Agreement on Major Pathological Response in NSCLC Patients Receiving Neoadjuvant Chemotherapy.

INTRODUCTION: We have suggested that major pathologic response (MPR) could serve as a surrogate endpoint for survival and provide rapid means of comparing different neoadjuvant treatment regimens. Here, we confirm that MPR is predictive of long-term overall survival (OS) in patients with non-small-cell lung cancer (NSCLC) who underwent neoadjuvant chemotherapy and surgical resection, to assess agreement on MPR between 2 observers, and to determine the minimum number of slides needed to obtain an accurate determination of MPR.

PATIENTS AND METHODS: We identified 151 patients with NSCLC who had been treated with neoadjuvant chemotherapy followed by complete surgical resection from 2008 to 2012. Tissue specimens were retrospectively evaluated by 2 pathologists who had been blinded to patients' treatment and outcome. We assessed the relationships between MPR and OS, the levels of agreement between the pathologists, and determined the number of slides needed to obtain an accurate determination of MPR.

RESULTS: Our results reveal that MPR examined by either observer 1 (experienced) or by observer 2 (trained) was significantly predictive of long-term OS after neoadjuvant chemotherapy. MPR was associated with long-term OS in patients with NSCLC undergoing neoadjuvant chemotherapy on multivariable analysis (hazard ratio 2.68; P = .01). The levels of agreement between 2 pathologists were high after direct in-person training by one pathologist or the other (R2  = 0.994). Our data suggest that at least 3 slides should be read to accurately determine MPR.

CONCLUSIONS: MPR is significantly predictive of long-term OS in neoadjuvant chemotherapy-treated patients with NSCLC. MPR may serve as a surrogate endpoint for evaluating novel chemotherapies and immunotherapy response in biomarker-driven translational clinical trials.