Women younger than age 45 years who were treated with lumpectomy and radiation for ductal carcinoma in situ were 68% more likely to have a local recurrence than were older women, a large population-based study found.
After a median follow-up of 8.5 years, women aged 44 and younger had a recurrence rate of 20%, compared with a 12% recurrence rate in those aged 45–50 years, the retrospective study showed. The 12% recurrence rate in the 45- to 50-year-old age group is similar to previously reported recurrence rates of 10%–15% in women older than age 50 in the 10 years after diagnosis, reported Dr. Iwa Kong of the University of Toronto.
She described the findings in a press briefing that preceded a breast cancer symposium sponsored by the American Society of Clinical Oncology. Dr. Kong reported having no conflicts of interest related to this study.
Previous studies have shown that treating ductal carcinoma in situ (DCIS) with lumpectomy and radiation results in a low overall recurrence rate of about 10% in the 10 years after diagnosis, but those studies included few women aged 50 or younger. Increasing concerns that younger women who are treated with lumpectomy and radiation may be at greater risk for recurrence inspired Dr. Kong and her associates to examine data on all women aged 50 and younger who were diagnosed with DCIS in Ontario, Canada, between 1994 and 2003.
Of the 583 who underwent breast conservation surgery and radiation therapy for DCIS, most received 50 Gy of radiation in 25 fractions, and 21% received a boost.
Local recurrences developed in 99 women (17%), and invasive local recurrences in 38 (7%). Recurrence rates were 23% in those aged 40 years or younger, 21% in those aged 40–44 years, and 14% in the 45- to 50-year-old women, for an unadjusted hazard ratio of 1.68.
These preliminary data do not imply that all young women with DCIS should undergo mastectomy, Dr. Kong cautioned. More research is needed to understand why young women had higher recurrence rates and to determine whether radiation boost, tamoxifen, or other treatments might be optimal for these patients. There may be a positive family history or genetic reasons for their DCIS, a correlation between breast density and higher recurrence rates, or other factors that deserve study, she said.
“I agree,” said Dr. Lori Pierce, moderator of the press briefing and professor of radiation oncology at the University of Michigan, Ann Arbor. “These are very important data, but we need to put them in context. When facing a young woman with DCIS, we need to make sure the margins are negative, and make sure the tumor is estrogen receptor positive if you discuss tamoxifen,” she explained. “Patients should be aware [of these data], but in the context of the limitations of a population-based study.”
The study design did not allow the capture of all treatment information that could have affected outcomes, such as the size of the DCIS, disease at margins, or the use of tamoxifen therapy, she said.
Overall, 88% of women remained free of local recurrence after 5 years, and 81% after 10 years. In addition, 95% of women at 5 years and 93% at 10 years were free of invasive local recurrence.
The investigators looked at follow-up data for a median of 8.5 years after diagnosis, and linked administrative databases to identify treatment and outcomes, followed by abstraction of primary charts for validation of the data.