Background
Adherence is a key determinant of treatment success in oncology and, according to the World Health Organization (WHO), describes how closely patients follow the recommendations agreed upon with their healthcare provider, including taking medications, adhering to dietary plans, or making lifestyle changes. Patient-reported outcome measures (PROMs) provide insights into patients’ perceptions, barriers, and beliefs. However, a comprehensive overview of adherence-related PROMs in oncology is lacking.

Methods
We conducted a systematic umbrella review in PubMed and Embase up to October 2024 in adult cancer patients. A qualitative synthesis was performed to classify adherence dimensions according to the WHO framework and to evaluate the validation status.

Results
Of 6,073 records screened, 89 systematic literature reviews (SLR) were included, encompassing 599 PROM applications. Most PROMs assessed medication adherence (41.1%). 4.8% of PROMs measured multiple adherence dimensions. 49.7% of PROMs were validated, while for 39.7% of PROMs validation status was not reported.

Conclusion
Adherence-related PROMs in oncology predominantly focus on medication, while lifestyle and multidimensional aspects remain underrepresented. Validation status is frequently unclear. Standardized and validated modular PROMs are needed to inform the choice of PROMs for monitoring patient adherence in clinical practice and to enhance health outcomes.