If you get all the recommended cancer screenings, how safe are you? Dr. Billy U. Philips Jr. and colleagues at Texas Tech University performed a unique study to find out. The purpose of cancer screening tests is to find the malignancy early, while it can be treated successfully. A major distinction between early and late stage cancer is the presence of metastases. Philips used data from the Texas Cancer Registry to check the ratio of metastatic to non-metastatic cancer diagnoses in Texas on a county by county basis. His team of researchers also analyzed data from the U.S. Census Bureau to quantify the degree of socioeconomic wealth or deprivation for each county. Statistical correlation then provided a measure of the success of improved health care for cancer.
For female genital system cancers, lung cancers, and all-type cancers taken as a whole, the ratio of metastatic to non-metastatic diagnoses were statistically correlated with socioeconomic deprivation. Philips and coauthors attributed these results to several factors, including better access to Pap smears in wealthier counties.
Surprisingly, the ratios of metastatic to non-metastatic cancer diagnoses were not correlated with socioeconomic status for breast cancer, prostate cancer, and colorectal cancers. Philips suggested these results tell us something about the success of screening tests. For colorectal cancer, the most common screening test (colonoscopy) is so effective that most patients never receive a diagnosis of cancer at all. Precancerous polyps are generally removed in the same procedure used for screening.
For breast cancer, the screening tests of mammography, clinical breast exam, and breast self-exam are not effective enough to produce a statistical correlation in the Texas county data, Philips reported. A report from the American Cancer Society echoes this evaluation. “Women also should be told about the limitations of mammography, specifically that mammography will not detect all breast cancers, and that some breast cancers detected with mammography may still have poor prognosis,” according to Dr. Robert A. Smith and colleagues.