Predictive factors for response to electrochemotherapy in canine oral malignant melanoma

Abstract

Background. Oral malignant melanoma is the most common oral cancer in dogs. Electrochemotherapy (ECT) is a therapeutic modality with very high local response rates and almost negligible side effects.
Patients and methods. Sixty-seven canines with oral malignant melanoma, non-candidates for first-line therapy, were enrolled. All dogs received ECT and follow-up exams for the span of two years.
Results. Based on RECIST criteria, the objective response rate was 100%, 89.5%, 57.7%, and 36.4%, in stage I, II, III and IV respectively. Only patients in stage I, II and III with partial or complete response improved their quality of life. Stages I and II were predictive factors for better local responses (p=0.0013). The median time to progression was 11, 7, 4 and 4 months, for stages I, II, III and IV respectively. Stages I (p=0.0005) and II (p=0.0094), and absence of bone involvement (p=0.043) were predictive factors for longer times to progression. The median disease-free survival time for patients who achieved a complete response was 12.5 (range 3-30) months. Median survival time after the treatment was 16.5, 9, 7.5 and 4.5 months, for patients in stage I, II, III and IV respectively. Stage IV (p=0.0001) was a negative predictive factor for survival. On the contrary, stage I (p=0.0083) and lack of bone involvement (p=0.0340) were positive predictive factors.
Conclusion. Canines with oral malignant melanoma of up to 4 cm and no bone infiltration are the most suitable patients to receive ECT as first-line therapy if no other alternative is available.