Surprisingly, in a retrospective study evaluating human epidermal growth factor receptor 2 positive (HER2+) non-metastatic breast cancer patients treated with trastuzumab from 2006 to 2012 and supplemented with low (<10,000 IU/week or 1400 IU/d) and high (>10,000 IU/peek or 1400 IU/d) doses of cholecalciferol, a significant improvement of disease-free survival has been shown, compared to the group treated with trastuzumab alone [20]. Here, ERBB2 is linked to breast cancer.