Canine primary liver tumors treated with stereotactic body radiation therapy: A case series.

Stereotactic body radiation therapy (SBRT) is an increasingly used alternative treatment option for nonresectable hepatocellular carcinoma (HCC) in people. Comparatively, the publication of SBRT of dogs with HCC is limited. The objective of this retrospective, descriptive case series was to evaluate the clinical outcomes and toxicity data of SBRT in dogs with HCC and imaging-documented primary liver tumors using volumetric-modulated arc therapy delivery at two private institutions. Medical records of 14 dogs treated between 2018 and 2023 were reviewed. All dogs had macroscopic tumors, and 9 of 14 dogs had HCC diagnoses confirmed on cytology or histopathology. The median longest tumor diameter was 5.5 cm. The median percentage of planning target volume relative to liver volume was 27.1%. Most dogs were treated with three daily fractions of 7-7.5 Gy. All dogs completed their radiotherapy protocols. Three of nine HCC dogs experienced partial responses and clinical improvement. Five of nine HCC dogs had stable disease. Overall median survival time was 164 days for nine HCC dogs (range: 93-706 days). One late grade 5 liver and two late grade 3 kidney side effects were reported. One dog received repeated SBRT to the same HCC treatment field, and one dog had two courses of SBRT to bifocal HCC treatment fields, both with no more than grade 2 acute and chronic toxicities.

Pilot study evaluating the feasibility of stereotactic body radiation therapy for canine anal sac adenocarcinomas.

The use of stereotactic body radiation therapy (SBRT) to treat many canine tumors is rapidly expanding. However, published studies are lacking regarding use of SBRT for management of canine anal sac adenocarcinoma (ASAC), primarily due to concerns regarding intolerable late effects. The objective of this retrospective, pilot study was to describe the efficacy and safety profile of coarse fractions administered with an SBRT regime to manage a group of dogs with ASAC. A total of 12 dogs with ASAC that received SBRT as a component of their treatment were sampled. Three patients had macroscopic primary tumors irradiated, while nine patients received SBRT following incomplete surgical resection. Seven patients also received metastatic regional lymph node irradiation. Primary tumor and nodal irradiation sites received three fractions totaling 22-24 Gy and 22.5-24 Gy, respectively, over three consecutive days. All patients developed acute effects including mild colitis, alopecia, and erythema. Late effects included alopecia, variable dermal pigmentation and leuko- or melanotrichia within radiation fields, and rectal stricture in one patient. A median progression free survival time of 549 days and median survival time of 991 days were achieved in this study. These results should be considered preliminary data suggesting that coarse fractionation administered with an SBRT technique is a safe and effective treatment regime for the management of canine ASAC, with the aim to conduct prospective studies in the future.

Pilot study evaluating stereotactic body radiation therapy for feline facial squamous cell carcinomas.

OBJECTIVES: The use of stereotactic body radiation therapy (SBRT) has not been assessed in advanced-stage feline solar-induced facial squamous cell carcinomas (SCCs). The objective of this study was to provide preliminary data on the use and safety profile of coarse fractions administered with an SBRT regime to manage advanced-stage feline solar-induced facial SCCs. METHODS: This retrospective study assessed five cats diagnosed with advanced-stage solar-induced facial SCCs that received SBRT as their primary treatment or, in one cat, following failed surgical intervention. Tumour sites received three fractions totalling 26.25-27 Gy over a 3-5-day period. RESULTS: All patients developed acute effects following SBRT including alopecia, epilation and erythema. Late effects were mild and included alopecia, variable pigmentation and leukotrichia within radiation fields. All patients were alive at the time of article submission, with overall survival times ranging from 118 to 991 days. CONCLUSIONS AND RELEVANCE: The results suggest that coarse fractions administered with an SBRT technique is a safe and effective treatment tool for the management of advanced-stage feline solar-induced facial SCCs. These data provide preliminary evidence to support larger, prospective studies evaluating the management of feline facial SCCs with SBRT.

The Elekta Fraxion™ system is not suitable for maxillary fixation in canine conformal radiation therapy techniques.

In this prospective, exploratory study, we evaluated the positioning accuracy in a group of 15 dogs undergoing fractionated stereotactic radiotherapy for tumors affecting the head, using a modified human maxillary fixation device (Elekta Fraxion™ system). Positioning was assessed using on-board volumetric imaging, with a six-degrees-of-freedom image registration technique. Prior to treatment delivery, CBCT images were obtained and patient alignment was corrected, in both translational and rotational planes, using a six-degrees-of-freedom robotic patient positioning system (HexaPOD Evo RT System). The maximum angular inter-fraction motions observed were 6.1° (yaw), 10.9° (pitch), and 4.5° (roll). The mean systematic translational errors were 4.7, 2.6, and 2.3 mm, mean random translational errors were 3.0, 2.2, and 2.5 mm, and mean overall translational errors were 2.4, 0.7, and 2.3 mm in the cranial-caudal, lateral, and dorsal-ventral directions, respectively. The mean systematic rotational errors were 1.17°, 0.77°, and 1.43°, the mean rotational random errors were 1.65°, 1.46°, and 1.34° and the mean overall rotational errors were 0.56°, 0.22°, and 0.29° in the yaw, pitch, and roll directions, respectively. The mean error of the three-dimensional vector was 6.9 mm with a standard deviation of 3.8 mm. Ninety-five percent of the three-dimensional vectors were <14.8 mm. This study demonstrates that this maxillary fixation device relies on six-degrees-of-freedom registration and an ability to apply corrections using a six-degrees-of-freedom couch for accurate patient positioning and tumor targeting. Its use in conformal radiation therapy in dogs is not recommended.