ORIGINAL ARTICLE Jpn J Radiol (2010) 28:283–289 DOI 10.1007/s11604-010-0423-3 Dosimetric comparison of field in field intensity-modulated radiotherapy technique with conformal radiotherapy techniques in breast cancer Tülay Ercan · S ¸efik I ˙ g ˘dem · Gül Alço · Funda Zengin Selin Atilla · Maktav Dinçer · Sait Okkan Abstract Purpose. The aim of this study was to be able to imple- ment the field-in-field intensity-modulated radiotherapy (FiF) technique in our daily practice for breast radiotherapy. To do this, we performed a dosimetric comparison. Materials and methods. Treatment plans were produced for 20 consecutive patients. FiF plans and conformal radiotherapy (CRT) plans were compared for doses in the planning target volume (PTV), the dose homogeneity index (DHI), doses in irradiated soft tissue outside the target volume (SST), ipsilateral lung and heart doses for left breast irradiation, and the monitor unit counts (MU) required for treatment. Averaged values were compared using Student’s t-test. Results. With FiF, the DHI is improved 7.0% and 5.7%, respectively (P < 0.0001) over the bilateral and lateral wedge CRT techniques. When the targeted volumes received 105% and 110% of the prescribed dose in the PTV were compared, significant decreases are found with the FiF technique. With the 105% dose, the SST, heart, and ipsilateral lung doses and the MU counts were also significantly lower with the FiF technique. Conclusion. The FiF technique, compared to CRT, for breast radiotherapy enables significantly better dose dis- tribution in the PTV. Significant differences are also found for soft tissue volume, the ipsilateral lung dose, and the heart dose. Considering the decreased MUs needed for treatment, the FiF technique is preferred over tangential CRT. Key words Breast radiotherapy · IMRT · Field-in-field Introduction In 2008, a total of 184 450 people were diagnosed with breast cancer in United States; 182 460 were female and 1190 were male. 1 Postoperative radiation treatment to the breast after conservative surgery is the gold stan- dard. A low morbidity rate is seen in this group of patients, and rare side effects occur in some patients with the expectation of long survival. Tangential photon beam irradiation to the intact breast is the standard approach to prevent subclinical disease at an early stage after conservative surgery. 2,3 With irradiation from tangential fields, exposure of the heart directly to radiation is prevented in patients with left breast cancer and the ipsilateral lung with tumors with a right or left breast location. However, dose distribution obtained with open field photon beams is complicated owing to the complex volume of the breast. Therefore, dose distribution can be improved only by using wedge filters to the medial and lateral fields or only to the lateral field. 4,5 For treatment performed with these techniques, homogeneous dose distribution is obtained in the central axis of the target volume, and high dose changes are observed owing to the decrease in separation at the superior and inferior aspects. In many studies, dose changes up to 15%–27% are seen in the irradiated volume. 6,7 When three-dimensional (3D) Received: November 9, 2009 / Accepted: January 21, 2010 © Japan Radiological Society 2010 T. Ercan (*) · G. Alço · F. Zengin · S. Atilla · M. Dinçer Department of Radiation Oncology, Florence Nightingale Gayrettepe Hospital, Cemil Aslan Güder Sok 8, Gayrettepe, I ˙ stanbul 34340, Turkey Tel. +90-212-336-5570; Fax +90-212-288-2969 e-mail: tulaye@doruk.net.tr S ¸. I ˙ g ˘dem · S. Okkan Department of Radiation Oncology, I ˙ stanbul Bilim University, School of Medicine, I ˙ stanbul, Turkey