AT-56 * TREATMENT OF LARGE LOW-GRADE OLIGODENDROGLIAL TUMORS WITH UPFRONT PROCARBAZINE, LOMUSTINE, AND VINCRISTINE CHEMOTHERAPY WITH LONG FOLLOW-UP: A RETROSPECTIVE COHORT STUDY WITH GROWTH KINETICS

Abstract

PURPOSE: We treated patients with newly diagnosed and large low-grade oligodendroglial tumors with upfront procarbazine, lomustine (CCNU) and vincristine (PCV) in our institution in order to delay RT. We now report long term follow-up on a cohort of patients treated between 1998 and 2006. METHODS: Patients were treated with PCV in cycles of 6 weeks, for a maximum of 6 cycles. Central pathology review, genotyping on 1p/19q loss and immunohistochemistry on the IDH1 mutational status and MIB-1 labeling was performed. The response to treatment was defined according to the RANO criteria; in addition change over time of mean tumor diameters (growth kinetics) was calculated. RESULTS: Thirty-two patients were treated, 18 of which were diagnosed with 1p/19q co-deleted tumors. Median follow-up duration was 8 years. The median overall survival (OS) was 120 months and the median progression-free survival (PFS) was 46 months. Growth kinetics showed an ongoing decrease of the mean tumor diameter after completion of chemotherapy, during a median time of 35 months (range 5-136 months), but an increase of the mean tumor diameter did not herald progression as detected by RANO criteria. 1p/19q co-deletion was associated with a significant increase in OS (median OS 83 months versus not reached for codeleted tumors; p = 0.003)) and PFS (median PFS 35 months versus 67 months for codeleted tumors; p = 0.024). Patients with combined 1p/19q loss had a 10 year PFS of 34% and the radiotherapy in these patients was postponed for a median period of more than 6 years. CONCLUSION: This long-term follow-up study indicates that upfront PCV chemotherapy is associated with long PFS and OS and delays radiotherapy for a considerable period of time in patients with low-grade oligodendroglial tumors, in particular with combined 1p/19q loss.