Purpose. The purpose of the current study was to determine whether there is a difference between high levels of microsatellite instability (MSI-H) and microsatellite stability (MSS) in DNA mismatch repair-deficient (DMMR) colorectal cancer (CRC) patients. Methods. A total of 452 CRC patients with DMMR from December, 2014, to April, 2021, in our hospital were selected retrospectively. However, only 105 patients underwent Sanger or next-generation-sequencing (NGS) to confirm their microsatellite status. Ultimately, 55 MSI-H patients and 20 MSS patients with intact medical record information were included in this study. Results. The MSS group was associated with a higher mutation rate in the KRAS gene ( P = 0.011 ). Meanwhile, MSI-H was related to colon cancer ( P < 0.01 ). However, no significant differences in other clinical characteristics were observed between the two groups of patients. There was no significant difference between the MSI-H and MSS groups in terms of overall survival (OS) ( P = 0.398 ) and disease-free survival (DFS) ( P = 0.307 ). Conclusion. The MSI-H status was associated with colon cancer and a lower mutation rate of the KRAS gene in DMMR patients. In CRC-DMMR patients, the MSS group exhibited better OS and DFS than the MSI-H group, although these differences were not statistically significant. Accordingly, in clinical practice, we should not confuse these two types of patients.

The lung is the most common extra-abdominal metastasis site of colorectal cancer (CRC). This study aimed to investigate the genetic variation of pulmonary metastases (PM) and primary tumors in resectable CRC. The clinical data of 410 patients with PM after CRC surgery and 33 paraffin-embedded tissue samples from January 2012 to July 2019 in our hospital were collected retrospectively. Next, 450-panel gene detection technologies based on next-generation sequencing (NGS) were used to analyze the changes in the gene map and the overall variation in cancer-related genes in PM and primary tumors. After quality control, 19 samples were included in the final gene analysis. The results showed that APC (89.5%), TP53 (89.5%), and KRAS (53%) were the most common mutations in PM and primary tumors, but the gene amplification variation was enriched in primary tumors (4.6% vs. 11.4%). KRAS G12D was the most common site variation of the KRAS gene in both PM and primary tumors of CRC. There was no hotspot mutation in the TP53 locus in CRC, and the TP53 mutation in the PM was consistent with that in the primary lesion. The microsatellite instability (MSI) levels of 10 patients were MSS. The mean tumor mutation burden (TMB) of the primary tumor (5.3 muts·Mb−1) was slightly higher than that of metastasis (5.0 muts·Mb−1). In our institution, the genetic characteristics of resectable PM from CRC may be highly consistent with those of the primary tumor.

A 70-year-old woman with a rectal diverticulum presented with anal pendant expansion and difficulty in defecation for more than 1 year. The patient was diagnosed with a rectal diverticulum by pelvic enhanced magnetic resonance imaging (MRI), computerized tomography (CT), rectal angiography, and colonoscopy. The endoscopic diverticulum incision procedure (EDIP) was implemented with this patient. At the 4-month follow-up, anal pendant expansion and difficulty in defecation were significantly relieved. Furthermore, colonoscopy proved that there were no vestigial feces in the diverticulum.

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 &lt; 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 &gt; 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.

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