Study: All DCIS is not the same: Young women and African American women at higher risk after DCIS diagnosis

IN DEPTH REVIEW OF RESEARCH

Study background:

Although DCIS cells are abnormal, they are not the same as invasive cancer cells. Unlike invasive cancer, DCIS lacks the ability to metastasize (spread to other areas of the body). Scientists long believed that untreated DCIS cells could turn into invasive cancer, which might then spread to other parts of the body and cause death.  For this reason, DCIS lesions are generally removed and the remaining breast is treated with radiation to kill off any lingering cancer cells.  However, data from previous studies and this more recent study show that even left untreated, DCIS seldom leads to death, and that removing DCIS does not help most women live longer.  This study was done to learn which risk factors are associated with breast cancer mortality after a DCIS diagnosis.

Researchers of this study wanted to know:

How many women previously diagnosed with DCIS eventually die from breast cancer, and which women are at greatest risk for breast cancer death after DCIS.

Population(s) looked at in the study:

Data from approximately 108,000 women who were diagnosed with DCIS from 1988-2011 were obtained from the National Cancer Institute’s SEER (Surveillance, Epidemiology and End Results) database. SEER collects information on all patients diagnosed with cancer, including the site of the primary cancer; the stage of cancer at diagnosis, the first course of treatment; specific markers, such as HER2, ER, and PR; and patient survival.  Research using databases such as SEER is useful in designing controlled studies that compare how different treatment options affect survival.

Study results:

• 20 years after DCIS diagnosis, the breast cancer mortality rate was approximately 3% for all women.
• Women who were diagnosed with DCIS before age 35 had the highest risk of death from breast cancer after 20 years. The 20-year risk was still low (approximately 8%).
  • Women who were diagnosed with DCIS between ages 35-39 had a 4.5% risk of developing invasive breast cancer after 20 years.
  • On average, women who were diagnosed with DCIS between ages 40 and 69 had an approximate 3% risk of developing invasive breast cancer after 20 years.
• African American women had a 7% risk of death at 20 years after DCIS diagnosis, compared to 3% for white, non-Hispanic women.
• Radiotherapy after lumpectomy reduced the risk of developing an invasive recurrent breast cancer from about 5% to 2.5%. However, this reduction did not translate to a reduction in risk of death from breast cancer.
• Of the 956 women who died of breast cancer (out of 108,196 women total) after their DCIS diagnosis, most (approximately 55% of the 956 women) did not have a record of invasive in-breast recurrence.

Limitations:

Researchers were unable to tell which cases of DCIS were detected through screening and which cases were symptomatic. The researchers did not have access to information that could affect risk of recurrence and/or second primary breast cancer such as:

• tamoxifen use after DCIS
• body mass index
• family history of breast cancer
• the presence of mutations in BRCA or other genes associated with increased cancer risk
• whether or not the later invasive cancer was a recurrence of the original cancer or a new breast cancer in the same or opposite breast

Conclusion:

This study highlights two populations who have a higher risk of breast cancer mortality after DCIS diagnosis: young women (under 40) and African American women. As breast surgeon Dr. Laura Esserman said in an editorial that was published on this study, “For young women (<40 years) who present with symptomatic DCIS—approximately 5% of the population—we should be cognizant that this is a different disease than typical DCIS.” Esserman noted that new tests that look at a patient’s tumor can help health care providers identify which patients with DCIS could benefit from more aggressive treatment.

This study did not look at patients’ BRCA status or their family history of breast cancer. While the study shows that the risk of dying from breast cancer after a DCIS diagnosis is generally low, young women and African American women should be monitored more regularly and more thoroughly.  Women diagnosed with DCIS before the age of 50 meet national guidelines for referral to genetic services; they may wish to discuss the possibility of genetic counseling and/or testing with their health care provider.

Experts note that this study alone does not mean that doctors should stop treating women with DCIS; rather, it is an indicator for further discussion and research on how to best treat DCIS in different populations.