Implementing Symptom Management Follow-up Using an Electronic Patient-Reported Outcome Platform in Outpatients With Advanced Cancer: Longitudinal Single-Center Prospective Study - Lili Tang; Yi He; Ying Pang; Zhongge Su; Jinjiang Li; Yening Zhang; Xu Wang; Xinkun Han; Yan Wang; Zimeng Li; Shuangzhi He; Lili Song; et al. (JMIR Formative Research, 2022)