Consensus criteria to diagnose unintentional weight loss, a condition often termed cachexia that affects most patients with advanced cancer, are based on 6-month changes by which time intervention is often ineffective. Leveraging the large and diverse population in Kaiser Permanente Northern California's community oncology practice, we studied 8,338 patients with advanced lung, pancreatic, or colorectal cancers. We calculated weekly weight change measurements from 2-months pre- to 6-months post-diagnosis to identify 4 weight change trajectories (Gain, Stable, Moderate Loss, and Severe Loss) and associated these trajectories with survival. With high agreement, we classified patients into these trajectories after 3 months and found them to be prognostic
those classified in Moderate (HR = 1.55
95%CI: 1.45-1.67) or Severe Loss (HR = 2.20
95%CI: 2.01-2.41) at 3 months had significantly increased risk of death compared to the Stable trajectory. Weight loss at 3 months post-diagnosis can accurately classify deleterious weight trajectories, allowing for earlier clinical intervention.