A new study published in the Canadian Journal of Cardiology found considerable evidence that using oestrogen blockers, namely aromatase inhibitors (AIs), does not raise the risk of coronary heart disease (CHD) in postmenopausal breast cancer survivors. This study sheds light on the long-term health of these patients, reducing concerns about potential cardiovascular side effects associated with protracted AI medication.

Oestrogen is known to play a role in cardiovascular health; thus, healthcare practitioners are concerned about the long-term repercussions of inhibiting oestrogen production in breast cancer patients. Postmenopausal women with hormone receptor-positive breast cancer frequently receive aromatase inhibitors, which function by decreasing oestrogen levels, thereby lowering the likelihood of cancer recurrence. However, past research has revealed that these inhibitors may hasten coronary atherosclerosis, a key cause of CHD. 

Dr. Yu Hiasa of Ehime University Graduate School of Medicine in Japan led the latest study, which addresses these concerns. The study investigated whether extended use of AIs promotes coronary artery calcification (CAC), a critical indication of coronary atherosclerosis. Strong links exist between CAC and an increased risk of unfavourable cardiovascular events such as angina and heart attacks.

"Although there is an ongoing discussion about the optimal duration of aromatase inhibitor therapy (5 years or 10 years), our data suggest that longer aromatase inhibitor use is safe, at least in terms of coronary artery calcification," said Dr Hiasa, allaying concerns that prolonged oestrogen suppression could harm heart health. 

The study included 357 postmenopausal breast cancer patients who began adjuvant AI therapy between August 2010 and October 2022. Researchers used a visual ordinal scoring system to quantify CAC levels while accounting for patient-specific risk factors such as age, hypertension, and diabetes. Even in patients diagnosed with coronary artery calcification before the trial, their findings showed no significant relationship between the length of AI therapy and the severity of CAC.

Dr. Akinori Higaki, co-investigator at Ehime University, emphasized that other illnesses, such as osteoporosis, were also unrelated to changes in CAC scores. "Our analysis of the postoperative breast cancer patient cohort revealed that the duration of treatment with aromatase inhibitors and the presence of osteoporosis were not associated with coronary artery calcification," Dr Higaki said. 

In addition to validating the cardiovascular safety of AI treatment, the study discovered a new risk factor for CAC: low haemoglobin. While well-known risk factors like age, hypertension, and diabetes remain important, the discovery of anaemia as an independent risk factor emphasises the need for improved screening practices for postmenopausal women undergoing AI medication. 

In an accompanying editorial, Dr. Ibrahim Alfaris of Stanford University School of Medicine emphasised the significance of this finding, stating, "Identifying low haemoglobin as a novel, highly significant risk factor for coronary artery calcification in this population raises the possibility of adding anaemia as an indication for cardiovascular screening." 

The study's findings are a crucial step towards safe long-term treatment of breast cancer survivors, who are already predisposed to cardiovascular disease due to anti-oestrogen medication. According to Dr. Alfaris, "understanding the association between the duration of aromatase inhibitor treatment and the severity of coronary artery calcification in postoperative breast cancer patients is crucial, as it impacts the long-term health management of breast cancer survivors."