Objective:

To report a case of immune checkpoint inhibitor-induced diabetes mellitus (ICI-DM) in a patient with metastatic lung adenocarcinoma and to discuss management strategies and long-term outcomes in the context of existing literature.

Approach:

• Case Presentation: A 72-year-old male with metastatic lung adenocarcinoma developed severe diabetes mellitus after treatment with pembrolizumab, requiring permanent insulin therapy.
• Management Insights: The case highlights the complexity of managing ICI-DM, emphasizing the need for individualized treatment decisions through multidisciplinary collaboration, including specific strategies such as regular monitoring and adjustment of insulin therapy.

Key Findings:

• ICI-DM is a rare but severe adverse event associated with immune checkpoint inhibitors, characterized by abrupt onset and irreversible insulin dependence.
• Lung cancer patients account for approximately 20-30% of reported ICI-DM cases.

Interpretation:

Current guidelines on managing ICI-DM are limited and often cursory, necessitating individualized approaches based on clinical circumstances and specific patient needs.

Limitations:

• The rarity of ICI-DM makes it challenging to establish comprehensive guidelines.
• Long-term outcomes and management strategies are not well-defined in existing literature.

Conclusion:

The case emphasizes the need for recognition and management of ICI-DM in patients undergoing immunotherapy for lung cancer.