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CHICAGO -- One-year survival in advanced lung cancer improved dramatically in patients who received the PD-1 inhibitor pembrolizumab (Keytruda) in addition to chemotherapy as initial therapy, according to results of a potentially practice-changing study.

Patients randomized to the combination had a 12-month survival of 69% compared with 49% for patients who received chemotherapy and placebo. Twice as many patients were alive without disease progression when they received pembrolizumab in addition to chemotherapy.

The survival benefit was similar across the range of tumor PD-L1 expression, Leena Gandhi, MD, PhD, of NYU Langone Medical Center in New York City, reported here at the (AACR) meeting.

"Adding pembrolizumab to pemetrexed and platinum induction therapy and pemetrexed maintenance therapy significantly improves overall survival, progression-free survival (PFS), and objective response rate in patients with untreated metastatic nonsquamous non-small cell lung cancer (NSCLC) without sensitizing EGFR or ALK alterations," Gandhi said during an AACR press briefing. "Pembrolizumab plus pemetrexed (Alimta) and platinum may be a new standard of care for first-line treatment of metastatic nonsquamous NSCLC, irrespective of PD-L1 expression."

The results supported the hypothesis that chemotherapy has immunogenic properties that might augment the activity of immunotherapeutic agents and extend the benefits of an agent like pembrolizumab to patients who have tumors that do not express PD-L1, she added.

Press briefing moderator Alice Shaw, MD, of Massachusetts General Hospital Cancer Center in Boston, said results did establish a new standard of care for untreated, advanced nonsquamous NSCLC.

"The improvement in overall survival with the addition of pembrolizumab to standard chemotherapy across all patients, regardless of PD-L1 status, is striking," said Shaw.

Roy Herbst, MD, PhD, of Yale Cancer Center in New Haven, said the results may surprise many lung cancer specialists.

"I never would have thought that chemotherapy combinations would be where we are going with immunotherapy, and I resisted for a long time because my feeling was that immunotherapy could be used without chemotherapy," Herbst told 名媛直播.

"I think the chemo combinations in nonsquamous lung cancer mean that 70% or 80% of patients are going to get immunotherapy in frontline," he added. "That's best for patients, to get the best drugs as early as possible. Whether that's pembrolizumab or nivolumab (Opdivo) or some combination, it will depend on the patient."

The study was published simultaneously in the .

Gandhi reported findings from the , which compared pembrolizumab plus pemetrexed-platinum chemotherapy and pemetrexed maintenance versus chemotherapy and placebo in patients with untreated stage IV nonsquamous NSCLC. Patients whose tumors had sensitizing EGFR mutations or ALK alterations were excluded. The rationale for the trial came from a that showed improved response rate and PFS in similar patients who received pembrolizumab and pemetrexed-platinum chemotherapy instead of chemotherapy alone.

Patients were randomized 2:1 to pembrolizumab plus chemotherapy or to placebo and the same chemotherapy. The trial had coprimary endpoints of overall survival (OS) and PFS, and the intention-to-treat analysis comprised 616 patients.

After a median follow-up of 10.5 months, patients randomized to pembrolizumab plus chemotherapy had a 51% reduction in the survival hazard versus the chemotherapy group (HR 0.49, 95% CI 0.38 to 0.64, P<0.00001). Median OS had yet to be reached, whereas the median OS in the placebo-chemotherapy arm was 11.3 months. Estimated 12-month OS was 69.2% with pembrolizumab and 49.4% with placebo.

Across the range of PD-L1 expression from <1% to 1%-49% to ≥50%, hazard reductions of 41%-58% were observed in patients treated with pembrolizumab and chemotherapy (P=0.0095 to P=0.0001).

The analysis of PFS yielded a 48% reduction in the hazard for progression or death in patients treated with pembrolizumab and chemotherapy (HR 0.52, 95% 0.43 to 0.64, P<0.00001). Median PFS was 8.8 months with pembrolizumab and 4.9 months with placebo. PFS favored pembrolizumab across PD-L1 expression status and achieved statistical significance for patients with tumors that had intermediate or high PD-L1 expression.

The overall response rate was 47.6% with pembrolizumab and chemotherapy versus 18.9% with placebo and chemotherapy (P<0.00001). Similar differences existed across the range of PD-L1 expression (P=0.0055 to P<0.0001).

The total incidence of adverse events, grade 3-5 events, and fatal adverse events was similar in the two groups. More treatment-related adverse events leading to discontinuation occurred in the pembrolizumab arm (13.8% versus 7.9%).