Background: Bioelectrical impedance analysis (BIA) is commonly used to assess fat-free mass (FFM) and fat mass (FM) in breast cancer patients. However, because of the prevalence of overweight, obesity and variable hydration status in these patients, assumptions for existing prediction equations developed in healthy adults may be violated, resulting in inaccurate body composition assessment. Methods: We measured whole-body FFM using single-frequency BIA (50 kHz) and dual-energy x-ray absorptiometry (DXA) in 48 patients undergoing treatment for breast cancer. We applied raw BIA data to 18 previously published FFM prediction equations (FFM BIA) and compared these estimates to DXA (FFM DXA ; reference method). Results: On average, patients were 52 ± 10 (mean ± SD) years of age and overweight (body mass index: 27.5 ± 5.5 kg/m 2 ; body fat by DXA: 40.1% ± 6.6%). Relative to DXA, BIA overestimated FFM by 4.1 ± 3.4 kg (FFM DXA : 42.0 ± 5.9 kg; FFM BIA : 46.1 ± 3.4 kg). Individual equationgenerated predictions of FFM BIA ranged from 39.6 ± 6.7 to 52.2 ± 5.6 kg, with 16 equations overestimating and 2 equations underestimating FFM BIA compared with FFM DXA. Based on equivalence testing, no equation-generated estimates were equivalent to DXA. Conclusion: Compared with DXA, BIA overestimated FFM in breast cancer patients during treatment. Although several equations performed better than others, none produced values that aligned closely with DXA. Caution should be used when interpreting BIA measurements in this clinical population, and future studies should develop prediction equations specific to breast cancer patients.

Aerobic and resistance exercise during and after cancer treatment are important for health-related outcomes, however treatment-specific barriers may inhibit adherence. We explored the effect of lower-frequency exercise training on fitness, body composition, and metabolic markers (i.e. glucose and lipids) in a group of recently diagnosed breast cancer patients. Fifty-two females ≥ 18 years with stage I–IIIB breast cancer were instructed to attend 2 cardiovascular and strength training sessions/week over 12 weeks, but program length was expanded as needed to accommodate missed sessions. Pre- and post-intervention, we measured: (1) cardiovascular fitness, (2) isometric strength, (3) body composition (dual-energy X-ray absorptiometry), and (4) fasting glucose, insulin, c-peptide, and lipids. Pre-intervention, participants were 53 ± 10 years old (mean ± SD) and overweight (BMI: 27.5 ± 5.4 kg m−2, 40.1 ± 6.5% body fat). Forty participants completed the program over a median 20 weeks (range: 13–32 weeks, median frequency: 1.2 sessions/week), over which predicted VO2peak improved by 7% (2.2[0.1–4.4] mL/kg/min) (delta[95% CI]), and strength increased by 7–9% (right arm: 2.3[0.1–4.5] N m; right leg: 7.9[2.1–13.7] N m; left leg: 7.8[1.9–13.7] N m). Body composition and metabolic markers were unchanged. An exercise frequency of 1.2 sessions/week stimulated significant improvements in fitness, and may represent a practical target for patients during active treatment.

Recent guidelines recommend exercising ≥ 3 times/week during and after cancer treatment, however treatment-specific barriers may inhibit adherence. We explored the effect of a flexible exercise program on fitness, body composition, and metabolism in a group of recently diagnosed breast cancer patients. Fifty-two females ≥ 18 years with stage I-IIIB breast cancer were instructed to target 2 cardiovascular and strength training sessions/week over 12 weeks, but program length was expanded as needed to accommodate missed sessions. Pre- and post-intervention, we measured: 1) cardiovascular fitness, 2) isometric strength, 3) body composition (dual-energy X-ray absorptiometry), and 4) fasting glucose, insulin, c-peptide, and lipids. Pre-intervention, participants were 53 ± 10 years old (mean ± SD) and overweight (BMI: 27.5 ± 5.4 kg∙m− 2, 40.1 ± 6.5% body fat). Forty participants completed the program over a median 20 weeks (range: 13–32 weeks, median frequency: 1.2 sessions/week). Final workrate during a graded exercise test improved by 13% (10[5–15] W) (delta[95% CI]), and strength increased by 7–9% (right arm: 2.3[0.1–4.5] N∙m; right leg: 7.9[2.1–13.7] N∙m; left leg: 7.8[1.9–13.7] N∙m). Body composition and metabolic markers were unchanged. An exercise frequency of 1.2 sessions/week, while below recommendations, stimulated significant improvements in fitness, and may represent a more realistic target for patients during active treatment.