An Important Question in Adjuvant Hormonal Treatment of Breast Cancer Has Been Answered

In postmenopausal women with hormone-sensitive breast cancer, preventive (adjuvant) treatment to reduce recurrence using 3 different aromatase enzyme blockers was investigated for the first time in a direct comparative study to see whether any was superior.

The study, Lancet Oncologypublished it on 23 February 2018, involving postoperative hormone receptor-positive breast cancer in 3697 patients enrolled between 9 March 2007 and 31 July 2012 at 76 Italian oncology centers. Participants were randomized to one of six treatment groups commonly preferred in oncology practice.

-Related Topic:  Types of Hormonal Treatment in Breast Cancer

The Italian research team reported that, in the first direct comparison of three adjuvant aromatase inhibitors used for postmenopausal hormone receptor-positive early-stage breast cancer, no significant differences in clinical efficacy or safety were found.

The three commonly used breast cancer hormone treatments, letrozole (Femara), anastrozole (Arimidex) and exemestane (Aromasin), were tested in an open-label study randomizing 3700 women, the phase 3 FATA-GIM3 clinical study. At 5 years, recurrence-free survival was %90 in anastrozole-treated patients, %88 in exemestane-treated patients and %89.4 in letrozole-treated patients.

No unexpected serious side effects potentially related to any of the three drugs or treatment-related deaths were identified. More than %50 of patients were overweight or obese , but no differences were observed between patient subgroups.

The study also tested another strategy used in routine practice: 2 years of tamoxifen followed by 3 years of one of these three drugs was compared with 5 years of these drugs alone. In this respect too, the study clarified an important uncertainty and found no difference in treatment efficacy. Over 5 years, musculoskeletal side effects were more frequent with 5 years of the three medicines called aromatase inhibitors, whereas patients receiving 2 years of tamoxifen followed by 3 years of an aromatase inhibitor had fewer muscle and skeletal side effects.

The study shows that both strategies are statistically similar and clinically appropriate.

At the end of the study, researchers emphasized:

• that tamoxifen remains a good option,
• that patient preferences should also be considered in choosing treatment for this group, and
• that choosing among the three drugs or switching one for another because of side effects would not cause a disadvantage.

A total of 1847 participants began directly with one of the three aromatase inhibitors and continued for 5 years. Over those 5 years, they received once-daily oral anastrozole 1 mg, exemestane 25 mg or letrozole 2.5 mg. A total of 1850 patients starting directly with tamoxifen received 2 years of tamoxifen 20 mg/day followed by 3 years of once-daily oral anastrozole 1 mg, exemestane 25 mg or letrozole 2.5 mg.

Early discontinuation due to side effects occurred in % 11 of tamoxifen-treated patients versus % 7 of aromatase inhibitor-treated patients. In those receiving tamoxifen followed by an aromatase inhibitor, early discontinuation was around %5.

This study is highly valuable for clarifying an important uncertainty in preventive hormonal treatment strategies for postmenopausal hormone-positive patients who have undergone breast cancer surgery. Science continues to offer our patients new light every day.

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