(ChemotherapyAdvisor) – Patients with oligodendrogliomas who lack chromosomes 1p and 19q have a better prognosis and near-doubling of median survival times when treated with chemotherapy and radiation therapy (RT) vs. RT alone.

“We now have unequivocal evidence that the chromosomal structure of 1p and 19q co-deletion can be used as a marker to determine which patients will benefit from combined chemotherapy and radiation therapy,” said J. Gregory Cairncross, MD, of the University of Calgary, Alberta, Canada, and Radiation Therapy Oncology Group (RTOG) 9402 trial principal investigator.

In the RTOG 9402 trial, 148 patients with pathologically confirmed pure or mixed anaplastic oligodendroglioma were randomized to procarbazine, lomustine and vincristine (PCV) plus RT and 143 to RT alone. Of these patients, 126 had the 1p and 19q co-deletion; at a median follow-up of 11 years, median survival time for 59 patients randomized to the PCV plus RT arm was 14.7 years vs. 7.3 years for 67 who received RT alone. If a patient had only one deletion (either 1p or 19q) or no deletions, no difference in median survival time was found between the treatment arms (2.6 vs. 2.7 years).

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Given the significance of these findings for patient care, RTOG reported these results in advance of a planned abstract submission to the ASCO 2012 annual meeting. In 2006, RTOG 9402 minimum 3-year follow-up results published in the Journal of Clinical Oncology noted that “tumors with 1p and 19q co-deletion are less aggressive or more responsive to PCV chemotherapy or both.”

In addition to RTOG, cooperative groups participating in the intergroup (INT 0149) trial are the Eastern Oncology Cooperative Group, SWOG, North Central Cancer Treatment Group, and the NCIC Clinical Trials Group.

RTOG Press Release