A 38-year-old woman undergoes surgical resection for a WHO Grade II diffuse astrocytoma of the left temporal lobe. Postoperative MRI confirms gross total resection. Molecular testing shows IDH1 mutation and 1p/19q codeletion. She is referred for adjuvant therapy. What is the drug of choice for chemotherapy in this patient?

Explanation

## Drug of Choice for IDH-Mutant, 1p/19q-Codeleted Low-Grade Glioma **Key Point:** PCV (procarbazine, CCNU, and vincristine) is the standard chemotherapy regimen for WHO Grade II gliomas with favorable molecular markers (IDH mutation + 1p/19q codeletion), particularly when adjuvant therapy is indicated. ### Molecular Classification and Prognosis This tumor has two favorable prognostic markers: 1. **IDH1 mutation** — indicates secondary glioma origin, better prognosis than IDH-wildtype 2. **1p/19q codeletion** — defines oligodendroglioma subtype, highly chemosensitive Tumors with both markers have significantly improved overall survival compared to IDH-wildtype or non-codeleted tumors. ### Evidence for PCV Regimen The **RTOG 9402** and **EORTC 26951** trials established PCV as the standard for anaplastic oligodendrogliomas (Grade III). For Grade II gliomas with 1p/19q codeletion, PCV is preferred because: - Superior response rates in 1p/19q-codeleted tumors - Better long-term progression-free and overall survival - Established safety and tolerability profile ### PCV Dosing Schedule | Drug | Dose | Schedule | |------|------|----------| | **Procarbazine** | 100 mg/m²/day | Days 8–21 | | **CCNU (Lomustine)** | 110 mg/m² | Day 1 | | **Vincristine** | 1.4 mg/m² (max 2 mg) | Days 8, 29 | | **Cycle length** | 56 days | Repeat × 6 cycles | **High-Yield:** 1p/19q codeletion is a **chemosensitivity marker** — these tumors respond exceptionally well to PCV. This is one of the most frequently tested molecular correlates in glioma pathology. **Mnemonic:** **PCV = Procarbazine, CCNU, Vincristine** — the classic regimen for chemosensitive oligodendrogliomas. **Clinical Pearl:** Temozolomide monotherapy is increasingly used as an alternative in some centers and is acceptable, but PCV remains the gold-standard comparator in clinical trials for 1p/19q-codeleted gliomas. [cite:Cairncross et al. RTOG 9402 / EORTC 26951. J Clin Oncol 2006; Harrison 21e Ch 397; Robbins 10e Ch 28]