Table 4.

Change in mammographic density among women treated with tamoxifen and breast cancer outcomes: current evidence

Study (location) and publication year	Design	Age range, y	Outcome	No. events/cases among tamoxifen users	Mammogram type	Density measurement method	Main density measure reported	Main association with outcome among tamoxifen users
IBIS-1 (UK/Finland) 2011 (16)	Nested case-control *	30–70	Incident breast cancer	51	Film, mediolateral oblique view	Visual assessment	Absolute change in percent density	≥10% reduction vs no change (Referent) OR = 0.32 (95% CI = 0.14 to 0.72)
Seoul National University (Korea) 2012 (2)	Hospital-based patient cohort	24–77	Loco-regional or distant recurrence	Not reported	Digital, craniocaudal view	Computer-assisted thresholding (Cumulus)	Absolute change in percent density	<5% reduction vs ≥5% reduction (Referent) HR = 1.52 (95% CI = 0.92 to 2.51)
Korea National Cancer Center (Korea) 2013 (3)	Hospital-based patient cohort	25–78	Loco-regional, contralateral or distant recurrence	67	Digital, view not specified	Visual assessment	Change in BI-RADS category	reduction in BI-RADS category (continuous) HR = 0.35 (95% CI = 0.17 to 0.68)
Karolinska Institute (Sweden) 2013 (15)	Patient cohort †	50–74	Breast cancer– specific death	75	Film, mediolateral oblique view	Fully-automated thresholding	Relative change in dense area	>20% reduction vs ≥10% increase (Referent) HR = 0.50 (95% CI = 0.27 to 0.93)
Kaiser Permanente Northwest (USA; current study)	Case-control	32–87	Breast cancer–s pecific death	97	Film, craniocaudal view	Computer-assisted thresholding (Cumulus)	Absolute change in percent density	>8.7% reduction vs <-0.5% reduction (Referent) OR = 0.44 (95% CI = 0.22 to 0.88)

* Sampled from a randomized clinical trial. BI-RADS = Breast Imaging Reporting and Data System; CI = confidence interval; HR = hazard ratio; OR = odds ratio.

† Sampled from a case-control study.