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ORAL 20 - Chemoradiotherapy (ID 124)
- Event: WCLC 2015
- Type: Oral Session
- Track: Treatment of Locoregional Disease – NSCLC
- Presentations: 1
ORAL20.06 - Outcomes of Intensity Modulated and 3D-Conformal Radiotherapy for Stage III Non-Small Cell Lung Cancer in NRG Oncology/RTOG 0617 (ID 938)
10:45 - 12:15 | Author(s): S.G. Chun
Intensity modulated radiation therapy (IMRT) has the potential to improve target coverage and spare toxicity in locally-advanced non-small cell lung cancer (NSCLC). However, the effect of IMRT on outcomes for NSCLC has not previously been assessed in a large prospective cooperative group clinical trial.
A secondary analysis was performed in patients with stage III NSCLC in NRG/RTOG 0617, a randomized phase III comparison of standard-dose (60 Gy) versus high-dose (74 Gy) chemoradiotherapy +/- cetuximab. Radiotherapy (RT) technique was stratified by IMRT and 3D-conformal radiotherapy (3D-CRT). Baseline prognostic and RT dosimetric parameters were compared between IMRT and 3D-CRT after adjusting for RT dose levels and cetuximab use. The prognostic value of RT technique with respect to toxicity and efficacy was assessed through multivariate logistic regression (MVA) and Cox proportional hazards model after controlling for RT dose level, cetuximab use and other factors.
Of the 482 eligible patients treated with RT, 53% and 47% were treated with 3D-CRT and IMRT, respectively. The IMRT group had more stage IIIB (38.6 vs. 30.3%, P = 0.056), larger PTVs (mean 486 vs. 427 mL, P = 0.005), and larger PTV:lung ratio (mean 0.15 vs. 0.13, P = 0.013). In spite of larger PTV volumes, IMRT was associated with lower lung V20 (P = 0.08), and lower heart doses (V5, V20, V40) than 3D-CRT. In turn, IMRT was associated with a lower rate (3.5 versus 7.9%) of Grade 3+ pneumonitis (P = 0.0653). On MVA, the lung V20 significantly predicted grade 3+ pneumonitis, while the lung V5 and mean lung doses did not. Larger heart V40 was associated with worse OS (HR=1.013, P < 0.001), and the heart V40 was significantly lower in patients treated with IMRT. Patients treated with IMRT were also more likely (37 versus 29%) to receive full doses of consolidative chemotherapy (P = 0.05).
Although IMRT was used to treat larger and less favorable tumors in RTOG 0617, it was associated with reduced risk of Grade 3+ pneumonitis and higher likelihood of receiving full doses of consolidative chemotherapy. The heart V40, shown to be highly prognostic for survival, can be substantially reduced with IMRT compared to 3D-CRT.
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