Skin dose evaluation for 3DCRT and VMAT breast cancer techniques

Abstract

Introduction Skin dose is a concern both in breast conservative and post-mastectomy irradiation. Although in most cases the skin is considered an organ at risk, in some there is the need to irradiate it with therapeutic doses. When Volumetric Modulated Arc Therapy (VMAT) technique is used for the treatments, because the Three-Dimensional Conformal Radiation Therapy (3DCRT) dose distribution is not clinically satisfactory, the issue about the skin dose arises. Purpose The purpose of this work is to evaluate the surface dose when each of these techniques is used, to compare the measured doses with the doses calculated by the Treatment Planning System (TPS) and to assess the need of using bolus during part or all the treatment fractions Materials and methods A MOSFET-based system was used. A complete characterization of the system performance was previously made. The skin dose was measured at two points tattooed on the skin, equally distanced from the breast/thoracic wall midline. Measurements were performed for 6MV 3DCRT and 6MV VMAT and compared with the dose values predicted by the TPS. Results The mean measured dose is higher for the 6MV 3DCRT technique than for VMAT (both without bolus). The surface dose difference between the two techniques is lower when bolus is used. The same differences were obtained for the mean calculated dose in both conditions. Conclusion Despite some discordant results in literature, one found from the present results, that skin sparing effect is better achieved with VMAT technique. Disclosure The authors have no relevant financial or non-financial relationships to disclose. Skin dose is a concern both in breast conservative and post-mastectomy irradiation. Although in most cases the skin is considered an organ at risk, in some there is the need to irradiate it with therapeutic doses. When Volumetric Modulated Arc Therapy (VMAT) technique is used for the treatments, because the Three-Dimensional Conformal Radiation Therapy (3DCRT) dose distribution is not clinically satisfactory, the issue about the skin dose arises. The purpose of this work is to evaluate the surface dose when each of these techniques is used, to compare the measured doses with the doses calculated by the Treatment Planning System (TPS) and to assess the need of using bolus during part or all the treatment fractions A MOSFET-based system was used. A complete characterization of the system performance was previously made. The skin dose was measured at two points tattooed on the skin, equally distanced from the breast/thoracic wall midline. Measurements were performed for 6MV 3DCRT and 6MV VMAT and compared with the dose values predicted by the TPS. The mean measured dose is higher for the 6MV 3DCRT technique than for VMAT (both without bolus). The surface dose difference between the two techniques is lower when bolus is used. The same differences were obtained for the mean calculated dose in both conditions. Despite some discordant results in literature, one found from the present results, that skin sparing effect is better achieved with VMAT technique.