Updates in Osteosarcoma

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

Update in Veterinary Radiation Oncology: Focus on Stereotactic Radiation Therapy

Stereotactic radiotherapy (SRT) involves the precise delivery of highly conformal, dose-intense radiation to well-demarcated tumors. Special equipment and expertise are needed, and a unique biological mechanism distinguishes SRT from other forms of external beam radiotherapy. Families find the convenient schedules and minimal acute toxicity of SRT appealing. Common indications in veterinary oncology include nasal, brain, and bone tumors. Many other solid tumors can also be treated, including spinal, oral, lung, heart-base, liver, adrenal, and prostatic malignancies. Accessibility of SRT is improving, and new data are constantly emerging to define parameters for appropriate case selection, radiation dose prescription, and long-term follow-up.

Canine primary liver tumors treated with stereotactic body radiation therapy: A case series

Stereotactic body radiation therapy (SBRT) is an increasingly used alternative treatment option for nonresectable hepatocellular carcinoma (HCC) in people. Comparatively, the publication of SBRT of dogs with HCC is limited. The objective of this retrospective, descriptive case series was to evaluate the clinical outcomes and toxicity data of SBRT in dogs with HCC and imaging-documented primary liver tumors using volumetric-modulated arc therapy delivery at two private institutions. Medical records of 14 dogs treated between 2018 and 2023 were reviewed. All dogs had macroscopic tumors, and 9 of 14 dogs had HCC diagnoses confirmed on cytology or histopathology. The median longest tumor diameter was 5.5 cm. The median percentage of planning target volume relative to liver volume was 27.1%. Most dogs were treated with three daily fractions of 7-7.5 Gy. All dogs completed their radiotherapy protocols. Three of nine HCC dogs experienced partial responses and clinical improvement. Five of nine HCC dogs had stable disease. Overall median survival time was 164 days for nine HCC dogs (range: 93-706 days). One late grade 5 liver and two late grade 3 kidney side effects were reported. One dog received repeated SBRT to the same HCC treatment field, and one dog had two courses of SBRT to bifocal HCC treatment fields, both with no more than grade 2 acute and chronic toxicities.

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.

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

OBJECTIVE

To report clinical features and outcomes of cats undergoing either stereotactic radiotherapy (SRT) or surgical excision for the treatment of intracranial meningioma.

ANIMALS

61 client-owned cats.

METHODS

Medical records were retrospectively reviewed of cats with intracranial meningiomas that were treated with surgical removal and/or SRT between 2005 and 2017. Signalment, clinical signs, duration of clinical signs, diagnostic imaging reports, histopathology reports, treatment protocol, complications, recurrence or progression, and survival time were obtained from the medical record and through follow-up phone calls.

RESULTS

Of the 61 patients, 46 had surgery, 14 had SRT, and 1 had surgery followed by SRT for initial treatment. Significantly more cats that underwent surgery had peritreatment complications compared to the SRT group (P < .0001). Cats that received surgery initially had a significantly longer median survival time (MST) of 1,345 days compared to the MST of 339 days for the SRT cats (P = .002). Fourteen (30%) cats in the surgery group and 4 cats in the SRT group (28%) had MRI- or CT-confirmed tumor regrowth or new tumor growth (P = 1.00). Five cases that had SRT for subsequent recurrence had an MST of 700 days (range, 335 to 1,460 days) after the last treatment.

CLINICAL RELEVANCE

SRT proved to be a safe, alternative treatment option for feline patients with intracranial meningiomas; however, the survival times with surgery alone were significantly longer. SRT for the treatment of recurrence following initial surgery may show promising results.

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

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

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.

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

BACKGROUND

Stereotactic radiotherapy (SRT) is an emerging treatment for sinonasal tumors in dogs. Reported results regarding tumor control and incidence of acute and late radiation morbidities are inconsistent.

OBJECTIVES

To determine treatment efficacy and prognostic indicators of SRT in dogs with sinonasal tumors and to quantify acute and late radiation morbidities.

ANIMALS

One hundred and eighty-two client-owned dogs with sinonasal tumors diagnosed cytologically, histologically, or radiographically that underwent SRT.

METHODS

Single-arm retrospective study by reviewing medical records of dogs treated with SRT (10 Gy × 3) between 2010 and 2015. Kaplan-Meier analysis was used to determine overall survival (OST; from the first day of SRT to death by any cause) and disease-specific survival times (DSST; OST but censoring tumor/treatment-unrelated death). Tumors were staged using modified Adams criteria.

RESULTS

Median OST and DSST of dogs treated with 1 course of SRT was 441 (95% CI: 389-493 days) and 482 (428-536 days) days, respectively with skin/oral cavity acute morbidities observed in 3% of dogs. DSST in dogs with stage 4 disease showed no statistical difference compared to other stages (P = .64). Oro-nasal (n = 2) or naso-cutaneous (n = 11) fistula development occurred in 7.1% of dogs with median time of 425 days (range: 83-1733 days). Possible chronic rhinitis after SRT was recorded in 54 of 88 dogs (61%) where information was available.

CONCLUSIONS AND CLINICAL IMPORTANCE

Results are comparable to other reports of treatment of SRT. Acute morbidities were minimal. Modified Adams stage scheme appeared to be inappropriate for prognostication for dogs with sinonasal tumors treated with SRT.

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

CASE DESCRIPTION

A 14-year-old 5.6-kg (12.3-lb) castrated male Toy Poodle was evaluated because of high serum activities of alkaline phosphatase and alanine aminotransferase and the presence of a hepatic mass.

CLINICAL FINDINGS

Abdominal CT revealed a large (approx 6.8 × 7.1 × 6.5-cm) soft tissue mass along the midline of the liver. The mass either originated from the papillary process of the caudate lobe or the left medial liver lobe.

TREATMENT AND OUTCOME

A partial liver lobectomy was performed, and approximately a third of the mass was successfully removed and submitted for histologic examination. Consultation with the oncology service was advised to determine whether radiation therapy could be used to treat the residual disease. On 5 consecutive days, the dog underwent imaging-guided intensity-modulated radiotherapy-stereotactic body radiation therapy (4 Gy/treatment) with a simultaneous integrated boost to the center of the tumor. The dog received a base dose of 20 Gy that was then boosted to 28 Gy. In the 10-month period after completion of radiation therapy, the hepatocellular mass continued to decrease in size, and overall improvements in the dog's serum liver enzyme abnormalities were evident.

CLINICAL RELEVANCE

There are few treatment options for dogs with incompletely excised hepatocellular carcinomas. On the basis of the positive outcome in this case, radiation therapy could be useful following incomplete surgical removal of hepatocellular carcinomas in dogs.

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

CASE DESCRIPTION

A 16-year old castrated male domestic shorthair cat was evaluated at a veterinary teaching hospital because of polyuria, polydipsia, and weight loss of 2 months' duration.

CLINICAL FINDINGS

Hematologic and biochemical examination results were within respective reference ranges except for moderately high pancreas-specific lipase concentration. Ultrasonographic and cytologic evaluation revealed a hepatic mass with findings consistent with mild cholestasis and inflammation and a pancreatic mass that was initially identified as a neuroendocrine tumor.

TREATMENT AND OUTCOME

The cat underwent additional CT assessment and stereotactic body radiation therapy (SBRT; 3 fractions of 8 Gy, administered every other day) for treatment of the pancreatic tumor. Follow-up ultrasonographic and CT examinations indicated a partial response to SBRT, with a maximum CT-measured size reduction from 3.6 × 4.8 × 4.0 cm at the time of treatment planning to 2.0 × 2.0 × 1.9 cm 8 months later. Increased pancreatic tumor size and signs of carcinomatosis were detected 15 months after SBRT treatment; the initial cytologic diagnosis was changed to exocrine pancreatic carcinoma on reevaluation of the slides by another veterinary pathologist. Carboplatin treatment was elected, and signs of carcinomatosis resolved. The cat was euthanized without further testing because of weakness 589 days after SBRT was started.

CLINICAL RELEVANCE

To the authors' knowledge, this is the first report of SBRT for suspected exocrine pancreatic carcinoma in a cat. Further investigation is needed to determine optimal fractionation schedules for SBRT of pancreatic tumors and utility of SBRT of exocrine pancreatic carcinoma in cats.

Stereotactic body radiation therapy for treatment of soft tissue sarcomas in 35 dogs

OBJECTIVE

To describe response rate, tumor progression, patient survival times, prognostic factors associated with tumor progression and patient survival times, and radiation toxicoses (acute and latent) in dogs treated with curative-intent stereotactic body radiation therapy (SBRT) for soft tissue sarcomas (STS).

ANIMALS

35 client-owned dogs with STS treated with curative-intent SBRT between October 2011 and May 2017.

PROCEDURES

Medical records were reviewed to identify dogs that underwent SBRT. Dogs with oral tumors, hemangiosarcoma, or histiocytic sarcoma were excluded. Data collected included patient-, STS-, and SBRT-related information, including follow-up information pertaining to tumor progression and patient survival time for ≥ 6 months, unless tumor progression or patient death occurred sooner.

RESULTS

Objective measurements allowing for evaluation of tumor response were available for 28 dogs, of which 13 (46%) had either a partial (10/28 [36%]) or complete (3/28 [11%]) response. Twenty-four dogs died, and the medians for progression-free survival time, time to progression of disease, overall survival time, and disease-specific survival time were 521, 705, 713, and 1,149 days, respectively. Low histologic grade and extremity locations of STSs were positive prognostic factors for patient survival times. Acute adverse effects were limited to skin, and 1 dog underwent limb amputation because of a nonhealing wound.

CONCLUSIONS AND CLINICAL RELEVANCE

Results indicated that SBRT for STS was well tolerated in most dogs and provided local tumor control. Additional studies are needed to determine the best SBRT protocol for treatment of STSs in dogs.

Outcomes and adverse effects associated with stereotactic body radiation therapy in dogs with nasal tumors: 28 cases (2011-2016)

OBJECTIVE To assess outcomes, factors associated with survival time, and radiation-induced toxicoses in dogs treated for nasal tumors with curative-intent stereotactic body radiation therapy (SBRT). DESIGN Retrospective case series. ANIMALS 28 client-owned dogs. PROCEDURES By use of a 6-MV linear accelerator, dogs were treated with SBRT (3 consecutive-day fractions of 9 or 10 Gy or once with 1 fraction of 20 Gy). Data regarding adverse effects, outcomes, and survival times were obtained from the medical records. RESULTS The median survival time to death due to any cause was 388 days. Of the 24 dogs known to be dead, 14 (58%) died or were euthanized because of local disease progression. Acute radiation-induced adverse effects developed in the skin (excluding alopecia) in 26% (6/23) of dogs and in the oral cavity in 30% (7/23) of dogs. Acute ocular adverse effects included discharge in 26% (6/23) of dogs and keratoconjunctivitis sicca in 4% (1/23) of dogs. Among the 22 dogs alive at > 6 months after SBRT, 4 (18%) developed a unilateral cataract; 4 (18%) developed other complications that may have been late-onset radiation toxicoses (excluding leukotrichia and skin hyperpigmentation). CONCLUSIONS AND CLINICAL RELEVANCE Results indicated that dogs treated with SBRT had outcomes comparable to those reported for dogs with nasal carcinomas and sarcomas that undergo conventionally fractionated radiation therapy. Administration of SBRT was associated with a comparatively lower frequency of acute radiation-induced adverse effects. For SBRT and conventionally fractionated radiation therapy, the frequencies of serious late-onset adverse effects appear similar.

Update in Veterinary Radiation Oncology: Focus on Stereotactic Radiation Therapy

Stereotactic radiotherapy (SRT) involves the precise delivery of highly conformal, dose-intense radiation to well-demarcated tumors. Special equipment and expertise are needed, and a unique biological mechanism distinguishes SRT from other forms of external beam radiotherapy. Families find the convenient schedules and minimal acute toxicity of SRT appealing. Common indications in veterinary oncology include nasal, brain, and bone tumors. Many other solid tumors can also be treated, including spinal, oral, lung, heart-base, liver, adrenal, and prostatic malignancies. Accessibility of SRT is improving, and new data are constantly emerging to define parameters for appropriate case selection, radiation dose prescription, and long-term follow-up."

Novel technique for high-precision stereotactic irradiation of mouse brains

BACKGROUND AND PURPOSE

Small animal irradiation systems were developed for preclinical evaluation of tumor therapy closely resembling the clinical situation. Mostly only clinical LINACs are available, so protocols for small animal partial body irradiation using a conventional clinical system are essential. This study defines a protocol for conformal brain tumor irradiations in mice.

MATERIALS AND METHODS

CT and MRI images were used to demarcate the target volume and organs at risk. Three 6 MV photon beams were planned for a total dose of 10 fractions of 1.8 Gy. The mouse position in a dedicated applicator was verified by an X‑ray patient positioning system before each irradiation. Dosimetric verifications (using ionization chambers and films) were performed. Irradiation-induced DNA damage was analyzed to verify the treatment effects on the cellular level.

RESULTS

The defined treatment protocol and the applied fractionation scheme were feasible. The in-house developed applicator was suitable for individual positioning at submillimeter accuracy of anesthetized mice during irradiation, altogether performed in less than 10 min. All mice tolerated the treatment well. Measured dose values perfectly matched the nominal values from treatment planning. Cellular response was restricted to the target volume.

CONCLUSION

Clinical LINAC-based irradiations of mice offer the potential to treat orthotopic tumors conformably. Especially with respect to lateral penumbra, dedicated small animal irradiation systems exceed the clinical LINAC solution.

Effect of laser treatment on first-intention incisional wound healing in ball pythons (Python regius)

OBJECTIVE

To evaluate effects of laser treatment on incisional wound healing in ball pythons (Python regius).

ANIMALS

6 healthy adult ball pythons.

PROCEDURES

Snakes were sedated, a skin biopsy specimen was collected for histologic examination, and eight 2-cm skin incisions were made in each snake; each incision was closed with staples (day 0). Gross evaluation of all incision sites was performed daily for 30 days, and a wound score was assigned. Four incisions of each snake were treated (5 J/cm(2) and a wavelength of 980 nm on a continuous wave sequence) by use of a class 4 laser once daily for 7 consecutive days; the other 4 incisions were not treated. Two excisional skin biopsy specimens (1 control and 1 treatment) were collected from each snake on days 2, 7, 14, and 30 and evaluated microscopically. Scores were assigned for total inflammation, degree of fibrosis, and collagen maturity. Generalized linear models were used to investigate the effect of treatment on each variable.

RESULTS

Wound scores for laser-treated incisions were significantly better than scores for control incisions on day 2 but not at other time points. There were no significant differences in necrosis, fibroplasia, inflammation, granuloma formation, or bacterial contamination between control and treatment groups. Collagen maturity was significantly better for the laser-treated incisions on day 14.

CONCLUSIONS AND CLINICAL RELEVANCE

Laser treatment resulted in a significant increase in collagen maturity at day 14 but did not otherwise significantly improve healing of skin incisions.

Avian Soft Tissue Surgery

Basic surgical instrumentation for avian soft tissue surgery includes soft tissue retractors, microsurgical instrumentation, surgical loupes, and head-mounted lights. Hemostasis is fundamental during the surgical procedures. The indications, approach, and complications associated with soft tissue surgeries of the integumentary (digit constriction repair, feather cyst excision, cranial wound repair, sternal wound repair, uropygial gland excision), gastrointestinal (ingluviotomy, crop biopsy, crop burn repair, celiotomy, coelomic hernia and pseudohernia repair, proventriculotomy, ventriculotomy, enterotomy, intestinal resection and anastomosis, cloacoplasty, cloacopexy), respiratory (rhinolith removal, sinusotomy, tracheotomy, tracheal resection and anastomosis, tracheostomy, pneumonectomy) and reproductive (ovocentesis, ovariectomy, salpingohysterectomy, cesarean section, orchidectomy, vasectomy, phallectomy) systems are reviewed.

Histologic Comparison of Canine Skin Biopsies Collected Using Monopolar Electrosurgery, CO2Laser, Radiowave Radiosurgery, Skin Biopsy Punch, and Scalpel

OBJECTIVE

To compare the histologic appearance of canine skin biopsies collected by use of a scalpel, skin biopsy punch, monopolar electrosurgery, CO2 laser, and radio wave radiosurgery in fully rectified wave form (RWRS).

STUDY DESIGN

Experimental, randomized design.

ANIMALS

Healthy adult grayhounds (n=4).

METHODS

Skin biopsies were collected using 5 techniques. Cut margins of biopsy specimens and adjacent peripheral skin were evaluated using light microscopy to compare penetration of the dermis by tissue carbonization (char).

RESULTS

No char occurred in skin specimens collected by biopsy punch and scalpel. Char penetration occurred in all specimens collected by electrosurgery, CO2 laser, and RWRS. Mean char penetration in skin biopsies collected by RWRS (0.158 mm) was significantly less than for monopolar electrosurgery (0.223 mm) and CO2 laser (0.215 mm). Mean char penetration in adjacent peripheral skin surrounding biopsies collected by RWRS (0.171 mm) was significantly less than monopolar electrosurgery (0.255 mm) but not less than CO2 laser (0.215 mm, P<.07).

CONCLUSIONS

RWRS (blended waves in cut-coagulate mode) caused less lateral thermal damage to canine skin biopsies than monopolar electrosurgery and CO2 laser and less lateral thermal injury to peripheral skin than monopolar electrosurgery.

CLINICAL RELEVANCE

Excision of canine skin biopsies with heat-generating devices may not allow reliable histologic interpretation, particularly when assessing margins of small biopsy specimens. RWRS may be less traumatic to canine skin than monopolar electrosurgery and CO2 laser when used to make incisions.

Stereotactic radiosurgery for treatment of osteosarcomas involving the distal portions of the limbs in dogs

Stereotactic radiosurgery (SRS) involves precise delivery of a single large dose of radiation to a designated tumor target. This report describes use of SRS in combination with a frameless stereotactic localization system to treat 11 dogs with appendicular osteosarcomas. Five dogs were treated with SRS alone; 6 were treated with a combination of SRS and chemotherapy. Overall median survival time was 363 days (range, 145 to 763 days), with 6 dogs still alive 90, 142, 234, 367, 633, and 763 days after SRS. Limb function was good or excellent in all 6 dogs that were still alive. Results in these dogs suggest that SRS may be a viable option for dogs with appendicular osteosarcoma, with the potential to provide long-term local tumor control and improvement in limb function, especially when combined with chemotherapy. Because of the destructive nature of osteosarcoma and limitations of SRS, dogs with tumors that are small and have caused minimal bone destruction would likely be the best candidates for this procedure.

Radiosurgery using a stereotactic headframe system for irradiation of brain tumors in dogs

Radiation therapy of brain tumors in dogs typically involves administration of multiple fractions over several weeks. Fractionation is used to minimize damage to normal tissue. Radiosurgery uses multiple non-coplanar stereotactically focused beams of radiation in a series of arcs to deliver a single dose to the target with extreme accuracy. The large number of beams facilitates a high degree of conformation between the treatment area and the target tumor and allows for a steep dose gradient; the use of nonintersecting arcs minimizes exposure of normal tissue. Computed tomography with a stereotactic localizer secured to the skull allows generation of a 3-dimensional image of the target and provides accurate spatial coordinates for computerized treatment planning and delivery. Three dogs were treated with radiosurgery, using 1,000 to 1,500 cGy. A linear accelerator mounted on a rotating gantry was used to generate and deliver the radiation. Two dogs with meningiomas survived 227 and 56 weeks after radiosurgery. A dog with an oligodendroglioma survived 66 weeks. No complications were observed following the use of this technique.

Thermal injury by in vitro incision of equine skin with electrosurgery, radiosurgery, and a carbon dioxide laser

Freshly harvested equine skin incised with an electrosurgical unit, a radiosurgical device, or a carbon dioxide (CO2) laser was examined by light microscopy to determine the extent of thermal injury caused by each instrument. There was no significant difference between the thermal injury caused by the electrosurgical unit in the pure-cut mode and the CO2 laser in the superpulse mode, or between the electrosurgical unit and the radiosurgical device in the fully filtered cut mode. However, thermal injury caused by the CO2 laser was significantly less than that caused by the radiosurgical device. The amount of thermal injury in this in vitro study was similar to that found in vivo with other species.