The chance that a case of ductal carcinoma in situ (DCIS) will recur locally in 10 years — either as DCIS or invasive cancer — might depend on the quality of the surgical procedure, new research indicates.
In a study of 720 women with DCIS, when the excision was "inadequate" (resulted in a margin of less than 1 mm), as it was in 124 women, the 10-year recurrence rate was 51% for low-grade disease and 70% for high-grade disease.
However, when the excision was "adequate" (resulted in a margin of at least 1 mm), as it was in 596 women, the 10-year recurrence rate was much lower: 13% for low-grade disease and 35% for high-grade disease.
Notably, only 5% of the low-grade recurrences at 10 years were invasive disease.
All of the patients in the study were treated with surgery alone; radiation was not used, said lead investigator Sadia Khan, DO, from the Hoag Memorial Hospital Presbyterian in Newport Beach, California.
She presented the study during a presscast yesterday held in advance of the 17th Annual Meeting of the American Society of Breast Surgeons.
Grade 1 and 2 DCIS was considered low grade, and grade 3 DCIS was considered high grade.
At 10 years, there was only one breast-cancer-related death in the study population, including the patients who had inadequate surgery.
Mean tumor size was 17 mm, mean age was 55 years, and mean follow-up was 79 months.
For their study, Dr Khan and her colleagues retrospectively examined a database of "pure" DCIS (no invasion or microinvasion) collected from three institutions, including Hoag Memorial.
Notably, all patients with margins less than 1 mm were advised to undergo re-excision but refused further treatment.
The group of 124 inadequately treated patients served as a "surrogate" for the management approach of no treatment or surveillance, the investigators explain. The idea is that if a patient is inadequately treated, it is on par with no treatment.
In terms of recurrence, these surrogate surveillance patients compared unfavorably with the 596 patients who were adequately treated, as noted above in the comparison between the inadequate and adequate groups.
Moreover, actual surveillance patients "will likely do worse" than this surrogate group because they would not benefit from surgery, even if it is an inadequate procedure, said Dr Khan. Thus, the surrogate group is a cautionary tale for patients considering the watch-and-wait approach to DCIS, she suggested.
"Women frequently come into our practice and say they have read that DCIS does not require treatment," Dr Khan said in a press statement.
But active surveillance is an out-of-bounds management approach, she told reporters.
"Doing a needle biopsy and just watching somebody with a mammogram is, at this point, inappropriate and unacceptable," she declared.
"We may be overtreating some women with DCIS," continued Dr Khan, "but we don't understand the biology of the disease enough to say which patients we're overtreating and which patients we are saving from invasive breast cancer."
There are clinical trials underway in Europe and the United States that are evaluating active surveillance for DCIS, reported presscast moderator Julie Margenthaler, MD, from Washington University in St Louis, Missouri.
"We would recommend that surgeons and patients use caution [when using] observation-only outside of a clinical trial," she said.
17th Annual Meeting of the American Society of Breast Surgeons: Scientific Session Oral Presentations Part I. Presented April 15, 2016.