Delineating the Role of PD-1/PD-L1 Blockade in Advanced SCLC

The benefits and risks of pembrolizumab in combination with chemotherapy as first-line therapy in small-cell lung cancer: a single-arm meta-analysis of noncomparative clinical studies and randomized control trials

BACKGROUND

Although pembrolizumab has shown clinical benefit in patients with small-cell lung cancer (SCLC), its actual efficacy in combination with a conventional chemotherapy drug has not been determined. We performed this study to discern the efficacy and risk of pembrolizumab in combination with chemotherapy as first-line therapy in SCLC patients.

METHODS

We systematically searched the PubMed, ScienceDirect, Cochrane Library, Scopus, Ovid MEDLINE, Embase, Web of Science, and Google Scholar databases for relevant studies. The main outcomes were overall survival (OS) and progression-free survival (PFS).

RESULTS

We identified 2980 articles and included 6 studies (5 were noncomparative open-label studies and 1 was a randomized controlled trial [RCT]) involving 396 patients in our meta-analysis. The pooled median OS (mOS) was 9.6 months (95% CI, 8.0-11.2), and the pooled median PFS (mPFS) was 4.2 months (95% CI, 2.2-6.1). The 1-year overall survival rate (OSR-1y) and 6-month progression-free survival rate (PFSR-6m) were 45.1% (95% CI, 33-57.2%) and 41.6% (95% CI, 24.3-59%), respectively. The objective response rate (ORR) was 38.8% (95% CI, 11.9-65.67%), disease control rate (DCR) was 69.30% (95% CI, 51.6-87.0%), complete response (CR) was 2.20% (95% CI, 0.8-3.7%), partial response (PR) was 34.70% (95% CI, 7.8-61.5%), and stable disease (SD) was 20.90% (95% CI, 9.1-32.6%). The grade 3-4 adverse effect (AE) rate was 20.88% (95% CI, 1.22-54.85%). The most common AEs were neutropenia (90.16%), anemia (53.21%), dysphagia (41.96%), platelet count decrease (34.87%), and esophagitis (32.89%); severe AEs included neutropenia, respiratory failure, pneumonitis, acute coronary syndrome, and colitis/intestinal ischemia.

CONCLUSIONS

The combination of pembrolizumab with conventional chemotherapy is an effective therapeutic schedule with acceptable and manageable efficacy and toxicity in patients with SCLC. More high-quality and well-designed RCTs with large sample sizes are warranted to further validate our findings.

[Present and Future of Efficacy Biomarkers in Immune Checkpoint Inhibitors of Small Cell Lung Cancer]

近年来，免疫治疗在小细胞肺癌领域取得了令人瞩目的突破，为患者带来生存获益。然而，现有的临床研究结果表明试验组通常在治疗开始3个月-6个月以后方可看出获益的趋势，因此如何筛选优势人群是免疫治疗研究的重点。目前已有的临床试验对生物标记物进行了不断地探索，但结果不尽一致。我们亟需有力可靠的疗效预测指标有效地筛选优势人群、扩大受益群体。故本文将对小细胞肺癌免疫治疗疗效预测指标的现状及未来的发展前进方向展开阐述。

Immune Oncology Biomarkers in Lung Cancer: an Overview

PURPOSE OF REVIEW

Lung cancer is still the first cause of cancer-related deaths worldwide. The development of immune checkpoint inhibitors (ICI) has drastically changed the prognosis of some patients, but the rate of long responders does not exceed 20%. Moreover, ICIs are not adverse events-free and remain expensive. Therefore, predictive biomarkers of long-term benefit to ICI are required.

RECENT FINDINGS

The two main fields being evaluated currently are PD-L1 expression and tumor mutational burden (TMB). The first one is the only one used in routine practice, and the second is being evaluated in phase 3 clinical trials. In addition, other biomarkers are being assessed as complex signatures, tumor-infiltrated lymphocytes, T cell receptor repertoire, or molecular profiling. The aim of this review is to summarize the current validated or promising biomarkers in lung cancer which could help to better select patients who will respond to ICI.

The evolving landscape of immunotherapy in small-cell lung cancer: A focus on predictive biomarkers

Small cell lung cancer (SCLC) was defined as a "recalcitrant cancer" because of its dismal prognosis and lack of outcome improvements in the last 30 years. Immunotherapy with checkpoint inhibitors revolutionized treatment in many cancer types and results from the IMpower133 study, a double-blind placebo-controlled phase III trial, showed overall survival benefit for atezolizumab when added to standard platinum-etoposide chemotherapy in first-line SCLC setting for the first time since years. Trials with other checkpoint inhibitors, e.g. pembrolizumab, durvalumab, nivolumab and ipilimumab, are ongoing in various settings, but, to date, there are no defined factors to identify patients who are more likely to benefit from such treatments. This review summarizes results of immunotherapy trials in SCLC for first-line, maintenance and further-line therapies for single-agents and combinations with checkpoint inhibitors. Predictive factors from these trials are reviewed in order to identify their clinical value, with particular emphasis on PD-L1 expression on both tumor cells and in stroma, especially in pembrolizumab-treated patients, and tumor mutational burden, for patients treated with the ipilimumab and nivolumab combination.

A Randomized Non-Comparative Phase II Study of Anti-Programmed Cell Death-Ligand 1 Atezolizumab or Chemotherapy as Second-Line Therapy in Patients With Small Cell Lung Cancer: Results From the IFCT-1603 Trial

INTRODUCTION

This randomized phase II trial aimed at evaluating the engineered programmed cell death ligand 1 (PD-L1) antibody atezolizumab in SCLC progressing after first-line platinum-etoposide chemotherapy.

METHODS

Patients were randomized 2:1 to atezolizumab (1200 mg intravenously every 3 weeks) until progression or unacceptable toxicity, or conventional chemotherapy (up to 6 cycles of topotecan or re-induction of initial chemotherapy). Patients were not selected based on PD-L1 tissue expression. The primary endpoint was objective response rate at 6 weeks. A two-stage design with 2:1 randomization and O'Brien-Fleming stopping rules was used. The null hypothesis was rejected if more than 12 of 45 patients were responders.

RESULTS

Overall, 73 patients were randomized (atezolizumab n = 49; chemotherapy n = 24). At 6 weeks, 1 of 43 eligible atezolizumab patients achieved an objective response (2.3%, 95% confidence interval [CI]: 0.0-6.8), whereas 8 others had stable disease (20.9% disease control rate; 95% CI: 8.8-33.1). Among eligible chemotherapy patients (n = 20), 10% achieved an objective response (65% disease control rate). Median progression-free survival was 1.4 months (95% CI: 1.2-1.5) with atezolizumab and 4.3 months (95% CI: 1.5-5.9) with chemotherapy. Overall survival did not significantly differ between groups. Median overall survival was 9.5 months versus 8.7 months for the atezolizumab and the chemotherapy group, respectively (adjusted hazard ratio_atezolizumab : 0.84, 95% CI: 0.45-1.58; p = 0.60). Two atezolizumab patients (4.2%) experienced grade 3 fatigue, and two others grade 1 dysthyroidism. Among 53 evaluable specimens, only 1 (2%) had positive immunohistochemical PD-L1 staining (SP142 clone).

CONCLUSIONS

Atezolizumab monotherapy in relapsed SCLC failed to show significant efficacy. No unexpected safety concerns were observed.