Diagnostic Performance of the PHQ-2 and Other Brief Screening Tools for Depression in Vulnerable Older Patients with Cancer: A Prospective Validation Study

Introduction: Depression is common but frequently underrecognized in older adults with cancer, as depressive symptoms often overlap with cancer- and treatment-related complaints. The current NCCN Older Adult Oncology guidelines recommend the two- and nine-item Patient Health Questionnaire (PHQ-2, PHQ-9) and the shortened four-item Geriatric Depression Scale (GDS-4) for emotional screening. However, these PHQ versions have not been validated in vulnerable older adults with cancer, and evidence for the GDS-4 remains limited. This study evaluated the diagnostic performance of several depression screening tools in vulnerable older patients with cancer, with validation of the PHQ-2 (cut-off ≥ 2) as the primary endpoint.

Methods: In this single-centre prospective cohort study, patients aged ≥70 years who were recently diagnosed with cancer and/or started a new line of active cancer treatment, and were classified as ‘vulnerable’ by the Geriatric 8 screening tool (score ≤ 14), were recruited at the Kortrijk Cancer Centre (Belgium). Participants completed the GDS-15 (including GDS-4) and the PHQ-9 (including PHQ-2). Diagnostic accuracy was assessed against the depression module of the Structured Clinical Interview for DSM-5 Clinician Version (SCID-5-CV). Receiver operating characteristic (ROC) analyses and diagnostic performance indices (sensitivity, specificity, LR+, LR-) were calculated.

Results: A total of 155 vulnerable patients were included (December 2023 – May 2026). According to the SCID-5-CV, 34 patients (21.9%) met criteria for minor depression (n=18) or major depressive disorder (n=16). The PHQ-2 showed excellent discriminative ability, with an AUROC of 0.944 (95% CI 0.897–0.991), outperforming the PHQ-9 (0.909), PHQ-9 after a positive PHQ-2 (0.889), GDS-15 (0.660) and GDS-4 (0.618). At the predefined cut-off of ≥2, the PHQ-2 demonstrated a sensitivity of 88.2% and specificity of 90.9%.

Discussion: These findings support the PHQ-2 as a practical first-line screening instrument to identify vulnerable older adults with cancer in need of further diagnostic evaluation for depression.