The U.S. Food and Drug Administration (FDA) approves labeling claims of drug efficacy based on substantial evidence of clinical benefit demonstrated in adequate and well-controlled investigations. Patient-reported outcomes (PROs) may support marketing claims of clinical benefit, either alone or with other study endpoints. Health-related quality of life (HRQL) is a PRO that comprehensively measures patients' reported health status. We present an overview of why HRQL-based efficacy claims have not to date been accepted by the FDA for inclusion in anticancer product labels. Persistent challenges to allowance of such claims include shortcomings in randomization and blinding of clinical trials, missing data, statistical multiplicity, and unclear intrinsic meaning of selected HRQL findings.