A major study in women with ductal carcinoma in situ (DCIS) – a breast condition that can become invasive cancer – has shown that surgery to remove tissue followed by radiation therapy offers better protection than surgery alone.
The study, presented at 12thEuropean Breast Cancer Conference, followed patients up to 27 years. While it demonstrates that the benefit of radiotherapy and surgery over surgery alone persists, it also suggests that this benefit diminishes over time.
The researchers say these new findings clarify the long-term risks for women with DCIS and can help women and their doctors decide which treatment is right for them.
DCIS is a condition in which the cells that line the milk ducts have begun to turn into cancerous cells but have not spread to other parts of the breast. DCIS is often detected by breast screening and affects tens of thousands of women in Europe every year.
Only a fraction of DCIS cases will progress to invasive cancer and little is known about which cases will progress, so the treatments available to patients are very similar to invasive breast cancer treatments.
The research was presented by Dr Maartje van Seijen of the Netherlands Cancer Institute (Amsterdam, The Netherlands). She said: “Most women who are diagnosed with DCIS are offered surgery to remove the abnormal breast tissue and are often offered radiation therapy as well, although most would not develop invasive breast cancer. We wanted to see how. this group of women goes on long-term, depending on the treatment received. “
The study included 10,045 women diagnosed with DCIS in the Netherlands between 1989 and 2004. Researchers collected data on whether women were treated with breast-sparing surgery to remove DCIS or breast-sparing surgery. breast followed by radiation therapy or mastectomy (removing the entire breast).
They gathered information on whether the women were subsequently diagnosed with DCIS in the same breast or with invasive breast cancer in the same breast.
In the first ten years after diagnosis, women who had undergone breast-sparing surgery but not radiotherapy had a 13.0% risk (130 out of 1000 women) of being re-diagnosed with DCIS and their risk of invasive breast cancer was 13.9% (139 of 1000). Women treated with conservative surgery and radiotherapy had a 4.6% (46 out of 1000 women) risk of DCIS in the first ten years and 5.2% (52 out of 1000 women) of invasive breast cancer.
But although women undergoing radiation therapy had lower risks in the first ten years, in subsequent years (ten or more years after diagnosis), their risks were closer to those of women who had undergone surgery. Ten years after diagnosis, women who had breast-sparing surgery but not radiotherapy had a 1.2% risk (12 out of 1000 women) of being re-diagnosed with DCIS and their risk of cancer invasive breast was 11.8% (118 out of 1000).
In women treated with conservative surgery and radiotherapy these figures were 2.8% (28 out of 1000 women) for DCIS and 13.2% (132 out of 1000 women) for invasive breast cancer.
The risk of DCIS recurrence or invasive cancer in these women will decrease over time, regardless of whether they have only undergone breast-sparing surgery or breast-sparing surgery with radiation therapy. This study shows that, overall, the addition of radiation therapy offers women the best chance. However, there remains a possibility of developing a new DCIS or invasive cancer that is unrelated to the initial diagnosis and we would expect this risk to be similar between the two types of treatment. In a very limited number of women, radiotherapy itself could cause new breast cancer, often many years after the radiotherapy was given. “
Dr Maartje van Seijen, Dutch Cancer Institute
The study also showed that women who underwent mastectomy to treat their DCIS had the lowest risks of invasive cancer. Dr van Seijen added: “Although patients who have a mastectomy have the lowest risk of recurrence, it is 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. “
Professor Emiel Rutgers is president of the European Breast Cancer Council, a member of the 12thScientific Committee of the European Breast Cancer Conference and was not involved in the research.
She said: “DCIS is a condition that affects thousands of women and some of them go on to develop invasive breast cancer. Most of these women will have decades of life ahead of them, so understanding the impact on them is crucial. long term of the treatments we offer.
“We still need to know a lot more about DCIS and, in particular, which women will develop invasive cancer and which won’t. Meanwhile, studies like this one provide patients and their doctors with more information on the benefits and costs of different treatments. at their disposal.
“Previous research shows that the risk of dying from cancer is only 1-2% in the 20 years following a diagnosis of DCIS. So, it’s important to remember that when treated with breast-conserving surgery alone or radiation therapy, the risk of dying from breast cancer in women with DCIS remains very low. “
European Organization for Cancer Research and Treatment