EGFR expression and survival in patients given cetuximab and chemoradiation for stage III non-small cell lung cancer: a secondary analysis of RTOG 0324.

Purpose: We investigated whether expression of epidermal growth factor receptor (EGFR) was associated with survival and disease control in this secondary analysis of a phase II trial of cetuximab+chemoradiation for stage III non-small cell lung cancer.
Methods: Patients received cetuximab weekly before and during radiation (63 Gy/35 fractions/7 weeks) with weekly carboplatin + paclitaxel. We analyzed EGFR expression by immunohistochemistry (IHC) and fluorescence in situ hybridization (FISH) in pretreatment biopsy specimens and compared findings with overall and progression-free survival (OS, PFS) and time to progression (TTP).
Results: Specimens for IHC and FISH were collected from 51 and 45 of 87 evaluable patients. Pretreatment characteristics did not differ for patients with (n = 51) or without (n= 36) EGFR IHC data, or with (n = 45) or without (n = 42) FISH data. However, patients without IHC data had worse OS (HR = 1.63, P = 0.05), worse PFS (HR = 1.88, P = 0.008), and worse TTP [HR = 1.99, P = 0.01] than those with IHC data. EGFR protein expression was not related to pretreatment characteristics or OS; FISH-positive disease was associated with better performance status but not with OS, PFS, or TTP.
Conclusions: Surprisingly, outcomes differed not by EGFR expression but by the availability of samples for analysis, underscoring the importance of obtaining biopsy samples in such trials.
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