Frontline Pembrolizumab Improves Survival in HNSCC

Roy Baynes, MD, PhD

Pembrolizumab (Keytruda) significantly improved overall survival (OS) compared with the standard frontline regimen of cetuximab (Erbitux) plus platinum chemotherapy and 5-FU in patients with recurrent or metastatic head and neck squamous cell carcinoma (HNSCC) and a PD-L1 expression level ≥20%, according to findings from the phase III KEYNOTE-048 trial.¹

Merck, the manufacturer of the PD-1 inhibitor pembrolizumab, reported in a press release that the coprimary endpoint of progression-free survival (PFS) in patients with PD-L1 expression ≥20% had not been reached. The trial is continuing, including evaluation of the third study arm examining pembrolizumab combined with platinum chemotherapy and 5-FU. No specific data have been made available, with Merck planning to present the results at a future medical conference and share them with regulatory agencies.

“We look forward to presenting these initial results from the KEYNOTE-048 trial at an upcoming medical meeting, and are grateful to the investigators and patients for their continued involvement in this important study,” added Baynes.

The open-label phase III KEYNOTE-048 trial randomized 825 patients to 1 of 3 arms: single-agent pembrolizumab at 200 mg IV on day 1 of each week in 3-week cycles for up to 24 months; the same pembrolizumab regimen plus investigator's choice of cisplatin at 100 mg/m² IV or carboplatin at AUC 5 IV on day 1 of each week in 3-week cycles (maximum, 6 cycles) plus 5-FU at 1000 mg/m²/day IV continuous from day 1 to day 4 of each 3-week cycle (maximum, 6 cycles); or cetuximab on day 1 at a dose of 400 mg/m² IV, and then 250 mg/m² IV on day 1 of each week plus cisplatin/carboplatin and 5-FU at the same dosages as in the pembrolizumab combination arm.

PD-L1 expression was measured by combined positive score (CPS), which includes levels on both tumor and inflammatory cells. Beyond the coprimary endpoints of OS and PFS, secondary outcome measures included response and quality of life. Merck noted in its press release that there were no new safety signals in KEYNOTE-048 compared with previous trials evaluating pembrolizumab in patients with HNSCC.

The FDA granted an accelerated approval to pembrolizumab in August 2016 as a treatment for patients with recurrent or metastatic HNSCC following progression on a platinum-based chemotherapy, based on objective response rates (ORR) in the phase Ib KEYNOTE-012 study.

The approval was based on an efficacy analysis of 174 patients treated with a prior platinum-based agent. In this assessment, the ORR with pembrolizumab was 16% (95% CI, 11-22), which included a complete response rate of 5%. Responses lasted for ≥6 months for 82% of patients.

Pembrolizumab was approved regardless of PD-L1 staining, and at a fixed dose of 200 mg every 3 weeks. In data from the KEYNOTE-012 presented at the 2016 ASCO Annual Meeting for 192 patients, pembrolizumab had an ORR of 18% and a stable disease rate of 17% in patients with recurrent/metastatic HNSCC.²

In results from the phase III KEYNOTE-040 trial presented at the 2017 ESMO Congress, pembrolizumab (Keytruda) reduced the risk of death by 19% compared with standard of care therapy in patients with relapsed/metastatic HNSCC, but the difference fell just shy of statistical significance.³

Lead study author Ezra Cohen, MD, associate director, Translational Science, University of California-San Diego Moore Cancer Center, said when presenting the data that subsequent immunotherapy in the standard of care arm may have confounded the OS analysis, as 3 times as many patients in the standard of care arm received immune checkpoint inhibitor therapy than in the pembrolizumab arm.

KEYNOTE-040 enrolled 495 patients with SCC of the oral cavity, oropharynx, hypopharynx, or larynx who had progressive disease after a platinum-containing regimen, or recurrence or progressive disease within 6 months of multimodal platinum-based therapy. They were randomly assigned 1:1 to 200 mg pembrolizumab every 3 weeks for 24 months (n = 246) or investigator’s choice of 40 mg/m² weekly methotrexate, 75 mg/m² docetaxel every 3 weeks, or 250 mg/m² weekly cetuximab (n = 234).

Randomization was stratified by ECOG performance status (0 vs 1), known p16 status for cancer of the oropharynx, and PD-L1 tumor proportion score (TPS) (≥50% vs&thinsp;<50%).The results were also analyzed according to CPS.

Treatment continued until confirmed disease progression or intolerable toxicity. The primary endpoint was OS in the intent-to-treat population. The one-sided prespecified efficacy boundary was an alpha of 0.0175, corresponding to a hazard ratio of 0.80.

After a median follow-up of 7.3 months, 22 patients in the pembrolizumab arm continue on pembrolizumab and 2 continue on standard of care therapy. About one fourth of the population in each treatment arm were p16-positive, one fourth in each arm had PD-L1 TPS ≥50%, and close to 80% in each arm had PD-L1 CPS ≥1.

There were 179 deaths in the pembrolizumab arm and 201 in the standard of care arm, for a hazard ratio (HR) of 0.81 (95% CI, 0.66-0.99) favoring pembrolizumab (P = .0204). Median OS was 8.4 months and 7.1 months, respectively.

In the population with PD-L1 CPS ≥1, the 1-year survival was 40.1% in the pembrolizumab arm versus 26.7% in the control arm (HR, 0.75; P = .0078). Median PFS was 8.7 months and 7.1 months, respectively.

In the population with PD-L1 TPS ≥50%, 1-year survival was again significantly improved from 25.8% in the control arm to 46.6% in the pembrolizumab arm (HR, 0.54; P = .0017). Median OS was 11.6 months in patients pembrolizumab and 7.9 months for those assigned to standard of care.

The ORR was also higher in pembrolizumab-treated patients. ORR was 14.6% with pembrolizumab compared with 10.1% with standard of care, respectively were (P = .0610) in the ITT analysis. Similarly, ORR favored pembrolizumab in both the PD-L1 CPS ≥1 subgroup (17.3% vs 9.9%; P = .0171), and the PD-L1 TPS ≥50% subgroup (26.6% vs 9.2; P = .0009).

Median progression-free survival (PFS) was not significantly different between the 2 treatment groups in the ITT analysis and in the subgroup with PD-L1 CPS ≥1, but in the subset with PD-L1 TPS ≥50%, median PFS was significantly superior at 3.5 months in the pembrolizumab group compared with 2.2 months in the standard of care arm (HR, 0.58; P = .0034).

Best overall response followed a similar pattern, with 4 complete responses versus 1 in the pembrolizumab and standard of care arms, respectively.

Pembrolizumab has approved indications in melanoma, lung cancer, head and neck cancer, classical Hodgkin lymphoma, primary mediastinal large B-cell lymphoma, urothelial carcinoma, microsatellite instability-high cancer, gastric cancer, and cervical cancer.

References

1. KEYTRUDA® (pembrolizumab) Monotherapy Met a Primary Endpoint in the Phase 3 KEYNOTE-048 Trial, Significantly Improving OS as First-Line Therapy in Head and Neck Squamous Cell Carcinoma Patients Whose Tumors Expressed PD-L1 (CPS ≥20). Posted July 25, 2018. Accessed July 25, 2018. https://bit.ly/2LNQhJU.
2. Mehra R, Seiwert TY, Mahipal A, et al. Efficacy and safety of pembrolizumab in recurrent/metastatic head and neck squamous cell carcinoma (R/M HNSCC): Pooled analyses after long-term follow-up in KEYNOTE-012. J Clin Oncol. 2016;34 (suppl; abstr 6012).
3. Cohen EEW, Harrington KJ, Le Tourneau C, et al. Pembrolizumab (pembro) vs standard of care (SOC) for recurrent or metastatic head and neck squamous cell carcinoma (R/M HNSCC): Phase 3 KEYNOTE-040 trial. Presented at ESMO 2017 Congress; September 8-12, 2017; Madrid, Spain. Abstract LBA45_PR.

“This interim analysis of the KEYNOTE-048 trial has shown that Keytruda monotherapy has the potential to help patients with head and neck cancer whose tumors express high levels of PD-L1,” Roy Baynes MD, PhD, senior vice president and head of Global Clinical Development, chief medical officer, Merck Research Laboratories, said in a statement.