Abstract
7047 Background: In EORTC 08941, no difference in overall and progression free survival was observed in 332 pts with irresectable stage IIIA-N2 NSCLC, treated with either S or RT after a response to platinum-based ICT (van Meerbeeck, JCO 2005; 23, 1095s). Postoperative radiotherapy (PORT) was given to 40% of pts. In the S-pts, non-randomized exploratory comparisons showed a statistically significant benefit in outcome for (bi-)lobectomy vs. pneumonectomy (p = 0.0088) and for mediastinal lymphnodes (MLN) downstaged vs.non-downstaged pts (p = 0.0009). No difference was observed between S-pts treated with/without PORT. By randomizing after response to ICT, MLN-downstaging is assumed to be equally distributed among both treatment groups but cannot be formally retrieved in RT-pts. In order to compare the influence of MLN-downstaging in each treatment arm, we estimated in an exploratory analysis the outcome in subsets of S-pts and matched paired subsets of RT-pts. Methods: The subsets of 129 actually resected S-pts are defined as follows: (i) pts with MLN-downstaging at resection, (ii) pts without MLN-downstaging. Each subset was compared to a randomly selected subset of 154 actually irradiated RT-pts, matched on 4 baseline factors: histological subtype, gender, T stage, response to ICT. Kaplan-Meier estimates for overall survival (OS) and logrank p-values were then computed. Results: A match was feasible for 54/61 downstaged, 59/68 non-downstaged pts. Estimated OS (with 95% CI) for each S-subset and RT-matched pair subset is in the table . Conclusions: From these exploratory analyses, it appears that: 1. RT improves OS in MLN-non-downstaged pts; 2. S does not improve OS in MLN-downstaged patients. This should however be prospectively assessed. [Table: see text] No significant financial relationships to disclose.
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