Tamoxifen or Anastrozole for DCIS? Age and Symptom Profiles Matter

Jack Cuzick, PhD

San Antonio Breast Cancer Symposium

Tamoxifen and anastrozole are similarly effective in preventing breast cancer recurrence in postmenopausal women with ductal carcinoma in situ (DCIS). The choice depends on patient preferences, side effect profiles, age, and other patient factors, according to separate studies presented at the 2015 San Antonio Breast Cancer Symposium.

In the large, placebo-controlled IBIS-II trial, 2980 postmenopausal women with DCIS were randomized to tamoxifen versus anastrozole. At a median follow-up of 7.2 years, there was no significant difference between these hormonal therapies in preventing recurrence after DCIS.

A substudy of the large, randomized NSABP B-35 trial compared patient-reported outcomes in 1193 postmenopausal women with DCIS treated with tamoxifen versus anastrozole. Again, either hormonal agent proved to be a good option for preventing breast cancer recurrence, but the symptom profiles of these agents differed, and this information should be incorporated in treatment selection.

Younger women (<60 years) seem to have fewer side effects of concern on anastrozole, and tamoxifen seems to be a better choice for women ≥60 years of age. 

IBIS-II Study Details

In this study, the rate of recurrence for all breast cancers (including invasive cancers and DCIS) was 7.4% for tamoxifen versus 6.6% for anastrozole at a median follow-up of 7.2 years, representing 11% fewer recurrences with anastrozole. The difference was not statistically significant. There were 67 cancers reported in the anastrozole group versus 77 in the tamoxifen group.

An exploratory post hoc subgroup analysis of rate of invasive breast cancers suggested that tamoxifen was superior for estrogen receptor–positive (ER+)/HER2+ DCIS, whereas anastrozole seemed to have a better effect in HER2– and ER+/HER2– patients.

“There is no clear difference between these agents in efficacy, but there were significant differences in toxicity profiles,” said lead author Jack Cuzick, PhD, Head of the Centre for Cancer Prevention and Director of Wolfson Institute of Preventive Medicine, Queen Mary University of London, UK. “Anastrozole is another agent to be considered for ER+ DCIS for women who can’t take tamoxifen because of a history of deep vein thrombosis or other factors.”

Adverse events more frequently reported with anastrozole included fracture and joint-related symptoms, while vasomotor and gynecologic symptoms (except vaginal dryness) were more frequently reported with tamoxifen.

Cardiovascular events, specifically stroke and transient ischemic attack, occurred more frequently in the anastrozole group; there were 13 strokes and 13 transient ischemic attacks compared with 4 and 5, respectively, in the tamoxifen group. Cuzick believes this is probably a “chance” finding, but said further study is needed.

NSABP B-35 Quality of Life

Previously reported results from NSABP B-35 showed that anastrozole was slightly better than tamoxifen in preventing recurrence in postmenopausal women with DCIS. The 10-year breast cancer–free interval rate was 89.2% for tamoxifen and 93.5% for anastrozole (P = .03). An interaction with age was observed, with significantly better results for anastrozole versus tamoxifen in patients younger than 60 years (94.9% vs 88.2% for tamoxifen; P = .04), whereas the rate of breast cancer–free interval was not significantly different for those older than 60 years: 92.2% versus 90.2%, respectively.

A separate analysis of quality of life (QOL) was undertaken in 1193 women enrolled in the trial to assess patient-reported outcomes using a battery of 5 validated QOL instruments in the hope of revealing the “real-life” experiences of women taking these agents. Patients were treated with tamoxifen (n = 601) or anastrozole (n = 592) for 4 years. About 53% were aged 60 years and older and about 47% were younger than 60 years.

Anastrozole significantly improved QOL in women younger than 60 years (P = .04), but there was no significant QOL benefit for either drug in women aged 60 years and older.

“Both drugs are well tolerated in patients with DCIS, but younger women under age 60 experience greater severity of some symptoms. The symptom profiles of both drugs differ in expected directions,” said lead author Patricia Ganz, MD, Director of the Center for Cancer Prevention & Control Research at the University of California Los Angeles Jonsson Comprehensive Cancer Center.

Vasomotor symptoms, bladder control, and gynecologic symptoms were significantly increased in the tamoxifen-treated group, while anastrozole-treated patients had significantly increased severity of musculoskeletal and vaginal symptoms compared with tamoxifen. Patients younger than 60 years had worse vasomotor and vaginal symptoms on either hormonal agent.

“With this kind of information on patient-reported outcomes in women with DCIS, patients and their physicians can now make personalized decisions on which of these two effective agents to select,” she told listeners at a press conference.

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