More than a third (35%) of patients with relapsed nonsmall cell lung cancer (NSCLC) treated with pembrolizumab (Keytruda, Merck) were still alive at 3 years, according to long-term results from a pivotal clinical trial.
The results also showed that, among the 10% of patients who completed all 35 cycles of pembrolizumab, the 3-year overall survival was approximately 99%, with progression-free survival (PFS) at around 70%.
"It is too soon to say that pembrolizumab is a potential cure...and we know that it doesn't work for all patients, but the agent remains very, very promising," said lead investigator Roy Herbst, MD, PhD, Department of Medical Oncology, Yale Comprehensive Cancer Center, New Haven, Connecticut.
These new results come from the KEYNOTE-010 trial, conducted in more than 1000 patients with NSCLC who had progressed on chemotherapy, randomized to receive immunotherapy with pembrolizumab or chemotherapy with docetaxel.
The results were published online on February 20 in the Journal of Clinical Oncology and were previously presented at the 2018 annual meeting of the European Society of Medical Oncology.
Overall survival at 3 years was 35% in patients with PD-L1 expression ≥ 50% in the tumor, and 23% in those with PD-L1 ≥ 1%.
This compares with 3-year overall survival of 11-13% with docetaxel.
These results are "really extraordinary," Herbst commented to Medscape Medical News.
The 3-year overall survival rate of 35% in patients with PD-L1 ≥ 50% "is huge," he said. "It really shows the durability of the response."
Herbst commented that the "almost 100%" survival at 3 years among patients who completed 35 cycles of pembrolizumab shows that this treatment period (of about 2 years) is "probably about the right time to treat."
"Currently, the agent is being used in all potential settings, before any other treatment, after other treatment, and with other treatments," he said.
"Our hope is to find the very best way to use pembrolizumab to treat individual lung cancer patients, assessing how much PD-L1 a tumor expresses, what stage the patient is in, as well as other variables and biomarkers we are working on. This is the story of tailored therapy," Herbst said.
Approached for comment, Solange Peters, MD, PhD, Oncology Department, Centre Hospitalier Universitaire Vaudois, Lausanne, Switzerland, said that the results are "very good" and "confirm the paradigms we have been seeing in melanoma," with good long-term control, which is "very reassuring."
However, she told Medscape Medical News that the trial raises an important question: "How long do you need to expose your patient with lung cancer to immunotherapy in order to get this long-term control?"
She said the "good news" is that, for the 10% of patients who completed 2 years of treatment per protocol, almost all of them are still alive at 3 years, "which is not observed with chemotherapy."
The question for Peters is "more about the definition of long-term control," as it was seen that almost one in three patients nevertheless had some form of progression.
This suggests that you have a group of people "who are nicely controlled, you stop the drug, and 1 year later a third of them have progressed."
Peters said: "So how long do you need to treat these patients? I would say I still don't know."
"If I were one of these patients probably I would still want to continue [on the drug]. Of course, some might have progressed even while remaining on the drug, but the proportion who would have progressed is probably smaller than this one."
Responses on Re-introduction of Therapy
The study also allowed patients who had completed 35 cycles of pembrolizumab to be restarted on the drug if they experienced progression.
The team found that, among 14 patients, 43% had a partial response and 36% had stable disease.
Herbst highlighted this finding and told Medscape Medical News that this "could be very important to physicians because they might want to think about using the drug again" in patients who have progressed on it.
He believes that the progression was not because of any resistance per se but rather a slowing down of the adaptive immune response.
"It's just that it needs a boost," he said, while noting that tissue specimens will nevertheless be required to demonstrate the theory.
Peters agreed that these results are "very promising," but questioned their overall significance, as it is "a very small number of patients" from a subset whose disease was controlled while on treatment and then progressed after stopping.
She also pointed out that, in another study in patients with lung cancer (CheckMate-153), some patients were rechallenged with immunotherapy after having stopped treatment at 1 year "with very poor results."
Peters said studies in melanoma have shown "rechallenge can be useful in a significant proportion of patients, but still you have not demonstrated that stopping and rechallenging is the same as not stopping."
KEYNOTE-010 involved patients with NSCLC from 202 centers in 24 countries with stage IIIB/IV disease expressing PD-L1 who had experienced disease progression after at least two cycles of platinum-based chemotherapy.
They were randomized 1:1:1 to open-label pembrolizumab 2 mg/kg, pembrolizumab 10 mg/kg, or docetaxel 75 mg/m2 every 3 weeks.
Pembrolizumab was continued for 35 treatment cycles over 2 years and docetaxel was continued for the maximum duration allowed by local regulators.
Patients who stopped pembrolizumab after a complete response or completing all 35 cycles, and who subsequently experienced disease progression, could receive up to 17 additional cycles over 1 year if they had not received another anticancer therapy in the meantime.
Among the 1034 patients originally recruited between August 2013 and February 2015, 691 were assigned to pembrolizumab at 3 mg/kg or 10 mg/kg and 343 to docetaxel.
For the intention-to-treat analysis in 1033 patients, the mean duration of follow-up was 42.6 months, with a median treatment duration of 3.5 months in the pembrolizumab group and 2.0 months in the docetaxel group.
Compared with docetaxel, pembrolizumab was associated with a significant reduction in the risk of death, at a hazard ratio of 0.53 in patients with PD-L1 ≥ 50% and 0.69 in those with PD-L1 ≥ 1% (both P < .0001).
In patients with PD-L1 ≥ 50%, median overall survival was 16.9 months in those given pembrolizumab and 8.2 months with docetaxel. Among those with PD-L1 ≥ 1%, median overall survival was 11.8 months with pembrolizumab versus 8.4 months with docetaxel.
Overall survival on Kaplan-Meier analysis was 34.5% with pembrolizumab and 12.7% with docetaxel in the PD-L1 ≥ 50% group, and 22.9% versus 11.0% in the PD-L1 ≥ 1% group.
PFS significantly improved with pembrolizumab versus docetaxel, at a hazard ratio of 0.57 (P < .00001) among patients with PD-L1 ≥ 50% and 0.83 (P < .005) in those with PD-L1 ≥ 1%.
In terms of safety, 17.7% of patients who completed 2 years of pembrolizumab had grade 3-5 treatment-related adverse events, compared with 16.6% among all pembrolizumab-treated patients and 36.6% of those given docetaxel.
The team reports that 79 patients completed 35 cycles of pembrolizumab, with a median follow-up of 43.4 months.
Compared with the overall patient group, these patients were less likely to be aged ≥ 65 years and to have received two or more prior treatment lines, although they were more likely to be current or former smokers and to have squamous tumor histology.
Patients who completed 35 cycles had an objective response rate of 94.9%, and 91.0% were still alive at the data cutoff. Overall survival rates were 98.7% at 12 months and 86.3% at 24 months.
Of 71 patients eligible for analysis, 23 experienced progression after completing pembrolizumab, at PFS rates at 12 and 24 months of 72.5% and 57.7%, respectively.
A total of 14 patients were given a second course of pembrolizumab, of whom six had a partial response and five had stable disease. At the data cutoff, five patients had completed 17 additional cycles and 11 were alive.
Pembro Approved at Fixed Dose
One notable aspect of the study is that patients in the pembrolizumab arm were given two different doses of the drug based on body weight, whereas the drug is approved in the United States at a fixed dose of 200 mg.
Herbst told Medscape Medical News he considers the 200-mg dose to be appropriate.
"I didn't think that the 3-mg versus 10-mg dose per kg that we used in our study made much difference in an average-sized person," he said, adding that the 200-mg dose "is something a little bit more than 3 mg/kg."
"So I think that this is clearly the right dos, and I don't think more would make any difference," he said.
The study was funded by Merck, the manufacturer of pembrolizumab. Herbst has reported having a consulting or advisory role for many pharmaceutical companies. Other coauthors have also reported relationships with industry, and some of the authors are Merck employees. Peters has reported receiving education grants, providing consultation, attending advisory boards, and/or providing lectures for many pharmaceutical companies.
J Clin Oncol. Published online February 20, 2020. Abstract
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Cite this: Pembro Ups Survival in NSCLC: 'Really Extraordinary' Results - Medscape - Mar 02, 2020.