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Table 1 Incidence of bone fractures and osteoporosis in patients treated with aromatase inhibitors versus tamoxifen or placebo in randomized phase III trials

From: Aromatase inhibitor-associated bone and musculoskeletal effects: new evidence defining etiology and strategies for management

Study Treatment arms (years of treatment) Symptom Aromatase inhibitor (%) Tamoxifen/placebo (%) P-value
ATAC [11, 21] Anastrozole (5) versus Tamoxifen (5) Fractures 2.93 1.9 < 0.0001
   Osteopenia or osteoporosis 11 7 < 0.0001
ABCSG8/ARNO95 [16] Tamoxifen (2-3) → Anastrozole (3) versus Tamoxifen (5) Fractures 2 1 0.015
ABCSG6a [17] Tamoxifen (5) → Anastrozole (3) versus Tamoxifen (5) → Placebo (3) Fractures 0.8 1.1 NA
BIG 1-98 [13] Letrozole (5) versus Tamoxifen (5) Fractures 8.6 5.8 < 0.001
IES [14] Tamoxifen (2-3) → Exemestane (2-3) versus Tamoxifen (5) Fracturea 4.3 3.1 0.03
   Osteoporosis 7.3 5.5 0.01
MA.17 [15] Tamoxifen (5) → Letrozole (5) versus Tamoxifen (5) → Placebo (5) Fracture 5.3 4.6 0.25
   Osteoporosis 8.1 6 0.003
  1. aFracture risk increased with exemestane versus tamoxifen (7 versus 4.9, respectively; P-value 0.003) after completion of therapy. ABCSG, Austrian Breast and Colorectal Cancer Study Group; ARNO, Arimidex-Nolvadex; ATAC, Arimidex, Tamoxifen, Alone or in Combination; BIG, Breast International Group; IES, International Exemestane Study; NA, not available.