Could counting immune cells help predict colorectal cancer patient outcome?

The authors examined whether eosinophils (white blood cells normally used to fight infections) levels in or around a colorectal tumor can help predict patient outcome. 

Colorectal cancer is often classified using the tumor node metastasis system (TNM system). This system depends upon the assessment of primary tumor (T), regional lymph nodes (N : tiny, bean-shaped organs that help fight infections) and distant metastasis (M, spreading of cancer from the original site to other parts of the body). The TNM system classifies colorectal cancer as stage I, II, III, or IV. In stage I, cancer grows into the inner layers of the intestine. In stage II, cancer spreads into the outer layers of the intestine. In stage III,  cancer spreads to the lymph nodes and in stage IV, cancer spreads to the distant organs.

Although the TNM system is very useful for predicting patient outcome, in some cases patients with an identical stage can have very different outcome. As a result of this, researchers are searching for other ways to help predict patient outcome. Measuring eosinophil levels in or around the patients’ colorectal tumor may help predict patient outcome. 

This study examined medical records from 381 patients with colorectal cancer (21% had stage I, 32% had stage II, 33% had stage III, and 14% had stage IV). All patients underwent surgery to remove the colorectal tumors. Eosinophils in or around the tumor were counted and patients were divided based on the levels (none, low, intermediate, or high levels). Patient survival and rate of cancer progression (cancer returning to the intestine or to a distant organ) were examined after the treatment.

There were eosinophils around 86% of tumors and in 75% of tumors. 13.9% of patients had no eosinophils around their tumors, 59.6% had low levels, 21.3% had intermediate levels, and 5.3% had high levels.

Eosinophil levels around the tumor were linked with patient outcome. After 5 years, the cancer had progressed in 60% of patients who had no eosinophils around their tumors, 43% of patients who had low levels of eosinophils, 33% of patients who had intermediate levels, and only 5% of patients who had high levels.

After 5 years 53% of patients with no eosinophils around their tumors had died of colorectal cancer compared to 35% of patients with low levels, 25% of patients with intermediate levels, and 5% of patients with high levels of eosinophils

The authors concluded that higher numbers of eosinophils around the tumor was linked with better patient outcome. They suggest that eosinophils should be counted during routine tumor examination.