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Most women with ductal carcinoma in situ (DCIS) had a significantly lower risk of invasive breast cancer after surgery, with or without radiation therapy (RT), as compared with no treatment, a large retrospective study showed.

Among women up to 69 years old, breast-conserving surgery (BCS) alone or with RT (BCSRT) reduced the risk of ipsilateral invasive recurrence by 62-87%. Women 70 or older had a numerically lower rate of recurrence, but the difference did not achieve statistical significance.

The overall risk of invasive recurrence was low across all age groups, reported Susie X. Sun, MD, of the University of Texas MD Anderson Cancer Center in Houston, and co-authors in .

"Our findings also indicate that BCS or BCSRT may not decrease future risk of ipsilateral invasive disease in women aged ≥70 years, thereby raising concerns of overtreatment in this age group," the researchers wrote. "This finding is likely attributable to the competing risks of death prior to developing invasive cancer. Several ongoing international randomized trials are currently evaluating active surveillance versus BCS or BCSRT in low-risk DCIS; however, it will take several more years before results become available."

"Given that guideline-concordant treatment of BCS or BCSRT among elderly women may lead to operative complications, impaired quality of life, and substantial healthcare costs, consideration should be given towards the study of active surveillance as an alternative approach to the management of low-risk DCIS," the team said.

Increased availability and participation in mammographic screening has led to more diagnoses of DCIS. Several studies have shown that untreated DCIS confers a risk of invasive breast cancer of 30-50% and is ongoing even 20 years after diagnosis, the authors noted.

Using data from the NCI Surveillance, Epidemiology, and End Results registry program, the investigators compared the risk of ipsilateral invasive breast cancer after no treatment for low-risk DCIS versus surgical excision with or without RT. They stratified outcomes by age because DCIS incidence is highest among women ≥60 and the risk of progression likely differs because of competing mortality risks.

The analysis covered the years 1992 to 2017 and was limited to women with newly diagnosed low- or intermediate-grade hormone receptor-positive DCIS. The study included 21,760 patients. Age stratification showed that 22.4% were younger than 50, 55.1% were 50-69, and 22.5% were ≥70. Low-grade disease accounted for 30.2% of the DCIS diagnoses and intermediate-grade disease for 67.8%.

Overall, 604 (2.8%) of the patients had no locoregional treatment, 8,005 (36.8%) had surgery alone, and 13,151 (60.4%) had surgery plus RT.

Among women <50, 7.26% developed invasive breast cancer after receiving no initial treatment, as did 5.15% of the 50-69 age group, and 2.4% of the patients ≥70.

For the youngest cohort, surgery alone reduced the risk of invasive breast cancer by 79% (95% CI 0.10-0.44) versus no treatment, and the addition of RT resulted in an 87% reduction in the hazard (95% CI 0.07-0.27). Among women 60-69, surgery reduced the hazard for invasive recurrence by 62% (95% CI 0.21-0.69) and surgery plus RT reduced the hazard by 85% (95% CI 0.08-0.27).

Women in the oldest age group had a 14% reduction in the hazard for invasive breast cancer with surgery alone and a 49% reduction with BCSRT, but neither difference achieved statistical significance (95% CI 0.34-2.16, 0.20-1.31, respectively).

The authors acknowledged that the registry-based data did now allow them to account for use of endocrine therapy, and that additional studies are needed to determine the optimal age for active surveillance after diagnosis of low-risk DCIS.

The study addressed an issue that has attracted considerable attention in the breast cancer community, according to Virginia Kaklamani, MD, of the Mays Cancer Center/UT San Antonio Health MD Anderson Cancer Center.

"Interestingly in older women the option of no treatment was not associated with worse outcomes," she told 木瓜直播 via email. "The limitation of this study is that this is not a randomized clinical trial so there are several biases that may have altered the results. However there are clinical trials being conducted worldwide looking at no treatment for women with low- and intermediate-grade DCIS. The thought from the medical community is that we are currently overtreating these women."

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