Endocrine Abstracts

Background: Immune checkpoint inhibitors (ICIs) have transformed cancer treatment by boosting the immune system to target and destroy cancer cells. However, they are associated with immune-related adverse events, including endocrine toxicities. Thyroid dysfunction, especially hypothyroidism following transient thyrotoxicosis, is a common side effect, with a reported incidence of 2.5-15%. The effects of ICIs on patients with pre-existing autoimmune thyroid disease, particularly Graves’ disease (GD), are not well-documented, and the concern would be risk of precipitating recurrent hyperthyroidism and thyroid eye disease (TED); we report three recent cases with a history of GD treated with ICIs.

Cases presentation: Case 1:57-year-old male with melanoma and past history of GD complicated by TED requiring IV methylprednisolone. After receiving two cycles of ipilimumab and nivolumab, followed by nivolumab alone, he developed transient thyrotoxicosis characteristic of ICI thyroiditis, which later progressed to hypothyroidism without exacerbation of his TED. He required levothyroxine treatment and had complete response to immunotherapy. Case 2: 56-year-old female with melanoma who received pembrolizumab. She had a history of GD treated with carbimazole, and after starting ICIs, she developed thyroiditis, followed by hypothyroidism requiring treatment with levothyroxine. Case 3: 76-year-old female with inoperable oesophageal SCC and newly diagnosed GD with thyroid eye disease. After starting chemotherapy and pembrolizumab, her thyroid function remained stable, with ongoing tapering down in carbimazole dosage and no worsening of mild TED.

Conclusion: No patient developed flare of GD/TED. Patients with past GD do need careful warning of theoretical risk of recrudescence and TED symptoms flagged. Vigilant monitoring for thyroid abnormalities is essential. Potential adverse outcome data are limited, and benefits of ICIs in treating cancer in patients with Graves’ disease outweigh the theoretical risk.

Keywords: immune checkpoint inhibitors, Graves’ disease, thyroid dysfunction, hypothyroidism, cancer treatment, endocrinopathies