HYPERTHERMIA AND RADIATION THERAPY IN CANCER TREATMENT*

Hyperthermia is a field of cancer research of increasing importance to veterinarians and physicians. The thermobiologic studies that are guiding the development of clinical research are reviewed. The interaction of heat, radiation, and drugs on tumors and normal tissues is presented, and the basis for producing a therapeutic gain is discussed. Current methods of inducing local, regional, and systemic hyperthermia in animals and humans are summarized. The areas of clinical research in which veterinary radiologists and oncologists could contribute by studying the effects of heat and radiotherapy on domestic animals with spontaneous tumors are emphasized.     

Olfactory esthesioneuroblastoma treated with orthovoltage radiotherapy in a dog

A 13-year-old neutered female mongrel dog presented with a 1-year history of stertorous respiration. On computed tomography examination, a mass was demonstrated in the nasal cavity. Open biopsy of the mass was performed and a diagnosis of olfactory esthesioneuroblastoma was made on histological examination. The dog was treated with orthovoltage x-ray radiation (total dose; 53 Gy given in 14 fractions over an 8 week period). Computed tomography after the twelfth irradiation revealed that tumour size had decreased. Although clinical signs were absent in the 4 months after irradiation, re-growth of the tumour was detected by radiographic evaluation and histological examination. The dog was again treated with orthovoltage x-ray radiation (total dose; 30 Gy given in three fractions over a 4-week period), however, tumour regrowth was again detected 3 months later. Clinical treatment of this tumour type has not been previously reported.     

COMPARISON OF TWO COARSE FRACTIONATED RADIATION PROTOCOLS FOR THE MANAGEMENT OF CANINE PITUITARY MACROTUMOR: AN OBSERVATIONAL STUDY OF 24 DOGS

Radiotherapy is a commonly used treatment for pituitary macrotumors in dogs, but the optimum protocol has not been established. Twenty four dogs with MRI confirmed pituitary macrotumors were treated with one of two radiotherapy protocols. Twelve dogs were treated with 10 fractions of 3.8 Gy/fraction on a “Monday–Wednesday–Friday” schedule, the remaining 12 with five “once‐a‐week” protocols (1 × 5 Gy, followed by 4 × 8.25 Gy) to a total dose of 38 Gy. The overall median survival time for all dogs was 235 days (range 28–1,328), dogs treated with 10 fractions had a median survival time of 961 days (range 28–1,328) compared to 182 days (range 42–507) in the five‐fraction group (P = 0.006). Clinical improvement was found in both groups, and no significant side effects were noted in either group. These results suggest that a “Monday–Wednesday–Friday” schedule may improve survival times, as compared to a “once‐a‐week” protocol. As this study was of an observational nonrandomized nature, future work is necessary to establish whether more highly fractionated protocols or different total doses will further improve outcome.     

Combined surgical and radiotherapy treatment of a mandibular ameloblastic carcinoma in a pony

A 9‐year‐old Welsh Section D gelding was referred to an equine hospital for evaluation and computed tomographic (CT) imaging of a left mandibular swelling. An expansile mass, found within the left mandible at the level of the caudal 2 cheek teeth, was surgically debulked and histology of the lesion identified it as an ameloblastic carcinoma. Radiotherapy using 4 fractions of 800 cGy, 7 days apart, was subsequently undertaken. The pony made excellent clinical progression following treatment. Repeat CT imaging at 7.5 and 19.5 months post surgery showed no apparent recurrence of the lesion and marked improvement in the remodelling of the mandible. In conclusion, radiotherapy in conjunction with surgical debulking appears to have been successful in treating an ameloblastic carcinoma in this pony and could be considered for similar tumours in other cases.     

前列腺癌二维与三维适形放疗剂量分布的比较

目的：评估前列腺癌适形放疗计划的剂量分布特点。方法：对20例前列腺癌患者分别进行二维常规放疔和三维适形放疗治疗计划设计．根据剂量-体积直方图等参数对两者剂量分布进行分析和评估。结果：与常规放疗相比,适形放疗的靶区剂量分布更均匀．直肠和膀胱的受照剂量及体积明显降低。结论：使用适形放疗可安全地增加前列腺癌的照射剂量．有助干提高前列腺癌局控率,同时又能更好地保护周围正常组织。     

Successful use of prednisolone and radiation therapy in a dog with intracranial histiocytic sarcoma

The ideal treatment for intracranial histiocytic sarcoma (HS) remains unclear. Herein, we report a case of intracranial HS that was successfully treated using prednisolone and radiation therapy. The patient was a 9-year-old spayed female Pembroke Welsh Corgi that presented with epileptic seizures. Magnetic resonance imaging revealed a contrast-enhancing mass adjacent to the right piriform lobe. Prednisolone administration (1 mg/kg/day) decreased the lesion size. Additional palliative radiation therapy (total dose, 37 Gy) resulted in complete disappearance of the lesion. However, on day 164, the dog’s neurological signs deteriorated, and she was euthanized. Necropsy revealed an intracranial metastasis of HS via the cerebrospinal fluid without any extracranial metastasis. Nonetheless, combined prednisolone and radiation therapy might be effective in treating intracranial HS.     

INTRAOPERATIVE RADIOTHERAPY OF CANINE BLADDER CANCER

Thirteen dogs had partial surgical extirpation followed by whole bladder intraoperative radiotherapy for urinary bladder cancer. Eleven of the neoplasms were transitional cell carcinomas (five Stage T1, six stage T2); one was rhabdomyosarcoma (Stage T2), and one was leiomyosarcoma (Stage T2). Histopathologic evaluation showed that neoplasia extended to the margins of the excised tissue in at least 11 of the 13 dogs. Radiotherapy from a ¹³⁷Cs teletherapy machine was applied to the surgically exteriorized bladder, with doses at the 90% isodose level varying from 2188 to 2888 cGy (10 of 13 dogs receiving 2670–2700 cGy). Sixty-one percent of the dogs were alive at 1 year, 30% at 18 months, and 15% at 2 years. From the time of initial clinical signs of bladder neoplasia, 69% of the irradiated dogs were alive at 1 year, 46% at 18 months, and 23% at 2 years (one dog is still living, at 70 months). Of the owner-reported or clinically determined posttherapy complications, there was increased frequency of urination in 46% of the dogs, urinary incontinence in 46%, cystitis in 38%, and stranguria in 15%. Either persistence or recurrence of neoplasia was found in six (46%) of the dogs and metastasis in four (30%), with two of these having both recurrence and metastasis. Qualitative assessment of the complications was not done, but owner-perceived severity of the complications, metastasis, or diagnosed persistence or recurrence of the neoplasm were the major reasons for ultimately killing most of the dogs.     

A VACUUM-FORMABLE MATTRESS FOR VETERINARY RADIOTHERAPY POSITIONING: COMPARISON WITH CONVENTIONAL METHODS

This prospective study was undertaken to compare the positioning repeatability and setup time of a rigid immobilization device (Vac-Lok mattress) to conventional positioning methods (sandbags, tape, foam wedges) in the clinical veterinary radiotherapy setting. Positioning repeatability was determined by using port films to verify appropriate patient positioning. Setup time was determined by recording the time required to set up each patient using each positioning method. Sixty-seven patients receiving radiotherapy were positioned using both the Vac-Lok mattresses and conventional positioning methods during their treatments. Seventy-eight total sites were treated. Forty-eight were treated daily (Monday through Friday, 2 to 4 weeks) and 30 were treated once weekly (4 weeks). Patients were grouped according to the site treated: head (29), neck/body (24), and limb (25). Vac-Lok mattresses were similar to conventional means in positioning repeatability and setup time. Vac-Lok mattresses are potentially advantageous in specific situations, including use during pre-radiotherapy tumor imaging. These mattresses are not recommended for distal limb positioning.