Safety and Efficacy of PD-1 Inhibitors Plus Chemotherapy in Advanced Soft Tissue Sarcomas: A Retrospective Study

Purpose: Programmed cell death 1 (PD-1) inhibitors are ineffective as monotherapy for the treatment of soft tissue sarcomas (STS). However, increasing evidence shows that the combination of PD-1 inhibitors and chemotherapy is efficacious and safe for many types of malignancies, including STS. This study aimed to assess the safety and efficacy of doxorubicin chemotherapy plus PD-1 inhibitor in the treatment of metastatic STS. Patients and Methods: We retrospectively reviewed 21 patients with metastatic STS who received doxorubicin chemotherapy plus a PD-1 inhibitor between November 2017 and October 2018. Results: The objective response rate was 47.6%, the disease control rate was 71.40%, and the median progression-free survival was 6 months (95% CI, 2-8 months). The average change in target lesion diameter from baseline was -25.15 +/- 41.61. Majority of the patients experienced grade 1/2 adverse events (AEs), the grade 3/4 AEs were few. The most common grade 3/4 AEs were as follows: leukopenia (23.8%) and anemia (19.0%). Immune-related AEs were common and included hypothyroidism (14.3%) and pneumonitiss (9.5%). No drug related deaths occurred. Conclusion: This study provides preliminary evidence that the combination of doxorubicin chemotherapy and PD-1 inhibitor for advanced STS is safe and effective. We plan to conduct randomized clinical trials to confirm and characterize the activity of the chemotherapy-immunotherapy combinations in the treatment of sarcomas.