Long-Term Remission with Ipilimumab/Nivolumab in Two Patients with Different Soft Tissue Sarcoma Subtypes and No PD-L1 Expression.

Checkpoint inhibitor therapy has been shown to improve outcomes in multiple solid malignancies; however, data are limited in soft tissue sarcoma. We present two cases of patients with advanced soft tissue sarcoma of different subtypes (dedifferentiated liposarcoma and myxofibrosarcoma) with zero percent PD-L1 expression by immunohistochemistry who were treated with ipilimumab and nivolumab followed by maintenance nivolumab. Both patients had failed multiple lines of systemic treatment and experienced long-term remission after starting ipilimumab and nivolumab. Genetic testing revealed that no genetic mutations were found in common between the two cases. One patient received concurrent cryoablation, which may have sensitized his tumor to immunotherapy. Checkpoint inhibitor therapy may improve outcomes in soft tissue sarcoma regardless of PD-L1 status, especially when combined with cryoablation. Studies are needed to evaluate whether treatment response varies by sarcoma subtype and what molecular markers can be used to guide patient selection.