Late Complications of Pelvic Irradiation in 16 Dogs

Abstract

When external beam radiation therapy is administered to the pelvis, normal tissues irradiated may include the colon, small intestine, urethra, bladder, bone, and spinal cord. The objectives of this retrospective study were to determine the incidence and severity of late radiation effects following pelvic irradiation in dogs and to identify factors that increase the risk of these effects. Medical records of all dogs treated with curative intent external beam radiation therapy to the pelvic region between 1993 and 1999 were reviewed. Patients with follow-up longer than 9 months or any patient that developed late complications earlier than 9 months were evaluated. Sixteen dogs met criteria for inclusion in this study. All dogs were treated with a 6-MV linear accelerator with bilaterally opposed beams. Diseases treated included transitional cell carcinoma of the bladder, transitional cell carcinoma of the prostate, and anal sac apocrine gland adenocarcinoma. Four dose/fractionation schemes were used: 49.5 Gy in 3.3 Gy fractions, 54 Gy in 3.0 Gy fractions, 54 Gy in 2.7 Gy fractions, and 18 Gy intraoperative radiation therapy followed by 43 Gy external beam radiation therapy in 2.9 Gy fractions. Implantable chemotherapy in the form of an OPLA-Pt sponge was used in six dogs as a radiation potentiator. Colitis was the major late effect following pelvic irradiation, occurring in nine dogs (56%). Colitis was characterized as mild in three dogs, moderate in one dog, and severe in five dogs. Three of the dogs with severe effects suffered gastrointestinal perforation. All dogs with severe late effects received 3 or 3.3 Gy per fraction, and 80% received radiation potentiators. In the seven dogs that received 2.7 Gy or 2.9 Gy per fraction, late effects were classified as none (n = 5), mild colitis (n = 1), and moderate colitis (n = 1). Radiation therapy can be administered to the pelvic region with a minimal risk of late effects to the colon by giving smaller doses per fraction and avoiding systemic radiation potentiators.

Tumors of the Urinary System

“…18 In another report, which involved 13 dogs, the 1-and 2-year survival rates were 69% and 23%, respectively, but complications of therapy (i.e., urinary incontinence and cystitis with accompanying pollakiuria and stranguria) detracted from the patients' quality of life. 19 A report of 10 dogs that received weekly coarse fraction external beam radiation therapy, along with mitoxantrone and piroxicam chemotherapy, indicated that this regimen was well tolerated; however, it showed no improvement on results obtained with mitoxantrone-piroxicam therapy without radiotherapy. 19 A report of 10 dogs that received weekly coarse fraction external beam radiation therapy, along with mitoxantrone and piroxicam chemotherapy, indicated that this regimen was well tolerated; however, it showed no improvement on results obtained with mitoxantrone-piroxicam therapy without radiotherapy.…”

“…20 Medical management of TCC is indicated in dogs with nonresectable or metastatic tumors and as a postoperative adjuvant in the rare patient that undergoes resection. 1,2,10,[18][19][20][21][22][23][24] The treatment that has resulted in the highest percentage of dogs in remission is cisplatin combined with piroxicam; however, this particular combination is not recommended because it causes unacceptable renal toxicity. 1,2,10,[18][19][20][21][22][23][24] The treatment that has resulted in the highest percentage of dogs in remission is cisplatin combined with piroxicam; however, this particular combination is not recommended because it causes unacceptable renal toxicity.…”

Evaluation of cisplatin administered with piroxicam in dogs with transitional cell carcinoma of the urinary bladder

“…2,4 Full-course and intraoperative radiation therapy can be effective against TCC, but urinary bladder fibrosis, urinary incontinence, cystitis, and toxic effects in surrounding organs have been common posttreatment complications. [5][6][7][8] Photodynamic therapy has shown some promise but is not widely available. Various single-agent chemotherapeutic protocols have been evaluated, including administrations of carboplatin, cisplatin, doxorubicin, and mitoxantrone.…”

“…1,2 Numerous treatments for urinary bladder TCC in dogs have been evaluated including surgery, radiation therapy, photodynamic therapy, and chemotherapy. [3][4][5] Surgical intervention has been largely unrewarding because of the typical trigonal tumor location (where complete resection is not possible) and the potential for metastatic and recurrent disease. 2,4 Full-course and intraoperative radiation therapy can be effective against TCC, but urinary bladder fibrosis, urinary incontinence, cystitis, and toxic effects in surrounding organs have been common posttreatment complications.…”

RADIATION THERAPY OF A PRESUMPTIVE URETHRAL TRANSITIONAL CELL CARCINOMA IN AN EASTERN GRAY SQUIRREL (SCIURUS CAROLINENSIS)

“…11 Radiation therapy was well-tolerated by this squirrel and side effects of the pelvic irradiation were typical of those seen in dogs. 1 In addition to radiation, medical treatment with piroxicam was also used in this squirrel, initiated following diagnosis of the primary renal tumor and continued throughout the remainder of the squirrel's life. Piroxicam, a nonsteroidal anti-inflammatory drug commonly used in medical treatment of TCC in humans and animals, is thought to inhibit cyclooxygenase 2 expressed on TCC cells as well as inhibit tumor angiogenesis.…”