What Are the Limitations of Breast Imaging?
Mammography is currently the gold standard of breast imaging. However, limitations of breast imaging are known. We need to fight these limitations of breast imaging in order to make breast cancer detection the most accurate it can be. This post will outline the drawbacks of utilizing visual interpretations available through imaging alone and offer a potential solution to work in conjunction with imaging in order to solve these problems.
Imaging sometimes leads to follow-up examinations, including biopsies, when there is no cancer. A false-positive is most likely following a woman's initial screening mammogram. Other factors that increase the likelihood of a false-positive include the use of postmenopausal hormone therapy and having dense breast tissue. On average, 10 percent of women will be recalled from each screening examination for further testing, but only 5 percent of these women will have cancer. According to one US study, over the course of 10 screening examinations, about one half of women will experience a false positive and bout 19 percent will undergo biopsy, increasing the cost, discomfort, inconvenience and anxiety of patients.
False-negative results occur when mammograms appear normal even though breast cancer is present. Overall, screening mammograms miss about 20% of breast cancers that are present at the time of the screening. The main cause of false-negative results is high breast density. Breasts contain both dense and fatty tissue, with dense tissue appearing white on a mammogram, just as a tumor would. Finding cancer in dense breasts has been likened to finding a snowball in a snowstorm. False negatives occur more often in younger women that older women, this is because younger women are more likely to have dense breasts. As a women ages, her breasts usually become more fatty ad false negative results become less likely. False negative results can lead to delays in treatment and a false sense of security for affected women and their families.
Over treatment and overdiagnosis might be caused by screening mammograms that lead to medical interventions for certain cases of ductal carcinoma in situ (DCIS) that may never have become clinically apparent, would have not caused a women any harm in her lifetime, would not have progressed or needed treatment, or otherwise been detected in the absence of screening. Since it is not currently possible to predict which cases of DCIS will progress to invasive cancer, over treatment is a potential harm associated with screening. Estimates of the rate of over diagnosis are highly variable ranging from <5 percent to over 30 percent.
Radiation exposure is a risk factor for breast cancer. Overall risk from a single exposure from mammography is very small. However, risk increases with the amount of exposure and with exposure at younger ages.
The pathologists diagnosis of breast tissue ranges from benign without atypia, to atypia, to DCIS, to invasive breast cancer. The incidence of atypia and DCIS breast lesions has increased over the past three decades as a result of widespread mammography screening. Misclassification of breast lesions may contribute to either over treatment or under treatment of lesions identified during breast screening. Studies have demonstrated challenges encountered by pathologists on agreeing about the diagnoses of breast tissue. The largest study on this topic included 115 practicing U.S pathology who interpreted a single breast biopsy slide per case and compared their interpretations with an expert consensus-derived reference diagnosis. Over interpretation of atypia was noted in 17% and over interpretation of benign without atypia was noted in 13%.
The above reasons highlight imaging faults. However these faults can be eliminated through the addition of a blood-based approach to the current standard-of-care. A blood-based approach would allow women with difficult to interpret results and/or dense breasts to gain a definitive diagnosis as the test would be based on physiology rather than anatomy. A test of this kind would reduce false positive and negative results, as well as overdiagnosis by catching cancer in real time, as early as possible. A blood-based approach would also give women peace of mind and save them money on unnecessary biopsies, while also saving the health care system as a whole money by reducing unnecessary invasive procedures. Though there is still a strong place for imaging in terms of breast cancer detection, adding a blood-based approach would allow for more accurate and earlier detection.