Co-lead investigator Dr. Jan Buckner, professor of oncology at the Mayo Clinic in Rochester, Minn., said all three chemotherapy drugs in the regimen are commercially available, so the treatment used in the clinical trial is available for use.
However, this form of chemotherapy is associated with some toxicities, such as reduced white blood cell counts leading to increased infection risk, and trial investigators recommend that it should be utilized only by physicians experienced with managing the side-effects that may occur.
Low-grade gliomas grow more slowly and have a better outcome than the more common type of brain tumor in adults, which is classified as glioblastoma.
The study enrolled 251 patients with low-grade gliomas between October 1998 and June 2002. Patients enrolled were at high risk compared to other low-grade glioma patients because they were age 40 years or older or had a less than complete surgical removal of their tumor if they were age 40 or younger.
All patients started treatment with surgery followed by radiation therapy. By random assignment, half stopped treatment after radiation therapy and the other half received six cycles of chemotherapy after completing radiation therapy.
Patients receiving chemotherapy got three drugs: procarbazine; CCNU, which generically is known as lomustine; and vincristine. This chemotherapy, termed PCV, was given over 21 days and repeated every eight weeks for a total of six cycles.
A significant improvement in overall survival was noted for study participants who received PCV chemotherapy plus radiation therapy -- 13.3 years median survival time -- compared with those receiving radiation therapy alone at 7.8 years median survival time, which is a difference of 5.5 years. Median follow-up after initial enrollment has been almost 12 years.
"The results of this study are practice-changing," Buckner said in a statement. "Additionally, ongoing analysis of patient tumor samples should allow us to further identify the patients who will, and who will not, benefit from chemotherapy, taking yet another step toward individualized therapy."