SAN ANTONIO — Patients with low- to intermediate-grade ductal carcinoma in situ had an “acceptably low” 5-year local recurrence rate of 6% following excision without radiation therapy in a large prospective study, Dr. Lorie Hughes said at a breast cancer symposium sponsored by the Cancer Therapy and Research Center.
In contrast, the ipsilateral recurrence risk without radiotherapy jumped to 15% in women with high-grade ductal carcinoma in situ. That's a rate many physicians and patients would consider unacceptably high, added Dr. Hughes, a surgeon at Emory University, Atlanta.
Surgical excision and adjuvant radiotherapy has been considered the standard in breast-conserving therapy for ductal carcinoma in situ because randomized, controlled trials have demonstrated that irradiation reduces the local recurrence risk by 50%–75%, compared with excision alone. But many patients and physicians have wondered whether all women with DCIS truly need to undergo the expense, inconvenience, and risks of side effects entailed in radiotherapy.
Dr. Hughes presented the 5-year results of a National Cancer Institute-sponsored multicenter, prospective, observational study known as E5194. The study was designed to learn if a subgroup of ductal carcinoma in situ patients at low risk for local failure following excision without radiotherapy could be defined based on tumor grade, extent, and surgical margins.
The study involved two groups. One consisted of 572 women with low- to intermediate-grade DCIS no more than 2.5 cm in diameter and a minimum surgical margin of 3 mm. The other included 99 patients with high-grade ductal carcinoma in situ at nuclear grade 3, with 2–3 mm of necrosis and 1 cm or less in size.
All participants underwent local excision without radiotherapy. Their median age was 60 years. Median tumor size was 6 mm in the low- to intermediate-grade group and 7 mm in the high-grade group.
Two-thirds of women in the low- to intermediate-grade group and three-quarters in the high-grade group had surgical margins of 5 mm or more.
The 6% ipsilateral recurrence rate at 5 years in the low- to intermediate-grade group involved invasive lesions in 52% of cases and DCIS only in 48%. The rate of new events in the contralateral breast was 4%.
Similarly, about half of the 15% ipsilateral recurrences in the high-grade group were invasive. The rate of new events in the opposite breast was 4%.
The 5-year relapse-free survival rate was 85% in women with low- to intermediate-grade ductal carcinoma in situ and 79% in those with high-grade lesions.
Adjuvant tamoxifen was taken by 31% of patients in each study arm. Their ipsilateral recurrence rate wasn't significantly different from that of patients who didn't take tamoxifen, in contrast to what has consistently been seen in placebo-controlled, randomized trials. However, this wasn't a randomized trial, and there was certainly room for selection bias among physicians and patients regarding who would receive the selective estrogen-receptor modulator, Dr. Hughes noted.
The investigators plan to follow the study participants for 10 years.