Tumor mutational burden (TMB) as a biomarker of response to immunotherapy in small cell lung cancer

Indirect comparison of nivolumab ± ipilimumab (CheckMate 032) versus other treatments for recurrent small-cell lung cancer

Aim: To estimate the comparative efficacy of nivolumab ± ipilimumab versus alternative treatments for small-cell lung cancer after at least one prior line of chemotherapy. Materials & m ethods: A systematic literature review identified six randomized controlled trials (RCTs) that could be connected in a network. The Kaplan-Meier survival curves from these RCTs were synthesized using network meta-analysis models. Aggregate-level matching was used to connect CheckMate 032 to the RCTs. Results: CheckMate 032 was connected to the network by Amrubicin Clinical Trial-1. Nivolumab ± ipilimumab had a more durable tumor response and more favorable long-term survival versus topotecan via intravenous and versus amrubicin. Conclusion: Compared with chemotherapies for recurrent small-cell lung cancer, nivolumab ± ipilimumab improves response duration, which may translate to long-term survival benefits.

Comprehensive genomic profiling of small cell lung cancer in Chinese patients and the implications for therapeutic potential

Background

Small cell lung cancer (SCLC) is one of the deadliest malignancies and accounts for nearly 15% of lung cancers. Previous study had revealed the genomic characterization of SCLC in Western patients. However, little is known about that in Chinese SCLC patients.

Methods

Formalin‐fixed paraffin‐embedded tumor tissues and matched blood samples from 122 Chinese SCLC patients were collected for next generation sequencing to detect 450 cancer‐related genes. All pathological diagnoses were confirmed by independent pathologists.

Results

The most frequently altered genes were TP53 (93.4%), RB1 (78.7%), LRP1B (18.9%), KMT2D (15.6%), FAT1 (11.5%), KMT2C (11.5%), SPTA1 (11.5%), STK24 (11.5%), FAM135B (10.7%), and NOTCH1 (10.7%). The gene fusion/rearrangement detection rate was 16.4%, and mostly occurred in chromosomes 7 and 17. The rate of co‐occurring mutations of TP53 and RB1 in these Chinese SCLC patients was 74.6%, and lower than the reported Western patients (90.9%, P = 0.007). The most common gene mutations (83.6%) were found in cell cycle signaling pathway in Chinese SCLC patients. Mutation of Wnt and Notch signaling pathways in the Chinese cohort were lower than Western cohort (P = 0.0013 and 0.0068). A significant association was found between high tumor mutation burden and mutations involved in FAT1, TP53, SPTA1, KEAP1, KMT2D, MAGI2, NOTCH2, NOTCH3, FLT1, KDM6A, and FAT4.

Conclusions

In this study, we characterized the genomic alterations profile of Chinese SCLC patients. Compared with westerners, the genetic alterations of Chinese SCLC patients presented different patterns. Our data might provide useful information in targeted therapy and drug development for Chinese SCLC patients.

Future Options of Molecular-Targeted Therapy in Small Cell Lung Cancer

Lung cancer is the leading cause of cancer-related deaths worldwide. With a focus on histology, there are two major subtypes: Non-small cell lung cancer (NSCLC) (the more frequent subtype), and small cell lung cancer (SCLC) (the more aggressive one). Even though SCLC, in general, is a chemosensitive malignancy, relapses following induction therapy are frequent. The standard of care treatment of SCLC consists of platinum-based chemotherapy in combination with etoposide that is subsequently enhanced by PD-L1-inhibiting atezolizumab in the extensive-stage disease, as the addition of immune-checkpoint inhibition yielded improved overall survival. Although there are promising molecular pathways with potential therapeutic impacts, targeted therapies are still not an integral part of routine treatment. Against this background, we evaluated current literature for potential new molecular candidates such as surface markers (e.g., DLL3, TROP-2 or CD56), apoptotic factors (e.g., BCL-2, BET), genetic alterations (e.g., CREBBP, NOTCH or PTEN) or vascular markers (e.g., VEGF, FGFR1 or CD13). Apart from these factors, the application of so-called 'poly-(ADP)-ribose polymerases' (PARP) inhibitors can influence tumor repair mechanisms and thus offer new perspectives for future treatment. Another promising therapeutic concept is the inhibition of 'enhancer of zeste homolog 2' (EZH2) in the loss of function of tumor suppressors or amplification of (proto-) oncogenes. Considering the poor prognosis of SCLC patients, new molecular pathways require further investigation to augment our therapeutic armamentarium in the future.

Current views on tumor mutational burden in patients with non-small cell lung cancer treated by immune checkpoint inhibitors

In the last few years, the treatment of patients with non-small cell lung cancer (NSCLC) has impressively benefitted from immunotherapy, in particular from the inhibition of immune checkpoints such as programmed cell death-1 (PD-1) and programmed cell death ligand-1 (PD-L1). However, despite the significant survival benefit for some patients with advanced NSCLC, the objective response rates (ORRs) remain relatively low no more than 20-30% with a large proportion of patients demonstrating primary resistance. Although the selection of NSCLC patients for the first-line treatment is currently guided by the expression of PD-L1 in tumor cells as detected by immunohistochemistry, this is not the case for the second-line setting. Moreover, the sensitivity and specificity of PD-L1 expression is modest which has prompted the search for additional predictive biomarkers. In this context, the assessment of the tumor mutational burden (TMB), defined as the total number of nonsynonymous mutations in the coding regions of genes, has recently emerged as an additional powerful biomarker to select patients for immunotherapy. The purpose of our review is to highlight the recent advances as well as the challenges and perspectives in the field of TMB and immunotherapy for patients with NSCLC.