Science's new discovery breaks the common sense: cancer does not need to pass through lymph nodes for metastasis

Source: bioprospecting 2017-07-11: researchers from Massachusetts General Hospital (MGH) found that the traditional pattern of cancer cell proliferation from primary tumors to nearby lymph nodes to other organs may not be applicable to all cases In an article in the July 7 issue of science, the researchers describe the findings: for most patients with colorectal cancer, "long-distance" cancer metastasis originates from the primary tumor and is independent of any lymph node metastasis "Our results provide exceptional evidence for a century old model in humans that 'lymph node metastasis is a precursor to distant metastasis', suggesting that it does not apply to all or most colorectal cancers," said Dr Kamila naxerova, first and corresponding author These findings fill an important gap in our understanding of the development of metastatic diseases and may guide the clinical treatment of lymph node metastasis " Repeat mutation as a label reveals that most colorectal cancers do not spread through lymph nodes The current research is the follow-up of the last PNAs research article in 2014 Naxerova and her colleagues described a simple experiment Based on the analysis of the small and mutated Poly-G repeats in the genome, we can reveal the evolutionary relationship between tumors in different parts of the patient's body The study found that the primary and metastatic tumors are different in various situations, for example, in some patients, the metastasis and diffusion occurs earlier, while in other patients, the development of the tumor is later The detection method can also identify which regions of primary tumor have become specific cancer metastasis sources according to its genetic map The treatment of most solid tumors is now divided into TNM: primary tumor (T), lymph node metastasis (n) and distant metastasis (m) Patients with lymph node metastasis are more likely to have distant metastasis, which means there is a link between the two However, in recent clinical trials, lymphadenectomy for cancer metastasis does not always improve the survival rate of patients Researchers have doubts about the relationship between lymphadenectomy and distant metastasis In order to better understand the relationship between primary tumor and two types of metastasis, the researchers used Poly-G classification to analyze more than 200 tissue samples of primary tumor, lymph node metastasis and distant metastasis in 17 colorectal cancer patients In 35% of patients, the results showed that both lymph nodes and distant metastasis originated from the same cell type of primary tumor, which was consistent with the traditional pattern of primary tumor spreading to lymph nodes and then to distant sites However, in 65% of patients, Poly-G classification showed that the cell types of lymph node metastasis and distant metastasis were different, matching different types of cells in primary tumors, indicating that these types of metastasis originated independently "We now suspect that lymph node metastasis is just an indication of the presence of a positive primary tumor, rather than the formation of distant metastases that are directly responsible," said the study authors, noting the significance of the study Now we need to study whether the clinical outcomes of patients with common origin of lymph nodes and distant metastasis are different from those with different evolutionary origins If there is a difference, our method may be a useful prognostic test in the future " "Lymph nodes are often thought to be the cause of distant metastasis," said Dr Rakesh K Jain, Professor of radiation oncology and senior author of the paper However, many retrospective and prospective studies have shown that complete lymphadenectomy does not have a survival advantage in many malignant tumors Our research provides the first direct genetic evidence to solve this mystery " Dr Jochen K lennerz, co-author of the study, from the pathology section of the Massachusetts General Hospital, added: "our traditional cancer assessment tools - typing, grading, staging - do not explain the relationship between multiple sites of cancer Now, we have a new and effective way to observe the spread of cancer Given the low cost and cost-effectiveness of this test, we are happy to send it to the clinic for application as soon as possible "