One Study Finds Breast Cancers Found by Mammograms To Be Less Aggressive (dateline May 1, 2000)
The results of a new study published in the April 24, 2000 issue of Archives of Internal Medicine show that breast cancer tumors detected by routine screening mammograms may be less aggressive than tumors detected by other breast imaging exams (such as ultrasound). The majority of tumors detected by mammograms in asymptomatic women (those who do not show any signs or symptoms of breast cancer) were also found to be slower-growing than tumors discovered after a woman showed signs that may indicate breast cancer, such as a breast lump, thickening, or skin dimpling.
Alvan R. Feinstein, MD and his colleagues studied 233 women who had been diagnosed with breast cancer for the first time in 1988. The researchers kept track of how the patients were diagnosed, the stage of their cancers, and the types of treatment they underwent. Women whose breast cancers were first identified with screening mammograms were found to have earlier stage cancers and were less likely to die of breast cancer than women whose cancers were detected by other means.
In all, 95% of women whose breast cancers were detected by mammograms were still living and free of cancer seven years after diagnosis compared to 79% of women whose cancer was found using other exams. The researchers say women whose cancers were detected during routine screening with mammography had slower-growing, less aggressive tumors than the other women.
The study addresses one of the key subjects of debate over mammograms: since routine screening mammograms have become more common, are physicians merely moving the time of breast cancer diagnosis back in time so that it appears as though women whose breast cancers are detected with mammography have better odds of surviving the disease?
The researchers say maybe, while some other physicians say no. In their report, the researchers wrote, “The results [of the study] suggest that many of the breast cancers found by mammography screening have excellent prognosis not just because of early detection, but also because many of the cancers are relatively benign, requiring minimal therapy.”
Additional studies are necessary before any conclusive data can be drawn from the study. However, the researchers say some of the breast cancer tumors found with mammography may not require aggressive treatments such as mastectomy (breast removal) or chemotherapy after breast cancer surgery. Instead, less invasive procedures, such as the removal of the breast lump with lumpectomy followed by close monitoring, may be suffice.
“Although the cure of breast cancer by ‘early detection’ and prompt treatment rests on the belief that all breast cancers grow at the same rate, many cancers have been shown to grow rapidly and others slowly,” the researchers wrote. “In particular, mammography screening may often detect the slow-growing, non-aggressive tumors that might not be found until much later, if at all.”
However, other physicians disagree with the implications of the study. These physicians argue that the appropriate treatment for a breast cancer tumor should be determined by its characteristics, and in some cases, patient factors (such as age). Though they admit that breast cancers found by mammography are often smaller and have a lower grade than cancers detected by other means, a histologic analysis of the breast cancer tumor should be conducted before the type of treatment is determined. A histologic analysis gives a physician insight into the breast tumor’s size, grade, tumor markers, whether it is estrogen-dependent, etc. Treatment should then be determined based on these factors.
Roy Smith, MD, director of medical oversight for the National Surgical Adjuvant Breast Project (NSABP) does not doubt the usefulness of mammography. Mammography helps detect breast cancer early, and if breast cancer is detected early, there is less probability that it has spread to other parts of the body, said Dr. Smith. However, it would be ideal if researchers were also able to characterize the different types of breast tumor cells detected by mammograms, said Dr. Smith. The researchers plan to focus further studies on the types of breast cancer tumors found by mammography.
The American Cancer Society, the American College of Radiology, the American College of Surgeons and the American Medical Association all recommend that screening mammograms should be performed on all women beginning at age 40. Women at high risk of breast cancer (such as those with a family history or BRCA1 or BRCA2 gene mutations) are encouraged to talk to their physicians about beginning screening mammograms before age 40, as early as age 25 in some cases.
- The study discussed in this articles appears in the April 24, 2000 issue of Archives of Internal Medicine and is available at http://archinte.ama-assn.org/issues/v160n8/full/ioi90169.asp
- The April 24, 2000 WebMD report by Elizabeth Tracy, “Are Breast Cancers Detected by Mammography Different?” is available at http://my.webmd.com/content/article/1728.56917
- The April 26, 2000 Reuters Health report, “Tumors Found on Mammograms Have Better Prognosis,” is available at http://www.reutershealth.com/archive/2000/04/26/eline/links/20000426elin015.asp
- To learn more about mammography, please visit http://www.imaginis.com/breasthealth/mammography.asp