OA02.03 Pembrolizumab Plus Platinum Chemotherapy and Radiotherapy in Unresectable, Locally Advanced, Stage III NSCLC: KEYNOTE-799

Purpose/Objective(s)KEYNOTE-799 (NCT03631784), a phase 2 study of the anti‒PD-1 antibody pembrolizumab (pembro) plus concurrent chemoradiation therapy (cCRT) in patients (pts) with unresectable, locally advanced stage III NSCLC, completed accrual and follow up is ongoing. Results in a subset of pts from this study showed an ORR of 69.6% in cohort A (squamous [sq]/nonsquamous [nonsq], n = 112) and 70.5% in cohort B (nonsq, n = 61), and grade ≥3 pneumonitis in 8.0% and 7.9% of pts, respectively. We assessed safety and efficacy of pembro + cCRT in all pts from KEYNOTE-799.Materials/MethodsThis nonrandomized, multisite, open-label trial enrolled pts aged ≥18 y with previously untreated, unresectable, pathologically confirmed, stage IIIA‒C NSCLC with measurable disease per RECIST v1.1. Pts in cohort A (sq and nonsq) received 1 cycle of carboplatin AUC 6 and paclitaxel 200 mg/m2 and pembro 200 mg. After 3 weeks, pts received carboplatin AUC 2 and paclitaxel 45 mg/m2 QW for 6 weeks and 2 cycles of pembro 200 mg Q3W + standard thoracic radiotherapy (TRT; using a standardized 3D conformal radiotherapy technique on a linear accelerator operating at ≥6 MV beam energy for a total target dose of 60 Gy in 30 daily fractions of 2 Gy). Pts in cohort B (nonsq) received 3 cycles of cisplatin 75 mg/m2, pemetrexed 500 mg/m2, and pembro 200 mg Q3W, and TRT in cycles 2 and 3. All pts received up to 14 additional cycles of pembro 200 mg Q3W. Primary endpoints were ORR per RECIST v1.1 by BICR and incidence of grade ≥3 pneumonitis (per NCI CTCAE v4.0); assessed in all pts as-treated.ResultsOf 216 pts enrolled (cohort A, n = 112; cohort B, n = 104), 112 in cohort A and 102 in cohort B were treated. As of October 28, 2020, the median (range) time from first dose to database cutoff was 18.5 (13.6–23.8) months in cohort A and 13.7 (2.9–23.5) months in cohort B. ORR (95% CI) was 70.5% (61.2%‒78.8%) and 70.6% (60.7%‒79.2%), respectively. Median DOR, OS, and PFS were not reached in either cohort. Twelve-month OS and PFS rates were 81.3% and 67.1% in cohort A; and 87.0% and 71.6% in cohort B. Grade ≥3 pneumonitis occurred in 9 pts (8.0%) in cohort A and 7 (6.9%) in cohort B. Median (range) time to onset of any pneumonitis was 4.3 (1.4–10.4) months in cohort A, and 4.4 (0.1–12.3) months in cohort B. Grade 3–5 treatment-related AEs occurring in ≥10% pts were neutropenia (cohort A, 16.1%; cohort B, 9.8%) and anemia (10.7% and 4.9%). See Table for additional safety data.ConclusionPembro + cCRT continues to demonstrate promising antitumor activity, and manageable toxicity in pts with previously untreated, locally advanced, stage III NSCLC with longer follow-up.