Counting circulating tumor cells before and after the start of treatment for patients with metastatic colorectal cancer could help doctors determine when or if a change in treatment should be made. The results of a large, multicenter, international study laying the groundwork for such decisions were presented today at the Annual Meeting of the American Society of Clinical Oncology. The study showed the number of circulating tumor cells, or CTC, is a significant predictor of survival and cancer progression.
Few studies have examined the relationship of CTC and a patient's prognosis in cancer. This is an important area of research in metastatic colorectal cancer because there are little data to help physicians chose which treatment is best for which patients or to determine when a change in treatment is warranted.
"If we had a way to know early on that a tumor isn't responding to a particular drug, we could switch to a different treatment before growth of the cancer is seen on a CAT scan," said Neal J. Meropol, director of the gastrointestinal cancer program at Fox Chase Cancer Center and lead investigator of the study. "If we could determine that the tumor was destined to grow after a few weeks of treatment, we'd be able alter course even before the first scan."
For this study, Meropol and his colleagues examined the association between the circulating tumor cell number and progression-free and overall survival for 430 adult patients with metastatic colorectal cancer.
The number of CTC was measured at baseline, one month, and several other points after the start of treatment. CTC were isolated and counted by an immunomagnetic cell separation technique, an FDA-approved technology developed by Immunicon Corporation (Nasdaq-Global Market: IMMC}. CT scans were obtained in usual practiceat baseline and every 6-12 weeks after starting treatment.