Graves disease during nivolumab treatment for HER2-positive metastatic gastric cancer

What happened, in summary

A 66-year-old man had been diagnosed with HER2-positive Stage IV gastric cancer about 1.5 years before he developed a new thyroid problem. His cancer involved the liver and a portal tumor thrombus, so surgery was not pursued. He received 8 cycles of S-1, cisplatin and trastuzumab, but imaging showed progression.

Second-line paclitaxel plus ramucirumab initially reduced the tumor after 4 cycles. By 10 cycles, however, the cancer was progressing again. Nivolumab immunotherapy was then started. Before the third dose, he developed marked thyrotoxicosis with fatigue and shortness of breath. Testing showed newly positive thyroid-stimulating antibodies and diffuse thyroid uptake, supporting new-onset Graves disease after nivolumab.

Nivolumab was stopped. His thyroid condition was treated with methimazole and potassium iodide, with later dose reduction as thyroid levels normalized. Cancer assessment also showed that nivolumab had not been effective, so irinotecan was started. After 2 cycles, MRI found brain metastasis. He received gamma-knife radiation and steroids for the brain disease.

The gastric cancer continued to progress despite multiple lines of treatment. He died 4 months after his first specialist evaluation for Graves disease, after living with Stage IV gastric cancer for more than 1.5 years.