It’s not the cancer tumor itself that kills people, but rather the spread of cancer cells is what ultimately may bring the killing blow to patients. This is called metastasis, and oddly enough not nearly enough is known about how it works. University of Minnesota researchers have devised a pathological method for doctors to assess whether or not in lymph nodes the immune cells are winning against cancer or not. This may help predict outcomes for patients.

Metastasis is responsible for 90% death related to human solid-organ cancer. Many of the metastasizing cells  accumulate into what are called lymph nodes  – an oval-shaped organ of the immune system, distributed widely throughout the body including the armpit and stomach and linked by lymphatic vessels. In these key locations, the immune system is on full on war with cancer cells, trying to seek out the cancer and destroy it. From the lymph glands, some cancer cells manage to escape through the bloodstream and sometimes can spread into other parts of the body. Doctors typically analyze lymph nodes thoroughly because they serve as a good indicator for metastasis concentration and staging cancer.

There are many things we don’t know yet about metastasis works, however. For instance, some lymph nodes may be positive or negative for cancer cells. Oddly enough, many patients diagnosed with positive lymph nodes (filled with cancer) out live those with negative lymph nodes. University of Minnesota prostate cancer researcher Akhouri Sinha and colleagues sought to understand why some patients with positive nodes survive a long time, while others die within a few years by looking deeper in nodes after cancer cells have metastasized there.

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After analyzing 32 cancer-positive pelvic lymph nodes from prostate cancer patients the researchers found that in some of these nodes the immune system was doing a pretty good job – it was winning the fight against cancer. In other nodes, however, the immune system was failing at killing cancer cells. So two types of nodes suddenly surface: one type where the immune system is more vulnerable to cancer, and the other where it’s less vulnerable.

Dead and dying metastatic prostate cancer cells (round light-colored area) inside a lymph node, surrounded by purple-stained lymphocytes of the immune system. Upper left and lower right corners: degenerating metastatic cells that still make prostate-specific antigen (PSA), which stains brown. (c) University of Minnesota

The researchers hypothesize that patients whose nodes show significant cancer cell death will do better than those whose nodes show little or none because that may signal the rise of cells resistant to attack by the immune system. These patients may require more aggressive therapy.  It’s important to note that his approach can be applied to breast, lung, pancreas, colon, and other solid organ cancers.

“Our paper shows that some populations of metastatic cells are [susceptible to immune attack], and others are not,” Dr. Sinha says. “This provides a potential explanation for the observation that some patients survive longer, even with metastatic disease.”

With this in mind, the researchers suggest that cancer patients asks their pathologists to analyze their lymph nodes, through a standard procedure, to see whether or not the immune system is winning against cancer cells. Next, the researchers plan on making a thorough correlation between the degree of cancer cell death in the nodes and patient survival rates. Also, the genetic markup of cancer cells in lymph nodes will be compared to those win the original tumor to see if this makes a vital difference in how cancer metastasizes.

Findings appeared in the journal Anticancer Research.