Results of the COSS-77 and COSS-80 studies on adjuvant chemotherapy in osteosarcoma of the extremities

In the first study, COSS-77, 100 patients with OS were treated for 12 months according to a CT-protocol consisting of high-dose methotrexate (HD-MTX), adriblastine (ADR) and cyclophosphamide (CP). At 40 months the expected continuous disease-free survival (CDFS) rate of the 71 evaluable patients was 55%. After exclusion of local recurrences (n = 2) and fatal chemotherapy toxicities (n = 0) a reduced group of 69 patients remained and the expected CDFS rate at 40 months became 56%. In the second study, COSS-80, the MTX dose was doubled. Two groups were randomly selected, one of which received cisplatinum (CPL) and the other the triple drug combination bleomycin + CP + dactinomycin (BCD) in addition to MTX and ADR, both groups being treated for 8 months. Furthermore some randomly selected patients received fibroblaste-interferon (IF). The expected CDFS rate at 40 months of the 115 evaluable COSS-80 patients was 67%. 106 patients remained in a reduced group defined as above (4 local recurrences and 5 CT toxicities) in which the expected CDFS rate at 40 months was 73%. This is significantly better (p less than 0.05) than the results obtained from the COSS-77 group. No differences were found between the CPL and BCD arms of the COSS-80 group or between the arms receiving or not receiving IF. A significant increase in the CDFS rate for young (less than 12 years) and male patients over that in COSS-77 was observed in COSS-80, probably due to the increased MTX dose.