Tumor biology in explanation of the failure of screening for cancer and in determination of future strategies.

Screening examinations for so-called "early cancer" are popular methods to decrease cancer mortality. This report reviews current concepts in tumor biology that explain why screening for cancer succeeds and why it fails. From this review, three biologic subgroups emerge for many cancers. In only one of these groups will screening methods be successful in decreasing death from cancer. Breast cancer and prostatic cancer are specifically considered to support this hypothesis. Implications for future investigations and the impact on public policy are discussed.