Adjuvant Hormone Therapy with Anastrozole
Anastrozole is an aromatase inhibitor commonly used as adjuvant hormone therapy for postmenopausal women with early-stage, hormone receptor-positive breast cancer
Benefits and Risk Reduction:
– Anastrozole significantly reduces the risk of breast cancer recurrence. The IBIS-II trial showed a 49% reduction in breast cancer incidence with anastrozole compared to placebo after a median follow-up of 131 months
– The risk reduction was larger in the first 5 years (61% reduction) but remained significant even after 5 years (37% reduction)
– Invasive estrogen receptor-positive breast cancer was reduced by 54%
– After 12 years of follow-up, the estimated risk of developing breast cancer was 5.3% in the anastrozole group compared to 8.8% in the placebo group
-The number needed to treat for 5 years to prevent one breast cancer was 29
Common side effects of anastrozole include:
Bone pain, Joint pain, Muscle pain, Hot flashes, Headache, Dizziness, Fatigue
More serious but less common side effects may include:
Increased risk of osteoporosis and fractures, Cardiovascular issues (though no excess was observed in long-term studies), Mood changes, Vaginal dryness or bleeding
It’s important to note that the IBIS-II trial found no excess of fractures or cardiovascular disease with anastrozole use
Role of Adjuvant Radiation Therapy
For stage 1 ER-positive breast cancer with a negative sentinel node biopsy, the role of adjuvant radiation therapy depends on the type of surgery performed:
- After lumpectomy (breast-conserving surgery):
– Whole-breast irradiation is typically recommended to reduce the risk of local recurrence
– In some cases, partial-breast irradiation may be considered for early-stage breast cancers
For patients over 70 years old with early-stage, ER-positive breast cancer, some studies have explored omitting radiation therapy in favor of hormone therapy alone, especially for those with smaller tumors and other favorable prognostic factors
References
[1] Cuzick J, Sestak I, Forbes JF, Dowsett M, Cawthorn S, Mansel RE, Loibl S, Bonanni B, Evans DG, Howell A; IBIS-II investigators. Use of anastrozole for breast cancer prevention (IBIS-II): long-term results of a randomised controlled trial. Lancet. 2020 Jan 11;395(10218):117-122. doi: 10.1016/S0140-6736(19)32955-1. Epub 2019 Dec 12. Erratum in: Lancet. 2020 Feb 15;395(10223):496. doi: 10.1016/S0140-6736(20)30323-8. Erratum in: Lancet. 2021 Feb 27;397(10276):796. doi: 10.1016/S0140-6736(21)00427-X. PMID: 31839281; PMCID: PMC6961114.
[2] https://www.thelancet.com/journals/lancet/article/PIIS0140-6736%2819%2932955-1/fulltext