The study purpose is to evaluate whether or not clinical characteristics of women with breast cancer can predict which position for radiation treatment, prone or supine, will be associated with a dosimetry gain. Dosimetry gain in this study means the lowest radiation dose to non-target organs (heart, lungs, contralateral breast), while giving the prescribed dose to tumor bed and ipsilateral breast.

Retrospectively identify women who received curative radiation treatment after breast conserving cancer surgery, in whom simulation in prone and in supine position was performed. Compare the treatment plans for doses to targets and to non-target organs, according to clinical parameters of body mass index, size of breast, location of tumor and side. Furthermore, evaluate whether a single CT slide is enough or not to predict a dosimetry advantage.

Inclusion Criteria:

• Breast conserving surgery
• Adjuvant radiation treatment
• Simulation done prone and supine

Exclusion Criteria:

• Simulation in only one position

Consecutive patients addressed for adjuvant radiation treatment after breast conserving surgery for breast cancer, in whom simulation was done prone and supine.