[Not Available]

Mason SL, Pittaway C, Gil BP, Russak OM, Westlake K, Berlato D, Benoit J, Morris J, Dobson JM. 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. Vet Intern Med. 2021 Nov;35(6):2853–2864.

Radiotherapie wird häufig zur post-operativen Anschlussbehandlung caniner kutaner bzw. subkutaner Mastzelltumoren eingesetzt. Vor allem bei inkomplett resezierten Tumoren oder solchen, bei denen die Resektionsgrenzen in der mikroskopischen Beurteilung nah an den Tumorrädern verlaufen gehört die adjuvante Bestrahlung zu den wichtigen Säulen der Therapie. Demgegenüber steht, dass die Datenlage zu verschiedenen Strahlenprotokollen und deren Behandlungsergebnissen sowie Verträglichkeit verbesserungswürdig erscheint. Ziel dieser Studie war es daher die Effektivität einer post-operativen Radiotherapie bei Mastzelltumoren der Kutis und Subkutis nach mikroskopisch inkompletter Resektion sowie deren Toxizität zu evaluieren.

Non-injection-site soft tissue sarcoma in cats: outcome following adjuvant radiotherapy

OBJECTIVES

Biological behaviour and treatment options of non-injection-site soft tissue sarcomas (nFISS) in cats are less well understood than in dogs. The aim of this retrospective study was to assess the outcomes of cats with nFISS following treatment with adjuvant radiotherapy.

METHODS

The medical records of cats with soft tissue sarcomas in locations not associated with, and histology reports not suggestive of, injection-site sarcomas were reviewed. All cats underwent adjuvant radiotherapy, either hypofractionated (32-36 Gy delivered in weekly 8-9 Gy fractions) or conventionally fractionated (48-54 Gy delivered in 16-18 3 Gy fractions) to microscopic disease.

RESULTS

In total, 18 cats were included in the study, 17 with extremity nFISS and one with facial nFISS. Nine received radiotherapy after a single surgery and nine after multiple surgeries for recurrent nFISS. Eight cats were treated with a hypofractionated protocol and 10 with a conventionally fractionated protocol. The median follow-up time was 540 days (range 51-3317 days). The tumour recurred in eight (44.4%) cats following adjuvant radiotherapy; it recurred in three (37.5%) cats following a hypofractionated protocol and in five (50%) cats following a conventionally fractionated protocol. The overall median progression-free interval (PFI) for 17/18 cats was 2748 days, while the median PFI for the 7/8 cats with recurrence was 164 days. The recurrence for one cat was reported, but the date was unknown and it was therefore censored from these data. When stratifying based on the protocol, the median PFI for hypofractionated and conventionally fractionated protocols was 164 days and 2748 days, respectively. Statistically, there was no significant difference between the two protocols (P = 0.636).

CONCLUSIONS AND RELEVANCE

Adjuvant radiotherapy resulted in good long-term tumour control in 12/18 cats with nFISS. Further studies in larger populations are required to assess the significance of radiation dose and fractionation on tumour control and the effect of multiple surgeries prior to initiation of radiotherapy on outcome.

Diagnosis and treatment of a periocular myxosarcoma in a bearded dragon (Pogona vitticeps)

A 5-year-old male Australian bearded dragon (Pogona vitticeps) was presented with a 2-month history of a periocular mass. The clinical evaluation included a physical examination, hematology, biochemistry, and radiographs. The mass was treated surgically and diagnosed as myxosarcoma. Strontium-90 plesiotherapy was attempted, but the mass recurred 5 mo later.

[Quality of life in primary and adjuvant veterinary radiation therapy. An owner survey]

OBJECTIVE

External radiation therapy has been available since 2011 for small animals at the University of Munich. The aim of the study was to evaluate the quality of life of treated pets and the satisfaction of their owners.

MATERIAL AND METHODS

The questionnaire was sent to the owners of all the pets (n = 91) that had undergone primary or adjuvant radiotherapy at the Clinic of Small Animal Medicine, University of Munich, since April 2011.

RESULTS

The questionnaire was returned by 68 (74.7%) owners. According to their assessment, the quality of life improved in 41 cases (60.3%) after treatment where- as in 13 patients (19.1%) a decline was described. The majority of owners (88.2%) would have decided for repeated radiation therapy.

CONCLUSION

Improvement of the animals' quality of life is related to a high satisfaction (83.8%) of the owners (p = 0.003) and their positive attitude towards radiotherapy (p = 0.027).

CLINICAL RELEVANCE

Analyses showed that for these owners, the treatment was a worthwhile therapy despite it requiring much time and money.

Non-thermal irreversible electroporation (N-TIRE) and adjuvant fractionated radiotherapeutic multimodal therapy for intracranial malignant glioma in a canine patient

Non-thermal irreversible electroporation (N-TIRE) has shown promise as an ablative therapy for a variety of soft-tissue neoplasms. Here we describe the therapeutic planning aspects and first clinical application of N-TIRE for the treatment of an inoperable, spontaneous malignant intracranial glioma in a canine patient. The N-TIRE ablation was performed safely, effectively reduced the tumor volume and associated intracranial hypertension, and provided sufficient improvement in neurological function of the patient to safely undergo adjunctive fractionated radiotherapy (RT) according to current standards of care. Complete remission was achieved based on serial magnetic resonance imaging examinations of the brain, although progressive radiation encephalopathy resulted in the death of the dog 149 days after N-TIRE therapy. The length of survival of this patient was comparable to dogs with intracranial tumors treated via standard excisional surgery and adjunctive fractionated external beam RT. Our results illustrate the potential benefits of N-TIRE for in vivo ablation of undesirable brain tissue, especially when traditional methods of cytoreductive surgery are not possible or ideal, and highlight the potential radiosensitizing effects of N-TIRE on the brain.

Intranasal malignant melanoma in a dog

A 10-year-old, female Newfoundland-cross dog was presented for evaluation of chronic intermittent unilateral epistaxis, nasal stertor, and sneezing. Nasal magnetic resonance imaging revealed a 3 x 5-cm mass in the left nasal cavity. Histopathological evaluation of nasal biopsies determined that the mass was a malignant melanoma. The mass was surgically resected and treated with bilateral opposed photon-beam radiation. This is the first report to describe the presentation, diagnosis, and treatment of an intranasal malignant melanoma in a dog.

Spontaneous lymphoma in a prairie dog (Cynomys ludovicianus)

A 4-year-old, female, black-tailed prairie dog (Cynomys ludovicianus) was examined for acute dyspnea and two skin masses. Tentative diagnosis of lymphoma was made based on cytology of pleural effusion and the skin masses. Administration of prednisolone was initially effective in improving the condition; however, the clinical signs deteriorated after radiation therapy and administration of cyclophosphamide. Postmortem examination revealed that neoplastic lymphocytes had infiltrated most of the organs, and the histopathological diagnosis was multi-centric lymphoma.

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.

Evaluation of primary re-excision after recent inadequate resection of soft tissue sarcomas in dogs: 41 cases (1999–2004)

OBJECTIVE

To determine the efficacy of primary re-excision alone for treatment of soft tissue sarcomas after recent incomplete resection, the frequency and clinical importance of detecting residual tumor in resected scars, and prognostic factors associated with the procedure.

DESIGN

Retrospective case series.

ANIMALS

41 dogs.

PROCEDURES

Medical records of dogs that had undergone recent incomplete excision of a soft tissue sarcoma at a referring veterinary practice and subsequent re-excision of the scar at the Colorado State University Veterinary Medical Center were reviewed. Owners and referring veterinarians were contacted for follow-up information. Slides from re-excised specimens were reviewed. Dogs that underwent radiation therapy after the re-excision procedure were excluded.

RESULTS

41 dogs met the inclusion criteria, and long-term follow-up information was available for 39 dogs. Median follow-up time was 816 days. Local recurrence of tumor developed in 6 of 39 (15%) dogs, and distant metastasis occurred in 4 of 39 (10%) dogs. Healthy tissue margins of 0.5 to 3.5 cm were achieved at re-excision. Residual tumor was identified in 9 of 41 (22%) resected scars. No tumor-, patient-, or treatment-related variables were associated with local recurrence except for the presence of liposarcoma or fibrosarcoma or whether fine-needle aspiration had been performed prior to surgery.

CONCLUSIONS AND CLINICAL RELEVANCE

After incomplete resection of soft tissue sarcomas, resection of local tissue should be performed, even if excisable tissue margins appear narrow. A long-term favorable prognosis is achievable without radiation therapy or amputation. The presence of residual tumor in resected scar tissue should not be used to predict local recurrence.

Role of carboplatin in multi-modality treatment of canine tonsillar squamous cell carcinoma - a case series of five dogs

Canine tonsillar squamous cell carcinoma is an aggressive disease with a poor prognosis. A retrospective study was undertaken of all dogs that were presented between January 1999 and January 2004 to the Animal Health Trust for the treatment of tonsillar squamous cell carcinoma. Five cases were identified, and their median survival time was 211 days (95 per cent confidence interval 80 to 352) with two of the five dogs remaining alive at the end of the study, 826 and 1628 days from diagnosis with no clinical signs of disease. The protocol was well tolerated with only one of the five dogs showing toxicity associated with carboplatin and all dogs that started radiotherapy completing it. Compared with results of previous studies, these cases suggest that surgical cytoreduction followed by coarse fractionated radiotherapy together with carboplatin may be a useful way to treat this tumour. Carboplatin alone caused partial remission in the two cases where it was used as neo-adjunctive therapy.

Palliative radiotherapy with electrons of appendicular osteosarcoma in 54 dogs

Radiotherapy is effective for the palliation of pain associated with primary and metastatic bony neoplasia in dogs and humans, but no standard treatment protocol has been established. The goal of this study was to evaluate a 3 x 8 Gy and a 4 x 6 Gy protocol using electrons with a betatron or linear accelerator for the treatment of appendicular osteosarcoma in 54 dogs. Thirty-three dogs received chemotherapy consisting of carboplatin IV concurrently with radiotherapy. Eighty-three % (n = 45) of the dogs experienced pain relief during or following treatment. The median duration of pain relief from treatment start was 53 days. In conclusion, both protocols are effective for palliation of clinical signs of canine appendicular osteosarcoma. The outcome reported here is similar to the results of other studies using Co photons. The use of chemotherapy did not improve the response to radiotherapy.

Tolerance of Cutaneous or Mucosal Flaps Placed into a Radiation Therapy Field in Dogs

OBJECTIVE

To determine the clinical outcome and factors affecting cutaneous or mucosal flaps in dogs treated with radiation therapy (RT).

STUDY DESIGN

Longitudinal clinical study.

ANIMALS

Twenty-six client-owned dogs.

METHODS

Dogs entered in the study had a flapping procedure and RT as part of their treatment. The sequence of flapping and RT included: (1) planned preoperative RT, (2) postoperative RT, and (3) flapping as a salvage procedure for management of complications or local tumor recurrence after RT. Flap complications were defined as necrosis, local infection, dehiscence, and ulceration. The risk and severity of flap complication were analyzed independently.

RESULTS

Twenty (77%) dogs had a complication; 6 dogs required an additional flapping procedure; and 4 dogs had an unresolved complication. Flapping procedures performed to correct a complication, or failure of RT, had a significantly greater risk for complication; however, postoperative RT decreased the severity of complication. A dose per fraction of 4 Gy compared with 3 Gy was prognostic for increased severity of complications, whereas the head and neck location was prognostic for decreased severity of complication.

CONCLUSIONS

Although morbidity was substantial, cutaneous or mucosal flaps were used successfully in an RT field in 85% of the dogs. Flaps that were part of the planned therapy as opposed to those used to correct a complication or failure of RT had a better clinical outcome.

CLINICAL RELEVANCE

Cutaneous or mucosal flaps can be part of the treatment of dogs with tumor when adjuvant or neoadjuvant RT is to be used.

Effects of treatment with and without adjuvant radiation therapy on recurrence of ocular and adnexal squamous cell carcinoma in horses: 157 cases (1985-2002)

OBJECTIVE

To determine the effects of treatment with and without adjuvant radiation therapy on recurrence of ocular and adnexal squamous cell carcinoma (SCC) at specific anatomic locations in horses.

DESIGN

Retrospective study.

ANIMALS

91 horses.

PROCEDURES

Medical records of horses with histologically confirmed ocular and adnexal SCC evaluated from 1985 to 2002 were reviewed. Sex, breed, age, type of treatment, location, and recurrence of SCC were recorded. Two treatment groups determined by recurrence of SCCs treated with and without adjuvant radiation therapy were established.

RESULTS

The anatomic site with the highest recurrence rate was the limbus (junction of the cornea and sclera) or bulbar conjunctiva (477%), independent of treatment group. There was a significant difference in recurrence rates of ocular and adnexal SCCs between the 2 treatment groups, independent of anatomic location. Recurrence rates of SCCs treated with and without adjuvant radiation therapy were 11.9% and 44.1%, respectively. Recurrence rates for SCCs of the eyelid, limbus or bulbar conjunctiva, and cornea treated with adjuvant radiation therapy were significantly different from those for SCCs treated without adjuvant radiation therapy. The most frequently represented anatomic site for ocular and adnexal SCCs was the eyelid (28.7%). Coat color, breed, and the interaction of age and breed had a significant effect on tumor recurrence regardless of treatment type and anatomic location.

CONCLUSIONS AND CLINICAL RELEVANCE

Results indicated that ocular and adnexal SCCs treated with adjuvant radiation therapy had a significantly lower recurrence rate, compared with SCCs treated without adjuvant radiation therapy, independent of anatomic location.

Prognostic factors for survival of dogs with inguinal and perineal mast cell tumors treated surgically with or without adjunctive treatment: 68 cases (1994-2002)

OBJECTIVE

To determine the prognostic factors for survival and tumor recurrence in dogs with cutaneous mast cell tumors (MCTs) in the perineal and inguinal regions treated surgically with or without adjunctive radiation therapy, chemotherapy, or both.

DESIGN

Retrospective study.

ANIMALS

68 dogs.

PROCEDURE

Medical records of dogs with histologically confirmed MCTs in the perineal region, inguinal region, or both treated surgically with or without adjunctive radiation therapy, chemotherapy, or both were reviewed.

RESULTS

Mean tumor-free interval was 1,635 days (median not reached), and 1- and 2-year tumor-free rates were 79% and 71%, respectively. Median survival time was 1,111 days (mean, 1,223 days), and 1- and 2-year survival rates were 79% and 61%, respectively. Factors that negatively influenced survival time were age at diagnosis, tumor recurrence, and treatment with lomustine.

CONCLUSIONS AND CLINICAL RELEVANCE

Results indicated that dogs with MCTs in the inguinal and perineal regions, if appropriately treated, may have survival times and tumor-free intervals similar to dogs with MCTs in other locations.

Vaccine-associated fibrosarcoma in a cat

An 8-year-old, spayed, female domestic shorthair was diagnosed with a vaccine-associated fibrosarcoma and treated with full course radiation therapy, aggressive surgery, and postoperative chemotherapy. Histopathologic examination confirmed that excision of the tumor was complete. The cat was doing well 278 days after initial presentation.

Mortality rates of interventional and surgical procedures performed in domestic juvenile farm pigs and Yucatan mini-pigs

Perioperative and postoperative care are critical factors in cardiac catheterization and cardiothoracic surgical procedures. A retrospective analysis of mortality data in cardiovascular catheter and surgical studies performed in domestic juvenile swine (DJS) and Yucatan mini-swine (YMS) was conducted. A total of 529 animals in 35 studies were included in the analysis, which included six study categories: coronary stenting (Stent) and percutaneous transluminal coronary angioplasty (PTCA) alone; Stent and PTCA in combination with ionizing radiation (Stent/Rad, PTCA/Rad); myocardial ischemia (ISCH); and three non-ISCH surgical procedures grouped under "other surgeries" (Other Surg). Casualties were defined as animals that died spontaneously before the assigned termination date. The highest mortality rate occurred in the ISCH group (29.7% +/- 2.2%). Mortality of the Stent/Rad animals (26.1% +/- 6.3%) was significantly higher than those in the Stent and PTCA groups (12.1% +/- 3.1% and 7.9% +/- 3.2%; P< 0.05 for both). Similarly, mortality in the ISCH group was significantly higher than that in the Stent, PTCA, or Other Surg animals (29.7% +/- 2.2% versus 12.1% +/- 3.1%, 7.9% +/- 3.2%, and 3.0% +/- 3.0%, respectively; P< 0.05 for all comparisons). We did not observe differences between YMS and DJS. Most casualties in the ISCH group took place during weeks 1 (28.0% +/- 8.4%) and 4 (29.3% +/- 6.2%) after placement of the coronary ameroid constrictor. The majority of animals in the Stent/Rad and PTCA/Rad groups died within 1 week after the procedure (67.7% +/- 12.8% and 79.3% +/- 12.5%, respectively). We conclude that radiation therapy used in combination with stenting increases the mortality rate of this catheter-based procedure. Animals subjected to ISCH or a transcatheter procedure in combination with ionizing radiation should be monitored closely during the perioperative period to prevent unacceptably high mortality rates.

Surgery alone or in combination with radiation therapy for treatment of intracranial meningiomas in dogs: 31 cases (1989-2002)

OBJECTIVE

To compare, for dogs with intracranial meningiomas, survival times for dogs treated with surgical resection followed by radiation therapy with survival times for dogs treated with surgery alone.

DESIGN

Retrospective study.

ANIMALS

31 dogs with intracranial meningiomas.

PROCEDURE

Medical records of dogs with histologic confirmation of an intracranial meningioma were reviewed. For each dog, signalment, clinical signs, tumor location, treatment protocol, and survival time were obtained from the medical record and through follow-up telephone interviews.

RESULTS

Dogs that underwent tumor resection alone and survived > 1 week after surgery had a median survival time of 7 months (range, 0.5 to 22 months). Dogs that underwent tumor resection followed by radiation therapy had a median survival time of 16.5 months (range, 3 to 58 months).

CONCLUSIONS AND CLINICAL RELEVANCE

Results suggest that in dogs with intracranial meningiomas, use of radiation therapy as a supplement to tumor resection can significantly extend life expectancy.

Use of surgery and electron beam irradiation, with or without chemotherapy, for treatment of vaccine-associated sarcomas in cats: 78 cases (1996-2000)

OBJECTIVE

To evaluate responses of cats with vaccine-associated sarcomas to treatment with surgery and radiotherapy, with or without adjunctive chemotherapy.

DESIGN

Retrospective study.

ANIMALS

76 cats (78 tumors).

PROCEDURE

Medical records were reviewed. Factors potentially associated with survival time, time to recurrence, and time to development of metastases were evaluated.

RESULTS

Following excision, electron beam radiation, and, in some cases, chemotherapy, 32 (41%) cats experienced recurrence, and 9 (12%) cats developed metastases. One- and 2-year survival rates were 86 and 44%, respectively. Median survival time from onset of disease was 730 days (range, 30 to 2,014 days). Median disease-free interval was 405 days (range, 30 to 925 days). Cats that underwent only 1 surgery prior to radiotherapy had a lower recurrence rate than did cats that underwent > 1 surgery and had a significantly longer disease-free interval. Survival time and disease-free interval decreased as time between surgery and the start of radiotherapy increased. Cats that developed metastases had significantly shorter survival times and disease-free intervals than did cats that did not develop metastases. Castrated male cats had a significantly shorter survival time than did spayed female cats. Cats with larger tumors prior to the first surgery had shorter survival times. Twenty-six cats received chemotherapy in addition to surgery and radiotherapy. Whether cats received chemotherapy was not associated with recurrence rate, metastasis rate, or survival time.

CONCLUSIONS AND CLINICAL RELEVANCE

Results suggest that excision followed by electron beam irradiation may be beneficial for treatment of cats with vaccine-associated sarcomas. Extent of excision prior to radiotherapy did not seem to be associated with recurrence rate.

Treatment with a combination of doxorubicin, surgery, and radiation versus surgery and radiation alone for cats with vaccine-associated sarcomas: 25 cases (1995-2000)

OBJECTIVE

To compare use of doxorubicin, surgery, and radiation versus surgery and radiation alone for treatment of cats with vaccine-associated sarcoma.

DESIGN

Retrospective study.

ANIMALS

25 cats with vaccine-associated sarcomas.

PROCEDURE

Time to first recurrence and survival time were compared between the 2 treatment groups. The number of surgeries (1 or > 1) were compared with respect to time to first recurrence and survival time.

RESULTS

Median time to first recurrence was 661 days for the group that received doxorubicin, surgery, and radiation. Median time to first recurrence has not yet been attained for the group treated with surgery and radiation alone. Median survival time was 674 days for the group treated with doxorubicin, surgery, and radiation and 842 days for the group treated with surgery and radiation alone. For time to first recurrence and survival time, significant differences were not detected between cats that had 1 surgery and those that had > 1 surgery.

CONCLUSIONS AND CLINICAL RELEVANCE

Significant differences between the 2 treatment groups were not detected. The efficacy of doxorubicin in the treatment of vaccine-associated sarcomas is uncertain.

Postoperative radiotherapy for canine soft tissue sarcoma

Thirty-five dogs with 37 soft tissue sarcoma tumors that were incompletely excised and treated with radiotherapy in the postoperative, adjuvant setting were reviewed. Variables evaluated included age, sex, tumor site, tumor histology, total tumor radiation dose, radiotherapy field size. time to recurrence, and survival. The majority of tumors were fibrosarcomas and hemangiopericytomas, but small numbers of other tumor types were also represented. Total tumor radiation dose ranged from 42 to 57 Gy given in 3- to 4.2-Gy daily fractions on a Monday through Friday schedule. Overall median survival was 1,851 days. Median time to local recurrence was greater than 798 days. Soft-tissue sarcoma tumors at oral sites had a statistically significant lower median survival (540 days) as compared to other tumor sites (2,270 days). Radiotherapy may be a useful adjuvant therapy for incompletely excised soft-tissue sarcomas with a reasonable expectation for long-term patient survival.

Squamous cell carcinoma of the nasal planum in 17 dogs

Squamous cell carcinoma of the nasal planum was diagnosed in 17 dogs over a period of 11 years. Ulceration, bleeding and sneezing were the most common clinical signs. One dog had cytological evidence of metastasis to the local lymph node. The dogs were treated by surgical resection, fractionated megavoltage irradiation, or a combination of the two. Surgical resection gave the most favourable results; four of six dogs were cured but a recurrence of the tumour was predicted in the other two on the basis of incomplete or marginal resection. Radiotherapy alone was not as effective; one of four dogs was cured, and the tumour recurred in the others within 24 weeks (median eight weeks). Combined surgical resection and radiotherapy did not produce a cure in any of the seven remaining dogs, and the tumour recurred within 12 weeks (median nine weeks). Three dogs had cytological evidence of lymph node metastasis when the tumour recurred. The dogs' prognosis was adversely affected by the interval between their initial examination and treatment, but there was no apparent association between the histological grade of the tumour and the clinical outcome.

Principles of adjunctive radiation therapy

Radiation therapy is becoming increasingly available to the practicing veterinarian. It is important that veterinarians be familiar with mechanisms and biologic effects of radiation used as a therapeutic modality in the treatment of cancer. It is also important that the veterinarian understand oncologic decision making and indications for various modalities including radiation therapy, surgery, and chemotherapy. Surgery and radiation therapy can be particularly complementary in combined therapy to achieve a functional and cosmetic result. This review introduces basic radiation therapy concepts, particularly regarding combination of radiation and surgery in the treatment of cancer in animals.

Cranioplasty after en bloc resection of calvarial chondroma rodens in two dogs

The clinical features of chondroma rodens in two dogs and the treatment using radiation therapy, en bloc resection of the tumours and cranioplasties with a bone allograft (case 1) and a polymethylmethacrylate implant (case 2) are described. The dogs were still alive with no local recurrence of the tumours 30 and 18 months, respectively, after surgery. En bloc resection and calvarial reconstruction in the treatment of chondroma rodens are discussed.

Radiotherapy of incompletely resected, moderately differentiated mast cell tumors in the dog: 37 cases (1989-1993)

Thirty-seven dogs with moderately differentiated, cutaneous mast cell tumors had incomplete surgical excisions as determined by histopathology, but no gross evidence of tumor. All dogs were irradiated to a total dose of between 46.2 and 48.0 Gy using either an orthovoltage source (n = 20) or a linear accelerator (megavoltage) (n = 17). Radiation was delivered to an area bordered by margins of 3 cm or greater around the surgical scar. The mast cell tumors had not recurred in 97% of dogs by one year after radiation therapy and had not recurred in 93% of dogs by three years after radiation. Both orthovoltage and megavoltage radiation provide excellent local control of moderately differentiated mast cell tumors in dogs.

Surgical excision of soft tissue fibrosarcomas in cats

OBJECTIVE

The purpose of this study was to determine the tumor-free interval and survival times of cats who had one (group 1) or more (group 2) surgeries, or surgery and radiation therapy (RTH) (group 3) for treatment of soft tissue fibrosarcomas (FSA).

STUDY DESIGN

Retrospective study.

ANIMALS OR SAMPLE POPULATION

45 client-owned cats.

METHODS

Medical records of cats with soft tissue FSA were examined. Vaccination and feline leukemia virus (FeLV) status, age, sex, breed, tumor location, number of surgeries, completeness of excision, and histopathological grade were evaluated to correlate with tumor-free interval and survival periods.

RESULTS

Overall median tumor-free interval and survival times were 10 and 11.5 (range, 1 to 40) months. Median tumor-free interval and survival times were more than 16 months each in group 1, more than 5 and 13 months in group 2, and 4.5 and 9 months in group 3. Age, sex, breed, vaccination or FeLV status, tumor location, or histopathological grade did not affect median tumor-free interval or survival times (P > .05). Cats with complete excisions had significantly longer median tumor-free interval (> 16 versus 4 months) and survival time (> 16 versus 9 months) than those with incomplete excisions (P = .008). Radiation therapy did not seem to extend tumor-free interval and survival times (P = .013). However, most group 3 cats had incomplete surgical excisions, resulting in recurrent or progressive disease.

CONCLUSIONS

Complete surgical excision of FSA in cats is possible and can be curative.

CLINICAL RELEVANCE

Aggressive surgical excision with wide margins appears to contribute to extended tumor-free interval and survival times in cats with soft tissue FSA. Controlled prospective studies are needed to determine the efficacy of RTH in treatment.

Principles of adjunct radiotherapy and chemotherapy

Surgical resection offers the best chance to cure patients with localized disease. A multimodality approach, however, is often necessary to control or cure cancer in most veterinary oncology patients. This article discusses the principles of adjunct radiotherapy and chemotherapy in the management of solid tumors.