What is multiple primary rectal cancer and what are the risk factors?

With the continuous development of medicine, people's understanding of malignant tumors has been continuously improved. In the research of rectal cancer, multiple primary rectal cancer has received increasing attention.

Multiple primary rectal cancer is a type of multiple primary malignant tumors. If multiple tumors are all rectal cancers, it can be called multiple primary rectal cancers. According to the different time of occurrence of different tumors, it can be divided into synchronous and metachronous primary rectal cancers; and if rectal cancer is combined with tumors of other organs, it can be called recurrent multiple rectal cancers. Other tumors can appear before, at the same time or after the occurrence of rectal cancer, so there is a distinction between synchronous and metachronous, and metachronous can be divided into pre-occurring and post-occurring.

There are many factors that cause multiple primary rectal cancer. Currently, the following related factors are mainly considered from the perspective of etiology.

1. Genetic factors Many data show that patients with multiple primary colorectal cancers often have a family history of hereditary diseases. Hereditary non-polyposis colorectal cancer (HNPCC) is an important type of hereditary colorectal cancer. Different from common sporadic colorectal cancer, the molecular biological basis of HNPCC is the inactivation of mismatch repair gene (MMR) mutation, which causes genomic microsatellite instability (MIS) and accumulates thousands of somatic mutations on simple DNA repeat sequences.

(II) Iatrogenic factors: Patients with malignant tumors often need radiotherapy or chemotherapy in addition to surgical treatment, and radiotherapy and chemotherapy are likely to lead to the occurrence of a second cancer. For example, patients who have undergone radiotherapy for cervical cancer have an increased risk of colorectal cancer recurrence, which is about 4 times that of the general population. Similarly, patients with rectal cancer also have an increased risk of cervical cancer or endometrial cancer after radiotherapy, which may be due to mutations in normal tissue cells after radiotherapy.

The incidence of multiple primary colorectal cancer varies from one report to another. According to the literature, it accounts for about 2% to 10% of colorectal cancer. Most of the reports in the literature are from retrospective analysis, which is easily affected by various factors such as the doctor's level of understanding of the disease, the level of diagnostic technology, and the length of follow-up time. Therefore, the actual incidence should be higher.