Pathological response measured using virtual microscopic slides for gastric cancer patients who underwent neoadjuvant chemotherapy.

BACKGROUND Although pathological response is a common endpoint used to assess the efficacy of neoadjuvant chemotherapy (NAC) for gastric cancer, the problem of a low rate of concordance from evaluations among pathologists remains unresolved. Moreover, there is no globally accepted consensus regarding the optimal evaluation. A previous study based on a clinical trial suggested that pathological response measured using digitally captured virtual microscopic slides predicted patients survival well. However, the pathological concordance rate of this approach and its usefulness in clinical practice were unknown. AIM To investigate the prognostic utility of pathological response measured using digital microscopic slides in clinical practice. METHODS We retrospectively evaluated pathological specimens of gastric cancer patients who underwent NAC followed by surgery and achieved RO resection between March 2009 and May 2015. Residual tumor area and primary tumor beds were measured in one captured image slide, which contained the largest diameter of the resected specimens. We classified patients with < 10% residual tumor relative to the primary tumorous area as responders, and the rest as non-responders; we then compared overall survival (OS) and relapse-free survival (RFS) between these two groups. Next, we compared the prognostic utility of this method using conventional Japanese criteria. RESULTS Fifty-four patients were evaluated. The concordance rate between two evaluators was 96.2%. Median RFS of 25 responders and 29 non-responders was not reached (NR) vs 18.2 mo [hazard ratio (HR) = 0.35, P = 0.023], and median OS was NR vs 40.7 mo (HR = 0.3, P = 0.016), respectively. This prognostic value was statistically significant even after adjustment for age, eastern cooperative oncology group performance status, macroscopic type, reason for NAC, and T- and N-classification (HR = 0.23, P = 0.018). This result was also observed even in subgroup analyses for different macroscopic types (Borrmann type 4/non-type 4) and histological types (differentiated/undifferentiated). Moreover, the adjusted HR for OS between responders and non-responders was lower in this method than that in the conventional histological evaluation of Japanese Classification of Gastric Carcinoma criteria (0.23 vs 0.39, respectively). CONCLUSION The measurement of pathological response using digitally captured virtual microscopic slides may be useful in clinical practice.