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.

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.

Characteristics and outcomes for 61 cats that underwent either surgery or stereotactic radiotherapy as treatment for intracranial meningioma (2005-2017).

OBJECTIVE: To report clinical features and outcomes of cats undergoing either stereotactic radiotherapy (SRT) or surgical excision for the treatment of intracranial meningioma. ANIMALS: 61 client-owned cats. METHODS: Medical records were retrospectively reviewed of cats with intracranial meningiomas that were treated with surgical removal and/or SRT between 2005 and 2017. Signalment, clinical signs, duration of clinical signs, diagnostic imaging reports, histopathology reports, treatment protocol, complications, recurrence or progression, and survival time were obtained from the medical record and through follow-up phone calls. RESULTS: Of the 61 patients, 46 had surgery, 14 had SRT, and 1 had surgery followed by SRT for initial treatment. Significantly more cats that underwent surgery had peritreatment complications compared to the SRT group (P < .0001). Cats that received surgery initially had a significantly longer median survival time (MST) of 1,345 days compared to the MST of 339 days for the SRT cats (P = .002). Fourteen (30%) cats in the surgery group and 4 cats in the SRT group (28%) had MRI- or CT-confirmed tumor regrowth or new tumor growth (P = 1.00). Five cases that had SRT for subsequent recurrence had an MST of 700 days (range, 335 to 1,460 days) after the last treatment. CLINICAL RELEVANCE: SRT proved to be a safe, alternative treatment option for feline patients with intracranial meningiomas; however, the survival times with surgery alone were significantly longer. SRT for the treatment of recurrence following initial surgery may show promising results.

Stereotactic radiotherapy for advanced canine anal sac adenocarcinoma: an exploratory study.

For dogs with anal sac adenocarcinoma (ASAC), metastasis to intra-abdominal and pelvic lymph nodes occurs early in the disease course. Death is usually related to locoregional progression. Surgical excision is the treatment of choice, but may not be possible in advanced cases. Dogs treated with RT in the gross disease setting showed a 38%-75% overall response rate, but side effects to organs at risk in this area (especially the colon, bladder, and spinal cord) were reported. Stereotactic radiation therapy (SRT) utilizes highly conformal treatment planning with rapid dose fall-off and hypofractionation. SRT may help to reduce the risk of late side effects of radiation while also creating a larger biological effect on ASACs. A primary aim of this prospective, descriptive, exploratory study was to describe the safety and feasibility of an SRT protocol in a small sample of dogs with ASAC, using objective and subjective measures to monitor acute and late side effects. A secondary aim was to describe the anti-tumor response of the SRT protocol using CT at 3- and 6 months posttreatment. Five dogs completed the radiation protocol. Four had follow-up CT characteristics of complete response (1), partial response (2), and stable disease (1). Minimal acute side effects were observed. Despite some large tumor volumes, constraints for OAR were achieved in all but the spinal cord for one patient. Findings indicated that SRT is a safe and feasible treatment for dogs with ACAC. Future studies are warranted to compare patient outcomes for SRT versus other treatments.

Updates in Osteosarcoma.

Clinical care of osteosarcoma (OSA) in dogs has seen little change during the past 2 decades, relying on amputation and platinum-based chemotherapy for pain control and survival. Recent advancements offer hope for improved outcomes. Genomic research reveals shared genetic abnormalities between canine and human OSA. Multidimensional imaging provides valuable staging and prognostic information. Limb-sparing approaches including stereotactic body radiation therapy are routine. Ablative therapies such as microwave ablation and histotripsy show promise. Immunotherapy including cell therapy and immune checkpoint inhibition are available. Radiopharmaceuticals are tuned to target OSA cells directly. These innovations may enhance treatment and prognosis for dogs with OSA.

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.

A retrospective study of sinonasal tumors in 182 dogs treated with stereotactic radiotherapy (3 × 10 Gy) (2010-2015).

BACKGROUND: Stereotactic radiotherapy (SRT) is an emerging treatment for sinonasal tumors in dogs. Reported results regarding tumor control and incidence of acute and late radiation morbidities are inconsistent. OBJECTIVES: To determine treatment efficacy and prognostic indicators of SRT in dogs with sinonasal tumors and to quantify acute and late radiation morbidities. ANIMALS: One hundred and eighty-two client-owned dogs with sinonasal tumors diagnosed cytologically, histologically, or radiographically that underwent SRT. METHODS: Single-arm retrospective study by reviewing medical records of dogs treated with SRT (10 Gy × 3) between 2010 and 2015. Kaplan-Meier analysis was used to determine overall survival (OST; from the first day of SRT to death by any cause) and disease-specific survival times (DSST; OST but censoring tumor/treatment-unrelated death). Tumors were staged using modified Adams criteria. RESULTS: Median OST and DSST of dogs treated with 1 course of SRT was 441 (95% CI: 389-493 days) and 482 (428-536 days) days, respectively with skin/oral cavity acute morbidities observed in 3% of dogs. DSST in dogs with stage 4 disease showed no statistical difference compared to other stages (P = .64). Oro-nasal (n = 2) or naso-cutaneous (n = 11) fistula development occurred in 7.1% of dogs with median time of 425 days (range: 83-1733 days). Possible chronic rhinitis after SRT was recorded in 54 of 88 dogs (61%) where information was available. CONCLUSIONS AND CLINICAL IMPORTANCE: Results are comparable to other reports of treatment of SRT. Acute morbidities were minimal. Modified Adams stage scheme appeared to be inappropriate for prognostication for dogs with sinonasal tumors treated with SRT.

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.

Efficacy of stereotactic radiation therapy for the treatment of confirmed or presumed canine glioma.

Intracranial gliomas are the second most common brain tumour in dogs. Radiation therapy provides a minimally invasive treatment option for this tumour type. Earlier publications reporting on the use of non-modulated radiation therapy suggested a poor prognosis for dogs with glioma, with median survival times ranging between 4 and 6 months; more recent literature utilizing stereotactic radiation therapy (SRT) demonstrates that the prognosis for canine gliomas may be more promising, with survival times closer to 12 months. A single institution retrospective study was performed between 2010 and 2020 investigating the outcomes of dogs with biopsy-confirmed glioma or a presumptive diagnosis of intra-cranial glioma based on MRI characteristics that were treated with SRT. Twenty-three client-owned dogs were included. Brachycephalic breeds were overrepresented, totalling 13 dogs (57%). SRT protocols included 16 Gy single fraction (n = 1, 4%), 18 Gy single fraction (n = 1, 4%), 24 Gy in 3 daily fractions (n = 20, 91%), or 27 Gy in four daily fractions (n = 1, 4%). Twenty-one dogs (91%) had improvement of their presenting clinical signs following SRT. Median overall survival time (MST) was 349 days (95% CI, 162-584). Median disease specific survival time was 413 days (95% CI, 217-717). When SRT is incorporated into the management plan for dogs with confirmed or presumed intracranial glioma, a median survival time of approximately 12 months may be achievable.

Configuration of pathologic fractures in dogs with osteosarcoma following stereotactic body radiation therapy: A retrospective analysis.

For some cases of canine appendicular osteosarcoma (OSA), limb-sparing treatment options are often desired, one of which is stereotactic body radiation therapy (SBRT). A major complication of SBRT is fracture of the irradiated bone at the site of treatment. The present study evaluated 127 appendicular OSA sites in 122 dogs treated with SBRT to identify the most common pathologic fracture locations and configurations. A total of 50 tumours experienced a pathologic fracture, and 38 had imaging sufficient to identify fracture configuration. The distal tibia was more likely to develop a fracture than other sites. Multiple types of fracture configuration (transverse, oblique, spiral and comminuted) were observed. The distal radius was significantly more likely to develop a transverse fracture than other sites. Documentation of fracture location and configuration leads to the identification of the forces contributing to fracture occurrence, since each configuration is a result of different forces acting on each affected bone. Such knowledge is imperative for the development of new approaches to diminish the occurrence of pathologic fractures.

Stereotactic body radiation therapy as an alternative to adrenalectomy for the treatment of pheochromocytomas in 8 dogs.

The objective of this report is to describe the use and outcome of stereotactic body radiation therapy (SBRT) for treatment of pheochromocytomas in 8 dogs. Pheochromocytomas are an uncommon but challenging tumour to manage. Adrenalectomy is the standard of care for treatment of pheochromocytomas in both animals and humans; however, unpredictable catecholamine secretion from the tumour and vascular and local invasion of the tumour and thrombi can pose life-threatening perioperative and anaesthetic risks. SBRT has been investigated as an alternative to adrenalectomy in human patients with pheochromocytomas. Eight dogs with clinical signs, an adrenal mass, and cytology and/or urine normetanephrine/creatinine ratios consistent with pheochromocytoma were treated with SBRT in lieu of adrenalectomy. Three dogs presented with acute hemoabdomen. Seven dogs had caval tumour invasion, 3 with extension into the right atrium. Following SBRT, all dogs had complete resolution of clinical signs and reduced urine normetanephrine/creatinine ratio and/or tumour size. No significant anaesthetic complications were encountered. Acute radiation toxicity was limited to grade I gastrointestinal signs in 3 dogs and resolved within 1-2 days of symptomatic therapy. Five of 8 dogs were alive at the time of follow up, with a median follow up time of 25.8 months. SBRT resulted in a favourable outcome and mitigated the life-threatening risks of adrenalectomy in these 8 dogs. SBRT may be a safe and effective alternative to adrenalectomy for pheochromocytomas in dogs with non-resectable tumours, or for owners averse to the risks of surgery.

Stereotactic radiotherapy (10 Gy X 3) for canine nonlymphomatous intranasal tumors is associated with prolonged survival and minimal risk of severe radiotoxicity.

OBJECTIVE: To describe oncologic outcomes following administration of a uniform stereotactic radiotherapy protocol (SRT; 10 Gy X 3) for canine intranasal tumors and to identify whether any clinical or dosimetric factors were predictive of event-free or overall survival time (EFST or OST). ANIMALS: 129 dogs. PROCEDURES: In this single-institution retrospective study, the medical records database was searched for canine nonlymphomatous intranasal tumors treated with 10 Gy X 3 SRT between August 2013 and November 2020. Findings regarding adverse effects and outcomes were analyzed overall, for dogs grouped on the basis of life stage (mature adult, senior, or end of life), and for treatment-related or tumor-related variables to identify potential predictors of outcome. RESULTS: After SRT, most dogs clinically improved with minimal acute radiotoxicity. The median EFST was 237 days; median OST was 542 days. Receipt of other tumor-directed therapies before or after SRT was associated with improved EFST in senior dogs (hazard ratio [HR], 0.416) and improved OST in mature adult (HR, 0.241) and senior dogs (HR, 0.348). In senior dogs, administration of higher near-minimum radiation doses was associated with improved EFST (HR, 0.686) and OST (HR, 0.743). In senior dogs, chondrosarcoma was associated with shorter OST (HR, 7.232), and in dogs at end of life, having a squamous cell or transitional carcinoma was associated with worse EFST (HR, 6.462). CLINICAL RELEVANCE: This SRT protocol results in improved quality of life and prolonged OST for dogs of all life stages. Radiation protocol optimization or use of multimodal therapy may further improve outcomes.

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

BACKGROUND: The safety and efficacy of stereotactic body radiation therapy (SBRT) in the treatment of localized nasal lymphoma in cats has not been described. HYPOTHESIS: Stereotactic body radiation therapy with or without adjuvant chemotherapy is an effective and well-tolerated treatment for localized nasal lymphoma in cats. ANIMALS: Thirty-two client owned cats referred to Colorado State University for the treatment of nasal lymphoma. METHODS: Retrospective study of cats treated with SBRT between 2010 and 2020 at Colorado State University. Diagnosis of nasal lymphoma was obtained via cytology or histopathology. Signalment, radiation protocol, concurrent treatments, adverse effects, and survival were recorded. RESULTS: Progression free survival was 225 days (95% CI 98-514) and median survival time (MST) was 365 days (95% CI 123-531). No significant difference in survival was identified between cats that received 1 versus greater than 1 fraction (MST 427 vs. 123 days, P = 0.88). Negative prognostic factors included cribriform lysis (MST 121 vs. 876 days, P = 0.0009) and intracalvarial involvement (MST 100 vs. 438 days, P = 0.0007). Disease progression was noted in 38% (12/32), locally in 22% (7/32), and systemically in 16% (5/32). No cats developed acute adverse effects. Ten cats developed late adverse effects: keratitis/keratitis sicca (n = 2), alopecia (n = 4), and leukotrichia (n = 4). Twenty-four cats (75%) had signs consistent with chronic rhinitis. CONCLUSIONS: SBRT is effective and well tolerated for treating localized nasal lymphoma in cats. Outcomes for cats with lower stage disease (canine modified Adam's stage 3 and lower) are comparable to historic data of cats treated with fractionated radiation therapy.

Re-irradiation of canine non-lymphomatous nasal tumours using stereotactic radiation therapy (10 Gy x 3) for both courses: Assessment of outcome and toxicity in 11 dogs.

No uniformly beneficial treatments exist for dogs with non-lymphomatous nasal tumours (NLNT) that relapse after radiotherapy (RT). Reirradiation may prolong survival and improve quality of life. In this retrospective study, we describe outcomes for 11 dogs that had CT-confirmed locoregional progression of NLNT after an initial course of stereotactic RT (SRT#1; 10 Gy × 3) and were then re-treated with the same type of protocol (SRT#2, also 10 Gy × 3). The median time between SRT #1 and SRT #2 was 243 days (95% CI: 78-385 days). Ten dogs (91%) had a clinical benefit after SRT#1; five dogs (45%) had clinical benefit after SRT#2. Adverse events after SRT#2 included nasocutaneous or oronasal fistula formation (N = 3 at 180, 270, and 468 days), seizures (N = 2 at 78 and 330 days), bacterial or fungal rhinitis (N = 2 at 240 and 385 days), and facial swelling (N = 1 at 90 days). All 11 dogs have died, due to disease progression, presumed radiotoxicity, or declining quality of life; in most cases, it was difficult to discern between these conditions. The median overall survival time (OST) from SRT#1 was 745 days (95% CI: 360-1132). The median overall survival time (OST) from SRT #2 was 448 days (95% CI: 112-626). For these dogs, survival was prolonged, but adverse events after SRT#2 were common (8/11; 73%). Therefore, before consenting to re-irradiation with this protocol, pet owners should be counselled about survivorship challenges, including risk for severe toxicities, and persistence of clinical signs.

CT characteristics and proposed scoring scheme are predictive of pathologic fracture in dogs with appendicular osteosarcoma treated with stereotactic body radiation therapy.

Stereotactic body radiation therapy (SBRT) is an established limb-sparing treatment for dogs with appendicular osteosarcoma (OSA) and pathologic fractures are a common sequela. The objectives of this retrospective, observational, and descriptive study were to develop and evaluate objective CT criteria for predicting pathologic fractures and assess impacts on survival time. Included dogs had confirmed or suspected appendicular OSA, available CT scans, available outcome data, and were treated with SBRT. For each study, the number of quartiles affected by lysis on the most severely affected transverse slice, longest measurable length of contiguous full cortical lysis, presence of subchondral bone lysis, and ratio of the length of the affected bone to normal bone were recorded. A scoring system was developed for assigning grades (summed score 1-4 = grade 1, 5-7 = grade 2, and 8 or greater = grade 3.) A total of 127 CT datasets were sampled (123 patients). The median summed score was 7. The grade was correlated with pathologic fracture development (23% of grade 1, 35% of grade 2, and 57% of grade 3 resulting in fracture, P = 0.028). Subchondral bone lysis was correlated with fracture (odds ratio, 2.2, P = 0.02). Percent affected bone ≥40% was associated with decreased survival (P = 0.002). Dogs with <40% of affected bone had a median survival of 256 days versus 178 days for dogs with ≥40% affected bone. Findings from the current study can be used to assist in determining prognosis and planning radiation therapy for future dogs affected by appendicular OSA.

Comparative study of the collapsed cone convolution and Monte Carlo algorithms for radiation therapy planning of canine sinonasal tumors reveals significant dosimetric differences.

Computer-based radiation therapy requires high targeting and dosimetric precision. Analytical dosimetric algorithms typically are fast and clinically viable but can have increasing errors near air-bone interfaces. These are commonly found within dogs undergoing radiation planning for sinonasal cancer. This retrospective methods comparison study is designed to compare the dosimetry of both tumor volumes and organs at risk and quantify the differences between collapsed cone convolution (CCC) and Monte Carlo (MC) algorithms. Canine sinonasal tumor plans were optimized with CCC and then recalculated by MC with identical control points and monitor units. Planning target volume (PTV)air , PTVsoft tissue , and PTVbone were created to analyze the dose discrepancy within the PTV. Thirty imaging sets of dogs were included. Monte Carlo served as the gold standard calculation for the dosimetric comparison. Collapsed cone convolution overestimated the mean dose (Dmean ) to PTV and PTVsoft tissue by 0.9% and 0.5%, respectively (both P < 0.001). Collapsed cone convolution overestimated Dmean to PTVbone by 3% (P < 0.001). Collapsed cone convolution underestimated the near-maximum dose (D2 ) to PTVair by 1.1% (P < 0.001), and underestimated conformity index and homogeneity index in PTV (both P < 0.001). Mean doses of contralateral and ipsilateral eyes were overestimated by CCC by 1.6% and 1.7%, respectively (both P < 0.001). Near-maximum doses of skin and brain were overestimated by CCC by 2.2% and 0.7%, respectively (both P < 0.001). As clinical accessibility of Monte Carlo becomes more widespread, dose constraints may need to be re-evaluated with appropriate plan evaluation and follow-up.

Outcomes of dogs with thymoma treated with intensity modulated stereotactic body radiation therapy or non-modulated hypofractionated radiation therapy.

Canine thymomas are routinely treated with radiotherapy (RT). In this study, we investigate the response and toxicity of canine thymoma treated with intensity-modulated stereotactic body radiation therapy (SBRT) relative to dogs treated with hypofractionated non-modulated radiation therapy (NMRT). A retrospective study was performed of dogs with thymoma treated with RT (total: n = 15; SBRT: n = 8, NMRT: n = 7). Tumour response was evaluated in six dogs (40%); following SBRT, three dogs (100%) experienced stable disease (SD); following NMRT, one dog (33%) had a PR, and two dogs (67%) had SD. Median PFS was 116 days (range 66-727 days) for the SBRT group and 134 days (range 10-405 days) for the NMRT group. The MST for the SBRT group was 250 days (range 1-727 days) and 155 days (range 10-405 days) for NMRT. Median disease-specific survival was 250 days (range 1-727 days) for the SBRT group and 169 days (range 20-405 days) for the NMRT group. No significant differences in survival data were found between the treatment groups, however the results from the small number of dogs analysed are likely underpowered for statistical comparisons. Reported acute and late side effects were limited to the lungs and heart and were statistically significantly more common in the NMRT (71%) compared to the SBRT group (25%) (p = .04). We suggest similar treatment efficacy may be provided for canine thymoma treated with either approach, but SBRT could provide the clinical benefit of reduced incidence of radiation-induced toxicity and completion of RT in a shorter time frame.

Endocrine response and outcome in 14 cats with insulin resistance and acromegaly treated with stereotactic radiosurgery (17 Gy).

OBJECTIVE: To describe clinical outcomes in cats with insulin resistance and acromegaly treated with stereotactic radiosurgery (SRS). ANIMALS: 14 client-owned cats. PROCEDURES: Medical records of cats with insulin resistance and acromegaly treated with SRS (17 Gy) between August 2013 and November 2019 at a single institution were reviewed. Kaplan-Meier analysis was used to evaluate overall survival time. RESULTS: Acute adverse effects of SRS included somnolence (n = 2) and alopecia (1). Delayed adverse effects of SRS included unspecified neurologic complications (n = 1; 481 days), seizures (1; 1,541 days), and hypothyroidism (1; 64 days). Exogenous insulin requirements decreased in 10 of the 14 cats, with a median time to lowest insulin dose of 399 days (range, 42 to 879 days). Complete diabetic remission was achieved in 3 cats. The median overall survival time was 741 days (95% CI, 353 to 1,129 days). Six cats were still alive at the end of the study period, with a median follow-up time of 725 days. In 7 of the 8 cats that had died, death was presumptively attributed to acromegaly owing to continued insulin resistance, organ failure, or altered neurologic status. CLINICAL RELEVANCE: The SRS protocol was well tolerated and associated with survival times similar to those reported previously. Most cats had decreased exogenous insulin requirements after SRS. Latency to an endocrine response was highly variable, emphasizing the need for careful ongoing diabetic monitoring of acromegalic cats after pituitary gland irradiation.

Use of imaging-guided intensity-modulated stereotactic body radiation therapy to treat a well-differentiated hepatocellular carcinoma in a dog.

CASE DESCRIPTION: A 14-year-old 5.6-kg (12.3-lb) castrated male Toy Poodle was evaluated because of high serum activities of alkaline phosphatase and alanine aminotransferase and the presence of a hepatic mass. CLINICAL FINDINGS: Abdominal CT revealed a large (approx 6.8 × 7.1 × 6.5-cm) soft tissue mass along the midline of the liver. The mass either originated from the papillary process of the caudate lobe or the left medial liver lobe. TREATMENT AND OUTCOME: A partial liver lobectomy was performed, and approximately a third of the mass was successfully removed and submitted for histologic examination. Consultation with the oncology service was advised to determine whether radiation therapy could be used to treat the residual disease. On 5 consecutive days, the dog underwent imaging-guided intensity-modulated radiotherapy-stereotactic body radiation therapy (4 Gy/treatment) with a simultaneous integrated boost to the center of the tumor. The dog received a base dose of 20 Gy that was then boosted to 28 Gy. In the 10-month period after completion of radiation therapy, the hepatocellular mass continued to decrease in size, and overall improvements in the dog's serum liver enzyme abnormalities were evident. CLINICAL RELEVANCE: There are few treatment options for dogs with incompletely excised hepatocellular carcinomas. On the basis of the positive outcome in this case, radiation therapy could be useful following incomplete surgical removal of hepatocellular carcinomas in dogs.

Use of stereotactic body radiation therapy for treatment of a pancreatic tumor in a cat.

CASE DESCRIPTION: A 16-year old castrated male domestic shorthair cat was evaluated at a veterinary teaching hospital because of polyuria, polydipsia, and weight loss of 2 months' duration. CLINICAL FINDINGS: Hematologic and biochemical examination results were within respective reference ranges except for moderately high pancreas-specific lipase concentration. Ultrasonographic and cytologic evaluation revealed a hepatic mass with findings consistent with mild cholestasis and inflammation and a pancreatic mass that was initially identified as a neuroendocrine tumor. TREATMENT AND OUTCOME: The cat underwent additional CT assessment and stereotactic body radiation therapy (SBRT; 3 fractions of 8 Gy, administered every other day) for treatment of the pancreatic tumor. Follow-up ultrasonographic and CT examinations indicated a partial response to SBRT, with a maximum CT-measured size reduction from 3.6 × 4.8 × 4.0 cm at the time of treatment planning to 2.0 × 2.0 × 1.9 cm 8 months later. Increased pancreatic tumor size and signs of carcinomatosis were detected 15 months after SBRT treatment; the initial cytologic diagnosis was changed to exocrine pancreatic carcinoma on reevaluation of the slides by another veterinary pathologist. Carboplatin treatment was elected, and signs of carcinomatosis resolved. The cat was euthanized without further testing because of weakness 589 days after SBRT was started. CLINICAL RELEVANCE: To the authors' knowledge, this is the first report of SBRT for suspected exocrine pancreatic carcinoma in a cat. Further investigation is needed to determine optimal fractionation schedules for SBRT of pancreatic tumors and utility of SBRT of exocrine pancreatic carcinoma in cats.