Ductal carcinoma in situ (DCIS), also called intraductal carcinoma, refers to cancer cells that have formed in milk ducts but are confined there. Currently, approximately 20% of breast cancer diagnoses are DCIS. DCIS is classified as non-invasive because the abnormal cells have not spread beyond the walls of the duct to invade the surrounding breast tissue. If left untreated, at least a third of DCIS lesions will progress to invasive breast cancer. Even when treated, approximately 15% of patients treated for DCIS with surgery are subsequently diagnosed with invasive breast cancer. Nevertheless, it has been estimated that fewer than two percent of women die of breast cancer within 10 years of receiving a diagnosis of DCIS.
Incidence of DCIS has been increasing
DCIS incidence has been increasing in recent years, rising from 1.87 per 100,000 during the mid-1970s to 32.5 per 100,000 in the mid-2000s, according to a study commissioned by the National Institutes of Health. Incidence was found to rise in women of all ages, but more so in women over 50. Greater use of mammography screening for breast cancer accounts for some, but not all, of this increase. Magnetic resonance imaging (MRI) has been found to be more sensitive than mammography for detecting multicentric disease and estimating tumor size among patients with DCIS.
Invasive ductal breast cancer that co-exists with DCIS tends to be less aggressive than size-matched pure ductal breast cancer, especially if the ratio of DCIS to ductal breast cancer size is high.
Lumpectomy plus radiation is effective treatment for DCIS
Lumpectomy plus radiation treatment and mastectomy produce similar outcomes and both are superior to lumpectomy alone. Breast reduction surgery can be successfully combined with lumpectomy to treat DCIS in some patients. However, negative margins must be obtained during the procedure, otherwise, either re-excision or completion mastectomy and reconstruction should be performed.
DCIS and prescription drugs
Cyclooxygenase 2 (Cox-2) overexpression has been reported in 60% to 80% of DCIS cases. Based on this finding and other reports, it was hypothesized by the authors of one study that Cox-2 inhibitors would reduce progression to invasive breast cancer. However, treating mice prone to developing DCIS-like lesions with a Cox-2 inhibitor unexpectedly failed to reduce mammary tumor development or prevent metastasis.
There have also been a few studies that focus on DCIS risk and outcome as it relates to bisphosphonates and statins. Women who use bisphosphonates such as Fosamax, Boniva and Actonel to treat osteoporosis have been found to develop significantly fewer cases of invasive breast cancer, but more cases of DCIS. On the other hand, use of the lipophilic statin Lescol (fluvastatin) has been found to reduce tumor proliferation and increase cancer cell death in some cases of DCIS.
Partial breast irradiation may be effective for early stage ductal breast cancer
Partial breast irradiation performed on the tumor bed immediately after lumpectomy may be as safe and effective as the weeks of radiation therapy that early stage ductal breast cancer patients typically undergo, according to one study. However, any patients so treated must be very carefully selected (for example, they should not have multifocal disease or extensive DCIS).
There is also a risk of needle tract seeding if the path of the needle used in biopsy is not subsequently irradiated. The potential for tumor seeding along the needle path has long been a concern regarding breast cancer biopsies. Evidence exists to suggest that such seeding can and does occur up to half of the time. However, most cancer cells dispersed in such a manner do not survive. Nevertheless, cases have been described in which local recurrences were found in the biopsy path. Irradiation of the path in traditional whole breast irradiation probably contributes to the eradication of cancer cells that are dislodged during biopsy.
Viruses might influence ductal breast cancer development
The development of ductal beast cancer and its degree of aggressiveness might be influenced by viruses. Mouse mammary tumor virus sequences (found in naturally occurring mouse mammary tumors) have been found in human breast cancers, but not in normal breast tissue. Human papillomavirus (HPV), which causes most cases of cervical cancer, has also been found in breast cancer tissues. Women with HPV-positive breast cancer have been reported to be significantly younger than women with HPV-negative breast cancer, suggesting a different development pathway for the younger women involving a causal role for HPV. Bovine leukemia virus, which estimated to infect at least 14% of U.S. beef herds, is thought by some observers to be capable of contributing to human breast cancer development. Many women have antibodies to bovine leukemia virus, indicating exposure to the virus. However, causality has not been proven for any virus to date.
Additional comments
Please see our article on what ductal breast cancer patients and survivors should eat for information pertaining to diet and supplements. We also suggest that DCIS and ductal breast cancer patients and survivors refer to our web pages concerning their breast cancer subtypes (e.g., ER+/PR+, HER2 overexpressing, triple negative). Most studies relevant to ductal breast cancer focus on breast cancer subtypes rather than ductal breast cancer per se.