Monitoring the unmaintained remission of acute non-lymphoblastic leukemia by serial bone marrow cultures

Between 1974 and 1989, 217 patients with ANLL, aged less than 70 years, were submitted to an intensive remission induction chemotherapy. A complete remission was achieved in 100 (46%) cases. Ten (10%) patients survived in continuous remission beyond 16 months after cessation of remission maintenance therapy. In these 10 long-term survivors, bone marrow was serially cultured in semi-solid agar during the unmaintained remission for a median period of 40 (range 12-72) months. In another group of 18 patients bone marrow was cultured after cessation of remission maintenance chemotherapy at intervals of 29-43 (median 33) days until relapse, at most up to 16 months, when all patients relapsed. In both groups of patients a periodic return to a leukemic growth pattern in their marrow cultures was observed. The difference in the frequency of leukemic growth patterns between both groups is not significant, while the patients, who remained in prolonged remission, had a significantly higher mean number of colonies. It is suggested that monitoring the remission with the help of bone marrow cultures is useless in predicting an approaching relapse of ANLL. However, a high number of colonies in most marrow cultures is perhaps an indicator of a prolonged remission.