Surveillance Instead of Surgery for Low-Risk DCIS?

Ductal carcinoma in situ (DCIS) is an early form of breast cancer that begins in the breast ducts and has not yet spread to surrounding tissues. Treatment and monitoring strategies are important because it generally has the potential to progress to invasive cancer.

What Is the Standard Treatment for DCIS?

Standard treatment for DCIS generally includes surgery, radiotherapy, and sometimes endocrine therapy, depending on the extent and characteristics of the disease:

1. Surgery:

   • Lumpectomy: Removal of the cancerous tissue with a margin of surrounding healthy tissue.
   • Mastectomy: Removal of the entire breast if the disease is more extensive.

2. Radiotherapy:
   It may be given after lumpectomy to destroy any remaining tumor cells in the breast tissue.

3. Endocrine Therapy:
   For hormone-sensitive DCIS, drugs such as tamoxifen or aromatase inhibitors are used to suppress hormonal effects and reduce recurrence risk.

Treatment selection depends on factors such as the patient's age, general health, tumor size and grade, and hormone receptor status.

The difference between DCIS and conventional breast cancers is illustrated simply below, along with a summary of the surgical methods used for DCIS:

A New Study: Active Surveillance as an Alternative to Surgery

A large clinical study was launched to investigate the feasibility of active surveillance as an alternative to surgery for low-risk ductal carcinoma in situ (DCIS). Presented at the San Antonio Breast Cancer Symposium (SABCS) 2024, COMET (Comparison of Operative to Monitoring and Endocrine Therapy) tests the short-term safety of active surveillance without surgery or radiotherapy in patients with low-risk DCIS.

Low-risk DCIS was defined in COMET as follows:

1. Hormone Receptor Positivity (HR-Positive): DCIS positive for estrogen and/or progesterone receptors.
2. Grade: The lesion is classified as low or intermediate grade (grade 1 or grade 2) on pathological assessment.
3. Age: Women aged 40 and older.
4. No Invasive Cancer: No evidence of invasive breast cancer at diagnosis.

Patients meeting these criteria were considered low-risk and enrolled in the study. This definition targeted a group with a low potential risk of progression to invasive cancer.

The COMET Study: What the 2-Year Results Show

COMET's 2-year results show that active surveillance is safe in the short term. The same-breast cancer rate was 4.2% in the active surveillance group and 5.9% in the group receiving surgery and/or radiotherapy. Although these results suggest that active surveillance could potentially replace surgery, lead researcher Dr. Shelley Hwang said that the findings were not yet sufficient to change clinical practice.

The Importance of Long-Term Analyses

DCIS generally takes longer than 2 years to progress to invasive (conventional) cancer. Therefore, awaiting the planned 5-, 7-, and 10-year analyses is critical to evaluating the long-term safety of active surveillance. Dr. Hwang stated that, if these results persist, they could lead to an important change in the treatment of low-risk DCIS.

The Aim of Active Surveillance

The primary aim of active surveillance is to avoid overtreatment. DCIS does not always progress to invasive cancer, so surgery and radiotherapy may be unnecessary for some women. Under active surveillance, lesions are monitored closely for signs of progression to advanced disease; if this occurs, guideline-based treatment begins.

COMET's Methods and Participant Profile

COMET is a prospective, randomized, noninferiority study. It enrolled 957 women older than 40 with HR-positive (hormone receptor-positive) grade 1 or grade 2 DCIS and no invasive cancer. Participants were divided into two groups: 484 women were randomized to active surveillance and 473 to standard surgery.

Treatment Options and Endocrine Therapy Use

Participants in both groups could choose endocrine therapy. This treatment generally lasted 5 years, and 71% of patients in the active surveillance group and 65.5% in the surgery group chose it. Among patients receiving endocrine therapy, invasive cancer rates were 3.21% in the active surveillance group and 7.15% in the surgery group.

Clinical Meaning of the Results

COMET's findings suggest that endocrine therapy may reduce progression to invasive cancer. However, most patients in the surgery group had invasive cancer detected at their first operation. This suggests that similar invasive cancer rates might be observed if patients in the active surveillance group underwent surgery.

Patient Preferences and Quality-of-Life Analysis

COMET's patient-reported outcomes substudy found no significant differences between active surveillance and surgery in factors such as quality of life, anxiety, and depression. Patients reported similar experiences regardless of their treatment group.

Conclusion: Could Active Surveillance Create a New Treatment Approach?

COMET's 2-year findings could play an important role in informing patients. These data allow clearer communication with patients who prefer to avoid surgery about the likelihood that DCIS will progress to invasive breast cancer within 2 years. It should also be emphasized that DCIS is generally not an aggressive cancer and that patients have sufficient time to consider their treatment options.

COMET's short-term findings indicate that active surveillance may be an alternative to surgery for patients with low-risk DCIS. However, further analyses are essential to establish its long-term safety. If the findings prove durable, a new treatment paradigm could emerge to avoid unnecessary surgery and preserve patients' quality of life.