A large population-based study suggests that the utility of certain types of biomarkers, known as tumour-infiltrating lymphocytes (TILs), to predict colorectal cancer survival depends on where the tumour originates in the body.

Although prior research has shown an association between high TIL density and longer survival for patients with colorectal cancers, according to the authors this study is the first to examine the prognostic impact of TILs in regards to tumour location.

The study will be presented at the upcoming 2017 ASCO-SITC Clinical Immuno-Oncology Symposium in Orlando.

Colorectal cancer is the third most common cancer in both men and women worldwide.

In the United States alone, an estimated 95,500 new diagnoses of colon cancer and 39,900 diagnoses of rectal cancer are expected in 2017.

More than 50,000 deaths due to colon cancer will occur in the United States this year.

The researchers analysed tumours from 557 patients newly diagnosed with colorectal cancer who were enrolled in the Malmö Diet and Cancer study.

The primary goal of this prospective study was to investigate associations between various dietary factors and cancer incidence.

The Swedish study enrolled 30,446 participants between 1991 and 1996.

Data on adjuvant treatment were available for 126 patients with stage III colorectal cancer, of whom 61 had received adjuvant chemotherapy.

In each tumour tissue specimen, researchers assessed the density (total number) of three different types of TILs: cytotoxic T cells, regulatory T cells, and natural killer (NK) or natural killer T (NKT) cells.

Overall, high density of all three types was associated with improved five-year survival, regardless of primary tumour location.

This association was independent of patient age, cancer stage and other factors.

However, the prognostic impact of specific types of TILs differed by tumour location.

High density of regulatory T cells was associated with longer survival for patients with rectal tumours, but not for those with either left-sided or right-sided colon tumours.

High density of cytotoxic T cells predicted longer survival for patients with right-sided tumours, but not for those with either left-sided colon tumours or rectal tumours.

The prognostic impact of NK or NKT cells did not differ by tumour location.

“This study suggests we may need to give more weight to certain prognostic biomarkers based on tumour location,” said lead study author Jonna Berntsson, MD, a PhD student at Lund University in Sweden. “But more research is needed before we can recommend any change in treatment planning.”

Testing for TILs is not yet part of routine colorectal cancer care.

In utero, different segments of the colon develop from different parts of the embryo – which is the reason the left and right sides are biologically different.

Prior studies have reported on genetic and clinical differences between colorectal tumours that begin on the left side versus the right side of the colon, including poorer survival for patients with right-sided cancers.

Source: ASCO