Globally, ovarian cancer causes 206,956 deaths each year [1]. It has often spread beyond the pelvis by the time it is diagnosed, and, as a result, five-year survival is below 50 % [2]. It is thus important to identify factors that might improve survival in women with ovarian cancer.

Common heart/hypertension medications, including those that lower blood pressure through their effect on the renin-angiotensin system (RAS) antagonists, may have anti-cancer properties. In vitro studies have shown that overexpression of ACE and angiotensin II receptors, critical elements in the RAS pathway, is associated with increased tumor growth, metastasis, and progression [3], [4] and that ACE inhibitors and angiotensin receptor blockers (ARB) can inhibit these processes and tumor-associated angiogenesis [5]. The limited number of population-based studies largely support the preclinical data, reporting better survival among cancer patients who used hypertension medications, particularly RAS antagonists and beta-blockers; however, recent reviews have identified a high risk of immortal-time bias in previous reports [6], [7], [8]. Immortal-time bias occurs when unexposed time between the start of follow-up and initiation of exposure is included as exposed time and, if ignored, could wrongly suggest a benefit associated with use [9].

We studied the association between the use of ARBs or ACE inhibitors and ovarian cancer survival. We also included beta-blockers and calcium channel-blockers as preclinical studies suggest they may also have anti-cancer properties [10], [11], [12], [13], [14], and they are often used concurrently with renin-angiotensin system antagonists. We paid particular attention to minimizing bias, particularly immortal-time bias and confounding.