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). Tumor 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 (DSS) 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 analyzed 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=0.04). 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. This article is protected by copyright. All rights reserved.

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.

A tribute to Philip Marcus and the development of the clonogenic assay

Philip Marcus (1927-2013), a prominent and celebrated virus and interferon researcher, was also influential to the field of radiobiology. His work as a graduate student led to the development of the first mammalian cell clonogenic assay. This tribute to Philip Marcus is written to memorialize this inventive scientist and share the stimulating story of how he and his mentors developed the clonogenic assay.

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

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

Potential for BioXmark liquid fiducial marker to improve identification of superficial component of canine oral tumors for computer-based radiation therapy planning

The objective of this study was to evaluate a novel liquid fiducial marker, BioXmark, to improve identification of the superficial component of oral tumors in dogs with computed tomography imaging. Liquid fiducial marker was injected in 6 patients at the visible and palpable extent of each tumor. Gross tumor volumes with and without BioXmark were compared in terms of volume and conformity using a Paddick conformity index, Dice similarity coefficient, and gross tumor volumes mismatch analysis. All patients showed an increase in gross tumor volumes defined by BioXmark compared with the conventionally identified post-contrast gross tumor volumes contours. Volumetric conformity and gross tumor volumes mismatch analysis of the superficial component of gross tumor volumes resulted in a median conformity index of 0.61 and median Dice similarity coefficient of 0.76. The superficial gross tumor volumes showed a median increase of 47% when BioXmark was used. This study demonstrated a potential utility to combining liquid fiducial markers to post-contrast computed tomography images for improved oral tumor localization and gross tumor volumes contouring for radiation therapy planning.

A Retrospective Study Evaluating the Outcomes of Conventionally Fractionated Radiation Therapy as a Treatment for Infiltrative Lipomas in Twenty-One Dogs

Infiltrative lipomas represent a subcategorisation of rarer, potentially more aggressive, lipoma-related neoplasms. Twenty-one dogs treated with conventionally fractionated radiotherapy (CFRT) for infiltrative lipomas were included in this retrospective study. One patient had no prior surgical excision, 11 patients had one prior surgery and 9 patients had two or more surgeries prior to CFRT. Five patients (24%) had microscopic disease and 16 patients (76%) had macroscopic disease prior to treatment. A complete response or no regrowth was seen in 10 patients (48%), stable disease in 6 patients (29%) and progressive disease or regrowth in 5 patients (24%). Response to treatment of macroscopic tumours was significantly different between dogs that had one prior surgery versus two or more (p = 0.01). Dogs with a single surgery were most likely to result in stable disease compared with dogs with two or more surgeries resulting in a complete response. The dog without surgery developed progressive disease at 211 days, dogs with one surgery had a median progression or recurrence at 1369 days and dogs with two or more surgeries developed progression or recurrence at 826 days (p = 0.04). Twelve dogs were alive at the time of analysis. Overall median survival time (MST) was 1694 days. The prior number of surgeries did not significantly affect MST. While survival time is comparable to previous reports, the number of patients with progressive disease or recurrence of previous microscopic disease requires more investigation into the most appropriate protocol, dose and treated field size.

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 , PTV_{soft tissue} , and PTV_bone 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 (D_mean ) to PTV and PTV_{soft tissue} by 0.9% and 0.5%, respectively (both P < 0.001). Collapsed cone convolution overestimated D_mean to PTV_bone by 3% (P < 0.001). Collapsed cone convolution underestimated the near-maximum dose (D₂ ) to PTV_air 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.

Saline Lavage for Sampling of the Canine Nasal Immune Microenvironment

Evaluating the local immune microenvironment of the canine nasal cavity can be important for investigating normal tissue health and disease conditions, particularly those associated with local inflammation. We have optimized a technique to evaluate the local nasal immune microenvironment of dogs via serial nasal lavage. Briefly, with dogs under anesthesia and positioned in sternal recumbency, prewarmed sterile saline is flushed into the affected nostril using a flexible soft rubber catheter. The fluid backflow is collected into conical tubes, and this process is repeated. The fluids containing dislodged cells and proteins are pooled, and the pooled nasal lavage samples are filtered through a cell strainer to remove large debris and mucus. Samples are centrifuged and the cell pellets are isolated for analysis. Once the samples have been processed, analyses that may follow nasal lavage include flow cytometry, transcriptomic analysis of cells via bulk or single-cell RNA seq, and/or quantification of cytokines present in the lavage fluid.

3D-printed bolus improves dose distribution for veterinary patients treated with photon beam radiation therapy

Commercial bolus is frequently used to increase dose at the patient's surface for superficial radiotherapy; however, uneven surfaces can create air gaps and discrepancies between prescribed and delivered dose. The purpose of this study was to determine if a customizable, 3D-printed bolus would improve dosimetry compared with a commercial bolus. For each patient, a planned bolus was generated within planning software, then created with 3D-printing. The treatment plan was recalculated with each bolus in situ. When evaluating tumor volumes at prescription, the 3D-printed bolus was closer to prescription compared to the commercial bolus. There was a significant difference in air gaps in patients receiving radiotherapy to the head (P < 0.001) but the difference was not significant for air gaps in caudal body sites (P = 0.05). Overall, the 3D-printed bolus resulted in reduced air gaps, dosimetry closer to prescription, and should be considered for superficial treatment areas of high irregularity.

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.

Investigation of Gastrointestinal Toxicities Associated with Concurrent Abdominal Radiation Therapy and the Tyrosine Kinase Inhibitor Sunitinib in a Mouse Model

Tyrosine kinase inhibitors (TKIs) may be combined with radiation therapy (RT) to enhance tumor control; however, increased incidences of gastrointestinal (GI) toxicity have been reported with this combination. We hypothesize that toxicity is due to compromised intestinal healing caused by inhibition of vascular repair and proliferation pathways. This study explores underlying tissue toxicity associated with abdominal RT and concurrent sunitinib in a mouse model. Four groups of CD-1 mice were treated with 12 Gy abdominal RT, oral sunitinib, abdominal RT + sunitinib, or sham treatment. Mice received oral sunitinib or the vehicle via gavage for 14 days. On day 7, mice were irradiated with 12 Gy abdominal RT or sham treated. Mice were euthanized on day 14 and intestinal tract was harvested for semiquantitative histopathologic evaluation and immunohistochemical quantification of proliferation (Ki67) and vascular density (CD31). Non-irradiated groups had stable weights while abdominal irradiation resulted in weight loss, with mice receiving RT + SUN having greater weight loss than mice receiving RT alone. Semiquantitative analysis showed significant increases in inflammation in irradiated groups. The difference in the density of CD31+ cells was significantly increased in RT alone compared to SUN alone. Ki67+ density was not significant. In summary, we identify a lack of angiogenic response in irradiated GI tissues when abdominal RT is combined with a TKI, which may correlate with clinical toxicities seen in canine and human patients receiving combined treatment.

Case report: Chronic disseminated intravascular coagulopathy with concurrent paraneoplastic secondary hyperfibrinolysis in a dog with metastatic nasal adenocarcinoma

In human medicine, hemostatic disorders such as thrombocytopenia, hyperfibrinolysis, and disseminated intravascular coagulopathy (DIC) have been associated with many cancers. Acute hemorrhage secondary to hyperfibrinolysis has been predominantly reported with prostatic adenocarcinoma in human patients. To the author's knowledge, severe bleeding due to paraneoplastic hyperfibrinolysis has not yet been reported in veterinary medicine. The case involves an 8-year-old neutered male Border Collie who was evaluated for progressive and recurrent epistaxis, having a history of 1 year of treatment for metastatic nasal adenocarcinoma. A progressive and severe coagulopathy thought to be related to the known cancer was diagnosed. Advanced coagulation testing was consistent with a chronic DIC and secondary hyperfibrinolysis. Throughout 1 week of hospitalization, the dog was treated with multiple blood products, vitamin K1, and anti-fibrinolytic medications. While the dog was initially discharged home, the dog re-presented the following day and was humanely euthanized due to a perceived poor quality of life. Post-mortem analysis revealed a histopathologic diagnosis of disseminated adenocarcinoma. In dogs with disseminated nasal adenocarcinoma that are experiencing severe bleeding, paraneoplastic secondary hyperfibrinolysis should be considered as a differential. Knowing this association could help guide treatment recommendations for optimal patient management.

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.