The optimal mammography screening strategy for women aged 45–49 years is a matter of debate. We present the RIBBS study protocol, a quasi-experimental, prospective, population-based study comparing a risk- and breast density-stratified screening model (interventional cohort) with annual digital mammography (DM) screening (observational control cohort) in a real-world setting. The interventional cohort consists of 10,269 women aged 45 years enrolled between 2020 and 2021 from two provinces of the Veneto Region (northen Italy). At baseline, participants underwent two-view digital breast tomosynthesis (DBT) and completed the Tyrer-Cuzick risk prediction model. Volumetric breast density (VBD) was calculated from DBT and the lifetime risk (LTR) was estimated by including VBD among the risk factors. Based on VBD and LTR, women were classified into five subgroups with specific screening protocols for subsequent screening rounds: (1) LTR ≤ 17% and nondense breast: biennial DBT; (2) LTR ≤ 17% and dense breast: biennial DBT and ultrasound; (3) LTR 17–30% or LTR > 30% without family history of BC, and nondense breast: annual DBT; (4) LTR 17–30% or > 30% without family history of BC, and dense breast: annual DBT and ultrasound; and (5) LTR > 30% and family history of BC: annual DBT and breast MRI. The interventional cohort is still ongoing. An observational, nonequivalent control cohort of 43,000 women aged 45 years participating in an annual DM screening programme was recruited in three provinces of the neighbouring Emilia-Romagna Region. Cumulative incidence rates of advanced BC at three, five, and ten years between the two cohorts will be compared, adjusting for the incidence difference at baseline.

Trial registration This study is registered on Clinicaltrials.gov (NCT05675085).

45-49 岁女性的最佳乳房 X 光检查策略仍存在争议。我们提出了 RIBBS 研究方案，这是一项准实验性、前瞻性、基于人群的研究，在真实的环境中将风险和乳腺密度分层筛查模型（干预队列）与年度数字乳房 X 线摄影 (DM) 筛查（观察控制队列）进行比较。世界设定。干预队列由 2020 年至 2021 年间来自威尼托大区（意大利北部）两个省份的 10,269 名 45 岁女性组成。在基线时，参与者接受了双视图数字乳腺断层合成 (DBT) 并完成了 Tyrer-Cuzick 风险预测模型。根据 DBT 计算乳腺体积密度 (VBD)，并通过将 VBD 纳入危险因素来估计终生风险 (LTR)。根据VBD和LTR，将女性分为五个亚组，并为后续轮次筛查制定了具体的筛查方案：（1）LTR≤17%和非致密乳腺：每两年进行一次DBT； (2) LTR≤17%且致密乳腺：每两年DBT和超声检查； (3) LTR 17–30% 或 LTR > 30%，无 BC 家族史，且乳腺非致密：每年 DBT； (4) LTR 17–30% 或 > 30%，无 BC 家族史，且乳腺致密：每年进行 DBT 和超声检查； (5) LTR > 30% 和 BC 家族史：每年进行 DBT 和乳腺 MRI。干预队列仍在进行中。在邻近的艾米利亚-罗马涅大区的三个省份招募了一个由 43,000 名 45 岁女性组成的观察性非等效对照队列，参与年度糖尿病筛查项目。将比较两个队列之间三年、五年和十年的晚期 BC 的累积发病率，并调整基线的发病率差异。

试验注册本研究已在 ClinicalTrials.gov 上注册 (NCT05675085)。