Most ductal carcinoma in situ (DCIS) breast cancer will never become life-threatening, even if left untreated. However, there hasn’t been a good way to tell when DCIS should be treated and when treatment can be safely skipped—until now. A new study has identified six factors that determine when DCIS is most likely to become invasive breast cancer.

DCIS is cancer that starts in a milk duct and has not spread outside the duct. Often called “stage 0,” it’s such an early stage of cancer that some experts believe it’s actually a precancerous condition rather than actual cancer. DCIS has become increasingly common—possibly because women are living longer, more women are getting screening mammograms, and mammograms have become better at finding these small breast cancers. About 20% of all breast cancers are DCIS.

Most women with DCIS have a lumpectomy, and some also have radiation. The risk for DCIS recurrence after lumpectomy alone is about 25% to 30%…adding radiation therapy drops the risk to about 15%. Only half of recurrences are invasive cancer—the rest are DCIS again.

However, as there hasn’t been a way to reliably predict which women with DCIS will develop invasive breast cancer, guidelines call for all women with the condition to be treated with either surgery alone or surgery and radiation…and frequently hormonal therapy as well. Doctors are coming to believe that this is overtreatment for the majority of women.

Now: Researchers from the Netherlands Cancer Institute in Amsterdam reviewed 17 studies and identified 26 unfavorable prognostic factors associated with invasive breast cancer developing after DCIS. Six factors in particular emerged as the most significant indicators, with risk for invasive breast cancer after DCIS diagnosis ranging from 36% to 84%. They were…

  • Feeling a lump (84% risk). DCIS does not cause symptoms and 80% of the time is found only by mammography. However, when DCIS causes a palpable lump (one that can be felt), it is likely to be aggressive.
  • Involved margins (63% risk). When the tumor is removed, if tumor cells are found to extend out to the edge of normal breast tissue, the risk for recurrence increases—because surgery may leave some cells behind.
  • Diagnosed before menopause (59% risk). Younger women produce more estrogen, which may stimulate tumor growth. They also have more of their lives still ahead, allowing more time for recurrence to occur.
  • High p16 (51% risk). Overexpression of p16, a protein involved in regulating tumor-cell growth that is detected during biopsy, has been linked to more aggressive tumor growth.
  • Being African-American (43% risk). For reasons that are not clearly understood, African-American women have higher rates of all types of breast cancer recurrence.
  • High histologic grade (36% risk). Histologic grade refers to how different from normal cells tumor cells look when studied under a microscope. The more abnormal, or poorly differentiated (meaning that it is hard to tell if the cells are normal or cancer), the higher their grade—and, not surprisingly, the greater their risk for becoming aggressive cancer.

The researchers hope that their findings will be independently validated and help to inform new guidelines…and that future studies will continue to look for other factors that might play a role. In the meantime, if you have been diagnosed with DCIS, it’s a good idea to include these six factors in the conversation you have with your doctor to determine the best next steps.