This study determined whether expression levels of a panel of biologically 
relevant microRNAs can be used as prognostic or predictive biomarkers in 
patients who participated in the International Adjuvant Lung Cancer Trial 
(IALT), the largest randomized study conducted to date of adjuvant chemotherapy 
in patients with radically resected non-small cell lung carcinoma (NSCLC). 
Expression of miR-21, miR-29b, miR-34a/b/c, miR-155, and let-7a was determined 
by quantitative real-time PCR in formalin-fixed paraffin-embedded tumor 
specimens from 639 IALT patients. The prognostic and predictive values of 
microRNA expression for survival were studied using a Cox model, which included 
every factor used in the stratified randomization, clinicopathologic prognostic 
factors, and other factors statistically related to microRNA expression. 
Investigation of the expression pattern of microRNAs in situ was performed. We 
also analyzed the association of TP53 mutation status and miR-34a/b/c 
expression, epidermal growth factor receptor and KRAS mutation status, and 
miR-21 and Let-7a expression. Finally, the association of p16 and miR-29b 
expression was assessed. Overall, no significant association was found between 
any of the tested microRNAs and survival, with the exception of miR-21 for which 
a deleterious prognostic effect of lowered expression was suggested. Otherwise, 
no single or combinatorial microRNA expression profile predicted response to 
adjuvant cisplatin-based chemotherapy. Together, our results indicate that the 
microRNA expression patterns examined were neither predictive nor prognostic in 
a large patient cohort with radically resected NSCLC, randomized to receive 
adjuvant cisplatin-based chemotherapy versus follow-up only.