The study suggests that surgery for DCIS followed by radiotherapy reduces the odds of cancer initially but this benefit diminishes over time, compared with surgery alone.
The findings were presented October 3 during the 12th European Breast Cancer Conference (EBCC12) by Dr. Maartje van Seijen of the Netherlands Cancer Institute in Amsterdam.
"Most women who are diagnosed with DCIS are offered surgery to remove the abnormal breast tissue and they are often also offered radiotherapy, even though the majority would not go on to develop invasive breast cancer. We wanted to look at how this group of women get on in the long term, according to which treatment they received," Dr. van Seijen explains in a conference statement.
The study included more than 10,000 women diagnosed with DCIS in the Netherlands between 1989 and 2004. Of these, 2,647 underwent breast-conserving surgery (BCS) only, 2,604 had BCS plus radiotherapy (RT) and 4,794 had mastectomy.
In the first 10 years after DCIS diagnosis, women who had BCS only had a 13.0% risk of subsequent ipsilateral DCIS and a 13.9% risk of ipsilateral invasive breast cancer. In contrast, corresponding percentages in the first 10 years in women treated with BCS+RT were 4.6% and 5.2%.
But while women who had RT had lower risks in the first 10 years after DCIS diagnosis, after 10 years, the risks in women who had RT were closer to their peers who opted for surgery only.
After 10 years post-diagnosis, women who had BCS only had a 1.2% risk of being diagnosed with DCIS again and an 11.8% risk of invasive breast cancer. In women treated with BCS+RT, these figures were 2.8% and 13.2%, respectively.
"The risk of DCIS or invasive cancer recurring in these women will diminish over time, whether they had just the breast-sparing surgery or breast-sparing surgery with radiotherapy. This study shows that, overall, the addition of radiotherapy gives women the best chances," Dr. van Seijen said in a conference statement.
"However, there remains a chance of a new DCIS or invasive cancer developing that is not related to the initial diagnosis and we would expect this risk to be similar between the two types of treatment. In a very small number of women, radiotherapy itself might cause a new breast cancer, often many years after the radiotherapy was given," Dr. van Seijen added.
The data also show that women with DCIS who opted for mastectomy had the lowest risks of invasive cancer. "Although patients who have a mastectomy have the lowest risk of recurrence, it's important to remember that, according to previous research, overall survival in patients who have a mastectomy is the same as in patients who have less aggressive treatments. For the majority of women with DCIS, whose condition will never become invasive, mastectomy would be considered over-treatment," Dr. van Seijen said.
In the statement, Dr. Emiel Rutgers, with the EBCC12 scientific committee, noted, "Previous research shows that the risk of dying of cancer is only 1-2% in the 20 years following a DCIS diagnosis. So, it's important to remember that whether treated with breast conserving surgery alone or surgery with radiotherapy, the risk of dying from breast cancer in women who had DCIS remains very low."
In an email to Reuters Health, Dr. Sarah P. Cate, professor of breast surgery at Icahn School of Medicine at Mount Sinai, in New York City, who wasn't involved in the study, said it highlights that "DCIS is likely to be an indolent disease. We certainly do know that patients when treated with lumpectomy and radiation or mastectomy for a diagnosis of DCIS have a lower risk of another breast cancer."
"Some patients with DCIS may not even need surgery," said Dr. Cate, who directs the surveillance and breast program at the Blavatnik Family - Chelsea Medical Center at Mount Sinai.
Figuring out which DCIS patients can safely skip surgery is the goal of the COMET study (https://dcisoptions.org/comet), which is currently accruing nationally, and the LORIS study (https://bit.ly/2GInit9), which is accruing patients internationally.
"In these studies, patients are treated with anti-estrogen pills only, and no surgery or radiation. Unfortunately, until these studies are published, we simply do not know which patients can avoid standard of care for DCIS, which is surgery, radiation, and anti-estrogen treatment if the patient's DCIS is driven by estrogen and progesterone," Dr. Cate told Reuters Health.
By Megan Brooks
SOURCE: https://bit.ly/36pumFU 12th European Breast Cancer Conference, presented October 3, 2020.
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