C/EBPα expression by immunohistochemistry lacks prognostic or predictive significance in primary resected non-small cell lung cancer

Abstract

7202 Background: The transcription factor CCAAT/enhancer binding protein alpha (C/EBPα) is down-regulated in a majority of lung cancers. We sought to determine if C/EBPα could be a prognostic or predictive factor in non-small-cell lung cancer (NSCLC). Methods: Our cohort originated from ECOG 3590/4592 (randomized trial of postoperative adjuvant therapy with thoracic radiation or cisplatin and etoposide plus thoracic radiation in patients with completely resected stages II and IIIA NSCLC; and its laboratorial study). 166 tumor samples contained material for immunohistochemical (IHC) analysis of C/EBPα expression. We used a scoring system comparing tumor staining to that of basal bronchial cells (3+). 0 or 1+ (weak) staining suggested lack of, while 2 or 3+ (strong) suggested C/EBPα expression. Our primary outcomes were differences in progression-free and overall survival between the groups with weak or strong staining. Results: Among the 166 patients analyzed for C/EBPα IHC, the median progression free and overall survival were 30.7 and 40.3 months, respectively; which do not differ from the complete E4592 cohort. 92 patient samples (55%) had 0 or 1+ staining, and the remaining 74 (45%) 2 or 3+. The median progression free survival for patients with weak and strong C/EBPα IHC expression was 31.5 and 30.2 months, respectively (p = 0.84). The median overall survival between the weak and strong groups was 47.5 and 38.3 months, respectively (p = 0.54). 10 years after enrollment, 27% (25/92) of patients were alive in the weak, and 24% (18/74) in the strong C/EBPα IHC group. No difference between our primary outcomes by C/EBPα expression was identified. There was no difference in outcome by treatment arm, tumor histology, stage, or patient’s characteristics. There was a trend towards loss of C/EBPα and less differentiated tumor samples (p = 0.07). Conclusions: C/EBPα is a novel tumor suppressor gene in lung cancer with loss of expression in over 50% of NSCLC. However, our data demonstrate that in a subset of patients with resected NSCLC, C/EBPα IHC status is neither a prognostic nor a predictive marker. Further studies are needed to establish the molecular mechanisms of C/EBPα inactivation in lung cancer and its possible role as a new therapeutic target. No significant financial relationships to disclose.