Patterns of co-expression of ERCC1 and p27 in resected non-small cell lung cancer by immunohistochemistry.

7595 Background: Excision repair cross-complementation group 1 protein (ERCC1) and p27 have emerged as biomarkers which predict a lack of benefit from cisplatin-based adjuvant therapy in patients with resected non-small cell lung cancer (NSCLC). Retrospective analysis of tumor tissue from patients enrolled in the International Adjuvant Lung Trial (IALT) suggests that co-expression of these proteins is a stronger predictor of a lack of benefit than either marker independently (Pirker, JTO 2007 (abstract D3-03);2:S397-8). We analyzed in parallel the distribution of these markers in a series of patients with NSCLC.,Surgical resection specimens from 18 patients with NSCLC were analyzed by immunohistochemistry (IHC) for ERCC1 (8F1; Lab Vision) and p27 (Dako). In addition, IHC expression profiles were correlated with clinicopathologic parameters, including tumor type, grade, and stage.,Of 18 tumors, 7 (39%) were ERCC1-positive, and 3 (17%) were p27-positive. Co-expression of ERCC1 and p27 was as follows: 1 case (6%) double-positive, 9 cases (50%) double-negative, 6 cases (33%) ERCC1-positive/p27-negative, and 2 cases (11%) ERCC1-negative/p27-positive. p27 expression correlated with better differentiated adenocarcinoma, as previously reported. There was no correlation of ERCC1 or p27 with other clinicopathologic parameters.,The most common pattern of ERCC1 and p27 expression is double negativity, characteristic of 50% of NSCLC, predicting the patient is more likely to benefit from cisplatin-based adjuvant chemotherapy. Only 6% of patients show co-expression of these markers, which would predict the lowest likelihood of benefit. A significant proportion of patients (44%) show discordant reactivity for ERCC1 and p27. The value of these biomarkers has not been validated in a prospective trial or retrospective case series other than IALT and should not override pathologic stage as the major criteria for selection of adjuvant therapy until more data are available. Our results suggest that concurrent analysis of p27 and ERCC1 is most likely to bolster a clinical decision to treat a patient with adjuvant chemotherapy. No significant financial relationships to disclose.