Retreating recurrent breast cancer with the same CMF-containing regimen used as adjuvant therapy. The International Breast Cancer Study Group.

Abstract

Breast cancer metastases appearing soon after adjuvant chemotherapy (within 12 months of its completion) are usually resistant to retreatment with the same cytotoxic agents, while relapses occurring later (beyond 12 months) regress when rechallenged with the same agents, showing similar response rates observed in non-pretreated patients with advanced disease. The International Breast Cancer Study Group (IBCSG) prospectively explored the efficacy of retreatment for patients upon relapse using the same therapy administered during the adjuvant programme. 87 patients previously treated with an adjuvant CMF (cyclophosphamide, methotrexate, 5-fluorouracil) combination chemotherapy (with or without the addition of low-dose prednisone and tamoxifen), who had measurable first breast cancer relapse, usually after at least 6 months of completion of the adjuvant treatment, were treated with CMF. Pretreatment consisted of 1-3 CMF courses in 27 patients and 4 or more courses in 60 patients. 17 patients were retreated with additional tamoxifen or had tamoxifen stopped at relapse. The data of these patients are shown separately. 47 of the 86 fully evaluable patients (55%) had an objective response, which was complete in 25 (29%). The dominant metastatic type and the number of involved sites were the most important factors influencing response to retreatment. Patients with soft tissue metastases had a high response rate (36/52, 69%) compared with those who had visceral involvement (9/24, 38%) or those with bony disease (2/10, 20%) (P = 0.002). In conclusion, response rates to retreatment with CMF were similar to those expected in a non-pretreated population. The patterns of relapse and the number of metastatic sites were the most important factors predicting response to retreatment, while treatment-free interval (usually longer than 6 months due to the study design) did not influence response rates. This study supports the hypothetic effectiveness of late reintroduction of adjuvant cytotoxic therapy (prior to evidence of systemic relapse), upon which several current trials are based.