A retrospective study of 101 dogs with oral melanoma treated with a weekly or biweekly 6 Gy × 6 radiotherapy protocol

Abstract

One radiotherapy (RT) protocol used for canine oral melanoma (OM) gives 36 Gy total, in six weekly or biweekly fractions (6 Gy × 6). This retrospective study characterizes oncologic outcomes for a relatively large group of dogs treated with this protocol and determines whether radiation dose intensity (weekly vs. biweekly) affected either progression‐free or overall survival (PFS and OS). Dogs were included if 6 Gy × 6 was used to treat grossly evident OM, or if RT was used postoperatively in the subclinical disease setting. Kaplan–Meier statistics and Cox regression modelling were used to determine the predictive or prognostic value of mitotic count, bony lysis, World Health Organization (WHO) stage (I, II, III, or IV), using systemic anti‐cancer therapies, tumour burden at the time of RT (macroscopic vs. subclinical), radiation dose intensity (weekly vs. biweekly), and treatment planning type (manual vs. computerized). The median PFS and OS times for all dogs (n = 101) were 171 and 232 days, respectively. On univariate analysis PFS and OS were significantly longer (p = <.05) with subclinical tumour burden, WHO stages I or II, and weekly irradiation. On multivariable analysis, only tumour stage remained significant; therefore, cases were grouped by WHO stage (I/II vs. III/IV). With low WHO stage (I/II), PFS and OS were longer when irradiating subclinical disease (PFS: risk ratio = 0.449, p = .032; OS: risk ratio = 0.422, p = .022); this was not true for high WHO stage (III/IV). When accounting for other factors, radiation dose intensity had no measurable impact on survival in either staging group.

Prognostic Factors for the Efficiency of Radiation Therapy in Dogs with Oral Melanoma: A Pilot Study of Hypoxia in Intraosseous Lesions

“…This study revealed that advanced clinical stage was significantly associated with a shorter TTR and OS, as suggested by previous studies [ 3 , 4 ]. Median OS in our clinical setting was 144.5 days, which was shorter than that reported in a previous study (233 days) [ 3 ].…”

“…However, recurrence after radiation therapy is common. Several prognostic factors, such as tumor size, bone destruction, and clinical stage, to predict overall survival time have been identified in dogs with oral melanoma who have undergone radiation therapy [ 3 , 4 , 5 ]. Of those, the influence of tumor location and bone destruction on the efficiency of radiation therapy is a topic of debate, because there are few reports regarding time to recurrence after radiation therapy.…”

Canine salivary gland carcinoma treated with stereotactic body radiation therapy: a retrospective case series

“…In this study, 4/6 of patients (66.6%) received prophylactic regional lymph node irradiation at the discretion of the attending radiation oncologist. In veterinary medicine, prophylactic nodal irradiation has been described for different tumor types, such as high-grade mast cell tumors in dogs ( 25 , 26 ), feline nasal lymphoma ( 27 ), and oral malignant melanoma ( 28 ). However, there is not a standard consensus for elective nodal irradiation in veterinary radiation oncology.…”

Limited Clinical Efficacy with Potential Adverse Events in a Pilot Study of Autologous Adoptive Cell Therapy in Canine Oral Malignant Melanoma

“…Several factors that were proven to be prognostic in previous studies, including tumor information (tumor location [1], size [1], bone invasion status [28], and residue tumor before treatment [29]), clinical stage [1,29], histopathological features (mitotic count and lymphovascular invasion) [28,30], and treatments other than ACT were recorded. The response, adverse events of ACT, and peripheral blood neutrophil/lymphocyte ratio (NLR) before and after ACT, were also documented.…”