Image guided Pre-operative Accelerated partial Breast Irradiation (PAPBI): Defening radiotherapy sensivity.

Patients with early stage breast cancer are treated with a combination of surgery, radiotherapy and often with systemic therapy. Radiotherapy is part of breast conserving therapy and is known to reduce LR rates in all patients with 60-70% although the absolute benefit differs in different subgroups. So far, no patient groups can be defined in whom radiotherapy would not be necessary. It is estimated that in approximately half of the patients whole breast radiotherapy is not necessary, while in others the tumor might be resistant to radiotherapy. It is likely that tumor cells differ in their response to radiotherapy and thus influence the LR rate after BCT. If it would be possible to predict tumor response to radiotherapy, a more tailored treatment can be advised to individual patients (higher boost dose or primary mastectomy).

Pre-operative accelerated partial breast radiotherapy will be superior compared to conventional radiotherapy for fibrosis and cosmetic outcome, and we think this new treatment will be superior to conventional post-operative whole breast radiotherapy which is used up till now.

1. 60 Patients will be studied as a test set to identify predictive profiles;

2. 60 patients will be used as a validation set.

The additional procedures in this study are:

1. Biopsies before radiotherapy;

2. Cytology at day 2 and 12 of radiotherapy;

3. MRI before operation;

4. A Pet scan will be done twice;

5. Also, the sentinel procedure will take place before radiotherapy.