A Novel Histopathological Evaluation Method Predicting the Outcome of Non-small Cell Lung Cancer Treated by Neoadjuvant Therapy: The Prognostic Importance of the Area of Residual Tumor

BackgroundHistopathological evaluation method for predicting the outcome of non-small cell lung cancer (NSCLC) treated by neoadjuvant therapy has not been fully assessed. The purpose of this study was to assess a novel histopathological evaluation method for predicting the outcome of NSCLC treated by neoadjuvant therapy.MethodsWe reviewed the histopathology of the tumors of 53 NSCLC treated by neoadjuvant chemotherapy, chemoradiotherapy, or radiotherapy followed by complete resection and identified the histologic features produced by neoadjuvant therapy by comparing them with the histologic features of the tumors in 138 NSCLC cases treated by surgery without neoadjuvant therapy. We also measured the area of residual tumor (ART) on the maximum cut surface of the tumors and analyzed the relationships between the histologic features, ART, and the outcome.ResultsThe proportions of cases with the histologic features “cholesterin clefts,” “foreign body reactive giant cells,” “stromal hyalinosis,” and “bizarre nucleus in more than 50% of the cancer cells” were significantly higher in the neoadjuvant therapy group than in the surgery alone group. However, the presence of none of these features had any significant effect on survival. Although pathologic T factor and N factor had no significant effect on overall survival, smaller ART (≤400 mm2) and absence of pleural invasion (p [−]) were predictors of a outcome (p = 0.014 and p = 0.003, respectively).ConclusionsSmaller ART and p (−) predict a better outcome of NSCLC treated by neoadjuvant therapy. We concluded that ART is a novel histopathological evaluation method for predicting the outcome of NSCLC treated by neoadjuvant therapy.