Pembrolizumab Combo Prolongs Survival Outcomes in NSCLC

Pembrolizumab (Keytruda) plus standard chemotherapy in the frontline setting reduced the risk of death by over 50% in patients with nonsquamous non—small cell lung cancer (NSCLC) without EGFR or ALK mutations, according to the phase III KEYNOTE-189 trial results presented at the 2018 AACR Annual Meeting.¹

Results were also simultaneously published in the New England Journal of Medicine.²

In KEYNOTE-189, patients received frontline pembrolizumab or placebo in combination with pemetrexed (Alimta) and either cisplatin or carboplatin. At a median follow-up of 10.5 months, the estimated 12-month overall survival (OS) rate was 69.2% (95% CI, 64.1-73.8) in the pembrolizumab arm compared with 49.4% (95% CI, 42.1-56.2) in the control group (HR, 0.49; 95% CI, 0.38-0.64; P <.001).

The median OS was not reached in the pembrolizumab cohort, compared with 11.3 months (95% CI, 8.7-15.1) in the chemotherapy-alone arm. The OS benefit was observed, irrespective of PD-L1 status. The study also met the coprimary endpoint of progression-free survival (PFS), with a median PFS of 8.8 months (95% CI, 7.6-9.2) in the pembrolizumab group versus 4.9 months (95% CI, 4.7-5.5) in the control arm (HR, 0.52; 95% CI, 0.43 to 0.64; P <.001).

“Adding pembrolizumab to pemetrexed and platinum induction therapy and pemetrexed maintenance therapy significantly improved overall survival, progression-free survival, and overall response rate, in patients with previously untreated metastatic nonsquamous non—small cell lung cancer without EGFR or ALK alternations,” lead author Leena Gandhi, MD, PhD, associate professor in the Department of Medicine and director of Thoracic Medical Oncology Program, Perlmutter Cancer Center at NYU Langone Health, said at an AACR press conference.

The regimen may represent, “a new standard of care for first-line treatment of this group, irrespective of PD-L1 expression,” Gandhi added.

The double-blind phase III KEYNOTE-189 study accrued 616 patients with advanced or metastatic nonsquamous NSCLC, regardless of PD-L1 expression. Patients were not EGFR- orALK-positive, and had not received systemic therapy for advanced disease. The trial randomization was 2:1 in favor of the pembrolizumab arm.

In the experimental arm (n = 410), patients received pembrolizumab at a 200-mg fixed dose every 3 weeks plus 500 mg/m² of pemetrexed plus either 75 mg/m² of cisplatin or carboplatin (AUC 5) on day 1 every 3 weeks for 4 cycles, followed by 200 mg of pembrolizumab plus 500 mg/m² of pemetrexed every 3 weeks. The regimen administered to the control group (n = 206) was identical, except that pembrolizumab was replaced with placebo.

Treatment was administered until disease progression, unacceptable toxicity, physician decision, or consent withdrawal. Patients in the control arm with disease progression were allowed to cross over to receive pembrolizumab. Beyond the primary OS and PFS endpoints, secondary endpoints included overall response rate (ORR) and duration of response.

Patient characteristics were well balanced between the 2 arms. The median age was 65.0 years in the pembrolizumab arm (range, 34.0-84.0), 62.0% of the patients were male, and all but 1 of the patients had an ECOG performance status of 0 or 1. Current/former smokers comprised 88.3% of the cohort and 96.1% of patients had adenocarcinoma.

Also in the pembrolizumab group, PD-L1 expression level as measured by tumor proportion score (% of tumor cells with membranous PD-L1 staining) was <1% in 31% of patients; ≥1% in 63.4%; 1% to 49% in 31.2% of patients; ≥50% in 32.2%; and not evaluable in 5.6%.

The pembrolizumab OS benefit was observed across PD-L1 subgroups, including the <1% expression group (12-month OS rate, 61.7% vs. 52.2%; HR, 0.59; 95% CI, 0.38-0.92); the 1% to 49% cohort (12-month OS rate, 71.5% vs. 50.9%; HR, 0.55; 95% CI, 0.34-0.90), and those with a score of 50% or greater (12-month OS rate, 73.0% vs. 48.1%; HR, 0.42; 95% CI, 0.26-0.68).

Commenting on the need for PD-L1 testing, given the efficacy across these subgroups, Gandhi said, “I think that for most of us in the field, we would be quite hesitant to give up on PD-L1, or some biomarker to select patients because clearly still not all patients are benefiting. We do need to focus more on how to differentiate the patients who will get the most benefit. PD-L1 may be part of that story here, but maybe not the whole story.”

The ORR per blinded, independent central radiologic review was 47.6% (95% CI, 42.6-52.5) in the pembrolizumab arm and 18.9% (95% CI, 13.8-25.0) with chemotherapy alone (P <.001). The disease control rate was 84.6% versus 70.4%, and the median duration of response was 11.2 months versus 7.8 months in the pembrolizumab versus control arms, respectively.

The rate of discontinuation of all study drugs due to adverse events (AEs) was 13.8% in the pembrolizumab arm compared with 7.9% in the control arm. The discontinuation rate of pembrolizumab was 20.2% and placebo was 10.4%. Death related to AEs occurred in 6.7% versus 5.9% of the pembrolizumab versus control arms, respectively.

Diarrhea (30.9% vs 21.3%) and rash (20.2% vs 11.4%) were the only 2 AEs occurring in ≥10% of patients that occurred more commonly in the pembrolizumab versus the chemotherapy-alone arm. Grade ≥3 AEs occurring in at least 10% of patients in either arm were anemia (16.3% with pembrolizumab vs 15.3% in the control group) and neutropenia (15.8% vs 11.9%, respectively).

The rate of acute kidney injury was 5.2% in the pembrolizumab arm versus 0.5% in the chemotherapy-alone arm. Eight patients (2.0%) receiving the PD-1 inhibitor had grade ≥3 acute kidney injury.

Immune-mediated AEs occurred in 22.7% of the pembrolizumab group versus 11.9% of the control group, including grade ≥3 AEs in 8.9% versus 4.5%, respectively. Pneumonitis led to 3 deaths in the pembrolizumab cohort.

Despite the higher rates in the pembrolizumab cohort, Gandhi noted, “The immune-mediated side effects…overall were not significantly more than they are with monotherapy, with similar numbers of grade 3 to 5 events and those leading to death as has been seen with monotherapy with pembrolizumab.”

References

• Gandhi L, Rodgríguez-Abreu D, Gadgeel S, et al. KEYNOTE-189: Randomized, double-blind, phase 3 study of pembrolizumab (pembro) or placebo plus pemetrexed (pem) and platinum as first-line therapy for metastatic NSCLC. Presented at 2018 AACR Annual Meeting; April 14-18, 2018; Chicago, Illinois. Abstract CT075.
• Gandhi L, Rodgríguez-Abreu D, Gadgeel S, et al. Pembrolizumab plus chemotherapy in metastatic non—small-cell lung cancer [published online April 16, 2018]. N Engl J Med. doi: 10.1056/NEJMoa1801005.