Adding a chemotherapy combination to radiation therapy for initial treatment of low-grade gliomas significantly improved overall survival and progression-free survival, regardless of the tumor type, investigators report in the New England Journal of Medicine.
Grade 2 glioma patients who received radiation plus the combination of procarbazine, lomustine (also called CCNU), and vincristine (PCV) had a longer median overall survival than those who received radiation alone (13.3 vs. 7.8 years; hazard ratio for death, 0.59; P = .003). Of those who received radiation plus chemotherapy, the progression-free survival rate at 10 years was 51%, compared with 21% for the group who received radiation alone, Dr. Jan Buckner and his colleagues report (N Engl J Med. 2016;374:1344-55. doi: 10.1056/NEJMoa1500925).
“The magnitude of treatment benefit from combined chemotherapy plus radiation therapy is substantial, but the toxic effects are greater than those observed with radiation therapy alone,” wrote Dr. Buckner, professor of oncology at the Mayo Clinic, Rochester, Minn., and associates. Patients who received radiation plus PCV had more toxic side effects from their therapy, though most effects were grade 1 and 2.
For this study, 254 patients were randomized, with 128 assigned to radiotherapy alone, and 126 assigned to radiotherapy plus PCV. A total of 126 patients in the radiotherapy arm were included in the analysis, with one patient not receiving the intervention and 14 patients lost to follow-up at some point during the 10 years of the study. In the radiotherapy plus PCV arm, 125 patients were eligible for evaluation, and all of those patients were included in the analysis. Twenty-six patients in this arm were lost to follow-up, and 72 patients discontinued the intervention in this arm (this figure included four patients who died).
Tumor types included in the study were grade 2 astrocytoma, oligoastrocytoma, or oligodendroglioma.
Patients were included if they were between 18 and 39 years of age and had received a subtotal resection or biopsy of their tumor, or if they were 40 years of age or older and had any resection or biopsy of their tumor. Exclusion criteria included previous radiation to the head or neck, any previous chemotherapy, significant pulmonary disease, and a 5-year history of other cancers except cervical cancer in situ and non-melanoma skin cancer. Tumors could not have spread to noncontiguous leptomeninges, and patients could not have gliomatosis cerebri. Patients had to have a Karnofsky performance score of 60 or higher, and a neurological function score of 3 or less.
Dr. Buckner and his collaborators also assessed tumors for IDH1 mutational status by performing immunostaining with the mutation-specific monoclonal antibody IDH1 R132H; appropriate tissue was available for testing in slightly less than half of the patients in each study arm. The mutation was present in 35/57 patients (61%) in the radiotherapy-only arm, and 36/56 patients (64%) in the radiotherapy plus PCV arm. Patients with oligodendroglioma were most likely to have IDH1 R132H mutations. Sample sizes were too small to determine the effect of other IDH mutations or co-deletion of chromosome arms 1p and 19q.
In multivariable analysis, the presence of the IDH1 R132H mutation was identified as an independent prognostic factor for better overall survival (OS) and progression-free survival (PFS), regardless of the treatment administered. Those with the mutation still benefited significantly from receiving radiotherapy plus PCV rather than radiotherapy alone (P = .02 for OS, P less than .001 for PFS).
Exploratory analysis that broke down OS and PFS by cancer type showed that “the superiority of radiation therapy plus chemotherapy over radiation therapy alone was seen with all histologic diagnoses, although the difference did not reach significance among patients with astrocytoma,” wrote Dr. Buckner and his collaborators.
When all patients lost to follow-up in both groups were assessed as having died, the sensitivity analysis still showed benefit for radiotherapy plus PCV (HR for death, compared with radiotherapy alone, 0.72; P = .03).
The value of the long-term follow-up, wrote Dr. Buckner and his colleagues, was that “The separation of the progression-free survival curves of the two treatment groups did not begin until 2 to 3 years after randomization, although approximately 25% of the patients in each group had disease progression by then.”
Dr. Buckner and his collaborators emphasized that the patient-physician team should consider all factors in making treatment decisions, saying, “Patients and their physicians will have to weigh whether the longer survival justified the more toxic therapeutic approach.“
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