PURPOSE: To investigate the mean changes over time in health-related quality of life among advanced cancer patients who did not receive any intervention, comparing changes among all patients versus changes in subgroups of patients with high initial symptom scores.

METHODS: Patients with advanced cancer answered two questionnaires, containing the EORTC QLQ-C30 (15 multi- or single-item scales), with approximately 1 month in between and received no known intervention in between. For each QLQ-C30 scale, we estimated the mean change among all patients and in subgroups of patients scoring at least 33, 50, and 66 %, respectively, of maximum (maximal symptom score or maximally reduced function score) in the first questionnaire.

RESULTS: In total, 1014 patients completed both questionnaires. As hypothesized, we found no change over time in mean scores when including all patients [average mean change = -0.9 (95 % CI -1.5;-0.6)]. In the subgroups of patients initially scoring at least 33, 50, or 66 % of maximum, the score improved with mean changes of -9.2 (95 % CI -10.1;-8.4), -13.1 (95 % CI -14.4;-11.8), and -15.6 (95 % CI -17.2;-13.9), respectively.

CONCLUSIONS: We quantified the magnitude of change over a 1-month period in health-related quality of life in advanced cancer patients, and in subgroups selected according to certain initial symptom levels. This information may help the interpretation of longitudinal studies of patients selected via screening.