You’re unlikely to see a case of metastatic conjunctival melanoma, statistically speaking. It is exceedingly rare. But it is equally deadly. And those unfortunate few patients who develop this cancerous lesion have cause for hope. Programmed cell death 1 (PD-1) inhibitor immunotherapy could be used to treat this condition, according to a new study. Researchers have found that adult patients treated with the cancer drug nivolumab had a complete response to the therapy.

The team conducted a retrospective review of five conjunctival melanoma patients treated with PD-1 inhibitors. Four patients treated with nivolumab had no evidence of disease at one, seven, nine and 36 months after completing treatment. However, two of those patients stopped immunotherapy after they developed autoimmune colitis and were treated with either systemic corticosteroids or infliximab.

The one metastatic conjunctival melanoma patient treated with another PD-1 inhibitor, pembrolizumab, had stable metastasis for the first six months of therapy. However, later disease progression resulted in treatment cessation after 11 months and the patient switched to another therapy.

The study concludes that longer follow-up is needed to determine the long-term disease-free survival. Future studies could assess the potential for immune checkpoint inhibitors’ use to avoid the need for surgical eye removal in selected patients with locally advanced disease.