Radiation Therapy After Surgery for Low-Risk DCIS Reduces Recurrence Risk

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DCIS (ductal carcinoma in situ) is the most common form of non-invasive breast cancer and is considered stage 0 cancer. While DCIS isn’t considered life threatening, it does increase the risk of developing invasive breast cancer later in life.

DCIS usually is treated with surgery to remove the cancer -- lumpectomy in most cases. After surgery, hormonal therapy may be recommended if the DCIS is hormone-receptor-positive (most are). Radiation therapy after DCIS surgery was common in the past, but some newer DCIS treatment guidelines say that women at low risk of recurrence (the cancer coming back) may be able to skip radiation therapy after surgery.

Now a study has found that radiation therapy after lumpectomy to remove low-risk DCIS reduces the risk of recurrence, but had no effect on overall survival.

The research was presented on Oct. 21, 2018, at the American Society for Radiation Oncology Annual Meeting. Read the abstract of “Randomized Trial Evaluating Radiation following Surgical Excision for “Good Risk” DCIS: 12-Year Report from NRG/RTOG 9804.” (PDF)

Post-surgery radiation vs. observation

In the study, the researchers defined “good-risk” or “low-risk” DCIS as DCIS that was causing no symptoms and was found incidentally during a breast biopsy or a mammogram.

The study included 636 women diagnosed with low-risk DCIS between 1999 and 2006. More than 75% of the women were postmenopausal. After lumpectomy, the women were randomly split into two treatment groups:

  • a conventional regimen of whole-breast radiation therapy
  • observation instead of radiation (the control group)

The average follow-up time was 12.4 years.

DCIS recurrence rates were:

  • 2.8% for women treated with whole-breast radiation
  • 11.4% for women in the control group

Invasive breast cancer recurrence rates were:

  • 1.5% for women treated with whole-breast radiation
  • 5.8% for women in the control group

The differences in both recurrence rates were statistically significant, which means they were likely because of the difference in treatment, rather than due to chance.

Still, the researchers found no statistically significant differences in overall survival between the two groups. Overall survival is how long the women lived, whether or not they had a recurrence of DCIS or invasive breast cancer.

"We really feel that, because this is not a life-threatening disease, the patient and her doctor should really use this information for a meaningful patient-doctor discussion about risks, benefits, and the patient's own degree of comfort, which varies greatly," said Beryl McCormick, M.D., of the Memorial Sloan Kettering Cancer Center who presented the research, in an interview. "For many patients, a recurrence risk of 1% per year is not really worrisome, while other patients would really like to do anything they can to not have this come back, including radiation."

Treatment should be based on ALL risk factors and personal preferences

Several other large, randomized studies have shown that radiation after lumpectomy for DCIS reduces the risk of recurrence in the same breast by about half. Other studies have shown that taking tamoxifen after lumpectomy for hormone-receptor-positive DCIS reduces the risk of both DCIS recurrence and invasive disease in both breasts.

Still, no study has shown that radiation or tamoxifen after lumpectomy for DCIS improves overall survival or reduces the rate of metastatic recurrence (cancer coming back in a part of the body away from the breast).

How DCIS considered to have a low risk of recurrence should be treated is somewhat controversial right now. Some women and their doctors prefer careful monitoring instead of surgery, some prefer lumpectomy alone, and some prefer lumpectomy followed by radiation and hormonal therapy.

While the study had 12 years of follow-up, which is a long time, the research did have some weaknesses. It’s important to know that the study didn’t look at whether the women diagnosed with DCIS had other breast cancer risk factors, such as a strong family history of breast cancer or a known abnormal gene. To accurately assess a woman’s risk of invasive disease and develop a treatment plan for DCIS, doctors have to look at ALL risk factors.

It’s also important to know that there have been new developments in testing since this study was started. The Oncotype DX DCIS test is a genomic test that analyzes 12 genes in a DCIS and assigns a Recurrence Score that estimates the risk of both DCIS coming back and invasive disease in the future. It gives women and their doctors more information so they can make more informed decisions about whether treatment is needed after DCIS has been surgically removed.

If you’ve been diagnosed with DCIS, the goal is to provide you with the best treatment for your unique situation. Your treatment plan should consider:

  • your family history of breast cancer and other diseases
  • your personal health history
  • many other breast cancer risk factors you may have
  • your preferences
  • the characteristics of the DCIS
  • any genomic test results

Together, you and your doctor will develop a DCIS treatment plan that makes the most sense for you.

For more information, visit the Breastcancer.org DCIS pages.

To talk with others who have been diagnosed with DCIS, join the Breastcancer.org Discussion Board forum DCIS (Ductal Carcinoma In Situ).


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