Study: Improved Predictor of Colorectal Cancer Prognosis Found

An imbalance in specific genetic material on chromosomes 8 and 18 may be a better predictor of colorectal cancer prognosis than conventional assessment of tissue changes, according to researchers at Johns Hopkins University in Baltimore and Emory University School of Medicine in Atlanta.

Imbalances in chromosomes occur in many types of cancers but measurement of these imbalances is difficult. Previous research has suggested that imbalances on specific areas of chromosome 8 and 18 could prevent the action of tumor-suppressor genes and lead to a poor outcome of the disease.

Researchers developed a new, quantitative method to analyze the prognostic value of chromosome imbalances in early-stage colorectal cancer. One hundred eighty patients with localized colorectal cancer had their tumors' DNA tested for genetic imbalances on the shorter part of chromosome 8 and on the longer part of chromosome 18 by digital SNP (single-nucleotide polymorphism).

Surviving patients were followed for approximately 5.5 years. The patients' tumors were divided into three groups: "L" tumors (93 patients) had allelic imbalances of chromosomes 8 and 18, "L/R" tumors (60 patients) had allelic imbalances of either chromosome 8 or 18 but not both, and "R" tumors (27 patients) had allelic balance for both chromosomes.

Five-year disease-free survival was 100 percent for patients with R tumors, 74 percent for patients with L/R tumors, and 58 percent for those with L tumors, the researchers reported in The Lancet.

"The long-term potential of genome-based markers for cancers is tremendous," said Garth Anderson and Bruce Brenner of Roswell Park Cancer Institute in Buffalo, New York in an accompanying commentary. "As the genetic events giving rise to such tumors become defined, exploitation of markers for use as diagnostic and prognostic tools must continue to be a focus, because surgical resection can remove even the most heterogeneous tumor cell population if it is detected early.

"Patients with an increased risk of recurrence despite adequate surgery who may benefit from adjuvant therapies can also be identified," Anderson and Brenner said. "Those genes in particular whose loss influences the progress and course of the tumor by reducing overall genomic stability may prove most valuable as markers; the relevant genes on 8p and 18q, once identified and confirmed, may fall into this category."

Other Sources: The Lancet