QoLIDia: Quality of Life in Cancer Patients With Diabetes During Immunotherapy

Immune checkpoint inhibitors (ICIs) have transformed the management of multiple solid malignancies by improving survival and enabling durable disease control. By targeting inhibitory immune checkpoints such as PD-1, PD-L1, and CTLA-4, these therapies enhance anti-tumour immune responses. However, immune activation may also result in immune-related adverse events (irAEs), which can affect multiple organ systems and range from mild to life-threatening. As survival improves, long-term and chronic toxicities are increasingly recognised, highlighting the importance of patient-centred outcomes such as health-related quality of life (HRQoL).

Diabetes mellitus (DM) is a common comorbidity among patients with cancer and is associated with increased symptom burden, functional impairment, and reduced HRQoL. Type 2 diabetes (T2D) has also been associated with adverse cancer outcomes and may influence both the effectiveness and toxicity profile of systemic anticancer therapy, including ICIs. In addition, ICIs can induce immune-related diabetes mellitus (ir-DM), a rare but clinically significant form of new-onset insulin-dependent diabetes requiring lifelong insulin treatment. Despite its clinical relevance, the interaction between pre-existing diabetes, ICI therapy, and longitudinal HRQoL remains insufficiently characterised.

Although HRQoL is generally reported to remain stable during ICI therapy in unselected cancer populations, it is unknown whether similar patterns are observed in patients with pre-existing DM or in those who develop ir-DM during treatment. Given the metabolic, functional, and psychosocial burden associated with diabetes, this patient group may be particularly vulnerable to deterioration in HRQoL during immunotherapy.

The primary aim of this study is to compare longitudinal changes in HRQoL between patients with T2D and non-diabetic patients from baseline to 3 and 6 months after initiation of ICI therapy. The primary hypothesis is that patients with T2D will experience a greater decline in HRQoL over the first six months of treatment compared with non-diabetic patients.

This is a prospective, multicentre cohort study of adult cancer patients initiating ICI therapy. Data will be collected prospectively using a secure electronic case report form across participating centres.

At baseline, demographic characteristics, cancer type and stage, treatment intent and planned ICI regimen, diabetes status (no diabetes, type 1 diabetes, or type 2 diabetes), diabetes treatment status, performance status, and baseline patient-reported outcomes will be recorded.

During follow-up, data will be collected on ICI exposure, treatment discontinuation and reasons for discontinuation, immune-related adverse events, hospitalisations, disease progression, survival status, and the occurrence of immune-related diabetes mellitus.

Patient-reported outcomes will be assessed using the EORTC QLQ-C30 and EQ-5D-5L questionnaires in all participants, and the PAID questionnaire in participants with diabetes. Assessments will be performed at baseline and at 3 and 6 months after treatment initiation.

Immune-related diabetes mellitus will be defined as new-onset insulin-dependent diabetes occurring after initiation of ICI therapy and consistent with marked beta-cell failure, classified according to established international clinical recommendations.

This study will provide prospective real-world data on HRQoL trajectories and survival among cancer patients with and without diabetes receiving ICI therapy, and will estimate the incidence and clinical characteristics of immune-related diabetes mellitus in a nationwide setting.

• Change in EQ-5D-5L Index Value [Time frame: Baseline to 3 months and 6 months]
• Change in EQ-5D-5L Visual Analogue Scale (EQ-VAS) score [Time frame: Baseline, 3 months and 6 months]
• Incidence of immune-related diabetes mellitus [Time frame: Within 12 months after initiation of ICI.]
• Hospital Admissions [Time frame: Within 6 months after initiation of ICI therapy.]
• Time to Treatment Failure [Time frame: Within 6 months after initiation of immune checkpoint inhibitor therapy]
• Time to death from any cause (Overall Survival) [Time frame: Within 12 months after initiation of immune checkpoint inhibitor therapy]
• Association Between Clinical Events and HRQoL Outcomes [Time frame: Baseline to 6 months]
• Change in Problem Areas in Diabetes Score [Time frame: Baseline to 6 months (assessed at baseline, 3 months, and 6 months)]