Abstract 5133: Genetic characteristics & clonal evolution of Chinese resectable colorectal cancer patients with lung metastases

Abstract

Background Colorectal cancer (CRC) has a high incidence and mortality. In CRC, the lung is the most common extra-abdominal site of metastasis. Understanding the genetic characteristics and clonal evolution of primary tumor and lung metastases (LM) will help oncologists better outline treatments. To date, few studies for CRC with LM exist. As such, revealing the genetic characteristics and clonal evolution of resectable CRC with LM was the goal of this study. Methods From January 2012 to July 2019, clinical data and formalin-fixed, paraffin-embedded samples were collected from 33 Chinese CRC patients. Nineteen (19) primary tumors and 10 matched LM samples were examined using a 450 cancer gene next-generation sequencing assay. Genomic alterations, including single base substitutions, indels, copy number variations (CNVs), and gene fusion and rearrangement, were assessed. A phylogenetic reconstruction of sequencing data using LICHeE was also performed for each patient. Results Median patient age was 60 years old (48-67 years), with most having right lung metastasis. A significant difference existed between single (21/33, 63.6%) and multiple LM (12/33, 36.4%) (P < 0.01). Median disease-free survival was 20 months (95% CI, 0-84), from primary CRC to LM. The most frequently mutated genes were TP53 (90%), APC (90%), KRAS (53%), MUC16 (26%), ARID1A (21%). A comparison of mutational profiles for primary and matched LM samples revealed that 65.70% of alterations were consistent and that the most frequently mutated genes, including APC, TP53, and KRAS, of the primary tumor were completely consistent with LM. However, some differences between metastatic and primary samples were determined. More CNVs were found in primary samples (11.4% vs. 4.6%), indicating that CNVs are early molecular events for tumorigenesis and disease progression. SMAD4 was only present in two primary samples, while LRP1B was only present in two LM samples. Clonal evolution for eight patients indicated that phylogenetic structure was similar across patients. All patients had at least seven mutations on trunks. In trunks, TP53 (87.5%), APC (87.5%), KRAS (50%), and LRP2 (37.5%) were frequently identified. A new actionable gene (BRCA2) emerged in LM sample was identified in one patient. The mean value of TMB for the primary was almost the same as that for the LM site (5.3 vs. 5 muts/Mb, P > 0.05). Conclusions Our data indicated that the genetic characteristics and clonal evolution of LM are highly consistent with those of the primary tumor, suggesting that suitable treatments can be selected based on the genetic characteristics of primary tumor in CRC patients with LM that cannot be surgically treated. Citation Format: Yong Cheng, Ming-Jian Ge, Peng Dong, Yan-Yu Qiu, Xin-Peng Shu, Jin-Dou Li, Jun-Wei Wang, Xiao-Fang Qi. Genetic characteristics & clonal evolution of Chinese resectable colorectal cancer patients with lung metastases [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 5133.