A study conducted by researchers from Cedars-Sinai has found that the simple process of counting how many lymph nodes (LNs) are cancerous may be the best option to determine cancer patient’s disease outlook and mortality for 16 major cancers.
“Count the number of metastatic [cancerous] lymph nodes,” co-author Assoc Prof. Zack Zumsteg said. “We found that this simple process is much better for determining prognoses for solid tumors than all the other factors used today.”
The study found that the quantitative method of counting the number of lymph nodes that have cancer cells is the best predictor of determining the cancer stages of patients for 16 cancers, with the 16 cancers examined: lung, breast, kidney, colon, stomach, prostate, skin, thyroid, pancreas, cervix, esophagus, hepatobiliary [liver and its associate organs], head and neck, bladder, ovary, and endometrium cancer.
Cancer staging is determined by a doctor during or not long after a cancer diagnosis, with the patient assigned to stages from 1 to 4 with stage 1 having the most optimistic outlook for patients and stage 4 being the most critical.
The three key areas the doctors may look at will be the primary tumor called tumor staging, the LNs around the primary tumor known as lymph node staging (LN staging), as well as the presence of secondary tumors formed from cells in the primary tumor named metastasis staging.
LNs are organs of the immune system, they are small bean-shaped structures distributed all across the body that filter tissue fluid and fluid in the blood.
As part of LN staging, nodes will be checked for the presence of cancer cells to see if cancers have broken off the main tumor and spread to other locations, LNs that have cancerous cells are called cancerous or metastatic LNs.
However, apart from checking for cancerous LNs, other observations will also be made on LNs, with no strict criteria on cancer staging, as different doctors for different cancers will regard different features as important, making criteria for determining cancer stages extremely variable.
“Conventional teaching is that nodal metastases behave differently among different cancer types, which accounts for the different staging systems used for each cancer,” Zumsteg said, expressing concern at the variability of something fundamental to cancer treatment.
To find a more common predictor, the team examined data from the National Cancer Database on over 1,300,000 patients who were diagnosed with solid tumor cancer across 16 common cancer areas from 2004 to 2015.
The authors found that though other predictors for LN staging such as the size of tumors in LNs, location of cancerous LNs, spread outside of LNs, all worked as a predictor for some cancers; it could not be applied to all, creating variability in predictions once again.
However, the team observed that counting the number of cancerous LNs stayed consistent as a strong predictor for mortality across all 16 cancer sites.
“Consistently across disease sites, mortality risk increased continuously with increasing number of metastatic LNs,” the authors wrote.
“It [counting cancerous LNs] should be the backbone of nodal staging because it is the best predictor of mortality, irrespective of the disease site,” said Zumsteg.
Though the study’s findings are promising, there are also limitations, with the key amongst them is that the data only focused on survival, not on cancer recurrences and metastases which lead to secondary tumors and further cancerous lymph nodes, Zumsteg explained.
“We need more detailed patterns of recurrence and need to understand the intermediate step,” he said, expressing a need for answers as to why counting cancerous LNs predict mortality.
He said more study is needed to determine the processes that lead to deaths after surgery as well as the implication of having higher lymph node counts.
The study has been published in the Journal of the National Cancer Institute, a peer-reviewed journal on original research.