Neoadjuvant letrozole in postmenopausal estrogen and/or progesterone receptor positive breast cancer: A phase IIb/III trial to investigate optimal duration of preoperative endocrine therapy

Table 6 Relationship between treatment duration and tumor response

	Clinical assessment		Mammography		Breast ultrasound
	ITT (n = 28)	PP (n = 24)	ITT (n = 21)	PP (n = 17)	ITT (n = 27)	PP (n = 23)
Pearson correlation	r = -0.3146	r = -0.4003	r = -0.2396	r = -0.2956	r = -0.2099	r = -0.3188
	p = .1030	p = .0526	p = .2955	p = .2494	p = .2934	p = .1382
Spearman correlation	r = -0.3839	r = -0.5092	r = -0.1037	r = +0.0409	r = -0.4111	r = -0.3371
	p = .0437	p = .0110	p = .6548	p = .8761	p = .0331	p = .1158
Multiple regression analysis	F = 1.96	F = 1.66	F = 0.87	F = 0.60	F = 0.73	F = 1.05
	p = 0.1471	p = 0.2070	p = 0.4748	p = 0.6278	p = 0.5465	p = 0.3928
	R² = 0.1967	R² = 0.1996	R² = 0.1334	R² = 0.1212	R² = 0.0866	R² = 0.1424
	R²* = 0.0963	R²* = 0.0795	R²* = -0.0195	R²* = -0.0816	R²* = -0.0326	R²* = 0.0070

* adjusted.
Threefold statistical analysis performed for clinical tumor assessment, MG, and breast US included: a) Pearson correlation of percent change in tumor size from baseline to Individual End vs. days on letrozole treatment; b) Spearman correlation of tumor response categories (1 = CR to 4 = PD) at Individual End vs. days on letrozole treatment; and c) multiple regression analysis of percent change in tumor size as criterion vs. days on treatment, age, and tumor size at baseline as predictors (3 degrees of freedom). Deviations in ITT and PP population sizes from 29 and 25, respectively, were due to non-analyzable patients.

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