Evaluation of the skin doses in breast cancer radiotherapy with treatment planning system and termoluminescent dosimeter

For postmastectomy radiotherapy, administration of the minimum effective dose to the skin and confirming this dose by termoluminescent dosimeter (TLD) is important for both efficacy and toxicity of the treatment. In most cases, modern radiotherapy dose planning systems accurately estimate the dose, however it might be inaccurate on skin and areas close to the skin. The aim of this study is to compare the dose calculated by treatment planning systems (TPS) and the dose measured by termoluminescent dosimeters (TLD). Chest wall irradiation was performed on 13 different patients for 4 different conditions which are 6 MV chest wall irradiation with bolus, 6 MV chest wall irradiation without bolus,4 MV chest wall irradiation with bolus and 4 MV chest wall irradiation without bolus. For each patient, 11 different anatomical points were determined during computed tomography scan with radiopaque markers. For each patient, the mean scar and skin doses which were calculated using TPS compared with the mean scar and skin dose which were measured with TLD in the same anatomical positions on the patient skin. The analysis of mean skin doses measured by TPS and TLD's were similar in these 4 different conditions. Likewise, the analysis of mean scar doses for 2 systems which were used in our study were found similar for 4 different conditions. For 4 MV chest wall irradiation with bolus, measured mean TLD dose is closer to prescribed dose than mean dose of measured TPS's dose and show statistically significant difference. This difference is thougt to be mainly based on not enough data in this condition. In the other 3 different conditions for skin and scar doses, there are no statistically significant differences. In our study, we reiterate that chest wall irradiation with 4-6 MV with bolus is appropriate to provide adequate dose coverage to the skin and also to prevent recurrence or adverse skin reactions.