Long term risk of distant metastasis in women with non‐metastatic breast cancer and survival after metastasis detection: a population‐based linked health records study

Objectives To estimate the long term risk of distant metastases (DM) for women with initial diagnoses of non-metastatic breast cancer; to estimate breast cancer-specific and overall survival for women with DM. Design Population-based health record linkage study. Setting, participants Women diagnosed with localised or regional primary breast cancer recorded in the NSW Cancer Registry, 2001-2002. Major outcome measures Time from breast cancer diagnosis to first DM, time from first DM to death from breast cancer. Secondary outcome: time to death from any cause. Results 6338 women were diagnosed with non-metastatic breast cancer (localised, 3885; regional, 2453; median age, 59 years [IQR, 49-69 years]). DM were recorded (to 30 September 2016) for 1432 women (23%; median age, 62 years [IQR, 51-73 years]). The 14-year cumulative DM incidence was 22.2% (95% CI, 21.1-23.2%; localised disease: 14.3% [95% CI, 13.2-15.4%]; regional disease: 34.7% [95% CI, 32.8-36.6%]). Annual hazard of DM was highest during the second year after breast cancer diagnosis (localised disease: 2.8%; 95% CI, 2.3-3.3%; regional disease: 9.1%; 95% CI, 7.8-10.3%); from year five it was about 1% for those with localised disease, from year seven about 2% for women with regional disease at diagnosis. Five years after diagnosis, the 5-year conditional probability of DM was 4.4% (95% CI, 3.7-5.1%) for women with localised and 10.4% (95% CI, 9.1-12.0%) for those with regional disease at diagnosis. Median breast cancer-specific survival from first DM record date was 28 months (95% CI, 25-31 months); the annual hazard of breast cancer death after the first DM record declined from 36% (95% CI, 33-40%) during the first year to 14% (95% CI, 11-18%) during the fourth year since detection. Conclusions DM risk declines with time from diagnosis of non-metastatic breast cancer, and the annual risk of dying from breast cancer declines with time from initial DM detection. These findings can be used to inform patients at follow-up about changes in risk over time since diagnosis and for planning health services.