Effects of a controlled-release cisplatin delivery system used after resection of mammary carcinoma in mice

OBJECTIVE: To evaluate efficacy of a controlled-release cisplatin delivery system, used after marginal resection of mammary carcinoma (ie, resection of grossly evident tumor) in mice, to prevent tumor regrowth and metastasis. ANIMALS: 42 female C3H-HeJ mice. PROCEDURE: Mice were inoculated with mammary carcinoma cells. Between 2 and 6 days later, tumors were marginally resected and mice were assigned to 1 of 3 groups: no treatment (control; n = 14), cisplatin administered intraperitoneally (i.p. cisplatin; 14), and cisplatin delivered by use of an open-cell polylactic acid system placed within the tumor bed (slow-release cisplatin; 14). Tumor regrowth was measured daily. Mice were euthanatized 14 days after surgery, and complete necropsies were performed. RESULTS: Tumor regrowth was not detected in the slow-release cisplatin group; however, tumor regrowth was detected in 7 of 14 mice in the i.p. cisplatin group and 14 of 14 mice in the control group. Median (+/-SD) number of days to tumor regrowth was 13.5+/-0.64 and 7.79+/-0.87 in the i.p. cisplatin and control groups, respectively. Mice in the i.p. cisplatin group had significantly delayed tumor regrowth, compared with control mice. Metastases to lungs were detected in 8 of 14 control mice but were not detected in mice in either cisplatin treatment group. CONCLUSIONS AND CLINICAL RELEVANCE: The open-cell polylactic acid with cisplatin delivery system was successful in delaying local tumor regrowth and metastasis in mice with marginally resected mammary carcinoma. Use of a controlled-release cisplatin delivery system may be an effective adjunct treatment following excision of mammary carcinoma in humans and other animals.