Use of calcium-channel blockers for 10 years or more is associated with a greater than two-fold risk of breast cancer, claim researchers.
The eight-year US study included 1,900 post-menopausal women between 55 and 74 years with breast cancer, and 856 controls without breast cancer. The researchers measured antihypertensive medication use for ≥6 months and whether women were currently using them within six months of their reference date (the date each woman was diagnosed with breast cancer). Additionally, the researchers assessed risks associated with different sub-classes of calcium-channel blockers.
Current, former, and short-term use of antihypertensives was not associated with risk of breast cancer. Use of calcium-channel blockers for ≥10 years was associated with over a two-fold increased risk of invasive ductal carcinoma (240%) and invasive lobula carcinoma (260%) compared with patients who had never taken antihypertensive medication. The relationship between calcium-chanel blocker and risk of breast cancer did not vary appreciably by the subclass of drug used (short-acting vs long-acting, dihydropyridines vs non-dihydropyridines) or oestrogen-receptor status. In contrast, use of diuretics, β-blockers, and angiotensin II antagonists were not associated with any increased risk of breast cancer compared with compared with patients who had never taken antihypertensive medication. There was also some indication that current use of ACE inhibitors for ≥10 years was associated with reduced risks of both invasive ductal carcinoma and invasive lobula carcinoma, by 30% and 40% respectively.
What this means for GPs
The researchers note that their results ‘suggest that long-term current use of calcium-channel blockers is associated with an increased risk of both invasive ductal carcinoma and invasive lobula carcinoma’ and that ‘these associations do not vary according to oestrogen receptor status’. The researchers suggest that ‘quantification of the potential relationships between use of these medications and breast cancer risk has the potential to aid clinical decision making regarding selection of antihypertensive agents for patients with hypertension, as the benefits and risks of potential medications are weighed.’