CLOCK and cancer: Here, we showed that I < O was an objective and continuously assessable biomarker of selected PROMs, which contributed with additional information to HR‐QoL, as well as being an independent prognostic factor of overall survival in cancer patients.29, 31, 35, 36, 37 The results support the development and testing of interventions targeting the circadian clock to relieve drug‐refractory systemic symptoms and improve HR‐QoL in cancer patients.