Most Metastatic Colorectal Cancers Have Spread Before Diagnosis

Colorectal cancers often spread before the initial tumor is detected, according to a new Stanford study. Identifying patients in whom early metastasis is likely could better guide treatment decisions. Up to 80% of metastatic colorectal cancers are likely to have spread to distant locations in the body before the original tumor has exceeded the size of a poppy seed, according to a study of nearly 3,000 patients by researchers at the Stanford University School of MedicineIdentifying patients with early-stage colorectal tumors that are born to be bad may help doctors determine who should receive early treatments, such as systemic chemotherapy, to kill cancer cells lurking far from the tumor’s original location.

This finding was quite surprising,” said Christina Curtis, PhD, assistant professor of medicine and of genetics at Stanford. “In the majority of metastatic colorectal cancer patients analyzed in this study, the cancer cells had already spread and begun to grow long before the primary tumor was clinically detectable. This indicates that metastatic competence was attained very early after the birth of the cancer. This runs counter to the prevailing assumption that metastasis occurs late in advanced primary tumors and has implications for patient stratification, therapeutic targeting and earlier detection.”

Researchers and clinicians have assumed that cancers acquire the ability to metastasize through the gradual accumulation of molecular changes over time. These changes, the thinking goes, confer specific traits that eventually allow cancer cells to escape the surrounding tissue, enter the bloodstream and take up residence in new locations. In this scenario, metastasis, if it occurs, would be a relatively late event in the evolution of the primary cancer.

Curtis, who co-directs the molecular tumor board at the Stanford Cancer Institute, is the senior author of the study, which was published online June 17 in Nature Genetics. Postdoctoral scholar Zheng Hu, PhD, is the lead author.

Source: http://med.stanford.edu/

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