Dr. Patel on the Background of the SWOG S1801 Trial in Melanoma

Sapna Patel, BA, MD, medical oncologist, associate professor, director of the Uveal Melanoma Program and Melanoma Fellowship Program, The University of Texas MD Anderson Cancer Center, discusses the rationale for evaluating the use of pembrolizumab (Keytruda) before and after surgery for patients with advanced melanoma.

The phase 2 SWOG S1801 trial (NCT03698019) examined the use of neoadjuvant and adjuvant pembrolizumab vs adjuvant pembrolizumab alone in patients with high-risk, stage III/IV melanoma. It was hypothesized that administering neoadjuvant immunotherapy may assist the body's immune system in attacking the cancer, leading to an interference of tumor cell growth.

At median follow up of 14.7 months, findings showed that the addition of neoadjuvant pembrolizumab significantly improved event-free survival (EFS) vs adjuvant pembrolizumab alone, with a hazard ratio of 0.58 (95% CI, 0.39-0.87; P = .004). The landmark 2-year EFS rate was 72% in the neoadjuvant arm, compared with 49% in the adjuvant arm.

The rationale for the phase 2 trial that if immunotherapy is administered while the tumor is still intact, particularly in an immune-responsive tumor such as melanoma, there is the potential to expand a larger number of T cells, compared with treatment with immunotherapy only after surgery, Patel notes.

Patients enrolled in SWOG S1801 were randomly assigned in a 1:1 fashion to surgery followed by 200 mg of intravenous (IV) pembrolizumab every 3 weeks for 18 cycles, or 200 mg of IV pembrolizumab once every 3 weeks for 3 cycles, followed by surgery, the 15 cycles of adjuvant pembrolizumab. The primary end point of the trial was EFS measured from the time of randomization until a patient was unable to receive surgery, a patient was unable to start adjuvant therapy within 84 days, melanoma recurrence after surgery, or death, Patel concludes.