Validity of the Japanese version of functional assessment of cancer therapy-gastric (FACT-Ga) and its sensitivity to ascites volume change: a retrospective analysis of Japanese clinical trial participants

The functional assessment of cancer therapy-gastric (FACT-Ga) questionnaire was designed to evaluate quality of life (QOL) in patients with gastric cancer. We aimed to explore the reliability and validity of FACT-Ga in Japanese patients, and assess the sensitivity of the gastric cancer subscale for detecting changes in cancer-related variables over time. The Japanese version of FACT-Ga was used, and data were obtained from Japanese patients who participated in either of two clinical trials: treatment for advanced or recurrent gastric cancer with ascites (advanced-GC group), or adjuvant chemotherapy after curative resection of gastric cancer (adjuvant group). Psychometric data including data used to determine reliability, internal consistency, and clinical validity were analyzed. Clinical validity was evaluated by comparing subscale scores for patients in the two groups, and by comparing subscale scores for patients with different performance status scores. Correlation between gastric cancer subscale scores and gastric cancer-related variables was also examined. In addition, sensitivity of the gastric cancer subscale to changes in ascites volume, abdominal girth, and Eastern Cooperative Oncology Group (ECOG) performance status (PS) was examined by evaluating their correlation in the advanced-GC group. We collected data on 156 patients (62 advanced-GC group patients and 94 adjuvant group patients). Response rates for the subscales were over 80 % at most time points for both the groups. Cronbach’s coefficient alpha revealed good internal consistency for each subscale. At baseline, the adjuvant group had higher QOL scores than the advanced-GC group (P