Outcome of stereotactic body radiation for treatment of nasal and nasopharyngeal lymphoma in 32 cats

Do Pre-Treatment Biopsy Characteristics Predict Early Tumour Progression in Feline Diffuse Large B Cell Nasal Lymphoma Treated With Radiotherapy?

The standard of care treatment for localised feline nasal lymphoma (FeNL) is radiation therapy (RT). Early local or systemic failure occurs in 17%-45% of cats treated with RT with or without chemotherapy. The aim of this study was to determine if pre-treatment biopsy characteristics could predict early tumour progression in FeNL. Inclusion criteria consisted of histologically confirmed FeNL, available paraffin blocks of diagnostic quality, localised to the sinonasal cavity on staging pre-RT, treated with IMRT/IGRT (10 × 4.2 Gy) without chemotherapy and at least 1 year follow-up. All pre-RT biopsies were reviewed and evaluated with CD3, CD20, CD79a, pan-CK and Ki-67 immunohistochemistry and the mitotic activity index was determined. The primary endpoint was progression-free survival (PFS) at 1 year and hazard-ratios (HR) with confidence interval (CI) were calculated. Twenty-eight cats fit the inclusion criteria, and all had diffuse large B-cell lymphoma. Seventeen cats (61%) were progression free at 1 year. Of the 11 cats that progressed in the first year, two had local progression, two had both local and systemic progression and seven had systemic progression. The mitotic index (HR: 1.03, CI 0.9-1.19, p = 0.645), Ki-67 (HR: 1.00, CI 0.98-1.02, p = 0.845) and > 30% of tumour-infiltrating T cells (HR: 0.38, CI 0.09-1.56, p = 0.175) were not significantly associated with PFS. In this uniformly RT treated population of FeNL, none of the evaluated pre-RT histologic parameters could predict early treatment failure.

Response of Spontaneous Oral Tumors in Canine Cancer Patients Treated with Stereotactic Body Radiation Therapy (SBRT)

The objective of this study is describe outcome and toxicity for dogs with oral tumors, specifically oral malignant melanoma (OMM), squamous cell carcinoma (SCC), and soft tissue sarcoma (STS) after stereotactic body radiation therapy (SBRT). A single institution retrospective study was conducted. Outcomes were analyzed using Kaplan-Meier analysis and Cox proportional hazard analysis. Treatment responses at different time points were evaluated with Pearson's Chi-squared test to identify prognostic factors. Acute and late toxicities were recorded according to VRTOG criteria and were analyzed to identify risk factors. Adverse events other than acute and late toxicities were recorded. A total of 98 patients met the inclusion criteria (OMM n = 37; SCC n = 18; STS n = 43). The SBRT prescription was 1-6 fractions, with a total dose range of 12-40 Gy. Local progression-free survival (PFS) for OMM, SCC, and STS was 187, 253, and 161 days, respectively. Overall PFS was 152 days and median survival time (MST) was 270 days, with no statistical difference between tumor types. The presence of lymph node metastasis and the use of elective nodal irradiation (ENI) were associated with shorted PFS and MST. Severe acute toxicities to organs at risk affected 10/85 (11.8%) of patients. Osteoradionecrosis and oronasal fistula formation occurred in 23/81 (28.4%) of patients and was significantly associated with tumor type (SCC, P = 0.006). SBRT can be offered as a treatment option for oral tumors in dogs. Toxicities were common and warrant risk factor considerations and adjustments to current SBRT protocols.

Prospective pilot study utilizing changes in quantitative values obtained on serial fluorine-18 fluorodeoxyglucose (18F-FDG) positron emission tomography-computed tomography (PET/CT) in dogs with appendicular osteosarcoma before and after stereotactic body radiation therapy (SBRT) and carboplatin chemotherapy to assess for prediction of survival and therapeutic effectiveness

Serial fluorine 18 fluorodeoxyglucose (18F-FDG) positron emission tomography-CT (PET/CT) is commonly used in human oncology to prognosticate and evaluate for therapeutic effectiveness. In this pilot study, dogs with naturally occurring appendicular osteosarcoma were evaluated with serial 18F-FDG PET/CT in an attempt to assess for response to therapy, prognostic factors, and appropriateness of imaging intervals. Fourteen dogs were enrolled in the trial. All dogs had the initial 18F-FDG PET/CT (PET1), with nine dogs having their end-of-therapy 18F-FDG PET/CT (EoT PET) 3 months after stereotactic body radiation therapy (SBRT) to the primary tumor. The median percent change from the PET1 to the EoT PET for the standard uptake value maximum (SUVmax%) was -58% (range: -17 to -88%), metabolic tumor volume (MTV%) was -99.8% (range: -65 to -100%), and total lesion glycolysis (TLG%) was -99.8% (range: -75 to -100%), all of which were significant (P < .05, <.05, and <.05, respectively). On evaluation, it was found that volumes of GTV and CTV were significant for survival (P < .05 and <.05), MTV1, TLG1, and SUVmax on the EoT PET (SUVmaxEoT) were predictive of metastasis (P < .05), and the SUVmax% was significantly correlated to the time to first event (P < .05). Based on this data, serial 18F-FDG PET/CT performed 3 months after SBRT can show a significant reduction in avidity, and the quantitative data collected may help predict metastatic disease in canine appendicular osteosarcoma.

Update in Veterinary Radiation Oncology: Focus on Stereotactic Radiation Therapy

Stereotactic radiotherapy (SRT) involves the precise delivery of highly conformal, dose-intense radiation to well-demarcated tumors. Special equipment and expertise are needed, and a unique biological mechanism distinguishes SRT from other forms of external beam radiotherapy. Families find the convenient schedules and minimal acute toxicity of SRT appealing. Common indications in veterinary oncology include nasal, brain, and bone tumors. Many other solid tumors can also be treated, including spinal, oral, lung, heart-base, liver, adrenal, and prostatic malignancies. Accessibility of SRT is improving, and new data are constantly emerging to define parameters for appropriate case selection, radiation dose prescription, and long-term follow-up.

The Expression Levels of CD20 as a Prognostic Value in Feline B-Cell Nasal Lymphoma: A Pilot Study

The effect of the semi-quantitative expression of CD20 in the prognosis of feline nasal lymphoma has not been described. This study investigated the prognostic significance of CD20 expression, clinicopathological characterization, and treatment outcomes in cats with nasal lymphoma. Clinical data from cats diagnosed with nasal lymphoma were retrospectively collected, including signalment, clinical signs, clinicopathological variables, treatment outcomes, and survival times. Using ImageJ software, CD20 expression was semi-quantitatively measured based on the proportion of CD20-positive areas. Correlations between laboratory findings, immunohistochemical expressions, and survival outcomes were investigated. All cats included in the study exhibited the B-cell immunophenotype. During treatment, a reduction in PCV was noted in the cats at the second and sixth weeks (p = 0.01 and p = 0.01, respectively). The cats with low CD20 expression exhibited a significantly shorter MST (91 days; 95% CI, 41-141) than those with high CD20 expression (MST, 214 days; 95% CI, 76-351) (p = 0.01). Stage T1 cats displayed a higher MST (143 days; 95% CI, 144-172) than those in other stages > T1 (120 days, 95% CI, 71-169 days) (p = 0.04). Anemia, a common adverse effect in feline nasal lymphoma, did not impact MST. T1 clinical staging and high CD20 expression showed a trend for better MST.

Outcomes of 35 dogs with craniomaxillofacial osteosarcoma treated with stereotactic body radiation therapy

Canine craniomaxillofacial osteosarcoma (OSA) is most commonly treated surgically; however, in cases where surgery is not feasible or non-invasive treatment is desired, stereotactic body radiation therapy (SBRT) may be elected for local tumour control. In this study, we evaluated 35 dogs treated with SBRT. Nine dogs (26%) had calvarial, seven (20%) had mandibular and 19 (54%) had maxillary OSA. Median time to first event (TFE) was 171 days, and overall median survival time (MST) was 232 days. Site-specific MSTs were 144 days for mandible, 236 days for calvarium and 232 days for maxilla (p = .49). Pulmonary metastatic disease was observed in 12/35 (34%) patients and was detected pre-SBRT in six dogs (17%) and post-SBRT in the remaining six dogs (17%). Eighteen adverse events post-SBRT were documented. Per veterinary radiation therapy oncology group criteria, five were acute (14%) and three were late (9%) grade 3 events. Neurological signs in two dogs were suspected to be early-delayed effects. Cause of death was local progression for 22/35 (63%) patients, metastasis for 9/35 (26%) patients and unknown for four. On univariate analysis, administration of chemotherapy was associated with a longer TFE (p = .0163), whereas volume of gross tumour volume was associated with a shorter TFE (p = .023). Administration of chemotherapy and five fractions versus single fraction of SBRT was associated with increased survival time (p = .0021 and .049). Based on these findings, a treatment protocol incorporating chemotherapy and five fractions of SBRT could be considered for dogs with craniomaxillofacial OSA electing SBRT with careful consideration of normal tissues in the field.

Retrospective study evaluating the efficacy of stereotactic body radiation therapy for the treatment of confirmed or suspected primary pulmonary carcinomas in dogs

Canine primary pulmonary carcinomas (PCCs) are commonly treated with surgery with overall median survival times (MST) around a year; however, due to extent of disease, prognosis, or client preference, alternative treatments have been considered. Stereotactic body radiation therapy (SBRT) has been utilized in human cancer patients for local control of lung tumours as a surgical alternative. Twenty-one PCCs in 19 dogs that received SBRT for local control were retrospectively evaluated. Dogs were staged according to the canine lung carcinoma stage classification (CLCSC) system with three as Stage 1, five as Stage 2, three as Stage 3, and eight as Stage 4. Overall MST was 343 days with 38% of patients alive at 1 year. Stage did not significantly impact survival time (p = .72). Five (26%) dogs had lymphadenopathy and MST was not significantly different from dogs without lymphadenopathy (343 vs. 353 days; p = .54). Five out of 18 evaluable dogs (28%) experienced acute lung VRTOG effects and 2 of 12 dogs (17%) experienced late lung VRTOG effects. Median lung dose, V5, V20, and D30 to the lung did not correlate significantly with the development of adverse radiation events. Twelve dogs had follow-up imaging and the best response included a complete response (17%), partial response (42%), and stable disease (42%). Progressive disease was noted in seven dogs a median of 229 days after SBRT. SBRT was documented to be a safe and effective alternative to surgery and may have survival advantages for Stage 3 or 4 dogs according to the CLCSC.

Contouring in the optic plane improves the accuracy of computed tomography-based segmentation of the optic pathway

Canine optic pathway structures are often contoured on CT images, despite the difficulty of visualizing the optic pathway with CT using standard planes. The purpose of this prospective, analytical, diagnostic accuracy study was to examine the accuracy of optic pathway contouring by veterinary radiation oncologists (ROs) before and after training on optic plane contouring. Optic pathway contours used as the gold standard for comparison were created based on expert consensus from registered CT and MRI for eight dogs. Twenty-one ROs contoured the optic pathway on CT using their preferred method, and again following atlas and video training demonstrating contouring on the optic plane. The Dice similarity coefficient (DSC) was used to assess contour accuracy. A multilevel mixed model with random effects to account for repeated measures was used to examine DSC differences. The median DSC (5th and 95th percentile) before and after training was 0.31 (0.06, 0.48) and 0.41 (0.18, 0.53), respectively. The mean DSC was significantly higher after training compared with before training (mean difference = 0.10; 95% CI, 0.08-0.12; P < 0.001) across all observers and patients. DSC values were comparable to those reported (0.4-0.5) for segmentation of the optic chiasm and nerves in human patients. Contour accuracy improved after training but remained low, potentially due to the small optic pathway volumes. When registered CT-MRI images are not available, our study supports routine addition of an optic plane with specific window settings to improve segmentation accuracy in mesaticephalic dogs ≥11 kg.