Research on the different techniques in breast cancer radiotherapy

In breast cancer radiotherapy, internal mammary lymphatic chain is treated in the target volume in a group of patients with high risk criteria. Intenal mammary lymphatic chain is not treated in the target volume in a group of patients with no high risk criteria. There are a number of different techniques in breast radiotherapy because of the variability of the anatomic region, structures and risk criteria in the irradiation field. While irradiating the target volume we also consider to homogeneity dosedistribution and minimize the dose to critical structures such as the heart and lung. In this study, we have evaluated the dose distribution of different radiotherapy techniques in twelve patients with left breast cancer who had breast conserving surgery or mastectomy. Two dimensional computerized planning system (2-DCPS) was used for each patient to compare wide-field, oblique photon-electron, perpendicular photon-electron and oblique-electron techniques in terms of dose homogeneities in the target volume, the doses received by the heart, lung and the coverage of the internal mammary chain. Data from 2DCPS were controlled by the Solid-water phantom and ionisation chamber. Critical structures were irradiated with acceptable dose percentages besides internal mammary chain with both wide-field, photon-electron and oblique-electron techniques. We detected more frequent hot spots in oblique photon-electron and oblique-electron techniques than other techniques and this situation necessitated changing the junctions. The wide-field technique was easy to perform and exposed less radiation dose to the heart than photon-electron techniques. The oblique electron thecniques provide us a minimal radiation dose to critic structures. In oblique electron techniques, if internal mammary chain was not covered in the target volume, the heart dose was minimised. In conclusion, we suggest to use oblique-electron techniques in breast irradiation where internal mammary is in the target volume.