Radiotherapy: one week (Arm 1) 2600 cGy in 5 fractions whole breast radiotherapy over one week versus 2 weeks (Arm 2), 3200 cGy in 10 fractions with a concomitant tumor bed boost to 3600 cGy. In Arm 2, if no cavity is visible due to oncoplastic surgery, we will deliver 32 Gy to the whole breast only, without a boost.
Hypothesis: A regimen of whole breast radiotherapy to 2600 in five fractions, the current UK standard for early breast cancer (Arm 2), is not inferior to 3200cGy with a concomitant tumor bed boost to 3600 cGy in 10 fractions (Arm 1), in terms of acute toxicity and long-term fibrosis, breast cosmesis and local control at 2 and 5 years. It will also test the hypothesis of superior local control at 10 years in Arm 2 compared to Arm 1.
