Adjuvant Pembrolizumab Significantly Improves DMFS and RFS in Patients with Stage II Melanoma

Use of adjuvant pembrolizumab (Keytruda) markedly improved distant metastasis-free survival (DMFS) and allowed for longer follow up for recurrence-free survival (RFS) vs placebo at the third interim analysis in patients with resected stage IIB or stage IIC melanoma after a median follow up of 27.4 months (range, 14.0-39.4). Georgina V. Long, MD, PhD, FRACP, of the Melanoma Institute Australia, The University of Sydney, Royal North Shore and Mater Hospital presented these results as part 1 of the KEYNOTE-716 trial (NCT03553836) at the 2022 American Society of Clinical Oncology (ASCO) meeting in Chicago, Illinois.¹

Patients in the pembrolizumab arm had a better 24-month DMFS rate of 88.1% compared with 82.2% for patients who received placebo. The 12-month DMFS also favored pembrolizumab with 94.7% vs 90.2% in the placebo arm. Neither the pembrolizumab nor placebo arm reached the median. Number of events were fewer in the pembrolizumab arm than the placebo, affecting 63 patients (12.9%) vs 95 patients (19.4%), respectively (hazard ratio [HR] 0.64, 95% CI, 0.47-0.88; P = .0029).

The KEYNOTE-716 study enrolled 976 patients who were randomized 1:1 to receive pembrolizumab (n = 487) or placebo (n = 489). In part 1 of the study, investigators administered 200 mg in adults, or 2 mg/kg for pediatric patients, of pembrolizumab intravenously once every 3 weeks for 17 cycles. Placebo was given every 3 weeks. The primary end point was RFS per investigator assessment, and the secondary end points were DMFS, overall survival (OS), and safety. Investigators defined DMFS as the time from randomization to the first diagnosis of distant metastasis at the third interim analysis which was planned after 146 distant metastasis events. The exploratory end point was health-related quality-of-life. In part 2 of the study, pembrolizumab was administered to all patients whose disease recurred.

The minimum age of eligible patients was 12 years. Patients were eligible if they had newly diagnosed, resected, high-risk, stage II melanoma with a negative sentinel lymph node biopsy and ECOG performance scores of 0 or 1. Patients were stratified by T-category 3b, 4a, and 4b, as well as pediatric status. Long noted a type 1 error was controlled at a one-sided alpha of 2.5% with 2.5% previously allocated to the RFS end point because of this study measure’s statistical significance in the first interim analysis.

DMFS favored pembrolizumab across all 3 T-subcategories. The number of events in the T3b subcategory was 23 in patients receiving pembrolizumab and 31 in patients receiving placebo (HR 0.71; 95% CI, 0.41-1.22), for T4a it was 8 and 20, respectively, (HR 0.42; 95% CI, 0.19-0.96), and for T4b it was 30 and 41, respectively (HR 0.7; 95% CI, 0.44-1.13). No median DMFS rate was reached; however, the 12-month and 24-month DMFS rates favored pembrolizumab in all of these subgroups.

Fewer distant metastasis events were recorded for the pembrolizumab arm at first recurrence compared with placebo. Forty-five patients (9%) in the pembrolizumab arm and 79 patients (16%) in the placebo arm experienced distant metastasis at first recurrence. However, a similar number of patients across both arms experienced distant metastasis events after locoregional occurrence: 18 patients (4%) with pembrolizumab and 16 patients (3%) in the placebo arm. Most events could be found in the lungs (n = 100) affecting 49% of patients receiving pembrolizumab vs 73% of patients receiving placebo.

RFS favored patients who received pembrolizumab as well. At a median of 37.2 months, patients in the pembrolizumab arm had 95 events (19.5%) vs 139 events (28.4%) events in the placebo arm (HR, 0.64; 95% CI, 0.50-0.84). The 24-month RFS rate favored pembrolizumab (81.2%) vs placebo (72.8%). Similarly, pembrolizumab had favorable RFS rates across all T-subcategories, and the 24-month RFS rates favored pembrolizumab vs placebo.

Median age of patients in the pembrolizumab arm was 60 years (range, 16-84) and the median age in the placebo arm was 61 years (range, 17-87). Both harms had similar distributions of age and sex among patients, and over 90% of patients in both arms had ECOG performance scores of 0.

No new safety signals were identified. Treatment-related adverse events (TRAEs) affected 83% of the pembrolizumab arm and 64% of the placebo arm. More grade 3 or worse TRAEs were reported in pembrolizumab patients (17%) than patients receiving placebo (5%). Seventy-seven (16%) in the experimental arm discontinued treatment because of TRAEs vs 12 patients (2%) in the placebo arm. No patients died as a result of TRAEs. The TRAEs reported were typical of this treatment, but Long commented, “Please note that fatigue in the placebo arm was 19% and 21% in the pembrolizumab arm, as was pruritis 11% in the placebo arm and 25% in the pembrolizumab arm.”

Pembrolizumab performed favorably across DMFS and RFS variables for patients with resected stage IIB and stage IIC melanoma. Safety signals were consistent with the previous 2 interim analyses, and the quality-of-life data will be presented at a later time during in the ASCO meeting.

_REFERENCE

_{Distant metastasis-free survival with pembrolizumab versus placebo as adjuvant therapy in stage IIB or IIC melanoma: The phase 3 KEYNOTE-716 study. Oral presentation at: the American Society for Clinical Oncology 2022 Annual Meeting; Chicago, Illinois; June 3-7, 2022. J Clin Oncol. 40, 2022 (suppl 17; abstr LBA9500). doi: 10.1200/JCO.2022.40.17_suppl.LBA9500. Abstract LBA9500}