hospitalization.

Relapse & Rescue Options

When the first remission ends, we move to rescue protocols. A second remission is achievable in 50-60% of cases, but it is typically shorter (around 50% the duration of the first).

* Lomustine (CCNU): A common first-line rescue agent. Dosed at 70-90 mg/m² PO every 3 weeks. Requires diligent monitoring for hepatotoxicity and cumulative myelosuppression.
* MOPP: (Mechlorethamine, Vincristine, Procarbazine, Prednisone). A more complex protocol but can be effective, especially if T-cell features emerge at relapse.
* Rabacfosadine (Tanovea): A newer, conditionally licensed drug specifically for canine lymphoma. It can be an excellent option for relapsed cases.

It’s a long road, but this protocol gives the patient the best chance for a long, high-quality remission. Let me know if you want to calculate the exact doses based on the dog's body surface area.