Establishment and validation of prognostic nomograms in first-line metastatic gastric cancer patients.

Background: It remains unclear whether human epidermal growth factor receptor 2 (HER2) status is an outcome-associated biomarker independent of known prognostic factors for metastatic gastric cancer. Moreover, there are few reports about nomograms in inoperable locally advanced or metastatic gastric cancer (AGC), although several studies have been reported regarding other cancer types. This retrospective study aimed to develop nomograms that combine HER2 status and other prognostic factors to predict the survival outcomes of AGC patients starting first-line treatment. Methods: In this study, 838 consecutive AGC patients starting first-line chemotherapy at the Aichi Cancer Center Hospital (ACC) were included to establish the nomograms that calculated the predicted probability of survival at different time points, 6 months and 1 and 2 years for overall survival (OS) and 3 and 6 months, and 1 year for progression free survival (PFS). Nomograms were independently validated with 269 consecutive AGC patients at the Cancer Center Hospital (SCC) who underwent first-line chemotherapy. The discriminatory ability and accuracy of the models were assessed using Harrell's c-index. IHC3+ or IHC2+/ISH+ tumors were defined as HER2 positive. Results: At a median follow-up of 12.3 (ACC) and 11.6 (SCC) months, the median OS was 12.5 and 12.4 months (P=1.00), and the median PFS was 4.8 and 5.8 months (P=0.03), respectively. The nomograms showed good C-index values: OS was respectively 0.688 and 0.576 and PFS was respectively for 0.643 and 0.544. Conclusions: The nomograms including HER2 status as covariate are crucial determinants of clinical care.