Chemotherapy plus radiotherapy (CT-RT) versus RT alone for patients with anaplastic oligodendroglioma: Long-term results of the RTOG 9402 phase III study.
2008b Background: Anaplastic oligodendrogliomas, pure (AO) and mixed (AOA), are chemosensitive tumors, especially if co-deleted for chromosomes 1p and 19q, but whether addition of CT to RT prolongs overall survival (OS), is unknown. Methods: In the RTOG 9402 Phase III trial, patients (pts) with AO/AOA were randomly assigned to PCV [procarbazine, CCNU (lomustine) and vincristine] followed by immediate RT vs. immediate RT alone. Early analysis showed no OS benefit for the PCV+RT group but combined therapy was associated with a longer progression-free survival (PFS). It also showed that the finding of 1p/19q co-deletion was associated with a longer OS independent of treatment. The current analysis has a median follow up of 11.3 years (yrs). Results: Two hundred ninety-one patients were randomized, 148 to PCV+RT and 143 to RT. PCV+RT was associated with longer PFS [2.5 vs. 1.7 yrs, hazard ratio (HR) 0.68, 95% confidence interval (CI) (0.53, 0.88), P = 0.003] and the 1p/19q co-deletion with a longer Median Survival Time (MST) [8.7 vs. 2.7 yrs, HR 0.41, 95% CI (0.30, 0.55), P < 0.001]. For the entire cohort, there was no difference in MST by treatment [4.6 yrs for PCV+RT vs. 4.7 yrs for RT, HR 0.79, 95% CI (0.60, 1.04), P = 0.1]. However, patients with 1p/19q co-deleted tumors lived much longer after PCV+RT (n = 59) than after RT (n = 67) [14.7 vs. 7.3 yrs, HR 0.59, 95% CI (0.37, 0.95), P = 0.03]. There was no difference in MST by treatment in pts without the 1p/19q co-deletion [n=137; 2.6 vs. 2.7 yrs, HR 0.85, 95% CI (0.58, 1.23), P = 0.39]. Re-operation rates upon progression were similar between treatment arms in co-deleted pts (43%, PCV+RT vs. 54%, RT) but salvage CT rates were higher in the RT arm [57% vs. 81% (P = 0.04)]. Conclusions: PCV followed by immediate RT was a highly effective therapy for patients with 1p/19q co-deleted AO/AOA. In this setting, 1p/19q co-deletion was both prognostic and predictive, and the early PFS benefit in co-deleted cases was a harbinger of their longer OS. [This work was supported by RTOG grants U10 CA21661 and U10 CA32115, NCCTG grant U10 CA25224, ECOG grants CA17145 and CA21115, SWOG grant CA32102, and CCOP grant U10 CA37422 from the National Cancer Institute (NCI)]