Up to 75 percent of invasive breast cancers are classified as ductal, which refers to the fact that the cancer developed in the milk ducts. The second most common histological type of invasive breast cancer, accounting for approximately 15 percent of cases, is lobular breast cancer, which forms in the cells that line the milk-producing glands (lobules) of the breast.
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 new breast cancer diagnoses are DCIS (without an invasive component) and over 40% of invasive breast cancers are associated with adjacent 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. DCIS diagnosed with a needle biopsy should be confirmed using open surgery since there is a one-in-four chance of finding invasive breast cancer in the location, according to one expert.
If left untreated, at least a third of DCIS lesions will progress to invasive breast cancer. Even when treated, approximately 12% of women treated for DCIS with surgery are subsequently diagnosed with invasive breast cancer. Progression from DCIS to invasive breast cancer is more likely in those with HER2+ or triple negative (ER-/PR-/HER2-) DCIS, or with a family history of breast cancer. Nevertheless, it has been estimated that fewer than 2% of women die of breast cancer within 10 years of receiving a diagnosis of DCIS. Atypical ductal hyperplasia is not considered cancer, but is a risk factor for DCIS and invasive breast cancer. Please see our article on DCIS recurrence for more information on outcomes after treatment for 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) of the breast has been found to be more sensitive than mammography for detecting multicentric disease and estimating tumor size among patients with DCIS.
Lumpectomy plus radiation is effective treatment for DCIS
Lumpectomy plus radiotherapy 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.
Ductal breast cancer, 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. Use of the lipophilic statin Lescol (fluvastatin) has been found to reduce tumor proliferation and increase cancer cell death in some cases of DCIS. On the other hand, a recent study reported that long-term statin use was associated with increased risks of both ductal and lobular breast cancer.
One 2013 study reported that long-term use of calcium-channel blockers (a type of high blood pressure drug) more than doubled the risk of ductal breast cancer in postmenopausal women. Another 2015 study reported that use of use of levonorgestrel intrauterine system (LNG-IUS), an IUD-type device, increased the risk of ductal breast cancer.
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).
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. There is a risk of needle tract seeding if the path of the needle used in biopsy is not subsequently irradiated during partial breast irradiation.
Viruses might influence ductal breast cancer development
The development of ductal breast 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 BLV which is estimated to infect the majority 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.
We 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) for information pertaining to food and supplements. Most studies relevant to ductal breast cancer focus on breast cancer subtypes rather than ductal breast cancer per se.