RTOG 0617

Background

Phase 3 RCT with 2×2 factorial design. 544 patients with unresectable stage III NSCLC (IIIA or IIIB). Randomized to: standard dose 60 Gy vs high dose 74 Gy, AND concurrent cetuximab vs no cetuximab. Chemotherapy backbone: weekly carboplatin AUC 2 + paclitaxel 45 mg/m² concurrent with RT, followed by 2 consolidation cycles. Enrolled 2007–2011 at RTOG institutions.

Interventions and follow up

Arm A: 60 Gy + carboplatin/paclitaxel (±cetuximab)
Arm B: 74 Gy + carboplatin/paclitaxel (±cetuximab)
Primary endpoint: OS
mFollow up: Median 22.9 month

Results

OS (dose comparison): 74 Gy 20.3 months vs 60 Gy 28.7 months, HR 1.38 (95% CI 1.09–1.76), P=.004 — dose escalation SIGNIFICANTLY WORSE
OS (cetuximab): HR 1.07 (95% CI 0.84–1.35), P=.46 — no benefit
Local-regional failure: Numerically worse with 74 Gy
Mean heart dose association with OS: HR 1.25 per 10 Gy increase (exploratory)

Adverse events

Main adverse events: Grade ≥3 esophagitis: 21% (74 Gy) vs 7% (60 Gy), P<.001. Grade ≥3 pneumonitis: comparable (~7% both arms). Cetuximab: grade ≥3 skin toxicity 7% vs 2%. Dose escalation associated with greater cardiac and esophageal dose; higher mean heart dose correlated with worse OS.

Conclusions

Dose escalation to 74 Gy paradoxically worsened OS compared to standard 60 Gy in stage III NSCLC treated with concurrent chemoRT (HR 1.38, p=0.004). Cetuximab added no benefit. 60 Gy with concurrent carboplatin/paclitaxel remains the standard RT dose. The trial also identified mean heart dose as an important predictor of OS.

Key Limitations

Key Limitations: The negative effect of dose escalation was unexpected and counter to radiobiological modeling. Likely explanations include excessive cardiac and esophageal doses with higher-dose plans (74 Gy required larger volumes), resulting in treatment interruptions and reduced chemotherapy delivery. Mean heart dose was identified post-hoc as a significant OS predictor — a post-hoc finding requiring prospective validation. Modern proton therapy or advanced IMRT might achieve 74 Gy with better normal tissue sparing — the question of dose escalation with superior technique may not be fully answered by this trial. Cetuximab addition to chemoRT in stage III NSCLC has since been consistently negative.

Clinical Context

RTOG 0617 confirmed 60 Gy as the standard RT dose for stage III NSCLC with concurrent chemoRT. The mean heart dose finding has reshaped treatment planning — cardiac avoidance is now a priority (mean heart dose <20 Gy where feasible). PACIFIC subsequently added durvalumab consolidation after 60 Gy CRT. Proton therapy may enable dose escalation with better OAR sparing; RTOG 1308 (proton vs photon) is evaluating this hypothesis.

References

References: Bradley JD et al, Lancet Oncol 2015 (RTOG 0617)