Completeness of reporting of radiation therapy planning, dose, and delivery in veterinary radiation oncology manuscripts from 2005 to 2010

The role of companion animal models in radiopharmaceutical development and translation

Advancements in molecular imaging and drug targeting have created a renaissance in the development of radiopharmaceuticals for therapy and theranostics. While some radiopharmaceuticals, such as Na[131I]I, have been used clinically for decades, new agents are being approved using small-molecules, peptides, and antibodies for targeting. As these agents are being developed, the need to understand dosimetry and biologic effects of the systemically delivered radiotherapy becomes more important, particularly as highly potent radiopharmaceuticals using targeted alpha therapy become clinically utilized. As the processes being targeted become more complex, and the radiobiology of different particulate radiation becomes more diverse, models that better recapitulate human cancer and geometry are necessary. Companion animals develop many of the same types of cancer, carrying many of the same genetic drivers as those seen in people, and the scale and geometry of tumours in dogs more closely mimics those in humans than murine tumour models. Key translational challenges in oncology, such as alterations in tumour microenvironment, hypoxia, heterogeneity, and geometry are addressed by companion animal models. This review paper will provide background on radiopharmaceutical targeting techniques, review the use of radiopharmaceuticals in companion animal oncology, and explore the translational value of treating these patients in terms of dosimetry, treatment outcomes, and normal tissue complication rates.

Stereotactic radiotherapy outcomes for intraventricular brain tumours in 11 dogs

Published radiotherapy data for canine intraventricular tumours are limited. In this retrospective, longitudinal study (9/2011-2018), 11 dogs with intraventricular masses were treated with stereotactic radiotherapy (SRT). Pathologic diagnosis was available from surgery or necropsy in 6/11 cases, revealing choroid plexus papilloma (3) or carcinoma (2), and ependymoma (1). The remainder were magnetic resonance imaging (MRI)-diagnosed as suspected choroid tumours or ependymomas. Tumours were located in the third or lateral ventricle (8), fourth ventricle (2), and cerebellopontine angle (1). Surgery was performed in three dogs prior to radiotherapy, and all showed gross residual/recurrent disease at treatment. Dogs received 8 Gray × 3 fractions (7), or 15 Gray × 1 fraction (4). Ten dogs were deceased at analysis, and one was living. The estimated median overall survival time (OS) from first SRT treatment was 16.9 months (515 days, 95% CI 33-1593 days). The survival time for two pathology-diagnosed carcinoma dogs were 24 and 133 days, respectively, and survival time for dogs with moderate to marked ventriculomegaly (4/11) ranged from 24 to 113 days. A total of 10/11 showed clinical improvement per owner or clinician, but two had short-lived benefits and were euthanized within 6 weeks of SRT. Limited conclusions on radiation-specific complications are possible due to the small dataset and limited follow-up imaging. This study provides preliminary evidence that radiotherapy outcomes are variable with intraventricular tumours, and some long-term survivors are noted.

Description and efficacy of a response-based "QUAD" cyclical hypofractionated palliative-intent radiation protocol in dogs with macroscopic solid tumours: 108 cases

Palliative-intent radiation therapy can alleviate pain and clinical signs in dogs with cancer, but optimal fractionation scheme is unknown. The objective of this retrospective case series is to evaluate clinical benefit, objective response, adverse effects, and outcomes in 108 dogs with macroscopic solid tumours treated with a cyclical "QUAD" hypofractionated palliative-intent radiation therapy protocol. Median QUAD dose was 14 Gy (14-16 Gy). Median total dose was 28 Gy (14-48 Gy). Clinical benefit rate was 93%, with median onset of subjective palliation 21 days after the first QUAD, lasting a median of 134 days. Tumour volumetric objective response was assessed with CT prior to the third QUAD in 36 dogs, with stable disease in 24 dogs (67%) and partial response in 9 dogs (25%). Sinonasal and oral were the most common tumour locations in 32 and 30 dogs, respectively. Median progression-free survival was 153 days (95% CI 114-200). Median overall survival was 212 days (95% CI 152-259). Number of QUAD cycles completed, clinical benefit achieved, anti-inflammatory received, total radiation dose, time to maximum clinical benefit, and response duration were positively associated with progression-free and overall survival. Acute toxicities were observed in 15 dogs (14%) with 3 high-grade (grade 3) toxicities (3%). Low-grade (grade 1 and 2) late skin and ocular toxicities were observed in 31 dogs (29%), predominantly leukotrichia, alopecia, keratoconjunctivitis sicca, and cataracts. This report demonstrates that QUAD radiation is an alternative protocol to be considered for palliation of dogs with inoperable or advanced stage solid tumours.

Conventional fractionated radiotherapy outcomes for young dogs with nephroblastoma of the spinal cord: 5 cases

Published radiotherapy results for spinal nephroblastomas in dogs are limited. In this retrospective longitudinal study (1/2007-1/2022), five dogs with a median age of 2.8 years received post-operative 3D conformal, conventional fractionated radiotherapy (CFRT) with 2-4 fields (parallel-opposed with or without two hinge-angle fields), for an incompletely resected nephroblastoma. Clinical findings prior to surgery included one or more of the following: pelvic limb paresis (5), faecal incontinence (2), flaccid tail (1), non-ambulatory (2) and deep pain loss (1). All masses were located between T11 and L3 and surgically removed via hemilaminectomy. Dogs received 45-50 Gray (Gy) in 18-20 fractions, and no dogs received chemotherapy post-radiation. At analysis, all dogs were deceased, with none lost to follow-up. The median overall survival (OS) from first treatment to death of any cause was 3.4 years (1234 days; 95% CI 68 days-upper limit not reached; range: 68-3607 days). The median planning target volume was 51.3 cc, with a median PTV dose of 51.4 Gy and median D98 = 48.3 Gy. Late complications or recurrence was difficult to fully determine in this small dataset; however, some degree of ataxia persisted throughout life in all dogs. This study provides preliminary evidence that post-operative radiotherapy may result in prolonged survival times dogs with spinal nephroblastomas.

Effect of pituitary-dependent hypercortisolism on the survival of dogs treated with radiotherapy for pituitary macroadenomas

BACKGROUND

Radiotherapy (RT) is an effective treatment for dogs presented with neurologic signs caused by pituitary tumors. However, its impact on the outcome of concurrent pituitary-dependent hypercortisolism (PDH) is controversial.

OBJECTIVES

Determine whether dogs with PDH have longer survival after pituitary RT compared with dogs with nonhormonally active pituitary masses and to evaluate whether clinical, imaging, and RT variables affect survival.

ANIMALS

Ninety-four dogs divided into 2 groups: PDH and non-PDH, based on the presence of hypercortisolism. Forty-seven dogs were allocated to the PDH group and 47 to the non-PDH group.

METHODS

Retrospective cohort study in which clinical records of dogs undergoing RT for pituitary macroadenomas between 2008 and 2018 at 5 referral centers were retrospectively evaluated.

RESULTS

Survival was not statistically different between PDH and non-PDH groups (median survival time [MST], 590 days; 95% confidence interval [CI], 0-830 days and 738 days; 95% CI, 373-1103 days, respectively; P = .4). A definitive RT protocol was statistically associated with longer survival compared with a palliative protocol (MST 605 vs 262 days, P = .05). The only factor statistically associated with survival from multivariate Cox proportional hazard analysis was total radiation dose (Gy) delivered (P < .01).

CONCLUSIONS AND CLINICAL IMPORTANCE

No statistical difference in survival was identified between the PDH and non-PDH groups, and longer survival was associated with higher Gy delivered.

Presumed pituitary apoplexy in 26 dogs: Clinical findings, treatments, and outcomes

BACKGROUND

Pituitary apoplexy refers to hemorrhage or infarction within the pituitary gland resulting in acute neurological abnormalities. This condition is poorly described in dogs.

OBJECTIVES

To document presenting complaints, examination findings, endocrinopathies, magnetic resonance imaging (MRI), treatments, and outcomes of dogs with pituitary apoplexy.

ANIMALS

Twenty-six client-owned dogs with acute onset of neurological dysfunction.

METHODS

Retrospective case series. Dogs were diagnosed with pituitary apoplexy if MRI or histopathology documented an intrasellar or suprasellar mass with evidence of hemorrhage or infarction in conjunction with acute neurological dysfunction. Clinical information was obtained from medical records and imaging reports.

RESULTS

Common presenting complaints included altered mentation (16/26, 62%) and gastrointestinal dysfunction (14/26, 54%). Gait or posture changes (22/26, 85%), mentation changes (18/26, 69%), cranial neuropathies (17/26, 65%), cervical or head hyperpathia (12/26, 46%), and hyperthermia (8/26, 31%) were the most frequent exam findings. Ten dogs (38%) lacked evidence of an endocrinopathy before presentation. Common MRI findings included T1-weighted hypo- to isointensity of the hemorrhagic lesion (21/25, 84%), peripheral enhancement of the pituitary mass lesion (15/25, 60%), brain herniation (14/25, 56%), and obstructive hydrocephalus (13/25, 52%). Fifteen dogs (58%) survived to hospital discharge. Seven of these dogs received medical management alone (median survival 143 days; range, 7-641 days) and 8 received medications and radiation therapy (median survival 973 days; range, 41-1719 days).

CONCLUSIONS AND CLINICAL IMPORTANCE

Dogs with pituitary apoplexy present with a variety of acute signs of neurological disease and inconsistent endocrine dysfunction. Dogs that survive to discharge can have a favorable outcome.

Treatment of intracranial neoplasia in dogs using higher doses: A randomized controlled trial comparing a boosted to a conventional radiation protocol

BACKGROUND

Local progression of intracranial tumors can be the consequence of insufficient radiation dose delivered. Dose increases in the brain must be made carefully so as not to risk debilitating adverse effects such as radiation necrosis.

HYPOTHESIS

A new protocol with 10 × 4 Gy + 11% physical dose increase limited to the macroscopic tumor volume results in a clinically better outcome compared to a 10 × 4 Gy protocol.

ANIMALS

Fifty-seven client-owned dogs with primary intracranial neoplasia.

METHODS

Randomized controlled trial. Twenty-eight dogs were assigned to the control protocol (10 × 4 Gy) and 29 to the simultaneous integrated boost (SIB) protocol with 4.45 Gy dose increase. Treatment groups were compared for outcome and signs of toxicity.

RESULTS

Mild, transient acute or early-delayed adverse radiation effects were observed in 5 dogs. Severe late adverse effects were not seen. Between the protocols, no significant differences were found for outcome (intention-to-treat analysis): overall time to progression (TTP) was 708 days (95% confidence interval (95% CI) [545,872]), in the control group it was 828 days (95% CI [401,1256]), and in the SIB group 627 days (95% CI [282,973]; P = .07). Median overall survival (OS) was 684 days (95% CI [516,853]), in the control group it was 724 days (95% CI [623,826]), and in the SIB group 557 days (95% CI [95,1020]; P = .47). None of the tested variables was prognostic in terms of outcome.

CONCLUSION AND CLINICAL IMPORTANCE

The dose escalation used with an 11% physical dose increase did not result in better outcome.

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.

Relative tumor volume has prognostic relevance in canine sinonasal tumors treated with radiation therapy: A retrospective study

Tumor volume is controversially discussed as a prognostic factor in dogs treated with radiation therapy for sinonasal tumors. Dogs’ body sizes vary widely and relative rather than absolute tumor volume might provide better prognostic information. Our hypothesis was that relative rather than absolute tumor volume (gross tumor volume, GTV) influences time to progression (TTP) and that a larger tumor volume is correlated with a higher tumor stage. We retrospectively investigated possible correlations of initial GTV to weight, body surface area (BSA), nasal cavity size and the tumor stage in 49 dogs with sinonasal tumors. Here, also presumed sinonasal tumors, esthesioneuroblastomas and histologically benign tumors were included. The possible impact of absolute and relative GTV on response and outcome were assessed according to imaging findings in 34 dogs with available follow-up computed tomographies (CTs) after definitive-intent radiation therapy with either a regular (10x4.2 Gy) or a simultaneously- integrated boost protocol (SIB; GTV boosted to 10x4.83 Gy). In contrast to absolute GTV (p<0.001), the relative GTVs were not correlated with dogs’ body sizes. Absolute GTV, GTV relative to weight and BSA were not associated with TTP based on CT imaging. However, GTV relative to nasal cavity showed a prognostic influence with a hazard ratio of 10.97 (95%CI:1.25–96.06). When looking at GTV relative to nasal cavity, stage 3 and 4 tumors were significantly larger than stage 1 and 2 tumors (p = 0.005). Our results suggest that GTV relative to nasal cavity could be prognostic for TTP and a larger tumor volume relative to nasal cavity is correlated with a higher tumor stage.

Dose-escalated simultaneously integrated boost radiation protocol fails to result in a survival advantage for sinonasal tumors in dogs

The prognosis for canine sinonasal tumors remains rather poor despite definitive-intent radiotherapy (RT). Theoretical calculations predicted improved outcomes with simultaneously integrated boost (SIB) protocols. With the hypothesis of clinically detectable differences in outcome between groups, our retrospective study evaluated prognostic variables and outcome in dogs treated with regular versus SIB RT. Dogs with sinonasal tumors treated with either a regular (10 × 4.2 Gy) or new SIB protocol (10 × 4.83 Gy to macroscopic tumor) were included. Information regarding signalment, tumor stage, type, clinical signs, radiation toxicity, response, and outcome was collected. Forty-nine dogs were included: 27 treated regularly and 22 treated with SIB RT. A total of 69.4% showed epistaxis, 6.1% showed epileptic seizures, 46.9% showed stage IV tumors, and 6.1% showed lymph node metastases. Early toxicity was mostly mild. Late grade 1 skin toxicity (alopecia/leucotrichia) was seen in 72.1% of dogs, and a possible grade 3 ocular toxicity (blindness) was seen in one dog. Complete/partial resolution of clinical signs was seen in 95.9% of patients as best clinical response and partial remission was seen as best imaging response in 34.7%. The median progression-free survival (PFS) was 274 days (95% CI: 117-383) for regular and 300 days (95% CI: 143-451) for SIB RT, which was not significantly different (P = 0.42). Similarly, the median overall survival (OS) was 348 days (95% CI: 121-500) for regular and 381 days (95% CI: 295-634) for the SIB RT (P = 0.18). Stratified by protocol, the hazard ratio of stage IV versus stage I-III tumors was 2.29 (95% CI: 1.156-4.551, P = 0.02) for OS but not PFS. All dogs showed acceptable toxicity. In contrast to theoretical predictions, however, we could not show a statistically significant better outcome with the new protocol.

Outcomes of adjunctive radiation therapy for the treatment of mast cell tumors in dogs and assessment of toxicity: A multicenter observational study of 300 dogs

Background

Radiation therapy is commonly used as an adjunct to incomplete surgical excision in dogs with mast cell tumors (MCT), but the optimal dose and fractionation regimen have yet to be determined.

Hypothesis

We assessed outcomes (time to local recurrence, patient survival and toxicity) of a large population of dogs with MCT that received adjunctive radiation therapy.

Animals

Three hundred dogs with 302 MCT treated using adjunctive radiation therapy.

Methods

Retrospective observational study. Clinical records of 4 veterinary radiation centers were reviewed.

Results

Local recurrence rates were similar regardless of radiation protocol with 6.6% of patients developing recurrent cutaneous MCT at a median of 526 days. Local recurrence rate was similar between high and low‐risk MCT. Mast cell tumor related death was reported in 19% of all dogs, with 13% of dogs with low‐risk MCT dying of their disease compared to 29% of dogs with high‐risk MCT. No SC MCT (SCMCT) recurred after radiation therapy and only 7% of dogs with SCMCT were reported to have died of their disease. Mild late toxicity was common in both protocols and severe late toxicity occurred in 1.9% of dogs many years after treatment.

Conclusions and Clinical Importance

Our study supports the use of adjunctive radiation for the long‐term control of incompletely or narrowly excised cutaneous and SCMCT in dogs. More moderate dose and fractionation protocols may be appropriate in the adjunctive treatment of low‐risk MCT in dogs. Large multicenter prospective studies are required to establish the optimal dose and fractionation for MCT of different risk categories.

Outcome After Radiation Therapy in Canine Intracranial Meningiomas or Gliomas

AIM

To characterize a group of dogs diagnosed with meningioma or glioma treated with radiation therapy and assess the clinical impact of diagnosis and radiation protocol on survival time.

PATIENTS AND METHODS

Canine patient records from a single veterinary referral hospital, between 2011 and 2015, were searched for intracranial tumour cases treated with radiation therapy, as a sole modality. Thirty-two dogs were included.

RESULTS

Median survival times were 524 days [95% confidence interval (CI)=287-677] in total, 512 days (95% CI=101-682) for the glioma group and 536 days (95% CI=249-677) for the meningioma group. No significant difference in survival was detected when using a definitive or a palliative protocol (p=0.130), nor other prognostic factors were found.

CONCLUSION

Our results highlight the efficacy of radiation therapy in the treatment of canine meningioma, as well as glioma, suggesting a change in the current perception of the response of glial tumours to radiation.

Retrospective evaluation of intranasal carcinomas in cats treated with external-beam radiotherapy: 42 cases

Background

Little is known regarding the comparative efficacy of various irradiation strategies used to treat intranasal carcinomas (INC) in cats.

Objectives

Investigate outcomes and prognostic factors associated with survival for cats with INC.

Animals

Forty‐two cats with INC that underwent radiotherapy (RT).

Methods

Single‐arm retrospective study. Medical record review for cats with INC that underwent RT at 1 of 7 veterinary RT facilities. Irradiation protocols categorized as: definitive‐intent fractionated RT (FRT), definitive‐intent stereotactic RT (SRT), and palliative‐intent RT (PRT). Median overall survival time (OST) and disease progression‐free survival (PFS; documented by advanced transverse imaging, or recurrence of symptoms) were calculated. Associations between tumor stage, RT protocol/intent, and adjunctive treatment usage and outcome were calculated.

Results

Cats underwent SRT (N = 18), FRT (N = 8), and PRT (N = 16). In multivariate modeling, cats received definitive‐intent treatment (DRT; FRT/SRT) had significantly longer median PFS (504 days, [95% confidence interval (CI): 428–580 days] vs PRT 198 days [95% CI: 62–334 days]; p = 0.006) and median OST [721 days (95% CI: 527–915 days) vs 284 days (95% CI: 0–570 days); p = 0.001]). Cats that underwent second DRT course at time of recurrence lived significantly longer than cats that received 1 RT course (either DRT or PRT [median OST 824 days (95% CI: 237–1410 days) vs 434 days (95% CI: 277–591 days); p = .028]).

Conclusion

In cats with INC, DRT is associated with prolonged OST and PFS as compared to PRT. If tumor progression occurs, a second course of DRT should be considered.

Long-term outcomes with conventional fractionated and stereotactic radiotherapy for suspected heart-base tumours in dogs

Published radiotherapy results for suspected heart-based tumours in dogs are limited. In this retrospective longitudinal study (3/2014-2019), eight dogs with either clinical signs attributable to a heart-base mass (6), or asymptomatic with a progressively larger mass on echocardiogram (2), received conventional fractionated radiotherapy (CFRT) or stereotactic body radiotherapy (SBRT). Clinical findings in symptomatic cases included one or more of the following: retching/coughing (4), exercise intolerance (2), collapse (1), pericardial effusion (2), rare ventricular premature contractions (2), abdominal effusion (1), or respiratory distress due to chylothorax (1). CFRT cases received 50 Gray (Gy) in 20 fractions and SBRT cases received 30 Gy in 5 or 24 Gy in three fractions. Two dogs received chemotherapy post-radiation. At analysis, 7/8 dogs were deceased and one was alive 684 days post-treatment. The estimated median overall survival (MOS) from first treatment was 785 days (95% CI 114-868 days, [range 114-1492 days]). Five dogs received CFRT (MOS 817 days; (95% CI 155 days-not reached [range 155-1492 days])). Three dogs received SBRT with one alive at analysis (MOS 414 days, (95% CI, 114 days-not reached [range 114-414 days])). No statistically significant difference was found between survival for CFRT and SBRT. Of the symptomatic patients, 5/6 showed improvement. Mass size reduced in 4/5 cases receiving follow-up ultrasounds. Possible complications included asymptomatic radiation pneumonitis (4), atrial tachycardia/premature beats (4) and pericardial effusion with heart failure coincident with tumour progression (1). This study provides preliminary evidence that radiotherapy may impact clinically relevant or progressively enlarging heart-base masses.

Treatment of canine oral papillary squamous cell carcinoma using definitive-intent radiation as a monotherapy-a case series

Canine oral papillary squamous cell carcinoma (COPSCC) is a rare neoplasm and although locally invasive it carries a favourable prognosis following wide surgical excision. Radiotherapy has been reported to be effective as an adjunct treatment to surgery. However, limited information is available on the role of radiotherapy as single treatment. This single‐institution retrospective study describes a series of 10 dogs diagnosed with macroscopic COPSCC that were treated with definitive‐intent radiotherapy (DRT) as a monotherapy. These dogs had a median age of 4 years (range: 0.4‐9.6 years). The tumour was located in the rostral oral cavity in all cases with a median tumour size of 2.5 cm (range: 0.8‐6.8 cm). No local or distant metastases were identified. All dogs were treated with electron beam DRT (>32Gy, 10‐16 daily fractions of 3.2Gy). The median follow‐up time was 961 days (range: 333‐3.498 days) with nine dogs achieving a complete response and one dog a partial response. The dog with the partial response developed disease progression at 228 days after initiation of radiotherapy. Two dogs died from non‐tumour‐related causes. The remaining seven dogs were still alive and in complete remission at the time of last follow‐up. Median progression‐free survival time and median survival time were not reached. DRT was generally well tolerated, but all dogs experienced self‐limiting acute radiation mucositis (grade 2‐3) and/or dermatitis (grade 1). No late radiation toxicity was observed. Macroscopic COPSCC appears to be a radiosensitive tumour that can be successfully treated with DRT eliminating the need for aggressive surgery in advanced cases.

Radiological protection of the patient in veterinary medicine and the role of ICRP

At the request of the Main Commission of the International Commission on Radiological Protection (ICRP), Task Group 107 (TG107) was set up to consider the issue of radiological protection of the patient in veterinary medicine. TG107, who authored this article, brought together information relating to the use of diagnostic imaging and radiation oncology in veterinary medicine. A number of specific areas were identified that appeared to be appropriate for attention by ICRP. These included the use of dose quantities and units, the need for re-evaluation of stochastic and deterministic risks from ionising radiation in animals, and the growing use of imaging and therapeutic equipment for animals that is little different from that available to humans. TG107 unanimously recommended that it was both appropriate and timely for ICRP to consider and advise on these issues, and the Main Commission agreed. This paper summarises the findings of TG107.

Outcome comparison between radiation therapy and surgery as primary treatment for dogs with periarticular histiocytic sarcoma: An Italian Society of Veterinary Oncology study

Localized histiocytic sarcoma may occur as a primary lesion in periarticular tissues of large appendicular joints. Treatment options for the primary lesion include radical surgical excision, radiation therapy (RT), or both, in combination with chemotherapy for potential systemic metastases. In an effort to better characterize the time to progression (TTP) following surgical vs non-surgical approaches for periarticular histiocytic sarcoma (PAHS), a contemporary European population of affected dogs was retrospectively surveyed. Medical records were queried for newly-diagnosed PAHS cases undergoing surgery (predominantly limb amputation) or RT followed by systemic chemotherapy. Of 49 dogs, 34 underwent RT and 15 underwent surgery. All dogs received adjuvant chemotherapy. There was no statistically significant difference in TTP or overall survival between groups. The median TTP was 336 days for the operated dogs and 217 days for the irradiated dogs (P = .117). The median overall survival time was 398 days for the operated dogs and 240 days for the irradiated dogs (P = .142). On multi-variable analysis, the variables significantly associated with an increased risk of both tumour progression and tumour-related death were regional lymph node and distant metastasis at admission. Survival and local control rates following RT may be comparable to radical resection. These data may better inform shared decision-making processes between multi-disciplinary care providers and owners.

Ocular and periocular radiation toxicity in dogs treated for sinonasal tumors: A critical review

Visual impairment from radiation‐induced damage can be painful, disabling, and reduces the patient's quality of life. Ocular tissue damage can result from the proximity of ocular organs at risk to irradiated sinonasal target volumes. As toxicity depends on the radiation dose delivered to a certain volume, dose‐volume constraints for organs at risk should ideally be known during treatment planning in order to reduce toxicity. Herein, we summarize published ocular toxicity data of dogs irradiated for sinonasal tumors from 36 publications (1976‐2018). In particular, we tried to extract a dose guideline for a clinically acceptable rate of ocular toxicity. The side effects to ocular and periocular tissues were reported in 26/36 studies (72%) and graded according to scoring systems (10/26; 39%). With most scoring systems, however, toxicities of different ocular and periocular tissues are summed into one score. Further, the scores were mostly applied in retrospect and lack volume‐ and dose‐data. This incomplete information reflects the crux of the matter for radiation dose tolerance in canine ocular tissues: The published information of the last three decades does not allow formulating dose‐volume guidelines. As a start, we can only state that a mean dose of 39 Gy (given in 10 x 4.2 Gy fractions) will lead to loss of vision by one or both eyes, while mean doses of <30 Gy seem to preserve functionality. With a future goal to define tolerated doses and volumes of ocular and periocular tissues at risk, we propose the use of combined ocular toxicity scoring systems.

Definitive-intent radiotherapy for sinonasal carcinoma in cats: A multicenter retrospective assessment

Treatment of epithelial sinonasal tumours in cats is not commonly reported. In the newer reports, palliative radiation protocols have been described more often than definitive-intent protocols. In this multi-institutional retrospective study, we included 27 cats treated with single-modality radiotherapy. Cats were irradiated using 10 daily fractions of 4.2 Gy. Three cats (11.1%) experienced a complete clinical response and 17 (63%) had a partial clinical response. Stable clinical disease was noted in three cats (11.1%). Four cats (14.8%) showed progression within 3 months following treatment. The median time to progression for all cases was 269 days (95 % confidence intervals [CI]: 225; 314). The proportion of cats free of progression at 1 and 2 years was 24% (95% CI: 22%; 26%) and 5% (95% CI: 5%; 6%), respectively. None of the prognostic factors evaluated were predictive of outcome (anaemia, tumour volume at the time of staging, modified Adams stage, intracranial involvement, facial deformity, epistaxis, inappetence or weight loss). Median overall survival (OS) for all deaths was 452 days (95% CI: 334; 571). The proportion of cats alive at 1 and 2 years was 57% (95% CI: 37%; 77%) and 27% (95% CI: 25%; 29%), respectively. Surprisingly, cats with epistaxis had a longer median OS of 828 days (95% CI: 356; 1301) compared to 296 days (95% CI: 85; 508) in cats without epistaxis, (P = .04, Breslow). Radiation therapy used as a single modality for the treatment of feline sinonasal carcinoma improved clinical signs and was well tolerated but progression within a year was common.

Definitive-intent intensity-modulated radiation therapy for treatment of canine prostatic carcinoma: A multi-institutional retrospective study

No standard of care is currently recognized for treatment of canine prostatic carcinoma (PC). This retrospective study assesses outcome following definitive-intent, intensity-modulated radiation therapy (RT) in dogs with PC. Medical records review was performed, including 18 patients from four institutions undergoing definitive-intent intensity-modulated radiotherapy to treat PC. Diagnosis was incidental in 7/18 (39%) patients. Five dogs (28%) had evidence of metastasis to loco-regional lymph nodes at diagnosis. Seventeen patients received concurrent non-steroidal anti-inflammatory drugs; 15/18 (83%) patients received maximally-tolerated dose (MTD) chemotherapy, with variable drugs and protocols employed. Total prescribed radiation dose ranged from 48 to 54 Gy (median 50 Gy) delivered as daily doses of 2.5-2.8 Gy. One patient was euthanized prior to completing radiotherapy. Acute toxicity was observed in nine patients; Grade 1-2 diarrhoea was the most common toxicity observed. Suspected late toxicity (urethral stricture, ureteral stricture and hindlimb oedema) was observed in three patients. Median event-free survival (EFS) following RT was 220 days, and median overall survival was 563 days. Local progression occurred in seven patients at a median of 241 days. Median overall survival was significantly longer in incidentally diagnosed dogs (581 vs 220 days in symptomatic dogs, P = .042). EFS was significantly longer in patients treated with MTD chemotherapy (241 vs 25 days, P < .001), and significantly shorter in patients presenting with evidence of metastatic disease (109 days) vs those without (388 days, P = .008). These findings suggest that definitive-intent radiotherapy is a valuable treatment option for local control of canine PC with moderate risk of toxicity.

Quality of reporting on thoracic radiotherapy technique in prospective lung cancer trials: A systematic review

BACKGROUND

The aim of this study is to assess the quality of reporting of thoracic (T) RT technique for curative intent treatment in prospective lung cancer trials.

METHODS

We searched MEDLINE for eligible trials published from 1996 to 2016. We assessed the included trials' reports on whether they reported the RT dose prescription method; RT dose-planning procedures; algorithm for tissue inhomogeneity dose corrections; organs at risk dose constraints; target volume definition, simulation and/or motion management procedures; treatment verification procedures; total RT dose; fractionation schedule; conduct of quality assurance as well as presence or absence of deviations in RT treatment planning and delivery adequately. We performed univariable and multivariable logistic regression to determine the factors that may influence the quality of reporting.

RESULTS

We found 85 eligible trial reports. Target volume definition, total RT dose, and fractionation schedules were reported adequately in more than 90% of the included trials. Algorithm for tissue inhomogeneity dose corrections, simulation and verification procedures, presence or absence of deviations in RT treatment planning and delivery were reported adequately in less than 20% of the included trials. Twenty-three trials (27%) reported 7 criteria or more adequately. Both univariable and multivariable logistic regression showed that trials with RT focused research question were more likely to have adequate quality in reporting (judged as adequate reporting in 7 criteria or more) than trials with non-RT focused question (odds ratio 4.11, 95% confidence interval 1.10 to 15.43, P value = .04).

CONCLUSION

There is significant variability in the quality of reporting on thoracic radiotherapy treatment in prospective lung cancer trials. Future research should focus on developing consensus guidelines to standardize the reporting of radiotherapy technique in clinical trials.

A retrospective analysis of radiation oncology related scientific articles in the journal Veterinary Radiology and Ultrasound: Trends over 40 years (1976-2015)

The journal Veterinary Radiology & Ultrasound is a veterinary specialty journal devoted to the fields of veterinary diagnostic imaging and radiation oncology. The purpose of this retrospective, observational study is to evaluate progressive trends in radiation oncology articles published in Veterinary Radiology & Ultrasound during the 40-year period (1976-2015) and describe a shift of trends through several viewpoints. This 40-year period was divided into four subperiods: Period 1 (1976-1985), Period 2 (1986-1995), Period 3 (1996-2005), and Period 4 (2006-2015). These articles were divided into six categories based on the nature of the study: 1) studies related to teletherapy with endpoints being patient outcome, 2) radiation therapy dosimetry/planning, 3) patient setup, 4) reviews, 5) case reports, and 6) others. The number of radiation oncology articles in Veterinary Radiology & Ultrasound has increased over the 40-year period. The number of authors per article has increased between Periods 1 and 3. The number of articles related to linear accelerator has increased between Periods 3 and 4. The median number of treated patients per clinical article related to teletherapy ranged from 15 to 21, which has not changed significantly over the 40-year period. The most commonly used radiation therapy protocols during Periods 2 and 3 were fine-fractionated protocols (defined as 10 or more fractions), whereas coarse-fractionated protocols were more common during Periods 1 and 4. Findings from this study highlight the notable changes of trends in veterinary radiation oncology articles published in Veterinary Radiology & Ultrasound, which clearly reflect changes in the field of veterinary radiation oncology during the past 40 years.

Long-term survival with stereotactic radiotherapy for imaging-diagnosed pituitary tumors in dogs

Published studies on the use of stereotactic radiotherapy for dogs with pituitary tumors are limited. This retrospective observational study describes results of stereotactic radiotherapy for 45 dogs with imaging-diagnosed pituitary tumors. All dogs were treated at a single hospital during the period of December 2009-2015. The stereotactic radiotherapy was delivered in one 15 Gray (Gy) fraction or in three 8 Gy fractions. At the time of analysis, 41 dogs were deceased. Four were alive and censored from all survival analyses; one dog received 8 Gy every other day and was removed from protocol analyses. The median overall survival from first treatment was 311 days (95% confidence interval 226-410 days [range 1-2134 days]). Thirty-two dogs received 15 Gy (median overall survival 311 days; 95% confidence interval [range 221-427 days]), and 12 received 24 Gy on three consecutive days (median overall survival 245 days, 95% confidence interval [range 2-626 days]). Twenty-nine dogs had hyperadrenocorticism (median overall survival 245 days), while 16 had nonfunctional masses (median overall survival 626 days). Clinical improvement was reported in 37/45 cases. Presumptive signs of acute adverse effects within 4 months of stereotactic radiotherapy were noted in 10/45, and most had improvement spontaneously or with steroids. Late effects versus tumor progression were not discernable, but posttreatment blindness (2), hypernatremia (2), and progressive neurological signs (31) were reported. There was no statistical difference in median overall survival for different protocols. Patients with nonfunctional masses had longer median overall survival than those with hyperadrenocorticism (P = 0.0003). Survival outcomes with stereotactic radiotherapy were shorter than those previously reported with definitive radiation, especially for dogs with hyperadrenocorticism.

Comparative evaluation of a novel, moderately hypofractionated radiation protocol in 56 dogs with symptomatic intracranial neoplasia

Background: Use of strongly hypofractionated radiation treatments in dogs with intracranial neoplasia did not improve outcomes and yielded increased rates of toxicosis.

Objectives: To evaluate safety and efficacy of a new, moderately hypofractionated radiation protocol of 10 × 4 Gy compared to a standard protocol.

Animals: Convenience sample of 56 client‐owned dogs with primary symptomatic brain tumors.

Methods: Retrospective observational study. Twenty‐six dogs were assigned to the control standard protocol of 20 × 2.5 Gy (group A) and 30 dogs to the new protocol of 10 × 4 Gy (group B), assigned on owners' informed consent. Statistical analysis was conducted under the “as treated” regime, using Kaplan‐Meier and Cox‐regression analysis. Treatment was delivered with technically advanced image‐guided radiation therapy. The 2 treatment groups were compared in terms of outcome and signs of toxicosis.

Results: Overall progression‐free interval (PFI) and overall survival (OS) time were favorable, with 663 (95%CI: 497;828) and 637 (95%CI: 403;870) days, respectively. We found no significant difference between the two groups: PFI for dogs in group A vs B was 608 (95%CI: 437;779) days and mean (median not reached) 863 (95%CI: 644;1083) days, respectively (P = .89), and OS for dogs in group A vs B 610 (95%CI: 404;816) and mean (median not reached) 796 (95%CI: 586;1007) days (P = .83).

Conclusion and Clinical Importance: In conclusion, 10 × 4 Gy is a safe and efficient protocol for treatment of primary intracranial neoplasia and future dose escalation can be considered.

A survey of stereotactic radiation therapy in veterinary medicine

Radiotherapy plays an important role in curative and palliative cancer treatment. As a novel radiation delivery technique, stereotactic radiotherapy utilizes three-dimensional-conformal treatment planning, high-precision beam delivery technology, and patient specific position verification to target tumors, often in one to five high-dose fractions. Currently, there is no consensus about best stereotactic radiotherapy practices in veterinary radiotherapy. The objective of this study was to document the breadth of perspectives, techniques, and applications of stereotactic radiotherapy in veterinary medicine. We conducted an online survey of American College of Veterinary Radiology members specializing in radiation oncology to assess how, when, and why stereotactic radiotherapy is being used. Both stereotactic radiotherapy users and nonusers completed the survey. The overall response and survey completion rates were 54% (67/123) and 87% (58/67), respectively. Overall, 55% of respondents reported providing stereotactic radiotherapy at their facility, with a median of 4.5 canine cases and one feline case per month. Delivery methods included C-arm linear accelerator with multi-leaf collimator, helical tomotherapy, and CyberKnife. Nonpituitary intracranial tumors, pituitary tumors, and sinonasal tumors were the most common cancers treated using stereotactic radiotherapy in both species. The most common fractionation scheme was three fractions of 10 Gy/fraction. The results of this survey suggest common availability of stereotactic radiotherapy in veterinary radiation facilities. These results provide valuable information regarding current stereotactic radiotherapy practices in veterinary medicine, and may provide an initial step toward standardizing methods and establishing consensus guidelines.

High dose hypofractionated frameless volumetric modulated arc radiotherapy is a feasible method for treating canine trigeminal nerve sheath tumors

The aim of this prospective pilot study was to evaluate the feasibility and effectiveness of curative intent high dose hypofractionated frameless volumetric modulated arc radiotherapy for treatment of canine trigeminal peripheral nerve sheath tumors. Client-owned dogs with a presumptive imaging-based diagnosis of trigeminal peripheral nerve sheath tumor were recruited for the study during the period of February 2010 to December 2013. Seven dogs were enrolled and treated with high dose hypofractionated volumetric modulated arc radiotherapy delivered by a 6 MV linear accelerator equipped with a micro-multileaf beam collimator. The plans were computed using a Monte Carlo algorithm with a prescription dose of 37 Gy delivered in five fractions on alternate days. Overall survival was estimated using a Kaplan-Meier curve analysis. Magnetic resonance imaging (MRI) follow-up examinations revealed complete response in one dog, partial response in four dogs, and stable disease in two dogs. Median overall survival was 952 days with a 95% confidence interval of 543-1361 days. Volumetric modulated arc radiotherapy was demonstrated to be feasible and effective for trigeminal peripheral nerve sheath tumor treatment in this sample of dogs. The technique required few sedations and spared organs at risk. Even though larger studies are required, these preliminary results supported the use of high dose hypofractionated volumetric modulated arc radiotherapy as an alternative to other treatment modalities.

Novel hyperthermia applicator system allows adaptive treatment planning: Preliminary clinical results in tumour-bearing animals

Hyperthermia (HT) as an adjuvant to radiation therapy (RT) is a multimodality treatment method to enhance therapeutic efficacy in different tumours. High demands are placed on the hardware and treatment planning software to guarantee adequately planned and applied HT treatments. The aim of this prospective study was to determine the effectiveness and safety of the novel HT system in tumour-bearing dogs and cats in terms of local response and toxicity as well as to compare planned with actual achieved data during heating. A novel applicator with a flexible number of elements and integrated closed-loop temperature feedback control system, and a tool for patient-specific treatment planning were used in a combined thermoradiotherapy protocol. Good agreement between predictions from planning and clinical outcome was found in 7 of 8 cases. Effective HT treatments were planned and verified with the novel system and provided improved quality of life in all but 1 patient. This individualized treatment planning and controlled heat exposure allows adaptive, flexible and safe HT treatments in palliatively treated animal patients.

Dynamic In Vivo Profiling of DNA Damage and Repair after Radiotherapy Using Canine Patients as a Model

Time resolved data of DNA damage and repair after radiotherapy elucidates the relation between damage, repair, and cell survival. While well characterized in vitro, little is known about the time-course of DNA damage response in tumors sampled from individual patients. Kinetics of DNA damage after radiotherapy was assessed in eight dogs using repeated in vivo samples of tumor and co-irradiated normal tissue analyzed with comet assay and phosphorylated H2AX (γH2AX) immunohistochemistry. In vivo results were then compared (in silico) with a dynamic mathematical model for DNA damage formation and repair. Maximum %DNA in tail was observed at 15–60 min after irradiation, with a rapid decrease. Time-courses of γH2AX-foci paralleled these findings with a small time delay and were not influenced by covariates. The evolutionary parameter search based on %DNA in tail revealed a good fit of the DNA repair model to in vivo data for pooled sarcoma time-courses, but fits for individual sarcoma time-courses suffer from the heterogeneous nature of the in vivo data. It was possible to follow dynamics of comet tail intensity and γH2AX-foci during a course of radiation using a minimally invasive approach. DNA repair can be quantitatively investigated as time-courses of individual patients by integrating this resulting data into a dynamic mathematical model.

Retrospective clinical study on outcome in cats with nasal planum squamous cell carcinoma treated with an accelerated radiation protocol

BACKGROUND

Cutaneous squamous cell carcinoma of the nasal planum in cats is a common indication for antitumor treatment such as external beam radiation therapy. Curative-intent radiation therapy has been described as a valuable treatment option, resulting in long and stable tumor control in these patients. The aim of the current study was to evaluate outcome and toxicity, as well as possible prognostic factors using an accelerated hypofractionated radiation therapy protocol. Cats with squamous cell carcinoma of the nasal planum treated with an accelerated radiation protocol (10 × 4.8 Gy, over one week) were retrospectively evaluated. Tumor- and treatment-associated variables were evaluated in respect to local control and survival.

RESULTS

Forty-four cats met the inclusion criteria for this study. All cats showed complete response to therapy. Median disease-free interval (DFI) for all cases was 916 days (95% CI: 456-1377). One- and two-year DFIs were 71% (95% CI: 56-86%) and 60% (95% CI: 43-77%). Of the tested variables, only tumor volume showed a tendency to influence DFI, with larger tumors having a 5.4 times greater risk of recurrence than the smaller ones (HR 1.33 (95% CI: 0.99-1.79), p = 0.054). Median overall survival (OS) was 902 days (95% CI: 862-942). One- and 2-year OSs were 79.3% (95% CI: 67.3-91.3) and 58.4% (95% CI: 42.8-74). Of the tested variables, again, only tumor volume influenced OS with larger tumors having a 6.3 times greater risk of dying than the smaller ones (HR 1.36 (95% CI: 1.07-1.73), p = 0.010). The acute and late toxicity profile was low and hence clinically acceptable.

CONCLUSIONS

Curative-intent radiation therapy with an accelerated fractionation schedule can be considered a safe, cosmetically superior treatment option for cutaneous squamous cell carcinomas of the nasal planum in cats, resulting in long and stable tumor control.

RETROSPECTIVE COMPARISON OF THREE-DIMENSIONAL CONFORMAL RADIATION THERAPY VS. PREDNISOLONE ALONE IN 30 CASES OF CANINE INFRATENTORIAL BRAIN TUMORS

Infratentorial tumors are relatively infrequent in dogs and a lack of data makes it difficult to offer prognostic information. Untreated, dogs with these neoplasms have shorter survival times than those with supratentorial tumors. The role of radiation therapy (RT) in the management of infratentorial tumors is poorly defined and tumoral/peritumoral swelling in this site is a potential cause of serious acute side effects. The aim of this retrospective, cohort study was to describe cases of infratentorial tumors treated with fractionated three-dimensional conformal RT (3D CRT) and glucocorticoids (GC), and compare outcomes and survival with dogs affected by tumors in the same location that received GC alone. Thirty patients with a MRI diagnosis of infratentorial tumors were recruited (15 received RT and GC and 15 GC alone). None had mentation changes at presentation. For both groups, MRI and medical records were reviewed; and factors associated with survival were evaluated with Kaplan-Meier product limit survival and Cox regression analysis. Overall median survival time (MST) was 294 days (95% CI 42-545). The MST in the RT group was 756 days (95% CI 209-1302) vs. 89 days (95% CI 34.7-143.3 days) for those dogs treated palliatively with GC alone. This difference was statistically significant (P = 0.001). No other factors (including neurological signs, MRI features, tumor volume and total RT dose) were statistically associated with survival in the RT group. This study suggests that 3D CRT offers a survival advantage for dogs with infratentorial tumors compared to GC alone, and significant complications are uncommon.

A complication probability planning study to predict the safety of a new protocol for intracranial tumour radiotherapy in dogs

Technical advances make it possible to deliver radiation therapy for canine intracranial tumours in fewer fractions, under the assumption of equivalent tumour control. With the aim of estimating the late toxicity risk profile for various tumour sizes and locations, the present paper evaluates the normal tissue complication probability (NTCP) values for the intracranial organs at risk. By making isoeffect calculations, a new 10-fraction radiation protocol was developed with the same tumour control probability (TCP) as a currently used 20-fraction standard protocol, and complication risk profiles for brain, brainstem and optic chiasm were modelled using a representative population of 64 dogs with brain tumours. For >59% of cases, the new 10-fraction protocol yielded an acceptable, low risk estimate of late toxicity (<10%). Our calculations suggest that it may be safe to treat small to intermediate-sized tumours that are neither located near the optic chiasm nor at the brainstem with 10 daily fractions of 4.35 Gy.

SINGLE INSTITUTION VARIABILITY IN INTENSITY MODULATED RADIATION TARGET DELINEATION FOR CANINE NASAL NEOPLASIA

Contouring variability is a significant barrier to the accurate delivery and reporting of radiation therapy. The aim of this descriptive study was to determine the variation in contouring radiation targets and organs at risk by participants within our institution. Further, we also aimed to determine if all individuals contoured the same normal tissues. Two canine nasal tumor datasets were selected and contoured by two ACVR-certified radiation oncologists and two radiation oncology residents from the same institution. Eight structures were consistently contoured including the right and left eye, the right and left lens, brain, the gross tumor volume (GTV), clinical target volume (CTV), and planning target volume (PTV). Spinal cord, hard and soft palate, and bulla were contoured on 50% of datasets. Variation in contouring occurred in both targets and normal tissues at risk and was particularly significant for the GTV, CTV, and PTV. The mean metric score and dice similarity coefficient were below the threshold criteria in 37.5-50% and 12.5-50% of structures, respectively, quantitatively indicating contouring variation. This study refutes our hypothesis that minimal variation in target and normal tissue delineation occurs. The variation in contouring may contribute to different tumor response and toxicity for any given patient. Our results also highlight the difficulty associated with replication of published radiation protocols or treatments, as even with replete contouring description the outcome of treatment is still fundamentally influenced by the individual contouring the patient.

Outcome in dogs with advanced (stage 3b) anal sac gland carcinoma treated with surgery or hypofractionated radiation therapy

Stage 3b anal sac gland carcinoma (ASGC) can be life-threatening. A surgical approach is not always possible or may be declined. Dogs with stage 3b ASGC treated with surgery or conformal radiation therapy (RT) with 8 × 3.8 Gy (total dose 30.4 Gy, over 2.5 weeks) were retrospectively evaluated. Patient characteristics, median progression-free interval (PFI) and median survival time (MST) were compared. Twenty-eight dogs were included; 15 underwent surgery, 13 underwent RT. At the time of presentation, 21% showed life-threatening obstipation and 25% showed hypercalcaemia. PFI and MST for surgery cases were 159 days (95% CI: 135-184 days) and 182 days (95% CI: 146-218 days), both significantly lower than for RT cases with 347 days (95% CI: 240-454 days) and 447 days (95% CI: 222-672 days), (P = 0.01, P = 0.019). Surgery as well as RT led to a fast relief of symptoms. PFI and survival of surgical patients were significantly inferior to that of a comparable patient group treated with conformal hypofractionated RT.

Treatment of MRI-Diagnosed Trigeminal Peripheral Nerve Sheath Tumors by Stereotactic Radiotherapy in Dogs

Background

Stereotactic radiotherapy (SRT) is an emerging technique for treating tumors in animals.

Objectives

To assess the outcome of dogs with suspected intracranial trigeminal nerve peripheral nerve sheath tumors (PNST) treated with SRT.

Animals

Eight dogs with presumptive PNST.

Methods

This was a retrospective study of dogs identified by searching UC Davis Veterinary Medical Teaching Hospital medical records for dogs treated with SRT for a presumed PNST. Presumptive diagnosis was based on magnetic resonance imaging. SRT was delivered in 3 dose fractions of 8 Gray (Gy) on consecutive days or every other day to a total dose of 24 Gy.

Results

Median disease‐specific survival was 745 days (range: 99–1375 days, n = 6). No signs of acute adverse effects of radiation treatment were recorded. Late radiation effects versus tumor progression could not be confirmed histopathologically because of few animals undergoing necropsy.

Conclusions and Clinical Importance

This study provides preliminary evidence that dogs with PNST benefit from SRT in terms of long‐term survival. The treatment appears to be well tolerated and requires fewer anesthetic events for animals compared to full‐course radiation.

OUTCOME OF DOGS WITH INTRANASAL LYMPHOMA TREATED WITH VARIOUS RADIATION AND CHEMOTHERAPY PROTOCOLS: 24 CASES

Tumors of the nasal cavity comprise approximately 1% of all neoplasms in dogs. Canine intranasal lymphoma is rare and reports evaluating the outcome of treatment are lacking. The goal of this observational, descriptive, multi-institutional study was to evaluate the overall median survival times (MSTs) in a group of dogs with intranasal lymphoma that were treated with irradiation and/or chemotherapy. Dogs meeting these inclusion criteria were retrospectively recruited from medical archives at multiple institutions. Eighteen cases of intermediate to high grade intranasal lymphoma and six cases of low-grade intranasal lymphoma were identified. The date of diagnosis, method of diagnosis, treatment received (radiation and/or chemotherapy protocols), and date of death were recorded. Kaplan-Meier survival analysis was performed on the intermediate to high grade group to calculate overall MST. Log-rank tests were performed to compare effects of treatment with radiation therapy ± chemotherapy and chemotherapy alone. Kaplan-Meier survival analysis was performed separately on the low-grade group. The overall MST was 375 days for the intermediate to high grade group. Cases treated with radiation ± chemotherapy had an MST of 455 days (n = 12) and those treated with chemotherapy alone (n = 6) had an MST of 157 days in the intermediate to high grade group. The MST was 823 days for the low-grade group. Results support the use of radiation therapy for treatment of canine intranasal lymphoma, however a randomized, controlled, clinical trial would be needed for more definitive recommendations. The role of adjunctive chemotherapy also may require further investigation.

HYPOFRACTIONATED RADIOTHERAPY FOR MACROSCOPIC CANINE SOFT TISSUE SARCOMA: A RETROSPECTIVE STUDY OF 50 CASES TREATED WITH A 5 × 6 GY PROTOCOL WITH OR WITHOUT METRONOMIC CHEMOTHERAPY

Wide surgical resection or a marginal/incomplete resection followed by full-course radiation therapy is the current standard of care for canine soft tissue sarcoma. The purpose of this retrospective, descriptive, bi-institutional study was to determine the effectiveness and toxicity of a hypofractionated 5 × 6 Gy protocol on macroscopic canine soft tissue sarcoma in terms of progression-free interval (PFI) and overall survival (OS), and to identify prognostic factors for patient outcome. Dogs with macroscopic soft tissue sarcoma irradiated with 5 × 6 Gy were eligible for the study. Progression-free interval and OS were compared with respect to different tumor and patient characteristics by the Kaplan-Meier method and multivariable Cox regression analysis. Fifty dogs with macroscopic disease were included. All dogs received the same radiation therapy protocol; part of the group (n = 20) received postradiation metronomic chemotherapy. Median PFI for all cases was 419 days (95% confidence interval (CI): 287-551) and median OS was 513 days (95% CI: 368-658). Dogs with tumors on the limbs had significantly longer PFI and OS, compared with head or trunk. Increasing tumor burden decreased OS. The addition of metronomic chemotherapy yielded a significantly longer OS (757 days (95% CI: 570-944) compared with dogs that did not receive systemic treatment (286 days (95% CI: 0-518), (P = 0.023)), but did not influence progression-free interval. Toxicity was low throughout all treatments. The 5 × 6 Gy radiation therapy protocol was well tolerated and provided long PFI and OS in dogs with macroscopic soft tissue sarcoma.

Osteonecrosis of the Jaws in Dogs in Previously Irradiated Fields: 13 Cases (1989-2014)

The aim of this report was to characterize osteonecrosis of the jaws (ONJ) in previously irradiated fields in dogs that underwent radiotherapy (RT) for oral tumors. Osteoradionecrosis of the jaw (ORNJ) was further defined as osteonecrosis in a previously irradiated field in the absence of a tumor. Thirteen dogs clinically diagnosed with 15 ONJ lesions were included in this retrospective case series. Medical records were reviewed for: breed, sex, weight, and age of the patient, tumor type, location in the oral cavity and size, location of the ONJ, time from RT to ONJ onset, known duration of the ONJ, and tumor presence. Where available, histological assessment of tissues obtained from the primary tumor, and tissues obtained from the ONJ lesion, was performed, and computed tomographic (CT) images and dental radiographs were reviewed. RT and other treatment details were also reviewed. Twelve dogs developed ONJ in the area of the previously irradiated tumor or the jaw closest to the irradiated mucosal tumor. Recurrence of neoplasia was evident at the time of ONJ diagnosis in five dogs. Time from RT start to ONJ onset varied from 2 to 44 months. In three cases, ORNJ developed after dental extractions in the irradiated field. Dental radiographs mostly revealed a moth-eaten pattern of bone loss, CT mostly revealed osteolysis, and histopathology was consistent with osteonecrosis. To conclude, development of ONJ/ORNJ following RT is a rare, but potentially fatal complication. Patients undergoing RT may benefit from a comprehensive oral and dental examination and treatment prior to RT.