Some Breast Cancers Regress

Invasive Tumors Detected by Mammogram Screening May Disappear

Jan 12, 2009

Screening mammography shows increased breast cancer rates, but increases may be due to cancers that would regress.

Detecting cancer at the earliest possible stage is desirable, but not all cancers grow the same way. Some tumors produce a clump of cells, which recruits a blood supply and then spreads, while others grow into a sizable, invasive tumor and then disappear. A new study in Norway shows that biennial mammographic screening paradoxically increases the number of invasive breast cancers, presumably because some of the detected cancers would regress on their own without treatment.

Mammography Reduces Breast Cancer Mortality

There are several types of procedures for breast cancer screening. These typically include self-exams, clinical exams, mammograms and ultrasound. The U.S. National Cancer Institute recommends clinical breast exams every three years until age 40 and then annually. Annual mammograms are to start at age 40. Self-exams are encouraged starting at age 20 so that women become familiar with the normal structures within their breasts and can become aware of changes. All of these different types of screening increase the chances that cancers will be detected at the earliest stage and improve the efficacy of treatment. When more powerful techniques are used, more early-stage tumors are found.

Recent Study Suggests That Some Breast Cancers Regress

A recent study was conducted in Norway to determine if the increasing rate of breast cancer detection actually produces a reduction in cancer risk. One group of women was studied for six years by biennial mammograms and a comparison group of the same ages (50-64) was examined by a single mammogram at the beginning of the biennial program. Data on invasive breast cancer detection was obtained for both groups from the Norwegian Cancer Registry. The more frequently screened group showed 22% more cancers over the six years than the group with a single mammogram at the end of six years. The researchers concluded that with more frequent screening, approximately one fifth of the tumors that would naturally regress on their own end up being treated.

Identifying Different Types of Breast Cancer

Regression of tumors is not unusual, but the difficulty is telling which tumors are going to progress to become life-threatening and which will disappear without treatment. The Norwegian study is encouraging, because it indicates that most of the tumors are detected with less aggressive and potentially damaging screening schedules. The troublesome aspect of the study is that some of the treatments are apparently unnecessary. More studies will reduce unnecessary treatment and provide early detection and effective treatment. Until it is possible to identify and treat just the dangerous tumors, most women will probably prefer to detect and treat all suspicious invasive breast cancers.

Zahl PH, Maehlen J, Welch HG. 2008. The natural history of invasive breast cancers detected by screening mammography. Arch Intern Med. 168(21):2311-6.

The copyright of the article Some Breast Cancers Regress in Breast Health is owned by Art Ayers. Permission to republish Some Breast Cancers Regress in print or online must be granted by the author in writing.