Purpose: The systematic use of patient-reported outcome measures (PROMs) has been advocated as an effective way to standardize cancer practice. Yet, the question of whether PROMs can lead to actual improvements in the quality of patient care remains under debate. This review examined whether inclusion of PROM in routine clinical practice is associated with improvements in patient outcomes, processes of care, and health service outcomes during active anticancer treatment. Methods: A systematic review of five electronic databases (Medline, EMBASE, CINAHL [Cumulative Index to Nursing and Allied Health Literature], PsycINFO, and Psychology and Behavioral Sciences Collection [PBSC]) was conducted from database inception to May 2012 to locate randomized and nonrandomized controlled trials of patients receiving active anticancer treatment or supportive care irrespective of type of cancer. Results: Based on prespecified eligibility criteria, we included 26 articles that reported on 24 unique controlled trials. Wide variability in the design and use of interventions delivered, outcomes evaluated, and cancer- and modality-specific context was apparent. Health service outcomes were only scarcely included as end points. Overall, the number of statistically significant findings were limited and PROMs' intervention effect sizes were predominantly small-to-moderate. Conclusion: The routine use of PROMs increases the frequency of discussion of patient outcomes during consultations. In some studies, PROMs are associated with improved symptom control, increased supportive care measures, and patient satisfaction. Additional effort is required to ensure patient adherence, as well as additional support to clinicians who will respond to patient concerns and issues, with clear system guidelines in place to guide their responses. More research is required to support PROM cost-benefit in terms of patient safety, clinician burden, and health services usage.