Severe colitis from pembrolizumab immunotherapy requiring additional treatment

What happened, in summary

An older man with lung adenocarcinoma was first treated with stereotactic body radiation for an early-stage tumor in the left upper lobe. Later surveillance showed progression to mediastinal lymph nodes and the right lower lobe. He began carboplatin, pemetrexed, and pembrolizumab and received 1 cycle.

Soon afterward, he developed severe immune-mediated colitis with 11-12 bloody bowel movements each day. High-dose methylprednisolone and then oral prednisone did not control the diarrhea. Surgery was considered, but his overall condition made an operation too risky.

Because stronger immune-suppressing treatment was needed, he was assessed for hepatitis B. Testing showed evidence of a past, inactive infection. To reduce the risk of viral reactivation, entecavir was started before infliximab.

After infliximab, the bleeding stopped and bowel movements fell to about 3-4 per day within 1 week. His symptoms improved enough for discharge, with plans for continued infliximab and close monitoring of the hepatitis B risk. The immediate priority became control of the severe treatment complication. At discharge, the lung-cancer response and next systemic treatment remained undecided. His care required coordination between gastroenterology, oncology, infectious-disease and surgical teams. Preventive hepatitis B medication allowed infliximab to be used more safely while the bowel inflammation came under control. Entecavir was planned for 12 months after biological therapy, with HBV DNA and liver tests every 3 months. The bowel bleeding had stopped and bowel movements had fallen substantially, while continued follow-up was needed for the colitis, hepatitis B reactivation risk and lung cancer.