EGFR mutations and anaplastic lymphoma kinase rearrangements are, to date, the only approved biomarkers to select treatment for non-small-cell lung cancer (NSCLC). However, there is considerable interest in identifying other predictive markers. The PTPRF gene has been suggested as a marker of interest in NSCLC and other tumor types.This hypothesis-generating retrospective analysis examined data from two studies of erlotinib in NSCLC, Marker Identification Trial (MERIT; n = 102) and Sequential Tarceva in Unresectable NSCLC (SATURN; n = 262), to determine whether PTPRF expression was prognostic and/or predictive of patient outcomes. Exploratory analyses were conducted using quantitative reverse transcription polymerase chain reaction on existing formalin-fixed paraffin-embedded samples, to assess gene expression levels, including PTPRF. High versus low levels of expression were dichotomized using the median with B2M as a control comparator. Progression-free survival and overall survival were then compared for patients with high versus low levels of PTPRF in the two studies.PTPRF expression was found to be prognostic for shorter overall survival but was also significantly predictive of improved survival with erlotinib versus placebo in SATURN (hazard ratio, 0.45 [95% confidence interval, CI, 0.30-0.69] in PTPRF high versus 0.96 [95% CI, 0.62-1.48] in PTPRF low; interaction p = 0.02), even in the EGFR wild-type subpopulation (adjusted hazard ratio, 0.44 [95% CI, 0.29-0.68] versus 0.96 [95% CI, 0.62-1.48]; interaction p = 0.01).PTPRF may have value as a predictive marker to identify which patients can obtain the greatest benefit from erlotinib in the post-first-line setting. Further research is warranted to determine the potential value of this marker in clinical decision-making.