Breast cancer. Coloured computed tomography scan of a woman's chest showing breast cancer. The scan shows a horizontal slice through the chest. The large purple area in the upper right is the abnormal breast. The black and pink areas in the centre are the lungs. Bones are outlined in yellow and include the sternum (upper centre), ribs and spine (lower centre). Breast cancer is the most common cancer in women, affecting about 1 in 20. Successful treatment depends on early detection, as once the cancer has spread it is much harder to cure. Surgical removal of the tumour cures around a third of patients. Radiotherapy and anticancer drugs are often also required.