Depth of response is a significant predictor for long-term outcome in advanced gastric cancer patients treated with trastuzumab

Abstract

// Choong-Kun Lee 1 , Seung-Seob Kim 2 , Saemi Park 3 , Chan Kim 1 , Su Jin Heo 1 , Joon Seok Lim 2 , Hyunki Kim 4 , Hyo Song Kim 1 , Sun Young Rha 1 , Hyun Cheol Chung 1 , Sohee Park 3 , Minkyu Jung 1 1 Division of Medical Oncology, Department of Internal Medicine, Yonsei Cancer Center, Yonsei University, College of Medicine, Seoul, Korea 2 Department of Radiology, Yonsei University College of Medicine, Seoul, Korea 3 Department of Biostatistics, Graduate School of Public Health, Yonsei University, Seoul, Korea 4 Department of Pathology, Yonsei University College of Medicine, Seoul, Korea Correspondence to: Sohee Park, email: soheepark@yuhs.ac Minkyu Jung, email: minkjung@yuhs.ac Keywords: gastric cancer, trastuzumab, depth of response, early tumor shrinkage, survival Received: December 14, 2016      Accepted: March 01, 2017      Published: March 10, 2017 ABSTRACT Purpose: We aimed to determine and compare the predictive values of depth of response (DpR) and early tumor shrinkage (ETS) on long-term outcomes in gastric cancer patients treated with trastuzumab. Results: From a total of 368 computed tomography examinations, DpR and ETS were evaluated. DpR was a significant tumor-size metric in predicting PFS and OS, and showed better discriminatory ability (higher Cτ indices, 0.6957 for PFS; 0.7191 for OS) than ETS. DpR ≥ 45% (vs. < 45%) was the optimal cutoff value, as it was best able to identify patients with longer PFS (median 9.0 vs. 6.3 months, hazard ratio [HR] = 0.608; 95% confidence interval [CI]: 0.335 to 1.104; P = 0.102) and OS (median 23.5 vs. 13.1 months, HR = 0.441; 95% CI: 0.203 to 0.955; P = 0.038). Materials and Methods: Sixty-one gastric cancer patients who received first-line trastuzumab-based chemotherapy were assessed for DpR and ETS. We employed Kaplan-Meier estimates, log-rank tests, Cox proportional hazards regression models, time-dependent receiver operating characteristics, and Youden’s J index to evaluate and determine cutoff values of DpR and ETS as predictors of progression-free survival (PFS) and overall survival (OS). Conclusions: DpR and ETS were significant predictors of long-term outcomes in gastric cancer patients treated with first-line trastuzumab. Validation in prospective trials with larger patient populations is needed.