Animal weight and tumor volume during tamoxifen treatment. Rats with DMBA-induced ER positive breast cancers were orally treated with either tamoxifen at a dose of 40 mg/kg bodyweight/day or received vehicle only for 14 days. Animals were weighed every third day for calculation of treatment dosage. Mean weights (± SD) are presented in the graph (A). Tumor number and size were measured every second day and the tumor volumes were calculated according to the formula (LxW2)/2. The mean tumor volume/rat (B) and mean relative tumor volume/rat compared to day 0 (C) during the treatment period are presented according to treatment group.