In order to study the effectiveness or cost effectiveness of treatments for recurrent cancer, you first have to discover the patients in medical databases who have recurrent cancer. Generally studies do this with billing or treatment codes - certain codes should identify who does and does not have recurrent cancer. A recent study published in the journal Medical Care shows that the commonly used data determinants of recurrent cancer may be misidentifying patients and potentially leading researchers astray.
"For example, a study might look in a database for all patients who had chemotherapy and then another round of chemotherapy more than six months after the first, imagining that a second round defines recurrent disease. Or a study might look in a database for all patients with a newly discovered secondary tumor, imagining that all patients with a secondary tumor have recurrent disease. Our study shows that both methods are leave substantial room for improvement," says Debra Ritzwoller, PhD, health economist at the Kaiser Permanente Colorado Institute for Health Research and investigator at the University of Colorado Cancer Center.
The study used two unique datasets derived from HMO/Cancer Research Network and CanCORS/Medicare to check if the widely used algorithms in fact discovered the patients with recurrent disease that the algorithms were designed to detect. They did not. For example, a newly diagnosed secondary cancer may not mark a recurrence but may instead be a new cancer entirely; a second, later round of chemotherapy may be needed for continuing control of the de novo cancer, and not to treat recurrence.
"Basically, these algorithms don't work for all cancer sites in many datasets commonly used for cancer research," says Ritzwoller.