Table 5 Definitions of outcomes for each study included in the systematic review

 Berrino et al. (2005) [20]

Recurrence (local relapse, distant metastasis, contralateral breast cancer)

Local relapse, distant metastasis, contralateral breast cancer occurred over 5.5 years of follow-up

 Pasanisi et al. (2006) [21]

Recurrence (local relapse, distant metastasis, contralateral breast cancer)

Local relapse, distant metastasis, contralateral breast cancer occurred over 5.5 years of follow-up

 Pasanisi et al. (2008) [22]

Recurrence (local relapse, distant metastasis, contralateral breast cancer)

Local relapse, distant metastasis, contralateral breast cancer occurred over 5.5 years of follow-up

 Berrino et al. (2014) [23]

Recurrence (loco-regional recurrences, distant metastasis and new primary breast cancer) and breast cancer mortality

Loco-regional recurrences, distant metastasis and new primary breast cancer, and deaths due to breast cancer occurred over a median of 2.8 years of follow-up

 Vasson et al. (2020) [24]

Disease-free survival (absence of local or distant (nodes, metastasis, and/or contralateral breast cancer))

Disease-free interval was computed as months elapsed from date of randomization to documented breast cancer recurrence during 7 years after breast cancer treatment completion. All recurrence types were considered, either local or distant (nodes, metastases, and/or contralateral breast cancer)

 Emond et al. (2011) [25]

Recurrence (local, regional, or distant, or new primary events)

Events were defined as local, regional, or distant recurrence, or new primary; the WHEL study did not include ductal carcinoma in situ or lobular carcinoma in situ as events. Time to outcome was date of randomization to date of additional event. Women who did not have an additional event were assessed for outcome at the date of last contact or study end (June 1, 2006). Women who died due to conditions unrelated to breast cancer were assessed for outcome at the date of death. WHEL further excluded women who had a breast cancer recurrence within the first year of study enrollment

 Al-Delaimy et al. (2011) [26]

Breast cancer event (recurrent/new primary breast cancer event)

Reported breast cancer recurrence or new primary breast cancer diagnosed after study enrollment

 Villaseñor et al. (2013) [27]

Additional breast cancer events (recurrence or new primary breast cancer) and breast cancer mortality

Women were followed during the follow-up for vital status, from study entry until end of study, June 1, 2006

All-cause mortality