Microsatellite instability: application in hereditary non-polyposis colorectal cancer

Types of DNA damage and research progress

DNA damage is a modification in the structure of DNA under the influence of endogenous or exogenous factors. DNA damage can cause different types of diseases and is closely related to genetic mutations, cancer, and aging. The cause of the corresponding reaction process is essential for the study of related cancers and other genetically related diseases. Therefore, it is essential to gain a deeper understanding of the various types of DNA damage. This paper provides a comprehensive review of recent advances in the types of DNA damage and associated reaction processes, including damage to DNA bases, nucleotides, and strands, as well as the biological implications of the damage.

High concordance rate of capillary electrophoresis workflow for microsatellite instability analysis and mismatch repair (MMR) immunostaining in colorectal carcinoma

Microsatellite instability (MSI) is the primary predictive biomarker for therapeutic efficacies of cancer immunotherapies. Establishment of the MSI detection methods with high sensitivity and accessibility is important. Because MSI is mainly caused by defects in DNA mismatch repair (MMR), immunohistochemical (IHC) staining for the MMR proteins has been widely employed to predict the responses to immunotherapies. Thus, due to the high sensitivity of PCR, the MSI-PCR analysis has also been recommended as the primary approach as MMR IHC. This study aimed to develop a sensitive and convenient platform for daily MSI-PCR services. The routine workflow used a non-labeling QIAxcel capillary electrophoresis system which did not need the fluorescence labeling of the DNA products or usage of a multi-color fluorescence reader. Furthermore, the 15 and 1000 bp size alignment markers were used to precisely detect the size of the DNA product. A cohort of 336 CRC cases was examined by MSI-PCR on the five mononucleotide MSI markers recommended by ESMO. The PCR products were analyzed in the screening gels, followed by high-resolution gel electrophoresis for confirmation if needed. In the MSI-PCR tests, 90.1% (303/336) cases showed clear major shift patterns in the screening gels, and only 33 cases had to be re-examined using the high-resolution gels. The cohort was also analyzed by MMR IHC is, which revealed 98.5% (331/336) concordance with MSI-PCR. In the five discordant cases, 4 (3 MSI-L and 1 MSS) showed MSH6 loss. Besides, one case exhibited MSI-H but no loss in the MMR IHC. Further NGS analysis, in this case, found that missense and frameshift mutations in the PMS2 and MSH6 genes occurred, respectively. In conclusion, the non-labeling MSI-PCR capillary electrophoresis revealed high concordance with the MMR IHC analysis and is cost- and time-effective. Therefore, it shall be highly applicable in clinical laboratories.

The impact of prophylactic oophorectomy on the survival for postmenopausal patients with pT4a colorectal cancer

PURPOSE

This study aimed to evaluate the prognostic effect of prophylactic oophorectomy (PO) in postmenopausal patients with pT4 colorectal cancers (CRC) in terms of overall survival (OS), disease-free survival (DFS), and peritoneal metastasis.

METHODS

The data of postmenopausal female patients with pT4 CRC undergoing surgical resection between 2000 and 2019 were analyzed. Kaplan-Meier analysis was used to evaluate survival outcomes between patients treated with and without PO. Risk factors for DFS and peritoneal metastasis were evaluated using Cox regression analysis. p-values <0.05 were considered statistically significant.

RESULTS

Totally, 176 (34.3%) patients received PO. There was no significant difference in estimated blood loss, rates of postoperative complications, and hospitalization between the PO and non-PO groups. The 5-year OS and DFS rates were similar in the two groups (47.9% vs. 54.1%, p = 0.278; 53.5% vs. 50.5%, p = 0.161, respectively). In the subgroup analysis of patients with peritoneal metastasis, the median survival was significantly longer for the PO group compared with the non-PO group (14 vs. 11 months, p < 0.001).

CONCLUSION

Undertaking PO in pT4 CRC female patients did not confer a survival benefit. Indication of PO even for advanced CRC patients should require caution. It has potential survival benefit only when the patients developed metachronous peritoneal metastases.

Noncathartic CT colonography to screen for colorectal neoplasia in subjects with a family history of colorectal cancer

PURPOSE

To prospectively assess the diagnostic performance of noncathartic computed tomographic (CT) colonography in the detection of clinically relevant colorectal lesions (≥6 mm polyps or masses) in a well-defined cohort of first-degree relatives of patients with colorectal cancer (CRC), using colonoscopy and histologic review as the standard of reference.

MATERIALS AND METHODS

Institutional review board approval was obtained, and all subjects provided written informed consent. Consecutive patients admitted with CRC (index cases) were prospectively evaluated, and those who agreed to contact their first-degree relatives who were at least 40 years old were included. Available first-degree relatives were invited to undergo noncathartic CT colonography (200 mL of diatrizoate meglumine and diatrizoate sodium). Colonoscopy was performed the following day, and findings from CT colonography were disclosed for each segment. Sensitivity, specificity, and positive and negative predictive values of CT colonography were assessed for detecting subjects with any lesion at least 6 mm, any lesion at least 10 mm, and advanced neoplasia at least 6 mm. Colonoscopy with segmental unblinding and histologic diagnosis were used as the standard of reference. Matching between findings from CT colonography and colonoscopy was allowed when lesions were located in the same or adjacent colon segments and when the size difference was 50% or less.

RESULTS

Three hundred four first-degree relatives (median age, 47 years; age range, 40-79 years; 46.7% women) identified from 221 index cases were included. Overall, CT colonography helped identify 17 of 22 subjects with polyps measuring at least 6 mm (sensitivity, 0.77; 95% confidence interval [CI]: 0.59, 0.95) and helped correctly classify as negative 278 of 282 subjects without lesions measuring at least 6 mm (specificity, 0.99; 95% CI: 0.97, 1.00). CT colonography helped detect eight of nine subjects with polyps measuring at least 10 mm as well as eight of nine subjects with advanced neoplasia measuring at least 6 mm (sensitivity, 0.89 for both). Per-subject positive and negative predictive values for lesions measuring at least 6 mm were 0.81 (17 of 21 subjects; 95% CI: 0.65, 0.97) and 0.98 (282 of 287 subjects; 95% CI: 0.96, 0.99), respectively.

CONCLUSION

Noncathartic CT colonography is an effective screening method in first-degree relatives of patients with CRC.

Inherited colorectal cancer syndromes

Colorectal cancer is one of the major causes of cancer deaths in both men and women. It is estimated that approximately 5% to 10% of patients with colorectal cancer have an inherited germline mutation that predisposes them to cancer. Clinically, hereditary colorectal cancer syndromes can be divided into those associated with colonic polyposis (familial adenomatous polyposis, attenuated familial adenomatous polyposis, and MYH-associated polyposis) and those not associated with colonic polyposis (hereditary nonpolyposis colon cancer). Treatment options for these patients include multiple aggressive screening regimens, chemopreventive medications, and prophylactic surgery. Selection of the appropriate management approach is best made using information obtained from the patient's clinical examination, the family medical history, and genetic evaluation. Compliance is improved when patients completely understand their disease and participate fully in the formulation of the treatment plan. Although not proved, it seems reasonable that this approach may prevent the poor outcomes so frequently associated with inherited cancer syndromes.

Hereditary non-polipomatous colorectal cancer: hereditary predisposition, diagnosis and prevention

BACKGROUND: Colorectal cancer is the third in frequency and the second in mortality in developed countries. In Brazil, it is among the six more common malignant neoplasias. About 20% of colorectal tumors have some hereditary component. AIM: This study presents a review of genetic and clinic aspects, as well as diagnosis and prevention of the hereditary non-polipomatous colorectal cancer, that is the more frequent form of hereditary colorectal cancer. This approach is important because, currently there are possibilities of management, prevention and surveillance specific to individuals at-risk for hereditary non-polipomatous colorectal cancer that can lead to a great improvement in patients' survival and their at-risk relatives.

Prophylactic oophorectomy

Because of the lack of effective alternatives and the simplicity of the procedure, prophylactic oophorectomy is viewed as the best available tool for reducing the individual risk of ovarian cancer. The genetics of hereditary ovarian cancer are described in this chapter and a careful risk-versus-benefit assessment is provided with respect to two populations of patients that appear suitable candidates for this procedure. These include patients with increased risk of developing ovarian cancer due to hereditary genetic predisposition, in which the lifetime risk of ovarian cancer may be as high as 16-65%, depending on the penetrance of the germ-line mutation. Additionally, routine salpingo-oophorectomy in patients over 40 years undergoing scheduled gynaecological surgery or colorectal surgery might reduce the overall incidence of ovarian cancer by as much as 5% in the general population.