Evaluating the Efficacy of Screening for Recurrence of Cancer

Extract

Many persons with cancer, although they receive a treatment that appears to be curative, later have a recurrence. For some forms of cancer, it seems likely that the early recognition of such recurrences could lead to a second round of treatment that proves effective, more so than if it were not given until later in the course of the disease. For example, efforts to diagnose recurrences of colon or ovarian cancer before they become clinically apparent offer the possibility of surgical extirpation of (what are hoped to be) isolated lesions.

Our goal in this commentary is to describe the research designs that have been used to determine the impact of early detection of recurrence on survival. Also, we will discuss the limitations inherent in some of these designs and the problems that often emerge when trying to implement them.

Examples Of Screening Modalities

Often, the available tools for early recognition of tumor recurrence are limited and physicians have resorted to highly invasive diagnostic approaches, such as second-look laparotomy for women at high risk of recurrent ovarian cancer. Sometimes, however, recurrent tumors express molecular markers that can be analyzed in a blood sample. For example, serum levels of a protease that is involved in the liquefaction of seminal fluid (prostate-specific antigen [PSA]) are high in the presence of abnormal prostate tissue growth. A serum glycoprotein that functions as a cell adhesion molecule, carcinoembryonic antigen (CEA), can be overexpressed by tumors of the colon and rectum. Elevated serum levels of PSA or CEA that are detected subsequent to apparently successful primary therapy for prostate and colorectal cancers, respectively, can be a signal to initiate more intensive efforts to identify the location(s) of cancer recurrence.