Methods for selection and optimisation of radiotherapy and early therapy evaluation in breast cancer

Abstract: Adjuvant systemic therapy for breast cancer, the most common malignancy in females, increases survival and this has recently also been demonstrated for postoperative radiotherapy. The aims of this study were to develop an optimised radiotherapeutic technique for postoperative treatment, to analyse the association between p53 status in node-negative patients and radiotherapy, to investigate the incidence of in-breast relapses after conservative surgery and radiotherapy and to determine if positron emissiontomography could be useful for early evaluation of polychemotherapy.A technique with mixed photon and electron beams from an accelerator equipped with a multileaf collimator was developed for irradiation of the breast parenchyma and regional lymph nodes after breast-conserving surgery.Lymph node negative patients with p53 mutated cancers treated with radiotherapy to either the ipsilateral breast parenchyma after sector resection, or the parasternal and supraclavicular fossa after modified radical mastectomy due to medial or central tumours had a statistically significant longer relapse-free, breast cancer-corrected, and overall survival (p=0.0007, p=0.001, p=0.02, respectively) compared with non-irradiated patients.In 672 patients with pT1N0M0 cancers treated with radiotherapy (54 Gy) after breast-conserving surgery 2.5% in-breast relapses appeared after a mean follow-up of 6.8 years.Positron emission tomography with 18FDG and 11C-methionine revealed a decrease in tumour metabolism one to two weeks after the first course of polychemotherapy in 11 of 12 clinically responding patients.