Radiotherapy Fractionation for High-Risk Locally Advanced (cT3b N0 M0) NSCLC
For high-risk locally advanced stage III NSCLC (cT3b N0 M0), the standard radiotherapy fractionation is 60 Gy delivered in 30 fractions of 2.0 Gy each, with treatment completed within 6 weeks when given with concurrent chemotherapy. 1
Standard Concurrent Chemoradiotherapy Fractionation
The evidence strongly supports conventional fractionation for concurrent chemoradiotherapy:
60-66 Gy in conventional daily fractions of 1.8-2.0 Gy represents the established standard for concurrent chemoradiotherapy in stage III NSCLC 1
Maximum overall treatment time should not exceed 7 weeks, as prolonged treatment duration significantly compromises outcomes 1
The landmark RTOG 0617 trial definitively established that 60 Gy in 30 fractions (2 Gy per fraction) is superior to dose escalation, with median OS of 28.7 months versus 20.3 months with 74 Gy in 37 fractions (HR 1.38, P=0.004) 1
Alternative Fractionation Schedules
Sequential Chemoradiotherapy (When Concurrent Not Feasible)
If the patient cannot tolerate concurrent chemoradiotherapy due to comorbidities:
66 Gy in 24 fractions (accelerated schedule) is a validated alternative that has demonstrated improved 5-year survival compared to conventional 2 Gy daily fractions 1
The CHART regimen (continuous hyperfractionated accelerated radiotherapy) showed significant survival benefit in phase III trials for stage III disease 1
Preoperative Setting (If Surgery Planned)
For potentially resectable disease requiring neoadjuvant treatment:
40-50 Gy in conventional fractionation (1.8-2.0 Gy per day) is the standard preoperative dose 1
40-45 Gy in accelerated hyperfractionation (1.5 Gy twice daily) is an alternative used in multiple phase III trials 1
Critical Treatment Principles
Treatment acceleration is not standard practice in concurrent chemoradiotherapy schedules (Level III, Grade B evidence) 1
Common Pitfalls to Avoid
Do not escalate beyond 60 Gy with concurrent chemotherapy outside clinical trials: Doses up to 70 Gy may be considered in highly selected patients with strict normal tissue constraints, but the RTOG 0617 trial showed harm with 74 Gy 1
Do not prolong treatment time beyond 7 weeks: This is associated with worse outcomes regardless of total dose delivered 1
Avoid higher preoperative doses (60-63 Gy) outside clinical trials: These increase toxicity risk including radiation pneumonitis and acute respiratory distress syndrome without proven benefit 1
Quality Assurance Requirements
Advanced radiotherapy techniques with rigorous quality assurance are essential when delivering these doses, with careful attention to cardiac mean dose, lung V20, esophageal mean dose, and spinal cord maximum dose 1