Tamoxifen or Anastrozole for DCIS? Age and Symptoms Matter

Phoebe Starr

April 2016, Vol 7, No 3 - Breast Cancer


Anastrozole and tamoxifen are similarly effective in preventing breast cancer recurrence in postmenopausal women with ductal carcinoma in situ (DCIS). The choice should depend on patient preferences, side-effect profiles, age, and other patient factors, according to 2 studies presented at the 2015 San Antonio Breast Cancer Symposium. In the large, placebo-controlled IBIS-II DCIS trial, 2980 postmenopausal women with DCIS were randomized to tamoxifen or to anastrozole. At a median follow-up of 7.2 years, there was no significant difference between the 2 hormonal therapies in the prevention of recurrence after DCIS. A substudy of the large, randomized NSABP B-35 trial compared patient-­reported outcomes in 1193 postmenopausal women with DCIS who received tamoxifen or anastrozole. The results show that either hormonal agent is a good option for the prevention of breast cancer recurrence; however, the symptom profiles of these agents differ, and this information should be incorporated into treatment selection. Younger women (aged <60 years) have fewer side effects as a result of taking anastrozole, and tamoxifen is a better choice for women aged ≥60 years.

IBIS-II DCIS Study Details

In the IBIS-II DCIS study, the rate of recurrence for all breast cancers (including invasive cancers and DCIS) was 7.4% with tamoxifen versus 6.6% with anastrozole, at a median follow-up of 7.2 years, representing 11% fewer recurrences of breast cancer with anastrozole. The difference was not significant. There were 67 recurrent cancers reported in the anastrozole group and 77 in the tamoxifen group. An exploratory post hoc subgroup analysis of the rate of invasive breast cancers suggested that tamoxifen was superior for estrogen receptor (ER)-positive, HER2-positive DCIS, whereas anastrozole had a better effect in patients with HER2-negative disease and in patients with ER-positive, HER2-negative disease. “There is no clear difference between these agents in efficacy, but there were significant differences in toxicity profiles,” said lead investigator Jack Cuzick, PhD, Director, Wolfson Institute of Preventive Medicine, Queen Mary University of London, England. “Anastrozole is another agent to be considered for ER-positive DCIS for women who cannot take tamoxifen because of a history of deep-vein thrombosis or other factors.” Adverse events that were more frequent with anastrozole included fracture and joint-related symptoms; vasomotor and gynecologic symptoms were more frequent with tamoxifen.

NSABP B-35 Quality of Life

The previously reported results of NSABP B-35 showed that anastrozole was slightly better than tamoxifen for preventing the recurrence of breast cancer in postmenopausal women with DCIS. The 10-year breast cancer–free interval rates were 89.2% for tamoxifen and 93.5% for anastrozole (P = .03). Significantly better results were seen for anastrozole than for tamoxifen in patients aged <60 years. A separate analysis of quality of life (QOL) in 1193 women was done to assess patient-reported outcomes using 5 validated QOL instruments. The patients received tamoxifen or anastrozole for 4 years. Anastrozole significantly improved QOL in women aged <60 years but there was no significant QOL benefit for either drug in women aged ≥60 years. “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 investigator Patricia Ganz, MD, Director, Center for Cancer Prevention and Control Research, Jonsson Comprehensive Cancer Center, University of California at Los Angeles. Vasomotor symptoms, bladder control, and gynecologic symptoms were significantly increased in the patients receiving tamoxifen, whereas the patients receiving anastrozole had significantly increased severity of musculoskeletal and vaginal symptoms compared with tamoxifen. The patients aged <60 years had worse vasomotor and vaginal symptoms while receiving 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 2 effective agents to select,” Dr Ganz commented at a press conference.