Matthieu Yver, MD (Anatomopathologist)
Cécile Bour, MD (Radiologist)
Breast Cancer Mortality After a Diagnosis of Ductal Carcinoma In Situ (DCIS)
Treating ductal carcinoma in situ does not reduce mortality from breast cancer
Autors : Steven A. Narod, MD, FRCPC1,2; Javaid Iqbal, MD1; Vasily Giannakeas, MPH1,2; Victoria Sopik, MSc1; Ping Sun, PhD1
JAMA Oncol. Published online August 20, 2015. doi:10.1001/jamaoncol.2015.2510
Treating ductal carcinoma in situ does not reduce breast cancer mortality, according to a recent observational study conducted by scientists at Women's College Hospital in Toronto and the University of Toronto, published in the journal "JAMA Oncology" in August, 2015.
Their conclusions are based on the largest recorded data ever analyzed, based on 18 U.S. registries including 100,000 women followed for 20 years with a diagnosis of ductal carcinoma in situ (DCIS).
It should be reminded that this is not a cancer, contrary to what its denomination might seem to indicate. It is a precancerous/adenomatous lesion that remains inside the mammary canal without invading the surrounding tissues. It is a lesion with a good prognosis, it corresponds to stage 0 of breast cancer. This type of precancerous lesion is diagnosed much more frequently since the widespread use of mammography. Some of these lesions are thought to be precursors of breast cancer. There is a risk for patients of local recurrence into either DCIS or infiltrating ductal carcinoma, which is potentially metastasizing and therefore life-threatening.
However, it is not yet known how to determine which DCIS will progress to infiltrating cancer and which will not. The patient usually is treated by a partial or total mastectomy, depending on the extent, and in any case a total mastectomy upon recurrence, followed by radiation therapy. Until now, this treatment was considered to have a preventive effect on the development of invasive cancer and was therefore beneficial for the patient's survival.
It now would seem that the treatment does not make a difference on survival and women with this condition and even heavily treated (sometimes by bilateral mastectomy) have the same probability of dying from breast cancer compared to women in the general population.
Prevention of recurrence with either radiotherapy or mastectomy did not prevent death from breast cancer.
Therefore, the treatment of precancerous lesions (DCIS) seems excessive in breast pathology. Moreover, in colonic pathology, precancerous lesions are never treated by radiotherapy.
According to Philippe Autier from the International Prevention Research Institute (IPRI), the situation is impossible to solve from a legal and practical point of view, especially since the diagnosis of DCIS can never be 100% certain until the surgical specimen is examined under the microscope. The problem, according to him, is inherent to mammography, especially digital mammography, which is too performant regarding the detection of small calcifications which are the most frequent radiological signs of these forms of precancerous lesions.
He believes that the problem of over-diagnosis, i.e. the detection of in situ or invasive cancers that would not have manifested themselves and would not have threatened patient's life, will not be eliminated as long as screening is based on this method.
This reasoning can be taken one step further: it seems quite pointless that current technology tends to invent increasingly sensitive detection methods that will serve for detecting precancerous lesions, of which many will never develop into cancer...