Platinum plus cyclophosphamide plus radiotherapy is superior to platinum alone in ‘high-risk’ epithelial ovarian cancer (residual negative and either stage I or II, grade 3, or stage III, any grade)

Patients with epithelial ovarian cancer (EOC) referred to our institution are stratified into risk groups based on their stage, grade and presence of residual cancer, with a specific treatment policy for each group. One-hundred and thirty-one patients with no visible residual tumor following primary surgery and either stage I, grade 3; stage II, grade 3; or stage III, any grade EOC were treated between November 1983 and the end of December 1991. Regimen A (cisplatin 75 mgm−2 and cyclophosphamide 600 mgm−2 intravenously every 4 weeks for 6 cycles with abdominopelvic irradiation between cycles 3 and 4) was used until April 1989 and was then replaced with Regimen B (cisplatin 75 mgm−2 intravenously every 3 weeks for 6 cycles). The 5-year actuarial overall and failure-free survivals were 78% and 64% respectively. Multivariate analysis identified increasing stage and treatment with Regimen B as independent adverse prognostic factors for failure-free survival. The importance of treatment regimen reached statistical significance for the stage I patients (P = 0.04) but not stage II (P = 0.11) or stage III (P = 0.79). It is possible to undertreat EOC as shown by the inferior results achieved with Regimen B (single agent cisplatin) compared to Regimen A (cisplatin-cyclophosphamide, irradiation). This effect of treatment regimen was particularly important for the lower-stage patients. Our postulate is that treatment resistant clones are less regularly present in lower-stage patients, and that a certain minimum amount of treatment is required to eliminate all the sensitive cancer.