Extending anastrozole therapy by five years provides no benefit over a two-year extension in women with hormone-receptor–positive breast cancer who have already received five years of adjuvant endocrine therapy, new results show.

As well,  the longer duration of treatment was associated with a higher risk of bone fractures (6.3% v 4.7%).

The Secondary Adjuvant Long-Term Study with Arimidex [anastrozole] (SALSA) study, published in the NEJM, comprised more than 3,000 postmenopausal women up to 80 years of age who had previously received five years of either tamoxifen, aromatase inhibitors or both sequentially.

It found disease free survival (73.6% in the 2-year group v 73.9% in the 5-year group) and overall survival (87.5% v 87.3%) were similar in both treatment groups.

Similarly, the hazard ratio for contralateral breast cancer was 1.15 and 1.06 for a second primary cancer.

“At a median follow-up of nearly 10 years (i.e., a median of 15 years after the first diagnosis of breast cancer), we found that a 5-year extension of adjuvant therapy with the aromatase-inhibitor anastrozole was not associated with a better outcome than a 2-year extension with respect to disease-free survival.”

Given the additional risk of fractures, they concluded there was no benefit from prolonged AI therapy in women at average risk for breast cancer recurrence.

They noted that the effect of extended AI treatment on patients’ quality of life was not trivial with musculoskeletal symptoms such as arthralgia and bone and joint pain that may persist for years.

“Although, as expected, the prevalence of these side effects was similar in the two groups in our trial, it is evident that having these sequelae and being at risk for them for 3 additional years was a disadvantage for patients in the 5-year group.”

An Editorial in the journal said the results provide strong evidence against the routine use of more than two years of extended aromatase-inhibitor therapy in women who are at low or average risk.

“It is also important to recognise that patients with breast cancer may have adverse outcomes other than breast cancer recurrence.”

They said lifestyle factors that are associated with breast cancer including obesity, physical inactivity and alcohol consumption, also increase the risk of diabetes and cardiovascular disease.

“The management of such serious conditions, including the involvement of non-oncology practitioners in follow-up care, is likely to improve the overall health of breast cancer survivors.”

The study was funded by AstraZeneca.