In their report, Kim and colleagues study the ability of changes in mammographic density over a period of 12 to 18 months to predict subsequent recurrence in 1,065 Korean women with oestrogen receptor-positive breast cancer. Based on 80 recurrences, a clear gradient for lower recurrence rates was seen among women with larger density reductions - with recurrence rates being more than twofold higher in women with no reduction compared with those presenting a reduction ≥10%. This extends previous work on predicting the effectiveness of tamoxifen in individual women from the preventive setting to the adjuvant setting, and also includes women treated with aromatase inhibitors, where a slightly larger effect was seen.