Impact of body mass index on compliance and persistence to adjuvant breast cancer therapy.

Several authors found that the prognosis of overweight and obese breast cancer (BC) patients was lower than that of normal weight patients. We present the first study which evaluates the impact of body mass index (BMI) on compliance (i.e. to start a recommended therapy) and persistence to adjuvant BC therapy. An unselected cohort of 766 patients (≤75 years) diagnosed from 1997 to 2009 was analyzed in relevance to the four adjuvant therapy modalities: (A) radiation, (B) chemotherapy, (C) therapy with trastuzumab, and (D) endocrine therapy. With respect to compliance, multivariate analyses calculated Odds ratios (ORs) >1 for increased BMI in all four therapy modalities, i.e. increased BMI had a positive influence on compliance. The results were significant for radiotherapy (OR,2.37;95%CI,1.45-3.88;p < 0.001) and endocrine therapy (OR,1.92;95%CI,1.21-3.04;p = 0.002) and showed a trend in chemotherapy (OR,1.42;95%CI,0.97-2.08;p = 0.063). Analyzing persistence, increasing BMI had ORs <1 for chemotherapy and therapy with trastuzumab, both not reaching statistical significance. For endocrine therapy, increasing BMI was a significant predictor for persistence (OR,1.35;95%CI,1.08-1.80;p = 0.042). Failure of compliance and persistence to adjuvant therapy does not pose a contributing factor for the observed unfavorable prognosis in overweight/obese BC patients. In most therapy modes, patients with increasing BMI demonstrated a higher motivation and perseverance to the recommended treatment.