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Abstract
Background Our study was designed to determine the safety, efficacy, and immunological effects of perioperative pembrolizumab in early-stage NSCLC.
Methods This is a single-arm phase II study of perioperative pembrolizumab in patients with untreated, clinical stage IB to IIIA NSCLC. Patients received two doses of 200 mg pembrolizumab, surgery, standard adjuvant chemotherapy, followed by four doses adjuvant pembrolizumab. The primary objective of this study was to determine surgical feasibility rate, and secondary objectives are pathological response rate, treatment adverse events, efficacy data, and exploratory analysis of biomarkers.
Results 30 patients initiated perioperative pembrolizumab, and 25 completed tumor resection. At median follow-up of 59 months after surgical resection, seven patients had disease progression, while six had died representing. A 5-year progression-free survival (PFS) from time of surgery was 72.0% (56.4%–91.9%) and overall survival (OS) from time of surgery was 75.8% (60.7%–94.7%). Major pathological response (MPR) was found in seven tumors (28%) including two complete responses (4%). Across all treated patients, four receiving neoadjuvant and four receiving adjuvant pembrolizumab experienced treatment-related adverse events of grade 3 or higher with no grade 5 events. Plasma proprotein convertase subtilisin/kexin type 9 (PCSK9) levels increased across our patient cohort over time from baseline until postsurgery and remained elevated at the end of treatment. There was a significant difference between mean plasma PCSK9 levels for patients with MPR versus all other patients on study when checked postoperatively.
Conclusions Perioperative pembrolizumab was safe and effective with promising MPR rate, PFS, and OS.
- Immune Checkpoint Inhibitor
- Lung Cancer
- Biomarker
- Immunotherapy
- Pathologic complete response - pCR
Data availability statement
Data are available on reasonable request. The data (deidentified participant data) generated in this study are available on request from the corresponding author, NR.
This is an open access article distributed in accordance with the Creative Commons Attribution Non Commercial (CC BY-NC 4.0) license, which permits others to distribute, remix, adapt, build upon this work non-commercially, and license their derivative works on different terms, provided the original work is properly cited, appropriate credit is given, any changes made indicated, and the use is non-commercial. See http://creativecommons.org/licenses/by-nc/4.0/.
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WHAT IS ALREADY KNOWN ON THIS TOPIC
Studying biomarkers before and after neoadjuvant PD-1 inhibition for early-stage non-small cell lung cancer (NSCLC) contributes important insights into factors associated with response to PD-1 checkpoint-based therapies. One such potential biomarker, PCSK9, is a member of the subtilisin-like proprotein convertase family which has roles both in cholesterol metabolism and affecting the tumor immune microenvironment.
WHAT THIS STUDY ADDS
We conducted a single-arm, phase II study of neoadjuvant and adjuvant pembrolizumab in patients with operable NSCLC. We found this strategy was safe and effective with promising major pathological response rate (MPR), progression-free survival, and overall survival. We found that PCSK9 may be a biomarker associated with MPR after neoadjuvant pembrolizumab.
HOW THIS STUDY MIGHT AFFECT RESEARCH, PRACTICE OR POLICY
At this time, two clinical trials (NCT 05144529, NCT 05553834) are underway at our institution investigating combination of anti-PCSK9 therapy with ICI therapy in the first-line metastatic, and second-line metastatic setting to test the hypothesis that PCSK9 inhibition can overcome PD1 checkpoint immune resistance.
Background
Lung cancer is the leading cause of cancer mortality in the USA with an estimated 234,580 new cases in 2024 and approximately 125,070 deaths in the USA.1 Standard-of-care treatment of advanced non-small cell lung cancer (NSCLC) has progressed significantly with the development of small molecule inhibitors active against oncogenic ‘driver’ alterations and immune therapy strategies for tumors without actionable alterations.2–4 These therapies initially demonstrated activity in patients with metastatic NSCLC, and since have demonstrated activity in early-stage and locally advanced disease settings.
Surgery can be curative in early-stage NSCLC. However, 5-year survival rates are low after surgery with or without adjuvant chemotherapy among patients with early-stage disease (57% 5-year survival) and patients with regional lymph node involvement (30% 5-year survival).5 Neoadjuvant immune checkpoint blockade strategies have shown significant antitumor activity and improvement in disease-free and overall survival (OS) in this population when given as monotherapy, in combination with CTLA4 inhibition, or in combination with chemotherapy.6–12 A surprisingly high rate of major pathological responses (MPR) has been reported in monotherapy neoadjuvant and perioperative immunotherapy trials.6 12 13 The phase II LCMC3 study of neoadjuvant atezolizumab met its primary endpoint with an MPR of 20% (6% CR) and showed low rates of treatment-related adverse events.12 The phase II CTONG1804 trial randomized patients to single-agent perioperative nivolumab versus neoadjuvant nivolumab plus chemotherapy and adjuvant nivolumab if their PDL1 Tumor Proportion Score (TPS) was >50%. They found an MPR of 16.7% for single-agent nivolumab versus 66.7% in the chemoimmunotherapy arm.14 Currently, adjuvant immune therapy, neoadjuvant chemotherapy plus immune therapy, or perioperative chemotherapy plus immune therapy followed by adjuvant immune therapy are standard treatments for early stage, potentially curable NSCLC.5–7 10–13 Important remaining questions include whether perioperative chemotherapy and immune therapy are superior to neoadjuvant therapy alone, and whether all patients need to receive chemotherapy.
Most patients with advanced NSCLC demonstrate primary or acquired resistance to immune checkpoint inhibitors (ICI), with 5-year OS rate of 20%–25%.2 Studying tumor and blood biomarkers before and after neoadjuvant PD-1 inhibition for early-stage NSCLC will contribute important insights into factors associated with sensitivity and resistance to PD-1 checkpoint-based therapies. Several clinical studies of monotherapy and combination immune therapy have focused on biomarker discovery.6 12 13
One potential biomarker, PCSK9, is a member of the subtilisin-like proprotein convertase family and plays a role in regulating plasma cholesterol levels.15 16 In preclinical experiments, it was discovered that genetic depletion of PCSK9 in murine tumor cells significantly attenuated their abilities to form tumors in a T cell-dependent manner, and PCSK9 depletion overcame resistance to PD-1 immune checkpoint therapy. 115 advanced NSCLC patients who received anti-PD-1 immunotherapy were retrospectively studied with respect to PCSK9 expression in baseline NSCLC tissues detected by immunohistochemistry. Patients with elevated PCSK9 levels were found to have a significantly shorter median progression-free survival (PFS) vs patients with low PCSK9 levels (3.6 vs 8.1 months, HR 3.450, 95% CI 2.166 to 5.496) highlighting PCSK9 expression as a deleterious factor for the efficacy of immunotherapy treatment strategies.16
We conducted a single-arm, phase II study of neoadjuvant and adjuvant single-agent pembrolizumab in patients with clinical stage IB, II, or IIIA NSCLC (TOP1501; NCT02818920). We have previously reported that neoadjuvant pembrolizumab was safe and feasible with no excess surgical morbidity or mortality.10 We report MPR rate, final survival analysis, tumor genomics, blood PCSK9 levels, and PDL-1 results in this study.
Methods
Patients
Eligible patients were 18 years or older with histologically proven clinical stage IB (tumor size >4 cm), II, or IIIA (N0–N2) NSCLC as assessed according to the American Joint Committee on Cancer staging system, seventh edition. Eligibility criteria included adequate performance status (Eastern Cooperative Oncology Group 0–1), no other history of active invasive malignancy 2 years prior to enrolment (other than non-melanomatous skin cancer), no autoimmune disease that would constitute contraindication to pembrolizumab, and no history of prior therapy for NSCLC. Diagnostic and staging workup included histological diagnosis, positron emission tomography/CT and brain imaging. All patients were deemed appropriate for surgery by their institutional thoracic surgery team prior to enrolment. Pathological mediastinal staging was performed before treatment when clinically indicated.10 Full eligibility criteria are provided in online supplemental table 1.
Supplemental material
Treatment and evaluation
Patients received 200 mg intravenous pembrolizumab administered over 30 min for two cycles prior to surgery. Standard surgical evaluation was performed at least 21 days after the second dose of pembrolizumab along with repeat chest CT scan and reassessment by the treating medical oncologist. Surgery was performed 29–56 days from the first dose of pembrolizumab per study protocol. After recovery from surgery, patients were re-evaluated by the treating medical oncologist and standard adjuvant chemotherapy was recommended but not required and administered per the discretion of the treating oncologist. Postoperative radiation therapy was considered per institutional standard. Patients then received four additional cycles of adjuvant pembrolizumab administered 3–6 weeks after completion of standard adjuvant therapy.
CT or MRI of the chest and abdomen was performed during screening, throughout all treatment phases, and during follow-up according to the schedule outlined in the protocol (online supplemental materials-study periods). To determine survival and recurrence status, data were collected every 3–4 months for 2 years after surgery, followed by every 6 months for 5 years after surgery. Adverse events and laboratory abnormalities were assessed throughout study and graded according to the National Cancer Institute Common Terminology Criteria for Adverse Events Version 4.0.10
End points and statistical analysis
The primary objective of this study was to determine the surgical feasibility rate following neoadjuvant pembrolizumab. Secondary objectives included evaluation of pathological response, disease-free survival, OS and adverse events. Exploratory objectives included evaluation of blood-based biomarkers and genomic analysis of resected tumors.
According to Pisters et al, approximately 80% of subjects undergo surgical exploration within 42 days of day 1 of the last cycle of standard neoadjuvant chemotherapy.17 In order to test the hypothesis: H0: p≥0.80 vs Ha: p≤0.65 where p is the true surgery feasibility rates after combined neoadjuvant chemotherapy and pembrolizumab. With 30 evaluable patients receiving protocol treatment, the study had approximately 84.6% power rejecting H0: p≥0.80 when p=0.65 at a one-sided significance level of 15%.
PFS is defined by the time from surgical resection to disease recurrence (first disease recurrence or death, whichever comes first) after surgery. OS is defined as the time between the time from surgery and date of death or last follow-up. Pathological response after neoadjuvant therapy was assessed by examination of H&E-stained slides of resected lung tissue and lymph nodes by one senior thoracic pathologist at Duke Cancer Institute. The data reported are from the most recent interim analysis (data cut-off date, October 11, 2023) which was performed 57 months after the last participant was enrolled.
A full description of statistical analysis is available per online supplemental materials (Supplementary Materials-Statistical Analysis). Kaplan-Meier methods were used to describe PFS and OS. Blood based biomarkers were evaluated for changes before and after protocol treatment. The association of baseline value and changes of these values in correlation with clinical outcomes was evaluated using logistics regression and Cox models.
Biomarker analysis
Programmed death-ligand 1 (PD-L1) was tested from the surgically resected tumor specimen via a central reference lab using automated staining with the 22C3 antibody (QualTek TekMate 500, QualTek Molecular Laboratories, Newton, Pennsylvania, USA).
To assess immunological parameters, blood specimens were collected from each patient prior to beginning treatment, prior to surgery after neoadjuvant treatment, following surgery, and after completion of adjuvant pembrolizumab. Peripheral blood mononuclear cells were collected at the above time points and viably cryopreserved for future correlative science studies. Immune profiling data will be published in a separate manuscript. PCSK9 levels in plasma samples were measured by colorimetric ELISA according to the manufacturer’s instructions (R&D Systems, Minneapolis, Minnesota, USA). In addition, following surgical pathology examination for standard of care tumor analysis, excess tumor was provided to the Duke Immune Profiling Core for immune profiling which will be presented in a separate publication. Whole exome sequencing was performed on tumor samples.
Results
Patient characteristics and treatment
Between April 10, 2017 and February 6, 2019, 35 patients provided informed consent and 30 patients received study therapy. Demographic characteristics of patients enrolled of note included: male (16, 53%), white (29, 97%), median age 72 years (range 47–81), current or former smokers (26, 87%), and squamous histology (17, 57%). Nine patients (30%) had stage IB disease, 7 patients (23%) had stage IIA disease, 6 (20%) had stage IIB disease, and 8 (27%) had stage IIIA disease (table 1). For information regarding representativeness of study participants, please see online supplemental table 2.
Baseline characteristics of patients receiving perioperative pembrolizumab (n=30)
Of the 30 patients who received neoadjuvant pembrolizumab, 5 were not deemed to be candidates for surgical resection. One patient had disease progression on restaging imaging after neoadjuvant therapy. The other four were found to have disease stage not appropriate for resection at the time of intended surgery (three who had N3 disease at mediastinoscopy and one with M1a pleural disease).10
17 patients (68%) received adjuvant chemotherapy. Adjuvant radiation therapy was received by 4 (16%) patients. 17 patients (68%) received adjuvant pembrolizumab therapy. Please see online supplemental figure 1 for the Consolidated Standards of Reporting Trials diagram describing patient disposition.
Surgical outcomes
Perioperative surgical outcomes for the 25 patients who underwent surgery were published.10 Overall, there were few delays between the administration of pembrolizumab and surgery. All patients underwent anatomic lung resection: lobectomy was performed in 18 patients (72%); bilobectomy was performed in 1 patient (4%); sleeve lobectomy was performed in 2 patients (8%); pneumonectomy was performed in 3 patients (12%); and right upper lobectomy with en bloc right lower lobectomy wedge resection was performed in 1 patient (4%).
The most common postoperative complications were atrial fibrillation 6 (24%), prolonged air leak 4 (16%), and atelectasis 3 (12%). No patients died within 30 or 90 days of surgery.10
Safety
Of the 30 patients who received treatment on study, 30 (100%) experienced treatment-related adverse events. Of the 30 patients who received neoadjuvant therapy, 4 (13.3%) experienced events considered grade 3 or higher. This was due to hyperglycemia (1), hyponatremia (1), hypophosphatemia (1), and a psoriasis flare (1). Of the 17 patients who received adjuvant pembrolizumab therapy, 4 (23.6%) experienced events that were considered grade 3 or higher. This was due to a pneumonitis (1), hypertension (2), and a thromboembolic event (1). The most common adverse events from perioperative pembrolizumab were rash (8), diarrhea (7), fatigue (6), and pruritus (6) (table 2). No treatment-related grade 5 events were observed. Treatment-related adverse events led to discontinuation of adjuvant pembrolizumab treatment in three study participants. Adverse events seen in >5% of patients who received at least one dose of pembrolizumab are shown in table 3.
Adverse events
Adverse events (AEs) occurring in ≥5% of 30 patients treated with pembrolizumab
Efficacy
Pathological outcomes were available for review from the 25 patients who underwent surgical resection (figure 1). An MPR, defined as less than or equal to 10% of viable tumor remaining at time of surgery, was observed in 7 specimens (28%). This included four specimens with adenocarcinoma histology, two with squamous histology, and one with adenosquamous histology. Two specimens (8%) were observed to have complete pathological response of which both had squamous histology documented before initiation of therapy. Of those patients who experienced an MPR, one of those seven patients experienced disease progression, recurrence or death (online supplemental figure 2). The two patients who experienced complete pathological response did not experience disease progression, recurrence, or death at time of final analysis.
Waterfall plot of pathological response for those patients that underwent surgical resection. Patients with major pathological response were considered to have >90% pathological response.
Of the 25 patients who underwent surgery, 7 (28%) patients had disease progression, recurrence or death. The median event-free and OS times were not reached in this patient cohort (figure 2). 18 (72%) patients were alive without an event at median follow-up of 59 months. A 5-year PFS rate was 72% (56.4%–91.9%) and 5-year OS rate was 75.8% (60.7%–94.7%). Of all patients in study who received neoadjuvant therapy including those who did not undergo surgery, 11 (36.7%) patients had experienced disease progression, recurrence or death. Of these 30 patients, 21 (70%) were alive at time of data cut-off (online supplemental figure 3). Of the nine patients who had died, seven were due to disease recurrence and progression while two were from other medical events. There were no treatment-related deaths.
Event-free survival and overall survival for patients who underwent surgical resection. (A) Kaplan-Meier curve indicating event-free survival. (B) Kaplan-Meier curve indicating overall survival for the 25 patients who underwent surgical resection on study.
PD-L1 expression was tested on the surgically resected tumor specimens via a central reference lab using automated staining (QualTek TekMate 500, QualTek Molecular Laboratories, Newton, Pennsylvania, USA). Of 20 patients with testing available, 10 patients had PD-L1 TPS≥50%, 7 with 1%–49%, and 3 with <1%. For patients with postsurgery TPS≥50%, there was not a significant difference in median disease-free or OS in comparison to patients with TPS<50% (online supplemental figure 4). In tumor specimens after neoadjuvant pembrolizumab, the PDL1 TPS was 80%–100% (median 80%) for tumors with MPR after neoadjuvant pembrolizumab vs 0%–90% (median 42.4%) for tumors without MPR after neoadjuvant pembrolizumab (p=−0.1724) (online supplemental table 5), and ROC curve (online supplemental figure 5).
Whole exome sequencing was performed for 21 patients on trial (online supplemental table 3), and efficacy was analyzed for tumors with TP53 and KRAS mutations (online supplemental figure 6). Mutations of interest included activating EGFR mutations, ALK rearrangements, ROS1 rearrangements, BRAF V600E mutation, NTRK1/2/3 gene fusions, RET rearrangements, ERBB2 mutations, STK11 mutations, and KEAP1 mutations which were not observed in our population. Eight tumors had TP53 mutations, and none of those tumors had an MPR. Two tumors had KRAS G12C mutations, and neither case has relapsed. One of the KRAS-mutated tumors had MPR at time of surgical resection.
PCSK9 Levels
Plasma PCSK9 levels were tested from each patient at baseline, after neoadjuvant treatment prior to surgery, following surgery, and after completion of adjuvant pembrolizumab PCSK9 levels were numerically lower in patients with MPR compared with patients without MPR at all time points. At the postsurgery time point, mean plasma PCSK9 was 165.8 (range 128.5–207.1) ng/mL for MPR vs 199 (147.3–255.1) ng/mL for patients without MPR, p=0.05. For the entire patient cohort, there was notably a significant increase in mean plasma PCSK9 from baseline to completion of neoadjuvant pembrolizumab (mean difference 25.0 ng/mL, p=0.0015), and from completion of neoadjuvant pembrolizumab to postsurgery time point (mean difference 40.2 ng/mL, p≤0.0001). There was no significant difference in PCSK9 values between the postsurgery time point and the completion of all adjuvant therapy time point (figure 3, online supplemental table S4). PCSK9 plasma values were similar at baseline in patients with cancer progression versus no cancer progression, and after two cycles of neoadjuvant pembrolizumab PCSK9 values were approximately 15% numerically higher in cases with cancer progression (online supplemental table S6).
Exploratory analysis of plasma PCSK9 levels in patients receiving perioperative pembrolizumab. (A) Plasma PCSK9 levels in patients with MPR (<10% of viable tissue remaining, green) versus patients without MPR. At pretreatment collection, post-neoadjuvant treatment collection, and post-adjuvant treatment collection, there was a trend toward lower PCSK9 levels in those with MPR, while at the postsurgery collection, there was a statistically significant difference in mean plasma PCSK9 level. (B) Across all patient on study, mean plasma PCSK9 levels were found to increase following exposure to neoadjuvant pembrolizumab. MPR, major pathological response; PCSK9, Proprotein Convertase Subtilisin/Kexin Type 9. * P < 0.05, ** P < 0.01, **** P < 0.0001.
Discussion/conclusion
This is one of the first studies reporting toxicity, efficacy, and biomarker data for perioperative monotherapy pembrolizumab in resectable NSCLC. This treatment was found to be feasible and safe with promising MPR rate, 5-year PFS, and 5-year OS. There were no cases in which neoadjuvant pembrolizumab was discontinued, and only three patients discontinued adjuvant pembrolizumab due to immune therapy-related toxicity. Preoperative pembrolizumab did not increase surgery-related adverse events or impede the feasibility of surgery.10
The use of perioperative immunotherapy provides an excellent platform to study biomarkers associated with sensitivity and resistance to ICI therapy. Preclinical studies at our institution identified PCSK9 as being important in tumor escape from immune-mediated tumor cell killing.18 It is hypothesized that inactivation or decreased PCSK9 levels will increase the surface expression of MHC-I on tumor cells thereby improving the recognition of tumor antigens by tumor-infiltrating lymphocytes. Plasma PCSK9 levels were shown to increase throughout the treatment course of patients receiving pembrolizumab therapy consistent with an adaptive resistance mechanism to PD-1 checkpoint inhibition. Further, our data suggest that patients who experienced MPR following neoadjuvant treatment tended to have lower PCSK9 plasma levels following surgical resection than those who did not have MPR. PCSK9 values after neoadjuvant pembrolizumab were numerically modestly higher in cases of cancer progression compared with cases without cancer progression consistent with a possible resistance mechanism to PD-1 checkpoint therapy (online supplemental table S6).
The majority of tumors that underwent WES had squamous or adenosquamous histology (15 out of 21 patients, 71.4%). Eight of the 21 tumors that had WES performed harbored TP53 single nucleotide variants. Functional analysis including RNAseq has suggested that TP53 mutation downregulates immune response in patients with metastatic carcinomas.19 In our limited patient sample size, none of the tumors with TP53 mutations had MPR after neoadjuvant pembrolizumab. The low number of tumors with activating molecular alterations is due, in part, to the high percentage of squamous cell lung cancers in this study.
At the time the study was carried out, it was not standard of care to test the tumor for actionable molecular alterations, or baseline PDL1 expression in early-stage NSCLC. Therefore, baseline tumor specimen for PD-L1 testing or a core biopsy for future correlative science was not required. PD-L1 analysis was carried out on patient’s surgically resected tumor. PD-L1 TPS scores were numerically higher and trended toward significance in tumors with MPR versus tumors that did not have MPR. Only 3 (15%) tumors had PD-L1<1% after neoadjuvant pembrolizumab. On review of clinical trials studying neoadjuvant, perioperative, or adjuvant PD-1 checkpoint therapy in early-stage NSCLC, they reported baseline PD-L1 scores <1% in 33%–43% of tumors.8 11 12 14 The lower percentage of tumors with PD-L1<1% identified in our study may be due to small sample size. On the other hand, it is also possible that exposure to neoadjuvant pembrolizumab increased the percentage of tumors that were PD-L1 positive. One major question remaining for neoadjuvant and perioperative immune therapy in NSCLC is which patients should receive adjuvant PD-1 checkpoint therapy after neoadjuvant chemoimmunotherapy and surgery. At least one important phase 3 trial studying adjuvant atezolizumab for NSCLC, IMPOWER 010 found that tumors with high PD-L1 scores benefit the most from adjuvant atezolizumab compared with tumors with low PD-L1.20 Neoadjuvant and perioperative studies showed efficacy was associated with increased PD-L1 scores, but PD-L1 negative tumors also appeared to benefit.7 8 11 If PD-L1 scores increase in some tumors after neoadjuvant PD-1 checkpoint therapy, then it may not be appropriate to use PD-L1 score in the resected tumor after neoadjuvant chemoimmunotherapy as a criterion for choosing whether or not to offer adjuvant PD-1 checkpoint therapy.
A limitation of our study is the under-representation of ethnic minorities in the clinical trial (online supplemental table S2). This is a national problem for which efforts are underway to correct both nationally and institutionally. However, one possible explanation unique to clinical trials of early-stage NSCLC is that under-represented populations present at more advanced stages of lung cancer due to less access to lung cancer screening.1 The Duke Cancer Institute has recently pioneered the nationally acclaimed JustASK program. Additionally, other targeted efforts are underway to increase enrolment of under-represented minorities into our clinical trials, including increased efforts at lung cancer screening. With these efforts, we anticipate a narrowing of the gap in future studies.
Overall, our study adds to the growing body of evidence supporting perioperative use of PD-1 checkpoint therapy. Perioperative pembrolizumab was found to be safe with promising MPR rate and long-term PFS and OS. The use of chemotherapy combined with ICI therapy continues to represent standard of care. In the future, it may be possible to offer patients neoadjuvant or perioperative PD-1 checkpoint monotherapy for biomarker-selected subsets of tumors.
Supplemental material
Data availability statement
Data are available on reasonable request. The data (deidentified participant data) generated in this study are available on request from the corresponding author, NR.
Ethics statements
Patient consent for publication
Ethics approval
This study involves human participants and was approved by Duke University Institutional Review Board:Duke IRB#: Pro00071629. Participants gave informed consent to participate in the study before taking part.
Acknowledgments
Non-author contributors to this work include the thoracic oncology clinical research teams at participating institutions (Duke, Dartmouth, Mayo Clinic).
References
Footnotes
Contributors Those listed as coauthors on this manuscript provided substantial contributions to the conception, analysis, and interpretation of data for this work in addition to efforts in drafting, reviewing the final version of publication, and agreeing to be accountable for all aspects of this work. The guarantor of this work is NR.
Funding Supported in part by a research grant from Investigator-Initiated Studies Program of Merck Sharp & Dohme.
Disclaimer The opinions expressed in this paper are those of the authors and do not necessarily represent those of Merck Sharp & Dohme. The study was an investigator-initiated trial where study design, data collection, analysis, interpretation of data, report writing, and decision to submit for publication were managed directly by NR without study sponsor influence.
Competing interests No, there are no competing interests.
Provenance and peer review Not commissioned; externally peer reviewed.
Supplemental material This content has been supplied by the author(s). It has not been vetted by BMJ Publishing Group Limited (BMJ) and may not have been peer-reviewed. Any opinions or recommendations discussed are solely those of the author(s) and are not endorsed by BMJ. BMJ disclaims all liability and responsibility arising from any reliance placed on the content. Where the content includes any translated material, BMJ does not warrant the accuracy and reliability of the translations (including but not limited to local regulations, clinical guidelines, terminology, drug names and drug dosages), and is not responsible for any error and/or omissions arising from translation and adaptation or otherwise.