This report describes 3-D conformal radiotherapy in a female breast cancer patient. A postmenopausal patient was admitted to the Department of Radiation Oncology, University Hospital for Tumors, Zagreb, Croatia for adjuvant radiotherapy treatment after right breast segmentectomy. Patohistology was ductal carcinoma in situ grade II (TisN0M0). With standard 2-D simulation, a relatively large lung volume in the irradiation field was defined (central lung distance - CLD > 2.5 cm). We decided to apply conformal radiotherapy, for its ability of homogeneous dose application and minimum radiation exposure of the surrounding normal tissues. A dose of 50 Gy was delivered to the whole breast in 2 Gy fractions, followed by a «boost» dose to the tumor bed of 12.5 Gy in 2.5 Gy fractions using electron beams (12 MeV). The patient tolerated treatment without any significant sequelae. At control examinations after 3 and 6 moths, the patient was well, with no signs of the disease, with normal clinical inspection results and without any skin changes.U radu je prikazano provođenje 3-D konformalne radioterapije u bolesnice s karcinomom dojke. Bolesnica je primljena u Službu radioterapijske onkologije Klinike za tumore radi provođenja adjuvantne radioterapije nakon segmentektomije desne dojke. Postavljena patohistološka dijagnoza je duktalni karcinom in situ gr. II (TisN0M0). Klasičnom 2-D simulacijom utvrđeno je da u polje zračenja ulazi relativno veliki volumen pluća (centralna plućna distanca, CLD > 2.5 cm). Odlučeno je provesti konformalnu radioterapiju, koja omogućuje apliciranje homogenije doze zračenja i bolju zaštitu okolnog zdravog tkiva. Aplicirana je tumorska doza 50 Gy na cijelu dojku u 25 frakcija po 2 Gy, nakon koje je slijedila „boost“ doza na ležište tumora od 12.5 Gy u 5 frakcija po 2,5 Gy korištenjem elektronskog snopa e12 MeV-a linearnog akceleratora. Pacijentica je dobro i bez prekidanja podnijela radioterapiju. Na kontrolnom pregledu nakon 3 i 6 mjeseci, pacijentica je dobro, bez znakova bolesti, uredan je klinički nalaz, bez vidljivih promjena na koži dojke
