What Is Ductal Carcinoma in Situ, and How Worried Should I Be? Can DCIS Recur, and How Is It Treated?

What does DCIS mean?

Ductal carcinoma in situ (Ductal Carcinoma In Situ= DCIS) describes lesions in which the cells lining the milk ducts of the breast have begun to become cancerous but have not yet become invasive.

According to the 2021 US Cancer Statistics, 50 thousand new DCIS cases are detected annually in the United States alone. There are no DCIS data for Turkey, but conventional breast cancer affects approximately 24 thousand women per year in Turkey.

What stage of breast cancer is DCIS?

Some call DCIS a very early stage of breast cancer, or "stage 0"; however, more precisely, describing DCIS as invasive — that is, true — breast cancer is not correct; rather, these lesions carry a 20% to 50% risk of developing breast cancer.

What does DCIS mean in a pathology report?

If a breast biopsy is reported as "ductal carcinoma in situ," it means that some cells in your breast ducts have begun to turn into cancer cells, but they have not yet become invasive and extend only along the milk ducts, not into the breast tissue.

The general approach to DCIS treatment

The main treatment for DCIS is surgery, in which the tumor is removed with some normal surrounding tissue. These breast-conserving operations are called "wide local excision" or "lumpectomy." In some cases, breast-conserving surgery is followed by radiotherapy, and for those who are estrogen receptor positive,  hormonal therapy is recommended.

The process by which cells in breast tissue become cancerous is illustrated simply below.

Can DCIS recur?

The main treatment for DCIS consists of mastectomy, in which all breast tissue is removed, or breast-conserving treatment (BCT). In breast-conserving surgery, the whole breast is not removed, only the area containing DCIS. This operation, also called lumpectomy, is generally followed by radiotherapy.

The likelihood of DCIS recurring after surgery for DCIS is very low, approximately 1-2%.

Both surgical approaches for DCIS result in similar breast cancer-specific survival rates.

Recommendations for DCIS Treatment

• Ductal carcinoma in situ (DCIS) of the breast represents a heterogeneous group of neoplastic lesions confined to the breast ducts. The goal of DCIS treatment is to prevent invasive breast cancer. The main treatment approach includes surgery, radiation therapy (RT), and adjuvant endocrine therapy.
• Candidates for breast-conserving surgery (BCS) include patients with DCIS localized to one quadrant that can be removed with negative margins and a cosmetically acceptable result, considering disease extent relative to breast size. If margins are close or positive, re-excision(s), mastectomy, or a radiation boost should be performed.
• For patients eligible for BCS, we recommend BCS rather than mastectomy. For most women undergoing BCS, we recommend RT in addition to lumpectomy.
• However, for patients with very small foci of low-grade DCIS, breast-conserving surgery alone (without RT) is an option with widely negative margins (ideally 10 mm). Nevertheless, prospective randomized evidence supporting omission of adjuvant radiation is limited even in selected low-risk cases.
• We do not recommend surgical assessment of the axilla for most patients with DCIS. However, we recommend sentinel lymph node biopsy in patients who do not meet BCS criteria and therefore require mastectomy.
• For women with estrogen receptor (ER)-positive DCIS treated with breast-conserving surgery, with or without RT, we recommend endocrine therapy rather than observation. For women choosing treatment, the choice between anastrozole and tamoxifen should be individualized according to each medication’s side-effect profile, menopausal status, and patient preferences.
• In general, for women who undergo unilateral mastectomy for ER-positive DCIS, we recommend endocrine therapy rather than observation. In these patients, endocrine therapy should be regarded as "chemoprevention," rather than treatment to prevent recurrence of this diagnosis. In other words, it is given to prevent a new primary cancer in the opposite breast. We do not recommend chemoprevention for women who undergo bilateral mastectomy for DCIS because the risks/adverse events outweigh any potential risk-reduction benefit.
• We do not recommend routine tamoxifen as chemoprevention for women with ER-negative DCIS, given that endocrine therapy has not reduced recurrence risk in this group. However, some women may choose tamoxifen to reduce the risk of developing a new endocrine receptor-positive DCIS or breast cancer.
• Treatment for a patient diagnosed with recurrence after primary DCIS treatment depends on whether the disease remains entirely in situ or has an invasive component, its extent and location, the previous surgical approach (mastectomy versus lumpectomy), and whether RT was given.

Is DCIS associated with breast cancer death?

For ductal carcinoma in situ (DCIS), how effective is surgical treatment at preventing recurrence as conventional breast cancer? Surgery, the main treatment for DCIS, aims to substantially reduce lifetime risks of breast cancer and breast cancer death, but do patients diagnosed with DCIS remain at risk of poor outcomes?

JAMA Network Open published a study in September 2020 examining a series of surgically treated patients diagnosed with DCIS, to compare their risks of breast cancer and related death with those without such a diagnosis. The researchers found that within 20 years of a DCIS diagnosis, the risk of breast cancer death might be higher than expected compared with those without the diagnosis.

The researchers obtained data from the US Cancer Statistics (Surveillance, Epidemiology, and End Results = SEER) registry database. Using this publicly available information, they examined DCIS cases diagnosed between 1995 and 2014 in 144 thousand women. Patients diagnosed with in situ carcinoma were included without evidence of an invasive component (on the condition that it was not conventional breast cancer); exclusion criteria included microinvasion, lobular carcinoma in situ, nonepithelial histological findings, Paget disease of the nipple, or extensive DCIS. All these women underwent surgery for DCIS, and 68 thousand also received radiotherapy. Women were followed until December 31, 2016, unless they died (from breast cancer or an unrelated cause), were lost to follow-up, or 20 years had elapsed since the initial DCIS diagnosis.

The researchers had predicted an estimated 458.6 breast cancer deaths among 144,524 patients (using age-specific breast cancer incidence rates). Instead, they observed more than 3 times the expected number: 1540 breast cancer deaths.

This ratio was similar across different periods. From 1995 to 1999, 426 deaths occurred in patients with DCIS, compared with 129.5 expected; from 2005 to 2009, 343 deaths were observed, compared with 104 expected. These were approximately 3.29-fold and 3.3-fold higher rates, respectively.

What factors increase mortality risk in patients with DCIS?

Young age and Black race were the main factors associated with observed deaths being substantially higher than expected.

Among women diagnosed with DCIS before age 49, the researchers observed 92 deaths, approximately 12 times the expected 8.2 breast cancer deaths. Thus, a DCIS diagnosis before age 50 markedly increased risk.

Of the women observed, 15,415 were Black. There were 319 observed deaths in Black women compared with 42.2 expected, more than 7.5-fold higher. Focusing on Black women under 40, a group of 692, the number of observed breast cancer deaths was 22 times higher than expected.

The researchers observed 238 breast cancer deaths among 17,313 women who underwent unilateral mastectomy for DCIS, compared with 57.8 expected deaths in this group. Among 63,827 women who underwent lumpectomy plus radiotherapy, 496 deaths were observed, compared with 176.7 expected.

- Related topic: 6 risk factors for ductal carcinoma in situ (DCIS) progressing to breast cancer

Conclusion

The researchers acknowledge the study’s limitations and state that the 2% lifetime risk of breast cancer death after DCIS is insufficient to recommend chemotherapy. Nevertheless, it is valuable to know that women may face a greater risk of breast cancer death after DCIS surgery than initially estimated, and that race may put women at even greater risk.