Standard Postoperative Regimen for WHO Grade 4 Astrocytoma
For WHO grade 4 astrocytoma (glioblastoma), the standard treatment after surgical resection is concurrent temozolomide 75 mg/m² daily with focal radiotherapy (60 Gy in 30 fractions), followed by 6 cycles of adjuvant temozolomide (150-200 mg/m²) for 5 days every 28 days. This is the established Stupp protocol that provides a statistically significant survival benefit 1.
Concurrent Phase (Chemoradiotherapy)
Temozolomide Dosing:
- 75 mg/m² daily throughout the entire radiation course
- Start on day 1 of radiotherapy and continue for 42 days (maximum 49 days if needed)
- Administer 7 days per week, including weekends 1
Radiation Therapy:
- 60 Gy total dose delivered in 30 fractions (2 Gy per fraction)
- Focal radiotherapy targeting the tumor bed or resection site with a 2-3 cm margin 1
Critical Safety Requirement:
- Pneumocystis pneumonia (PCP) prophylaxis is mandatory during concurrent therapy, regardless of lymphocyte count, and must continue until lymphocyte recovery to ≤Grade 1 1
Dose Interruption Criteria During Concurrent Phase:
- Hold temozolomide if ANC <1.5 × 10⁹/L or platelets <100 × 10⁹/L
- Discontinue permanently if ANC <0.5 × 10⁹/L or platelets <10 × 10⁹/L
- Hold for Grade 3-4 non-hematologic toxicity (except alopecia, nausea, vomiting) 1
Maintenance Phase (Adjuvant Chemotherapy)
Begin 4 weeks after completing chemoradiotherapy 1
Cycle 1:
- 150 mg/m² daily for 5 consecutive days, followed by 23 days rest (28-day cycle)
Cycles 2-6:
- Escalate to 200 mg/m² daily if all of the following are met:
- ANC ≥1.5 × 10⁹/L
- Platelets ≥100 × 10⁹/L
- Non-hematologic toxicity ≤Grade 2 (except alopecia, nausea, vomiting) 1
Monitoring Requirements:
- Complete blood count on Day 22 of each cycle (or within 48 hours)
- Weekly CBC monitoring until ANC >1.5 × 10⁹/L and platelets >100 × 10⁹/L 1
Evidence Supporting This Regimen
The pivotal trial of 573 patients demonstrated that temozolomide plus radiotherapy significantly improved overall survival compared to radiotherapy alone, with a hazard ratio of 0.63 (95% CI 0.52-0.75, p<0.0001). Median survival increased by 2.5 months with the addition of temozolomide 1. This regimen is endorsed by EANO guidelines as standard of care for IDH-wild-type glioblastoma 2.
Important Caveats
Do not confuse this with IDH-mutant astrocytoma, WHO grade 4, which has different treatment recommendations. For IDH-mutant astrocytoma grade 4, EANO guidelines recommend radiotherapy followed by maintenance temozolomide based on the CATNON trial, but the concurrent phase dosing may differ 2. The question specifically asks about "grade 4 astrocytoma" which in modern practice typically refers to IDH-wild-type glioblastoma.
CDKN2A/B deletion status in IDH-mutant tumors is a critical prognostic factor—patients with this deletion have significantly worse outcomes (median OS 5.0 years vs 10.1 years without deletion) and may warrant more aggressive monitoring 3.
Common pitfall: Failing to provide PCP prophylaxis during concurrent therapy, which is mandatory regardless of lymphocyte count 1. Another pitfall is not checking blood counts on Day 22 of maintenance cycles, risking severe myelosuppression.