Evaluation of single-agent chemotherapy for treatment of clinically evident osteosarcoma metastases in dogs: 45 cases (1987-1991)

Abstract

Summary: A study was undertaken to determine the effect chemotherapy had when used to treat 45 dogs with measurable metastatic osteosarcoma. The primary tumor was histologically confirmed as an osteosarcoma in each case. Thirty-nine dogs had the primary tumor surgically removed. Twenty-four of these dogs were treated adjunctively with cisplatin (70 mg/m2 of body surface, IV, q 3 weeks; median 2 doses, range 1 to 6 doses) prior to the onset of metastasis. The remaining 6 dogs from which the primary tumor was not surgically removed were diagnosed as having metastatic osteosarcoma in addition to the primary tumor on initial examination. The median time from initial examination until the development of metastatic disease was 115 days (range, 27 to 1,199 days). The location of the metastatic disease was lungs (31 dogs), bone (3 dogs), soft tissue (1 dog), and multiple sites including lungs, bone, and soft tissue sites (10 dogs). The metastatic lesions were confirmed by pretreatment biopsy (n = 8) or cytologic evaluation (n = 2) in 10 cases and at necropsy in 27 cases. The remaining 8 cases were diagnosed radiographically as multiple metastatic lesions in the lungs consistent with metastatic osteosarcoma. The metastatic disease was treated with cisplatin in 31 dogs (70 mg/m2, IV, q 3 weeks; median 2 doses, range 1 to 4 doses), doxorubicin in 11 dogs (30 mg/m2, IV, q 3 weeks; median 2 doses, range 1 to 3 doses), and mitoxantrone in 3 dogs (5 mg/m2, IV, q 3 weeks; median 2 doses, range 1 to 3 doses). Eight dogs that had metastatic disease treated with cisplatin were also given doxorubicin; 2 dogs treated with either doxorubicin or mitoxantrone were treated subsequently with cisplatin. The extent of neoplastic disease was determined immediately before the first dose of chemotherapy, and then every 3 to 6 weeks thereafter unless the dog had signs compatible with progressive disease, in which case, an evaluation was done more frequently. Each dog was treated with one chemotherapeutic agent until the dog developed progressive disease, or until the dog's quality of life diminished to an unacceptable level as determined by the owner or attending veterinarian. One dog treated with doxorubicin achieved partial remission. The duration of the partial remission was 21 days, and the lesion was confirmed to be osteosarcoma on necropsy 159 days after the metastatic disease was diagnosed. The median survival time of the other 44 dogs that did not respond to treatment from the time the metastatic disease was diagnosed was 61 days (range, 14 to 192 days). Cisplatin, doxorubicin, and mitoxantrone chemotherapy appear to be ineffective for the treatment of measurable metastatic osteosarcoma in the dog.