In newly diagnosed anaplastic oligodendroglial tumours, does adding PCV chemotherapy to radiotherapy improve long-term survival, particularly in 1p/19q-codeleted disease? [EORTC 26951 / RTOG 9402]
In newly diagnosed anaplastic oligodendroglial tumours, does adding PCV chemotherapy to radiotherapy improve long-term survival, particularly in 1p/19q-codeleted disease?
Absolute Effect
EORTC 26951 overall median OS 3.5 vs 2.6 years with PCV vs RT alone, HR 0.78 (95% CI 0.63–0.98), P=.033. In 1p/19q-codeleted disease, median OS 14.2 vs 9.3 years, HR 0.60 (95% CI 0.35–1.03), P=.063. RTOG 9402 codeleted disease showed median OS 13.2 vs 7.3 years, HR 0.61 (95% CI 0.40–0.94), P=.02.
Absolute effect: In the EORTC codeleted subgroup, estimated 20-year OS was 37.1% with PCV vs 13.6% without, an absolute difference of 23.5 percentage points. Because this is a molecular subgroup with limited sample size and the EORTC subgroup P value was .063, this should not be converted into a routine NNT.
NNT: not reported/calculated. The most striking absolute differences are in the molecularly defined subgroup, but the subgroup is relatively small and should not be treated as an independently powered NNT analysis.
NNH: not quantifiable from a single consistent fixed-time severe-toxicity endpoint across both historical trials.
Follow-up: Median follow-up 18–19 years.
Clinical results and treatment burden
- Intervention: Radiotherapy alone versus radiotherapy plus procarbazine, lomustine (CCNU) and vincristine (PCV), given in neoadjuvant/adjuvant or concurrent trial-specific sequences.
- Principal toxicity: PCV adds substantial hematologic toxicity and treatment burden compared with RT alone; historical treatment delivery also differs from modern temozolomide-based practice.
- Other efficacy/recurrence findings: The convergence of the two randomized programmes is important: both show a durable survival signal concentrated in 1p/19q-codeleted tumours, supporting the biological identity of oligodendroglial disease as particularly chemotherapy-sensitive.
- Quality of life: Formal QoL evidence is limited by the age and design of these trials.
Eligibility and clinical context
Two randomized phase III trials initiated in the 1990s, together enrolling more than 650 patients with newly diagnosed anaplastic oligodendroglial tumours; modern interpretation is anchored to IDH mutation and 1p/19q codeletion.
Limitations and maturity: The trials predate modern molecular classification, molecular imaging and contemporary supportive care. PCV is more toxic and cumbersome than temozolomide. The molecular subgroup results are the most clinically relevant but must be interpreted within the randomized parent trials.