Strong indicator for determining treatment and outcome for patients with oligodendroglioma brain tumours
A recent analysis of clinical trial results performed by the Radiation Therapy Oncology Group (RTOG) demonstrate that a chromosomal abnormality—specifically, the absence (co-deletion) of chromosomes 1p and 19q—have definitive prognostic and predictive value for managing the treatment of adult patients with pure and mixed anaplastic oligodendrogliomas. The presence of the chromosomal abnormality was associated with a substantially better prognosis and near-doubling of median survival time when treatment with combined chemotherapy and radiation therapy was compared to treatment with radiation therapy alone.
Oligodendrogliomas are uncommon tumours that represent approximately 4.0% of all brain tumours. Mixed oliogdendrogliomas (those also containing astrocytic elements) account for 1.0% of all brain tumours. Pure and mixed oligodendrogliomas that contain anaplastic (malignant) cells typically grow more rapidly than non-anaplastic tumours.
The RTOG 9402 trial A Phase III Intergroup Randomized Comparison of Radiation Alone vs. Pre-Radiation Chemotherapy for Pure and Mixed Anaplastic Oligodendrogliomas was conducted with four other National Cancer Institute (NCI)-supported co-operative groups. Trial participants had a pathologically confirmed pure or mixed anaplastic oligodendroglioma and were randomly assigned into one of two treatment arms. The 148 participants randomised to Arm 1 were treated with PCV (procarbazine, CCNU [lomustine] and vincristine) chemotherapy and radiation therapy (RT), and the 143 participants randomised to Arm 2 were treated with RT alone.
RTOG 9402 study results showed no survival benefit for patients treated with early PVC chemotherapy plus RT over RT alone. Although a significant impact on median progression-free survival time was realised (2.6 years versus 1.7 years for RT alone), the regimen was associated with significantly more adverse side effects. The study authors also reported that study participants in both arms whose tumour lacked chromosomes 1p and 19q had longer median survival times as compared with participants without these deletions (> 7 vs. 2.8 years, respectively). This led the study authors to conclude that ‘tumours with 1p and 19q co-deletion are less aggressive or more responsive to PCV chemotherapy or both.’
A recent analysis undertaken of the RTOG 9402 data (at a median study participant follow-up time of 11 years) is planned for submission to the 2012 American Society of Clinical Oncology Annual Meeting. However, due to the finding’s significance for patient care, results are reported here in advance of submission. Radiation Therapy Oncology Group
