Metronomic Chemotherapy for Palliative Treatment of Malignant Oral Tumors in Dogs

Clinical evaluation of HuDo-CSPG4 DNA electroporation as adjuvant treatment for canine oral malignant melanoma: comparison of two vaccination protocols

Canine oral malignant melanoma (OMM) is an aggressive, spontaneously occurring tumor carrying a poor to guarded prognosis and relatively limited therapeutic strategies. In this landscape, chondroitin sulfate proteoglycan (CSPG)4 represents a promising immunotherapeutic target. The objective of this bi-center prospective study was to examine the clinical outcome of OMM-bearing dogs treated with surgery and adjuvant electroporation using a DNA vaccine (HuDo-CSPG4) encoding both human (Hu) and canine (Do) portions of CSPG4 through two different vaccination protocols. Dogs with stage I-III surgically resected CSPG4-positive OMM underwent HuDo-CSPG4 plasmid electroporation starting at the 3rd-4th post-operative week; electrovaccination was repeated after 2 weeks. In protocol 1, electrovaccination was then delivered monthly while in protocol 2, electrovaccination was performed monthly four additional times followed by semestral boosters. The survival rates of HuDo-CSPG4-vaccinated dogs were estimated and compared with a control group treated with surgery alone. Significantly longer overall survival times were observed in HuDo-CSPG4 vaccinated dogs as compared with non-vaccinated controls. Dogs receiving protocol 2 showed similar outcomes to those of dogs undergoing protocol 1, despite fewer vaccinations. The comparable humoral response against CSPG4 resulting from the administration of protocol 1 and 2 appears to have similar clinical relevance, highlighting protocol 2 as the optimal vaccination schedule.

Metronomic chemotherapy: bridging theory to clinical application in canine and feline oncology

Veterinary oncology has experienced significant evolution over the last few decades, with chemotherapy being currently applied to several neoplasms with therapeutic success. Traditionally, chemotherapy protocols are based on classic cytostatic drugs under the concept of maximum tolerated dose (MTD), which has been associated with a greater risk of toxicity and resistance. Thus, new therapeutic alternatives have emerged, such as metronomic chemotherapy (MC), introducing a new paradigm in cancer treatment. MC consists of administering low doses of chemotherapy drugs continuously over a long period of time, modulating the tumour microenvironment (TME) due to the combination of cytotoxic, antiangiogenic and immunomodulatory effects. This multi-targeted therapy has been described as a treatment option in several canine and feline cancers since 2007, with positive results already published in the literature, particularly in mammary carcinomas and soft tissue sarcomas in dogs. The aim of this review article is to describe the current knowledge about the use of MC in small animal oncology, with emphasis on its mechanisms of action, the most commonly used drugs and clinical outcome.

A retrospective study of chemotherapeutic effect without wide-margin surgery or radiation therapy in dogs with oral malignant melanoma

Background

Effective treatment for canine oral malignant melanoma (e.g., curative-intent surgery) may not be feasible or radiation therapy may be unavailable. However, chemotherapy is usually an option, and more information is needed regarding its use without adequate local treatments.

Objective

Our objective was to investigate the efficacy of chemotherapy in canine oral malignant melanoma without adequate local control, using carboplatin with dose reduction in small-breed dogs and metronomic chemotherapy.

Animals and procedure

Client-owned dogs with histopathologically diagnosed oral malignant melanoma were retrospectively enrolled from 2016 to 2022. The chemotherapy protocol in each case was determined by the attending clinician.

Results

Thirteen dogs were included. The median progression-free interval of all 13 dogs was 42 d (14 to 953 d). The median overall survival time of dogs with chemotherapy as their only systemic treatment was 181 d (50 to 960 d; n = 11). The median dosage of carboplatin was 250 mg/m2. Response to treatment and clinical stage were significant prognostic factors.

Conclusion and clinical relevance

As chemotherapy provided a median survival of 6 mo, it could be considered when adequate local control is infeasible. Earlier clinical stages or achievement of at least stable disease during chemotherapy may indicate better survival in dogs.