As a breast imaging specialist, who has been reading mammograms for almost 20 years, I am being bombarded with questions by patients and friends about the Canadian National Breast Cancer Study, published on February 4 and now widely disseminated in the US media. The study concludes that mammography and its goal of early detection has no benefit. However, this conclusion has been rebuffed by the American College of Radiology (ACR) who found the study deeply flawed, and by the chief of cancer control for the American Cancer Society, who was quoted in the New York Times as saying their combined data shows that mammography reduces the death rate by 15 to 20 percent.
Mammography is not perfect but it continues to be the gold standard in breast cancer detection because, in good hands, it has been proven to save lives and reduce the need for more costly, invasive and aggressive treatment for cancers found at a later stage. It is still just the starting point in early detection of breast cancer. A patient with an inconclusive mammogram may need imaging with Ultrasound, MRI or molecular imaging. All patients should have an individual risk profile, including personal and family history as well as breast density, to determine the methods and frequency of screening best suited to them. Ultrasound has been found to almost double the number of cancers found in women with dense breasts when combined with mammography.
Many states now are requiring radiologists to inform women when their mammograms show they have dense breast tissue, as density compromises the accuracy of mammograms and additional imaging may be needed. New Jersey has just passed a similar law, requiring radiologists to tell all mammography patients that they may have dense tissue and should discuss their individual report with their doctors.
The argument that some cancers are found too early and would never cause any harm misses an important caveat: we don’t know which cancers are killers and which ones aren’t. Waiting until a cancer is big enough to felt as a lump and then treated is undertreatment at its worst. Larger cancers require more invasive treatment with ensuing complications such as lymphedema and side effects from chemotherapy. Ductal Carcinoma in Situ (DCIS), now being marginalized as not cancer, if untreated can become invasive. Yes, there is overtreatment. Many abnormal findings, when followed by breast imaging specialists, can be monitored instead of biopsied and when a biopsy is needed, it can be guided by Ultrasound or mammography and not done surgically as is often the case.
Radiologists would love to be able to relegate mammography to history – it is poorly reimbursed and the images are often difficult to interpret conclusively. There are some new screening methods in the pipeline now that look promising and may get FDA clearance soon. Until research can identify which tumors can safely be left undiscovered and untreated, we will continue to use mammography, and all the imaging modalities we have, to find breast cancer at its earliest stage.