Update on breast cancer treatment: Ductal carcinoma in situ (DCIS)

Ductal carcinoma in situ (DCIS) is considered stage zero breast cancer, with malignant cells confined to the milk duct and no evidence of invasion into surrounding breast tissue. Despite advances in breast cancer care, significant uncertainty remains regarding DCIS, with an estimated 50% to 80% of diagnosed cases never becoming invasive. Adding to this challenge is the fact that no reliable prognostic tool exists to predict which cases of DCIS will become invasive cancers.

Recently, Drs. Ashley Newman and Ramy Sedhom joined the Penn Medicine Penn Primary Care podcast to discuss DCIS during a comprehensive discussion of breast cancer treatment. Both specialists see breast cancer patients at Penn Medicine Princeton Health, where Dr. Newman is a surgical oncologist and Dr. Sedhom is the Section Chief of Medical Oncology.

Shared decision-making in DCIS care

Although the most important initial distinction in the management of DCIS is whether the disease is invasive, the information yielded by imaging and biopsy is inconclusive in most affected patients. The central challenge in the management of this type of breast cancer is determining which lesions require intervention and which can be safely monitored. Treatment decisions often rely on a broader assessment of disease characteristics, patient risk factors, and personal preferences.

Here, Drs. Newman and Sedhom say, is where the dialogue between clinician and patient begins. Conversation is a key theme throughout the podcast and a critical component in shared decision-making. Discussions between physicians and patients often focus on lifetime breast cancer risk, potential drivers of disease, treatment options, and strategies for future risk reduction.

Given the uncertainty surrounding which cases of DCIS will progress to invasive cancer, this connection between a physician presenting complicated information and a patient who may not understand or wish to hear about ambiguous findings is essential to DCIS care and helping patients understand their diagnosis and make informed treatment decisions. Much of what happens in the early management of the disease, Drs. Sedhom and Newman suggest, is dependent on the patient’s response to their diagnosis and their personal resilience in the wake of repeated equivocal imaging findings and repeat biopsies over time.

“There’s so much here around patient context and goals,” Dr. Sedhom notes. “Even in the situation of this early cancer, a lot really depends on patient values, their fears, what matters most, and what their experience has been with other family or friends.”

DCIS pathology and personalization as drivers of treatment

DCIS is driven by individual biology, Dr. Newman says, which in turn drives recommendations for surgical, medical, and radiation oncology management. However, she adds, because treatment plans are highly personalized, decision-making is shared with the patient.

“We take into account personal wishes and other risk factors that a patient may have to help them make decisions about their treatment, but also to help them understand the risk because it’s not the same.”

The recognition of individual differences in the character of DCIS—that the disease process differs in every patient—has become the biggest shift in terms of treatment for breast cancer.

According to Drs. Newman and Sedhom, the primary challenge in DCIS management is identifying which patients benefit most from intervention and which may be safely observed, while minimizing both overtreatment and the risk of future invasive cancer.

“A 35-year-old being diagnosed with DCIS and an 85-year-old being diagnosed with DCIS? That’s two totally different disease processes.” Dr. Newman explains. “You have to think about why it happened in the first place, what their risk factors are, what strategies do you have to offer them risk reduction in the future. It’s a very nuanced conversation.”

Because DCIS encompasses a spectrum of biologically distinct conditions, treatment decisions are complex and highly individualized. Factors such as age, hormone receptor status, grade, extent of disease, family history, and patient preferences all influence management recommendations. Management decisions have been much aided by the recent COMET trial, which compared active monitoring to immediate surgery for women with low-risk DCIS, and addressed a central issue: Historically, most patients diagnosed with DCIS underwent surgery because clinicians lacked reliable tools to identify which lesions should be monitored, and which treated.

“The COMET trial was really designed to help us understand which versions of DCIS are safest to monitor and which needs some treatment,” says Dr. Newman, who lauds COMET for its assistance with older patients who have very low risk DCIS—hormone positive, low to intermediate grade, less than two centimeters in extent. “These are the patients who have the option to do anything,” she says. “They can watch it, they can simply remove it, or they can remove it, and then take steps to reduce risk of it coming back.”

Recurrence and risk reduction in DCIS

Recurrence is an important consideration in DCIS management. When DCIS recurs, Dr. Newman says, it comes back as DCIS about half the time, and as invasive breast cancer the other half, reinforcing the importance of individualized treatment discussions. Much can be done to diminish the lifetime risk of developing an invasive cancer in DCIS.

“Our goal is to find those patients who benefit most from surgery and those who benefit from risk reduction strategies, whether that’s endocrine therapy to reduce the risk of a hormone-positive DCIS recurring and/or radiation therapy to the breast, depending on the surgical approach,” she says.

Aside from the pathologic subtype, Dr. Sedhom says, there are many risk calculators or family history indicators that may suggest the best way to risk-reduce cancer.

Management of DCIS

Approaches to the management of DCIS include either monitoring of women at low risk or surgery for excision (mastectomy and lumpectomy).

The choice between the two can be complicated. Because DCIS surgery involves larger margins than surgery for invasive ductal carcinoma, Dr. Newman says, women who undergo a lumpectomy have a slightly higher chance of needing a second surgery to clear a margin. This can be a big deal, she adds, for patients withholding anticoagulation or who have other medical comorbidities.

For Dr. Newman, recommendations for surgery depend upon the extent of what she thinks is happening locally in the breast.

“Can I realistically remove this, or attempt to remove this, with lumpectomy and expect a reasonable chance of clear margins and complete excision?” She explains. “Or do I think that the size or extent of this is larger and would require a mastectomy in order to clear all of the disease?”

In addition to potential avoidance of a second surgery, mastectomy has other practical advantages, Dr. Newman says. “In pure DCIS, the only time that we sample lymph nodes would be during a mastectomy, because it does allow me to do more of a targeted lymph node excision and decrease surgical morbidity in that way.” In addition, mastectomy can typically be achieved without post-surgical radiotherapy, and in double mastectomy with no or limited adjuvant endocrine therapy.

In considering the various roles of radiation and endocrine therapy, Dr. Sedhom observes that while whole-breast radiation after breast-conserving surgery reduces the risk of ipsilateral in-breast recurrence by approximately 50%, it has not been shown to improve overall survival. For patients with estrogen receptor–positive DCIS, adjuvant endocrine therapy is offered primarily as risk reduction, lowering the incidence of future breast cancer events, again without a demonstrated survival benefit.

Treatment decisions must balance the potential benefits of risk reduction against medication-related side effects and patient preferences. Dr. Sedhom also highlights emerging evidence supporting low-dose tamoxifen (“Baby Tam”) for selected patients, citing data demonstrating meaningful risk reduction with fewer treatment-related adverse effects compared with traditional dosing approaches.

The discussion ultimately underscores how dramatically the management of DCIS has evolved. Rather than a one-size-fits-all approach, treatment decisions increasingly incorporate tumor biology, patient-specific risk factors, and personal preferences, allowing for more individualized care than ever before.

Beyond DCIS, other topics discussed in the podcast include somatic genetic testing, numbness after mastectomy, treatment de-escalation, advances in breast reconstruction, the evolving management of metastatic disease, and the expanding role of immunotherapy in breast cancer care.