(ChemotherapyAdvisor) – Procarbazine, lomustine, and vincristine (PCV) plus radiotherapy (RT) “may be an especially effective treatment” for a subset of patients with 1p/19q co-deleted anaplastic oligodendrogliomas, both pure (AO) and mixed (anaplastic oligoastrocytoma [AOA]), long-term results of a study in the Journal of Clinical Oncology online October 15 has found.

Previously, studies have shown that patients with AO and AOA, which have a common molecular ancestry, are chemosensitive. However, to determine whether chemoradiotherapy can improve overall survival (OS), the Radiation Therapy Oncology Group (RTOG) 9402 phase 3 study randomly assigned 291 eligible patients with AO/AOA to PCV plus RT (n=148) or RT alone (n=143), reported lead author J. Gregory Cairncross, MD, of Foothills Medical Centre, Calgary, Alberta, Canada.

The investigators found no difference in median survival by treatment for the entire cohort; 4.6 years for PCV plus RT vs 4.7 years for RT (HR 0.79; 95% CI, 0.60 to 1.04; P=0.1).

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However, they observed “patients with co-deleted tumors lived longer than those with non−co-deleted tumors”: in the PCV plus RT arm, median OS was 14.7 years vs 2.6 years (HR 0.36; 95% CI, 0.23−0.57; P<0.001) and, in the RT alone arm, 7.3 vs 2.7 years (HR 0.40, 95% CI, 0.27−0.60, P<0.001). Median OS of those with co-deleted tumors treated with PCV plus RT was twice that of patients receiving RT (14.7 vs 7.3 years; HR 0.59; 95% CI, 0.37−0.95; P=0.03),” Dr. Cairncross reported.

Among patients with non−co-deleted tumors, no difference in median OS by treatment arm was observed, 2.6 vs 2.7 years (HR 0.85; 95% CI, 0.58−1.23; P=0.39). In an unplanned analysis, the adjusted OS for all patients was prolonged by PCV plus RT (HR 0.67; 95% CI, 0.50−0.91; P=0.01).

An accompanying editorial noted, “These results have several important implications…[and] establish a new standard of care for patients with AO tumors that harbor the 1p/19q loss. No longer is radiation considered an adequate treatment for this patient population.”Based on these results, an international cooperative group study of newly diagnosed AO with 1p/19q loss (CODEL) was halted because the control arm, radiation alone, is no longer viable.