Long-term follow-up results from two clinical trials have confirmed substantially longer survival for certain patients with anaplastic oligodendrogliomas if they are treated with a combination of chemotherapy and radiation therapy instead of radiation alone. Anaplastic oligodendrogliomas account for less than 10% of brain and central nervous system (CNS) cancers.
In both trials, those patients whose tumor cells had missing or deleted parts of chromosomes 1 and 19 and received the combination treatment lived substantially longer than patients whose tumors had these deletions but received radiation therapy alone. Both of the trials were launched in the mid 1990s. These chromosomal codeletions occur in about half of patients diagnosed with anaplastic oligodendroglioma. Survival was not improved for those patients whose tumor cells lacked the deletions.
“These studies establish a new standard of care for patients with [anaplastic oligodendroglioma] tumors that harbor the 1p19q loss. No longer is radiation considered an adequate treatment for this patient population,” wrote Dr. Mark Gilbert of the University of Texas MD Anderson Cancer Center in an accompanying editorial.
In the trial by the Radiation Therapy Oncology Group (RTOG), participants whose tumors harbored both chromosomal deletions and who received high-dose chemotherapy with procarbazine, lomustine, and vincristine (the PCV regimen), followed by radiation, had a median survival of 14.7 years. Those who received only radiation had a median survival of 7.3 years. Those patients whose tumors did not have the chromosomal deletion had a median survival of less than 3 years, regardless of which of the two treatments they received. The RTOG 9402 trial was published in Journal of Clinical Oncology (2012; doi:10.1200/JCO.2012.43.2674).
The other trial, EORTC 26951, treated patients with radiation therapy alone or radiation followed by a standard-dose PCV regimen. Currently, the median overall survival cannot yet be calculated for patients with the chromosomal codeletions who received the combination therapy, but there is a strong trend toward improved overall survival. The EORTC 26951 trial was published in Journal of Clinical Oncology (2012; doi:10.1200/JCO.2012.43.2229).
Uncertainty still exists about the preferred treatment for these patients, cautioned the principal investigator of the RTOG trial, Gregory Cairncross, MD, of the University of Calgary. For example, many oncologists appear to prefer using temozolomide to treat anaplastic oligodendroglioma because it can improve survival in glioblastoma, it has fewer side effects, and it is easier to administer than the PCV regimen.