Identifying Novel Germline Mutations and Copy Number Variations in Patients With SCLC

SCLC has traditionally been considered to arise from toxic exposure factors, such as smoking. Recent evidence has revealed that germline mutations may also affect the development of SCLC; however, these alterations remain understudied. We sought to identify novel germline mutations in SCLC including germline copy number variations (CNVs) in our cohort of patients.

We designed a custom hybrid-capture gene panel to evaluate germline alterations in 192 cancer-predisposition and frequently mutated genes in SCLC. We applied this panel to germline analysis of a treatment-naive cohort of 67 patients with SCLC at our institution. Subsequently, we annotated the variants using the American College of Medical Genetics criteria and further classified variants of uncertain significance using a set of in silico tools, including DeepMind AlphaMissense, MutationTaster, SIFT, and Polyphen2.

We identified American College of Medical Genetics pathogenic or likely pathogenic alterations in seven of 67 patients. Five (71%) were novel alterations (BCORL1, FANCC, ATR, and BBC3) and a novel CNV (SLFN11) with two (29%) previously described mutations (CHEK1 and BRIP1). We also identified 191 variants of uncertain significance in 60 of 67 patients, of which, depending on the in silico tool, 5% to 14% were predicted to be pathogenic. Patients with SCLC with the seven pathogenic alterations were observed to have a numerically longer overall survival (hazard ratio = 0.50) and progression-free survival (hazard ratio = 0.45) though not statistically significant compared with the remaining cohort.

Our study identifies novel germline alterations, including a CNV, and provides additional evidence that germline factors could be important contributing factors to the development of SCLC.