Does severe toxicity affect global quality of life in patients with metastatic colorectal cancer during palliative systemic treatment? A systematic review.

Background: New palliative systemic treatment regimens in patients with metastatic colorectal cancer (mCRC) have significantly improved overall survival and prognosis. These treatment regimens are often accompanied by increased toxicity, which may impair patients' quality of life (QOL). We systematically reviewed whether severe toxicity affects global QOL in patients with mCRC receiving palliative systemic treatment in recent published randomized controlled trials (RCTs). Materials and methods: Phase III RCTs evaluating palliative systemic treatments in patients with mCRC and published between 2004 and 2016 were considered. Studies were evaluated on the basis of global QOL scores, toxicity during treatment (assessed by scoring relevant adverse events) and primary outcomes (POs). Results: A total of 30 studies were identified in which 19863 patients were included. In 25 out of these 30 trials (83%), no difference in global QOL between treatment arms was observed. In contrast, 22 out of 30 trials (73%) showed increased toxicity during treatment in the experimental arm as compared with the control arm. In 19 out of 22 trials with higher toxicity (86%) global QOL outcomes remained unaffected or improved. In ten out of eleven studies with a better PO, no improvement in global QOL was seen. Conclusion: Global QOL of patients with mCRC included in phase III RCTs evaluating palliative systemic treatment did not differ across treatment arms despite consistently higher toxicity during treatment of the experimental compared with the standard treatment arms. Based on these findings we conclude that the use of global QOL for comparing treatment arms in RCTs for patients with mCRC does not provide information of clinical relevance. Further consideration of how to better assess the net effect of new agents on patients' QOL is urgently needed.