Medicine for People!
April 2005
Contents
A Second Look at Mammograms
I recently read Gilbert Welch, MD's book, "Should I Be Tested for Cancer? Maybe not and here's why" (University of California Press, 2004). In his book, this Dartmouth Medical School professor examines the nationwide practice of the annual mammogram. In this month's newsletter, we summarize some of Welch's concepts and give our own recommendations on breast cancer screening.
The Two Percent Advantage
Breasts cancer screening saves lives, but studies show that the numbers are modest. At best, mammography allows American women to reduce their risk of death by a little better than 2 percent over a ten-year period. Two percent is nothing to sniff at. The question is - at what price? The price, as we'll explain in this article - may be higher rates of unnecessary mastectomies and unnecessary radiation. Even more dangerous, the nationwide emphasis on screening causes us to ignore more crucial tests, (such as the 2/16 hydroxyestrogen ratio explained below) and distracts us from preventive strategies that can save many more lives.
You may have heard that mammography can reduce the risk of death from breast cancer by 25 percent. That is true; ovor a ten year period, the breast cancer death rate is 7 per thousand unscreened women, and about 5 per thousand with mammography. That's about a 25% drop. Yet most women, even those who have had breast cancer, don't die of breast cancer. They die of other causes. When researchers look at the overall death rate over a span of ten years, the advantage of breast cancer screening falls to 2 percent or so.
The newspaper reports that the five-year survival rate for breast cancer is much higher in women who catch it early with a mammogram. True, but here's what they don't tell you.
1. Screening finds more non-aggressive tumors. The death rate goes down, but that's because we've diluted the death rate from aggressive cancers by including the less-aggressive cancers.
2. Screening with mammograms identifies breast tumors when they are small. Without screening, the woman or doctor might not notice the tumor until it has grown larger. It's possible that, were you to measure survival based on tumor size rather than time of discovery, both screened and unscreened groups would have the same survival rate. The mammogram group just knew about their tumors for a longer period of time.
Non-aggressive Breast Cancer
The most common form of cancer detected by mammography is ductal carcinoma in situ (DCIS). This is a cancer confined within a milk duct within the breast. Currently, of women with DCIS, about 30 percent are getting a mastectomy, 40 percent lumpectomy and radiation, and 30 percent lumpectomy only. Let's ask a crazy question. What would happen if we did not identify or treat this cancer?
A number of studies suggest that women have lived healthy lives with a non-aggressive form of DCIS. Researchers in Tennessee and Italy reviewed thousands of breast biopsies that had been read in the 1950's and 60's as benign. They found about sixty that showed DCIS and located the women involved. After some thirty years, 10 to 30 percent of women had progressed to full-blown cancer. The flip side is, that 70-90 percent had not.
Several groups of researchers have done careful autopsies of women who died of causes other than breast cancer. On the average, 9 percent of these women were found to harbor undiagnosed DCIS. When researchers were particularly obsessive about looking for undetected cancer, they found more cancer, up to 14 percent. This research suggests that DCIS is more common than we think, and often not harmful to the patient.
DCIS cannot be ignored. Current medical knowledge makes it difficult to determine whether a particular woman's cancer is going to be quiescent or aggressive. However, in treating DCIS, both a woman and her physician should be aware that DCIS may not require radical treatment.
Unnecessary Treatments Still Occur
A biopsy is a specimen of tissue removed by needle or minor surgery. Technicians cut it into thin slices, stain it, and place it on a glass slide for the pathologist to examine under a microscope. Normal cells can be easily distinguished from an aggressive cancer. Unfortunately, the biopsy may also contain cells that are not so easy to categorize. A study in New Hampshire found that in only eight cases out of 30 did a group of pathologists agree that a patient had breast cancer; even among those eight, half the time there was disagreement over whether the cancer was aggressive or still localized.
In another study, limited to biopsies that were all in the "grey zone," pathologists with special training in breast cancer diagnosis disagreed one-third of the time.
The natural course for a pathologist is to err on the side of "do no harm." Better to call something cancer when it isn't than to tell the treating doctor that the lump is benign only to find out later the lump has grown larger and has spread. Better an unnecessary mastectomy or lumpectomy than a missed cancer.
The Bottom Line
I am NOT saying you should ignore your doctor's advice to have a mammogram. I am NOT saying that mammography is worthless. Mammography can save lives. I am NOT saying that you should disregard your doctor's advice on treatment of cancer. I AM saying that doctors and patients need to take a closer look at our assumptions about the yearly mammogram. Even more importantly, we need to look at measures to prevent breast cancer. If we can reduce the incidence of breast cancer, we may find that mammography no longer provides that 2 percent advantage.
You can Reduce Your Risk Of Breast Cancer - Here's How
Should I have a mammogram?
Let's not get distracted!
Screening tests can distract the doctor from more serious questions. All of us, at some point, develop various health problems. Too often, patients come to me for help with these problems because their primary care insurance-paid physician is too busy doing all the recommended screening tests and can't spare adequate time for the sore shoulder or upset stomach. I agree with their concerns.
CJk February 1, 2006
Medicine for People! is published by Douwe Rienstra, MD at Port Townsend, Washington. Edited by Carolyn Latteier.
Subscribe | Previous issues | Contact Dr. Rienstra | More information
©
Monroe Street Medical Clinic - Disclaimer
Monroe Street Medical Clinic is a trade name of and is operated
by
Integrative Health Systems, P.S., a Washington professional service
corporation.