ORIGINAL ARTICLE Field-in-field IMRT versus 3D-CRT of the breast. Cardiac vessels, ipsilateral lung, and contralateral breast absorbed doses in patients with left-sided lumpectomy: a dosimetric comparison Duygu Baycan • Didem Karacetin • Ayben Y. Balkanay • Yu ¨ cel Barut Received: 23 March 2012 / Accepted: 16 August 2012 / Published online: 19 September 2012 Ó Japan Radiological Society 2012 Abstract Purpose This study evaluated dose distribution and homogeneity of field-in-field intensity-modulated radiation treatment (FIF-IMRT) compared with standard wedged tangential-beam 3D conformal radiotherapy (CRT) of the left breast in patients who have undergone lumpectomy. Our aim was to improve dose-distribution homogeneity in the breast and decrease the dose to organs at risk (OAR), i.e, heart and vessels, ipsilateral lung, and contralateral breast. Materials and methods FIF-IMRT and wedge plans of 3D-CRT were carried out for 18 patients with cancer of the left breast. Plans were compared according to cumulative dose-volume histogram (c-DVH) analysis in terms of planned treatment volume (PTV), homogeneity index (HI), and conformity index (CI), as well as dose and volume parameters of OARs. Results When the targeted volumes receiving 105 % and 110 % of the prescribed dose in the PTV were compared, significant decreases were found with the FIF-IMRT technique. With the 105 % dose to the OARs, monitor unit (MU) counts were significantly lower with the FIF-IMRT technique. V2 of pulmonary artery, left atrium, and aorta and V1 for the contralateral breast were statistically sig- nificantly lower with FIF-IMRT plans (p = 0.001). PTV showed a better HI and CI with FIF-IMRT. Conclusions FIF-IMRT enables better dose distribution in the PTV and reduces dose to OARs in breast cancer radiotherapy. Keywords Field-in-field IMRT  FIF-IMRT  Wedged tangential beam 3D-CRT  Breast cancer  Dose homogeneity Introduction Breast cancer is the most common cancer in females worldwide. In the United States and Europe, the most common treatment is breast-conserving surgery, followed by adjuvant radiotherapy [1]. The purpose of radiotherapy following breast-conserving surgery is to improve local control in the treated breast, with minimum toxicity. Since radiation therapy efficacy has improved, the tissue-related posttherapy complications have become very important in patients treated on the left side, as there is a significantly increased risk of cardiac morbidity and mortality [2–4]. Breast irradiation is associated with a very small increased risk of long-term contralateral breast malignancies [5]. There is significant literature showing that field-in-field (inversed planned) intensity-modulated radiotherapy (FIF- IMRT) potentially leads to a more favorable dose distri- bution compared with 3D planned conformal radiotherapy (CRT) in radiotherapy of the whole breast after breast- conserving surgery [6, 7]. Different studies show that breast volume plays an important part in dose homogene- ity. Inhomogeneity is more pronounced for larger breasts, D. Baycan  D. Karacetin (&)  A. Y. Balkanay Istanbul Research and Training Hospital, Radiation Oncology Clinic Kocamustafapasa, Istanbul, Turkey e-mail: didemkaracetin@gmail.com D. Baycan e-mail: duygu.baycan@mntsaglik.com.tr A. Y. Balkanay e-mail: ayentek@yahoo.com Y. Barut Istanbul Research and Training Hospital, Radiology, Istanbul, Turkey e-mail: yucelbarut@yahoo.com 123 Jpn J Radiol (2012) 30:819–823 DOI 10.1007/s11604-012-0126-z