Contralateral breast cancer uncommon among women with ductal carcinoma in situ

Fewer than 6% of women with ductal carcinoma in situ developed contralateral breast cancer within 10 years, according to study results presented at the American Society of Breast Surgeons Annual Meeting.

Contralateral breast cancer incidence did not appear associated with age, family history or characteristics of initial ductal carcinoma in situ (DCIS), nor did it appear associated with factors that increase ipsilateral breast tumor recurrence.

“Overall survival after treatment for DCIS is excellent, yet many patients overestimate their risk for local recurrence and for contralateral breast cancer, potentially leading to a decision in favor of bilateral mastectomy,” Megan Miller, MD, breast fellow at Memorial Sloan Kettering Cancer Center, said during a press conference. “... Few studies have examined the risk for contralateral breast cancer after DCIS, particularly in women treated with breast-conserving surgery. Further, little data exists on factors associates with contralateral breast cancer following DCIS.”

Therefore, Miller and colleagues conducted their study to quantify the rate of contralateral breast cancer among women with DCIS who underwent breast-conserving surgery; compare risk for contralateral breast cancer with that of ipsilateral breast tumor recurrence; identify factors associated with contralateral breast cancer risk; and evaluate whether those risk factors were the same as those for ipsilateral breast tumor recurrence.

The researchers used a prospectively maintained database to identify 2,759 women with DCIS who underwent breast-conserving surgery from 1978 to 2011 and had a contralateral breast at risk. Investigators excluded women who had contralateral breast cancer prior to or synchronous with their index DCIS diagnosis, as well as those who had synchronous contralateral breast cancer and ipsilateral breast tumor recurrence.

First breast event — either contralateral breast cancer or ipsilateral breast tumor recurrence, defined as diagnosis of invasive cancer or DCIS — served as the primary outcome.

Miller and colleagues used cumulative incidence curves and competing risk regression to evaluate whether patient, tumor and treatment factors were associated with contralateral breast cancer or ipsilateral breast tumor recurrence.

Median follow-up was 6.8 years (range, 0-30), and 645 women were followed for at least 10 years.

During follow-up, 328 (11.9%) of women developed ipsilateral breast tumor recurrence and 127 (4.6%) developed contralateral breast cancer as their first breast event.

Researchers reported higher cumulative incidence of ipsilateral breast tumor recurrence than contralateral breast cancer at 5 years (7.8% vs. 2.8%) and 10 years (14.3% vs. 5.6%).

Univariate analysis showed premenopausal women were more likely than postmenopausal women to develop ipsilateral breast tumor recurrence at 10 years (17.4% vs. 12.7%; P = .001). Results showed no significant difference in contralateral breast cancer rates at 10 years between premenopausal and postmenopausal women (5.5% vs. 5.7%).

PAGE BREAK

Rates of ipsilateral breast tumor recurrence at 10 years were higher among women aged younger than 40 years (26.3%) than those aged 40 to 79 years (13.9%) and those aged 80 years or older (6.7%; P = .0008). However, researchers reported no significant difference in contralateral breast cancer incidence at 10 years between those age groups.

Women who presented with clinical findings — such as nipple discharge, Paget disease or a palpable mass — were more likely than those with screen-detected disease to experience ipsilateral breast tumor recurrence at 10 years (20.1% vs. 13.5%; P = .001). However, they were less likely to develop contralateral breast cancer by that time (2.3% vs. 6.1%; P = .01).

Neither nuclear grade nor family history of breast cancer appeared significantly associated with ipsilateral breast tumor recurrence or contralateral breast cancer.

Women treated in 1999 or later appeared significantly less likely than those treated in 1998 or earlier to develop ipsilateral breast tumor recurrence at 10 years (12.9% vs. 19.3%; P < .0001); however, results showed no significant association between treatment year and contralateral breast cancer incidence at 10 years.

Women treated with endocrine therapy appeared half as likely as those who did not receive endocrine therapy to develop ipsilateral breast tumor recurrence at 10 years (7.8% vs. 16.3%; P < .0001). Endocrine therapy also reduced risk for contralateral breast cancer at 10 years (3.2% vs. 6.4%), but the difference did not reach statistical significance.

Women who received radiation therapy were half as likely as those who did not receive radiation to develop ipsilateral breast tumor recurrence at 10 years (10.3% vs. 19.3%; P < .0001); however, contralateral breast cancer rates at 10 years did not vary significantly based on radiation receipt (6.3% vs. 4.9%).

Multivariable analysis identified several factors associated with reduced risk for ipsilateral breast tumor recurrence. They included postmenopausal status, radiographic diagnosis, diagnosis in 1999 or later, low nuclear grade, and receipt of endocrine therapy or radiation therapy.

Researchers identified no factors significantly associated with risk for contralateral breast cancer.

“For a woman undergoing breast-conserving surgery for DCIS, the 10-year ipsilateral breast tumor recurrence rate is 2.5-fold higher than the contralateral breast cancer rate,” Miller and colleagues wrote. “For a woman not receiving radiation therapy, the ipsilateral breast tumor recurrence rate is 4-fold higher than the contralateral breast cancer rate. Identification of factors associated with higher ipsilateral breast tumor recurrence risk may be important in decision-making between breast-conserving surgery and unilateral mastectomy, but should not prompt contralateral prophylactic mastectomy for DCIS.” – by Mark Leiser

Reference: Miller M, et al. Contralateral breast cancer (CBC) risk in women with ductal carcinoma in situ (DCIS): Is it high enough to justify bilateral mastectomy? Presented at: The American Society of Breast Surgeons Annual Meeting; April 26-30, 2017; Las Vegas.

Disclosure: Miller reports no relevant financial disclosures.