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.

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.

Evaluation of variables associated with outcomes in 41 dogs with incompletely excised high-grade soft tissue sarcomas treated with definitive-intent radiation therapy with or without chemotherapy.

OBJECTIVE: To evaluate potential prognostic indicators for local recurrence, distant metastasis, and survival time in dogs with incompletely excised high-grade soft tissue sarcomas (HGSTSs), as defined by a mitotic index ≥ 9, that underwent definitive-intent radiation treatment (RT; ≥ 48 Gy total dose) with or without adjuvant chemotherapy. ANIMALS: 41 client-owned dogs with HGSTSs treated with surgical resection followed by definitive-intent RT between January 1, 2000, and December 31, 2016. PROCEDURES: Medical records were reviewed retrospectively, and data were collected. The Kaplan-Meier method was used to evaluate the overall survival time (OST) of dogs and time to progression (TTP) of disease, starting from the first day of RT. The Cox proportional hazards model was used to analyze the impact of results for several variables on OST and TTP. RESULTS: The median OST was 981 days, with 1-, 3-, and 5-year survival rates of 85%, 43%, and 18%, respectively. The median TTP was not reached; however, the mean TTP was 1,581 days. Ten of the 41 (24%) dogs developed metastasis, and 8 (20%) developed local recurrence. Sixteen of the 41 dogs received chemotherapy. The hazard of disease progression over the study period increased as the mitotic index (hazard ratio [HR], 1.115) or duration of RT (HR, 1.427) increased. The hazard of death over the study period increased as the RT duration (HR, 1.372) or surgical scar length (HR, 1.272) increased. CONCLUSIONS AND CLINICAL RELEVANCE: Although adjuvant chemotherapy was not associated with improved survival time in dogs of the present study, results indicated that improved OST and TTP could be achieved through strict adherence to the prescribed irradiation schedule and avoidance of unnecessary prolongation of the course of RT.

Effects of ocular surface strontium-90 beta radiotherapy in dogs latently infected with canine herpesvirus-1.

Latent canine herpesvirus-1 (CHV-1) infections are common in domestic dogs, but stimuli causing viral reactivation and recrudescent disease are poorly understood. Immunosuppressive pharmaceuticals are currently the only experimentally established triggers for recurrent ocular CHV-1 infection in dogs; however, ocular CHV-1 shedding has been reported clinically following strontium-90 beta radiotherapy of the ocular surface and it has been speculated that radiotherapy can directly induce viral reactivation. Strontium-90 is used as a beta radiation source for the treatment of a variety of neoplastic and immune-mediated canine ocular surface diseases. In the present study, the effects of ocular surface strontium-90 beta radiotherapy in dogs latently infected with CHV-1 were evaluated. Ten mature dogs with experimentally induced latent CHV-1 infections were randomly divided into two groups: one group received a single fraction 50 Gy radiation dose in one application from a strontium-90 ophthalmic applicator and the second group received sham radiotherapy. Dogs were then monitored for 45 days for recurrent ocular CHV-1 infection using clinical and virological outcome measures. Clinical ophthalmic examinations, ocular sample CHV-1 PCR assays, and serum CHV-1 virus neutralizing antibody assays were performed at specified intervals. No abnormalities suggestive of recurrent CHV-1 ocular disease were observed on clinical examination in any dog during the study. Ocular viral shedding was not detected and CHV-1 virus neutralizing titers remained stable in all dogs. A single fraction 50 Gy radiation dose administered to the ocular surface by strontium-90 beta radiotherapy did not result in detectable recurrent ocular CHV-1 infection in mature dogs with experimentally induced latent infection.

A survey of veterinary radiation facilities in 2010.

A survey of veterinary radiation therapy facilities in the United States, Canada, and Europe was done in 2010, using an online survey tool, to determine the type of equipment available, radiation protocols used, caseload, tumor types irradiated, as well as other details of the practice of veterinary radiation oncology. The results of this survey were compared to a similar survey performed in 2001. A total of 76 facilities were identified including 24 (32%) academic institutions and 52 (68%) private practice external beam radiation therapy facilities. The overall response rate was 51% (39/76 responded). Based on this survey, there is substantial variation among facilities in all aspects ranging from equipment and personnel to radiation protocols and caseloads. American College of Veterinary Radiology boarded radiation oncologists direct 90% of the radiation facilities, which was increased slightly compared to 2001. All facilities surveyed in 2010 had a linear accelerator. More facilities reported having electron capability (79%) compared to the 2001 survey. Eight facilities had a radiation oncology resident, and academic facilities were more likely to have residents. Patient caseload information was available from 28 sites (37% of radiation facilities), and based on the responses 1376 dogs and 352 cats were irradiated in 2010. The most frequently irradiated tumors were soft tissue sarcomas in dogs, and oral squamous cell carcinoma in cats.

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

Surrounding a shift toward evidence-based medicine and widespread adoption of reporting guidelines such as the Consolidated Standards of Reporting Trials (CONSORT) statement, there has been a growing body of literature evaluating the quality of reporting in human and veterinary medicine. These reviews have consistently demonstrated the presence of substantive deficiencies in completeness of reporting. The purpose of this study was to assess the current status of reporting in veterinary radiation oncology manuscripts in regards to treatment planning methods, dose, and delivery and to introduce a set of reporting guidelines to serve as a standard for future reporting. Forty-six veterinary radiation oncology manuscripts published between 2005 and 2010 were evaluated for reporting of 50 items pertaining to patient data, treatment planning, radiation dose, delivery of therapy, quality assurance, and adjunctive therapy. A mean of 40% of checklist items were reported in a given manuscript (range = 8-75%). Only 9/50 (18%) checklist items were reported in > or = 80% manuscripts. The completeness of reporting was best in regards to a statement of prescription radiation protocol (91-98% reported) and worst in regards to specification of absorbed dose within target volumes and surrounding normal tissues (0-6% reported). No manuscripts met the current International Commission of Radiation Units and Measurements (ICRU) dose specification recommendations. Incomplete reporting may stem from the predominance of retrospective manuscripts and the variability of protocols and equipment in veterinary radiation oncology. Adoption of reporting guidelines as outlined in this study is recommended to improve the quality of reporting in veterinary radiation oncology.

Evaluation of anti-human leukocyte antigen-DR monoclonal antibody therapy in spontaneous canine lymphoma.

A pilot study of anti-human leukocyte antigen (HLA)-DR monoclonal antibody (mAb) in dogs with lymphoma was undertaken to verify the suitability of a canine model to address therapeutically relevant endpoints prior to a full trial in dogs, and ultimately human investigation. In vitro studies demonstrated that L243, a murine IgG1 anti-HLA-DR, binds to normal and malignant canine lymphocytes and induces apoptosis in canine lymphoma cells. Moreover, L243 was administered safely to normal dogs and dogs with lymphoma, and bound to malignant cells in nodal tissue. Preliminary evidence of transient disease stabilization was observed in a subset of dogs with advanced-stage lymphoma following L243 immunotherapy. hL243γ4P (IMMU-114), a humanized IgG4 anti-HLA-DR, currently under evaluation preclinically for human trials, was also shown to bind malignant canine lymphocytes, and safety and pharmacokinetic data from the administration of IMMU-114 to normal dogs indicate similar behavior to L243 in these assessments. These findings provide a rationale for the use of dogs with lymphoma in safety and efficacy evaluations of anti-HLA-DR mAbs for both veterinary and human applications.

Evaluation of the protective effects of all-trans-astaxanthin on canine osteosarcoma cell lines.

OBJECTIVE: To determine the effects of the antioxidant astaxanthin on growth of canine osteosarcoma cells with and without concurrent chemotherapeutic or irradiation insult. SAMPLE POPULATION: Cells from 3 established canine osteosarcoma cell lines (D17, OS 2.4, and HMPOS). PROCEDURES: Growth-curve kinetics and cell cytotoxic effects were assessed by means of various treatment combinations and a 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assay. Western blotting was performed to examine previously identified signaling pathways that astaxanthin reportedly affects. Additionally, cell-cycle kinetic evaluations, soft agar colony-forming assays, and antioxidant assays were performed to better understand the effect of astaxanthin on cell growth and function. RESULTS: Exposure to astaxanthin alone resulted in a mild to pronounced attenuation of cell proliferation in vitro, depending on the cell line, and did not interfere with the cell-death response to doxorubicin, irradiation, or peroxide-mediated insult. In some instances, astaxanthin acted in an additive fashion to augment cell death. Astaxanthin exposure increased the antioxidant potential of cells, whereas peroxide-mediated cell stress increased the antioxidant potential to the same degree as astaxanthin exposure or greater. No dramatic changes in phosphorylation of protein kinase B or upregulation of connexin 43 were detected. CONCLUSIONS AND CLINICAL RELEVANCE: Findings suggested that astaxanthin administration may be beneficial in treatment of dogs for osteosarcoma. Its actions as an antioxidant did not improve osteosarcoma cell survival during chemotherapeutic or irradiation insults, warranting further research into this natural compound as an adjuvant, antiproliferative treatment for osteosarcoma in dogs.

Production of donor-derived sperm after spermatogonial stem cell transplantation in the dog.

Spermatogonial stem cell transplantation (SSCT) offers unique approaches to investigate SSC and to manipulate the male germline. We report here the first successful performance of this technique in the dog, which is an important model of human diseases. First, we investigated an irradiation protocol to deplete endogenous male germ cells in recipient testes. Histologic examination confirmed >95% depletion of endogenous spermatogenesis, but retention of normal testis architecture. Then, 5-month-old recipient dogs (n=5) were focally irradiated on their testes prior to transplantation with mixed seminiferous tubule cells (fresh (n=2) or after 2 weeks of culture (n=3)). The dogs receiving cultured cells showed an immediate allergic response, which subsided quickly with palliative treatment. No such response was seen in the dogs receiving fresh cells, for which a different injection medium was used. Twelve months post-injection recipients were castrated and sperm was collected from epididymides. We performed microsatellite analysis comparing DNA from the epididymal sperm with genomic DNA from both the recipients and the donors. We used six markers to demonstrate the presence of donor alleles in the sperm from one recipient of fresh mixed tubule cells. No evidence of donor alleles was detected in sperm from the other recipients. Using quantitative PCR based on single nucleotide polymorphisms (SNPs), about 19.5% of sperm were shown to be donor derived in the recipient. Our results demonstrate the first successful completion of SSCT in the dog, an important step toward transgenesis through the male germline in this valuable biomedical model.

Use of surgical hemoclips in radiation treatment planning.

The goal of this prospective study was to determine the effect of hemoclip use on the size of radiation treatment fields based on a 3-cm margin around a surgical incision alone (field setup 1) vs. a 3-cm margin around the surgical incision plus hemoclips (field setup 2). Forty-seven dogs that underwent surgical resection of a total of 55 soft tissue masses had surgical hemoclips placed at the time of surgery and orthogonal radiographs made immediately postoperatively. Radiation treatment field simulation was done and field areas measured. Additional determinations included number of hemoclips outside of the radiation treatment field based on a margin around the incision alone, hemoclip distance from the incision, and association between incision length and greatest distance of hemoclips from the incision. There was a significant difference in radiation treatment field size using information regarding the location of hemoclips in conjunction with the surgical scar compared with the surgical scar alone for truncal (P = 0.0003) vs. extremity tumors (P = 0.087). In simulating radiation treatment fields hemoclips were located outside of field setup 1 for the majority of tumors (79%) resected from the trunk but only in a minority of tumors (10.7%) resected from extremity sites. The findings from this study suggest that surgical hemoclips have potential utility in simulation of radiation treatment fields in the postoperative setting.

Portal radiography in veterinary radiation oncology: options and considerations.

Portal radiography involves the acquisition of images to visualize radiation treatment field(s) using the radiation treatment source. The standard has been the use of film-based systems with improvements over the years in film-screen technology providing near diagnostic quality images. More recent advances have included the development of digital systems with such notable improvements including ability to window/level images to enhance viewing and readability, and significant shortening of the time required to acquire images.

Comparison of 3 protocols for treatment after induction of remission in dogs with lymphoma.

BACKGROUND: The optimal treatment after inducing complete remission (CR) in dogs with lymphoma has not been established. HYPOTHESIS: After inducing CR with L-asparaginase, vincristine, cyclophosphamide, doxorubicin, prednisone (L-CHOP); consolidation with either half-body radiation therapy (HBRT); or lomustine (CCNU) and mechlorethamine, vincristine, procarbazine, prednisone (MOPP) would improve first remission duration compared with continuing a CHOP-based protocol for an additional 4 months. ANIMALS: Dogs with stage III-V lymphoma. METHODS: Prospective clinical trial in which dogs initially were treated with an 8-week induction protocol that consisted of L-CHOP. Dogs in CR after induction were then allocated to 1 of 2 consolidation arms. A chemotherapy consolidation arm consisted of 2 treatments with CCNU and 1 cycle of MOPP. A HBRT arm consisted of 2 sequential 8.0-Gy fractions to the cranial and caudal half-body separated by 30 days. Vincristine was given between fractions. Results of the consolidation arms also were compared with a historical group treated with the same 8-week induction protocol followed by CHOP therapy until week 24. RESULTS: Overall, 67% of the dogs were in CR after 8 weeks of induction chemotherapy and were compared. Fifty-two dogs were in the historical arm, 23 in the CCNU/MOPP arm, and 27 in the HBRT arm. No difference in first remission duration was found among groups. Median first remission duration for the historical, CCNU/MOPP, and HBRT arms were 307, 274, and 209 days, respectively (P = .28). Overall second CR rate was 82% and was not different among groups (all P > or = .58). Overall remission duration (P = .28) and survival time (P = .48) were not different among groups. CONCLUSIONS AND CLINICAL IMPORTANCE: Consolidation with either CCNU/MOPP or HBRT showed no advantage over a standard CHOP-based protocol.

Sodium iodide I 131 treatment of dogs with nonresectable thyroid tumors: 39 cases (1990-2003).

OBJECTIVE: To determine outcome for dogs with nonresectable thyroid carcinomas treated with sodium iodide I 131 and identify factors associated with outcome. DESIGN: Retrospective case series. Animals-39 dogs. PROCEDURES: A definitive or presumptive diagnosis of thyroid tumor was made on the basis of cytologic or histologic examination, abnormal accumulation of sodium pertechnetate Tc 99m during scintigraphy, or both, and dogs were treated with sodium iodide I 131. Dogs with cervical thyroid tumors were evaluated 3 to 6 weeks after 131I therapy, and residual tumor was resected when feasible. RESULTS: Prior to 131I therapy, 32 dogs had a solitary mass and 7 had metastases; 21 were hyperthyroid, 16 were euthyroid, and 2 were hypothyroid. Median survival time for dogs with local or regional tumors (ie, stage II or III) was significantly longer (839 days) than median survival time for dogs with metastasis (366 days). Tumor site (cervical vs ectopic), dose of sodium iodide I 131, age, body weight, treatment (131I therapy alone vs 131I therapy followed by surgery), and serum T4 concentration prior to 131I therapy were not significantly associated with survival time. Three dogs died of radioiodine-associated myelosuppression within 3 months after treatment, but no specific factor associated with development of toxicosis was identified. CONCLUSIONS AND CLINICAL RELEVANCE: Results suggested that 131I therapy may result in prolonged survival times in dogs with nonresectable thyroid tumors, regardless of serum thyroxine concentration prior to treatment. Dogs undergoing 131I therapy should be monitored for signs of bone marrow suppression.

Phase I and pharmacokinetic evaluation of the combination of orally administered docetaxel and cyclosporin A in tumor-bearing dogs.

OBJECTIVE: To determine the maximum tolerated dose and characterize the pharmacokinetic disposition of an orally administered combination of docetaxel and cyclosporin A (CSA) in dogs with tumors. ANIMALS: 16 client-owned dogs with metastatic or advanced-stage refractory tumors. PROCEDURES: An open-label, dose-escalation, single-dose, phase I study of docetaxel administered in combination with a fixed dose of CSA was conducted. Docetaxel (at doses of 1.5, 1.625, or 1.75 mg/kg) and CSA (5 mg/kg) were administered concurrently via gavage twice during a 3-week period. Plasma docetaxel concentrations were quantified by use of high-performance liquid chromatography, and pharmacokinetic disposition was characterized by use of noncompartmental analysis. Dogs' clinical signs and results of hematologic and biochemical analyses were monitored for evidence of toxicosis. RESULTS: No acute hypersensitivity reactions were observed after oral administration of docetaxel. Disposition of docetaxel was dose independent over the range evaluated, and pharmacokinetic variables were similar to those reported in previous studies involving healthy dogs, with the exception that values for clearance were significantly higher in the dogs reported here. The maximum tolerated dose of docetaxel was 1.625 mg/kg. Gastrointestinal signs of toxicosis were dose limiting. CONCLUSIONS AND CLINICAL RELEVANCE: The absence of myelosuppression suggested that the docetaxel-CSA combination may be administered more frequently than the schedule used. Further studies are warranted to evaluate combination treatment administered on a biweekly schedule in dogs with epithelial tumors.

Evaluation of strontium 90 irradiation in treatment of cutaneous mast cell tumors in cats: 35 cases (1992-2002).

OBJECTIVE: To determine the efficacy of strontium 90 beta irradiation in the management of cutaneous mast cell tumors (CMCTs) in cats. STUDY DESIGN: Retrospective case series. ANIMALS: 35 client-owned cats with CMCTs. PROCEDURE: Medical records of cats with CMCTs in which tumors were radiated by use of a strontium 90 ophthalmic applicator from 1992 to 2002 were reviewed. Cats were included if CMCT was diagnosed, there were no other sites of MCT involvement at the time of treatment, and records contained adequate follow-up information to permit retrospective assessment of local tumor control. RESULTS: 54 tumors in 35 cats were treated with a median dose of 135 Gy of strontium 90 beta irradiation, resulting in local tumor control in 53 of 54 (98%) tumors with a median follow-up time of 783 days after treatment. Median survival time was 1,075 days. Adverse effects of treatment appeared to be infrequent and of mild severity. CONCLUSIONS AND CLINICAL RELEVANCE: Results indicated that strontium 90 beta irradiation resulted in long-term tumor control and should be considered an effective alternative to surgical resection in management of CMCTs in cats.

Veterinary radiation therapy: review and current state of the art.

Veterinary radiation oncology became a recognized specialty in 1994. Radiation therapy is an important component of a multimodality approach to treating cancer in companion animals. It is important to understand the many aspects of radiation, including the equipment used in external beam radiation therapy, the basic mechanism of action of ionizing radiation, the results of irradiating various histopathological types of tumors, as well as the associated potential acute and late side effects of radiation. A comprehensive review of radiation therapy is timely and provides information for clients on cancers that may benefit from external beam radiation therapy.

Recipient preparation and mixed germ cell isolation for spermatogonial stem cell transplantation in domestic cats.

The loss of genetic diversity poses a serious threat to the conservation of endangered species, including wild felids. We are attempting to develop spermatogonial stem cell transplantation in the cat as a tool to preserve and propagate male germ-plasm from genetically valuable animals, be they threatened wild species or lines of cats used as models for inherited diseases. In this study, we investigated the use of local external beam radiation treatment to deplete the endogenous germ cells of male domestic cats, a step necessary to prepare them for use as recipients for transplantation. Testes of 5-month-old domestic cats were irradiated with a fractionated dose of 3 Gy per fraction for 3 consecutive days. These cats were castrated at 2, 4, 8, 16, and 32 weeks posttreatment, and progress of spermatogenesis was evaluated histologically and compared against age-matched controls. Even at the latest time points, less than 10% of tubules contained germ cells at any stage of meiosis, showing the efficacy of this protocol. In addition, male germ cells were isolated from the testes of domestic cats using a 2-step enzymatic dissociation to establish a protocol for the preparation of donor cells. The presence and viability of spermatogonia within this population were demonstrated by successful transplantation into, and colonization of, mouse seminiferous tubules. The success of these protocols provides a foundation to perform spermatogonial stem cell transplantation in the domestic cat.

A survey of veterinary radiation facilities in the United States during 2001.

A survey of veterinary radiation therapy facilities in the United States was done in 2001 to determine the type of equipment available, radiation protocols used, case load, tumor types irradiated, as well as other details of the practice of radiation oncology. A total of 42 sites were identified and included 17 (40%) academic institutions, and 25 (60%) private practice external beam radiation facilities. The overall response rate was 79% (33/42 responded). Based on this survey there is substantial variation between facilities in all aspects ranging from equipment and personnel to radiation protocols and caseloads. American College of Veterinary Radiology boarded radiation oncologists direct 76% of the radiation facilities at academic institutions and 60% of the private practice facilities. Three facilities had orthovoltage radiation units only, and 30 facilities had mega-voltage equipment: cobalt 60 or linear accelerator. A total of 18 facilities had linear accelerators with three of these off site at a human radiation facility. Patient load information was available from 31 sites (74% of the radiation facilities in the United States), and based on the responses 2790 dogs and 1081 cats were irradiated in 2001. Canine mast cell tumors were the most frequently irradiated tumor. This represents the first survey of veterinary radiation facilities in the United States and provides information on the specialty of veterinary radiation oncology.

Malignant tumor formation in dogs previously irradiated for acanthomatous epulis.

In this retrospective study of 57 dogs irradiated for oral acanthomatous epulis, 2 (3.5%) dogs developed a second tumor (sarcoma, osteosarcoma) in the radiation treatment field at 5.2 and 8.7 years after the end of radiation therapy. As opposed to previous reports, no second epithelial tumors developed in the radiation treatment field. There is a risk of radiation-induced carcinogenesis, but it appears that it is a relatively low risk and an event that occurs years after radiation therapy. Radiation-induced tumors are of more concern in younger dogs that undergo radiation therapy for tumors that are radioresponsive, such as acanthomatous epulis, where long-term survival is expected. The only statistically significant variable in the survival analysis was age, with dogs less than 8.3 years old having a significantly longer median overall survival (2322 days) than dogs older than 8.3 years (1106 days; P<0.0001).

Postoperative assessment of surgical clip position in 16 dogs with cancer: a pilot study.

Metallic hemoclips or surgical staples were inserted in 16 tumor-bearing dogs at the time of surgical resection of the tumor. Orthogonal radiographs were taken immediately postoperatively and after wound healing to visualize the location and number of hemoclips or metallic staples. A shift in hemoclip/staple position was identified in nine dogs, mainly from positioning during radiography. In three dogs, an absolute shift in marker position was identified. Based on this study, it appears that the placement of surgical clips is potentially useful in identifying the tumor bed, which may be of benefit in establishing radiation treatment fields.