Dear Editor,

We read the recent study by Wu et al. (Reference Wu, Ketron and Pirl2026) with caution, which examined the tangible impact of a Collaborative Care Model (CoCM) embedded in supportive oncology services. The authors reported clinically meaningful improvements in depression response as defined by the PHQ-9, offering valuable implementation evidence for health systems seeking to measurably integrate behavioral health into the care of serious illnesses. As collaborative care expands into palliative and supportive settings, pragmatic data such as this are invaluable for informing policy, resource allocation, and ongoing program development.

At the same time, this study prompts reflection on a fundamental question: what constitutes success in collaborative care for patients living with serious illness? Symptom reduction is an important and measurable outcome, and previous trials have convincingly demonstrated its clinical relevance (Sharpe et al. Reference Sharpe, Walker and Hansen2014). However, in the context of advanced illness – where many patients face progressive disease and a limited prognosis – psychological distress often extends beyond the DSM-defined limits of depression. Demoralization, characterized by hopelessness, loss of meaning, and helplessness, is common in palliative care populations and is conceptually distinct from major depressive disorder (Rodrigues et al. Reference Rodrigues, Crokaert and Gastmans2018). Existential distress has also been associated with reduced quality of life and a desire for a hastened death, underscoring its clinical and ethical relevance in serious illness (Mitchell et al. Reference Mitchell, Chan and Bhatti2011).

Wu et al. (Reference Wu, Ketron and Pirl2026) rightly acknowledge the proportion of missing PHQ-9 data at 24 weeks as a methodological limitation. However, in serious illness settings, incomplete collection of patient-reported outcomes may also reflect the challenges of continued engagement amidst disease progression, functional decline, and existential burden. When evaluative frameworks focus primarily on symptom scores, they risk overlooking dimensions of suffering that palliative and supportive care explicitly seek to address.

Collaborative care has proven effective in improving outcomes for depression across diverse medical populations (Walker et al. Reference Walker, Mulick and Magill2021). Based on this strong evidence, the next phase of implementation science could involve aligning outcome measures more closely with the holistic ethos of serious illness care. Integrating multidimensional metrics that assess meaning, dignity, and existential well-being alongside remission of depressive symptoms may provide a more comprehensive assessment of therapeutic impact.

Wu et al. (Reference Wu, Ketron and Pirl2026) make important contributions to the practice of psychosocial oncology in the current era. As collaborative care continues to evolve, careful reconsideration of what constitutes success can ensure that our metrics reflect not only measurable symptom changes but also the broader human experience of suffering that defines serious illness.