Late Breaking Abstract – ASCO 2022: Improved Distant Metastasis-Free Survival with Adjuvant KEYTRUDA® in High Risk Stage II Melanoma

SUMMARY: The American Cancer Society’s estimates that for 2022, about 99,780 new cases of melanoma of the skin will be diagnosed in the United States and 7,650 people are expected to die of the disease. The rates of melanoma have been rising rapidly over the past few decades, but this has varied by age. Surgical resection with a curative intent is the standard of care for patients with early stage melanoma, with a 5-year survival rate of 98% for Stage I disease and 90% for Stage II disease. The current standard of care for patients following resection of high-risk Stage II disease is observation, even though patients with Stage IIB and IIC disease presenting with high-risk features (depth of invasion, T-category, ulceration) have 5 and 10 year melanoma-specific survival similar to that of patients with Stage IIIA and IIIB disease.

KEYTRUDA® (Pembrolizumab) is a fully humanized, Immunoglobulin G4, anti-PD-1, monoclonal antibody, that binds to the PD-1 receptor and blocks its interaction with ligands PD-L1 and PD-L2. By doing so, it unleashes the tumor-specific effector T cells, and is thereby able to undo PD-1 pathway-mediated inhibition of the immune response. The FDA in 2019, approved KEYTRUDA® for the adjuvant treatment of patients with melanoma, with involvement of lymph node(s), following complete resection (Stage III). The present study was conducted to evaluate the role of adjuvant immunotherapy in patients with high risk Stage II melanoma.

KEYNOTE-716 is a randomized, double-blind, Phase III trial, in which 976 patients aged 12 years or older, with completely resected cutaneous Stage IIB or IIC melanoma, and no lymph node involvement, were randomly assigned 1:1 to receive KEYTRUDA® 200 mg IV (2 mg/kg for pediatric patients) or placebo, every 3 weeks for 17 cycles (up to 1 year). Patients were stratified by T category 3b, 4a, 4b (adults) and with a separate stratum for pediatric patients. Approximately 65% had Stage IIB disease and 35% had Stage IIC disease. There was no prespecified analysis for PD-L1 or BRAF status in this study, as there was inconsistent and small amounts of tissue available for testing. This was the first part (Part 1) of this double-blind study. The Primary endpoint was Relapse Free Survival (RFS) per investigator assessment, and Safety. The second part (Part 2) of this study was open-label design, and adults and pediatric patients were eligible to receive up to 35 additional cycles of treatment, only if they had recurrence after receiving the placebo or completed 17 cycles of KEYTRUDA®. Patients in the KEYTRUDA® group who experienced disease recurrence within 6 months of completing the treatment were excluded from Part 2 of the study. Secondary end points included Distant Metastasis Free Survival (DMFS), Overall Survival (OS) and Quality of Life.

At median follow up of 14.4 months, adjuvant KEYTRUDA® significantly prolonged RFS compared to placebo (HR=0.65; P=0.00658), in patients with resected Stage IIB or IIC melanoma. At the time of this analysis, 11.1% of patients on KEYTRUDA® had a recurrence, compared to 16.8% of those receiving placebo. The 12-month RFS rate was 90.5% for KEYTRUDA® versus 83.1% for placebo.

The researchers herein presented new data from the analysis of Distant Metastasis-Free Survival (DMFS) and Recurrence Free Survival (RFS), with a longer median follow up of 26.9 months. Adjuvant KEYTRUDA® significantly improved DMFS when compared to placebo (HR=0.64; P=0.0029), representing a 36% reduction in the risk of recurrence. The 24-month DMFS rate was 88.1% versus 82.2%, respectively. Grade 3 or more Adverse Events occurred in 28.4% of patients in the KEYTRUDA® group, versus 20% in the placebo group. Hypothyroidism was the most common immune mediated Adverse Event with KEYTRUDA®, compared to placebo (17.2% versus 3.7%).

The authors concluded that adjuvant KEYTRUDA® for resected Stage IIB and IIC melanoma, significantly improved Distant Metastasis-Free Survival, with continued reduction in the risk of recurrence, and a favorable benefit-risk profile. KEYNOTE-716 is the first randomized Phase III trial of an anti-PD-1 therapy in resected Stage II melanoma, and these findings represent an important milestone for this patient group.

Distant metastasis-free survival with pembrolizumab versus placebo as adjuvant therapy in stage IIB or IIC melanoma: The phase 3 KEYNOTE-716 study. Long GV, Luke JJ, Khattak M, et al. DOI: 10.1200/JCO.2022.40.17_suppl.LBA9500 Journal of Clinical Oncology 40, no. 17_suppl (June 10, 2022) LBA9500-LBA9500.