Table 1. Summary of the letrozole P024, IMPACT and PROACT trials.

	Letrozole P024	IMPACT	PROACT
	Postmenopausal women with HR+ breast cancer
	337 randomised	330 randomised	451 randomised
Patient characteristics at baseline	None were BCS candidates at baseline; 14% deemed inoperable	Pretreatment surgical assessment available for 220 patients – 96 eligible for BCS	386 of the patients either required a mastectomy or were deemed inoperable at baseline
Definition of HR positivity	ER/PgR staining >10%	ER staining >1%	‘ER+/PgR+’
Neoadjuvant endocrine therapy	L for 4 months T for 4 months	A for 12 weeks A+T for 12 weeks T for 12 weeks	A for 3 months T for 3 months
Concomitant chemotherapy?	No	—	Yes
Primary end point	Clinical response by palpation	Overall response by caliper measurements	Overall response by ultrasound measurements
Response (per primary end point)	55% (L) vs 36% (T); P<0.001	37% (A) vs 39% (A+T) vs 36% (T)	39.5% (A) vs 35.4% (T)
Rate of down staging to BCS	45% (L) vs 35% (T); P=0.022	44%(A) vs 24% (A+T) vs 31% (T)	43.0% (A) vs 30.8% (T) in improved feasible surgery in hormone therapy-only group (n=314)

Abbreviations: A=anastrozole 1 mg daily; BCS=breast conserving surgery; ER=oestrogen receptor; HR=hormone receptor; IMPACT=Immediate Preoperative Anastrozole, Tamoxifen or Combined with Tamoxifen; L=letrozole 2.5 mg daily; PROACT=Preoperative ‘Arimidex’ Compared to Tamoxifen; PgR=progesterone receptor; T=tamoxifen 20 mg daily.