Original Article
In vivo dosimetry of skin surface for breast cancer radiotherapy using intensity-modulated radiation therapy technique and helical tomotherapy
Abstract
Background: Planning skills such as skin flash in intensity-modulated radiation therapy (IMRT), virtual bolus in helical tomotherapy (HT) and tissue equivalent materials are widely used in breast cancer radiotherapy (RT) to ensure coverage of superficial target under respiration. This study was conducted to evaluate the exact skin dose under above treatment technique and planning skills.
Methods: Women who received whole breast RT (WBRT) or post-mastectomy RT (PMRT) were included. Treatment machines included Synergy® (Elekta, Stockholm, Sweden) and TomoTherapy Hi-ART® (Accuray, Sunnyvale, CA, USA). For WBRT, 20 mm “skin flash” was used in IMRT, and 10 mm “virtual bolus” was used in HT. For PMRT, 5 mm bolus plus skin flash was used in IMRT and 10 mm bolus was used in HT. GafChromic EBT3 (International Specialty Products, Wayne, NJ, USA) films were placed on patient’s skin for measurement.
Results: Between July 2012 and December 2013, 17 patients in WBRT group and 13 patients in PMRT group were included. In WBRT group, patients received higher skin dose with IMRT than with HT (86.57% and 79.69% of prescribed dose, respectively, P<0.0001). IMRT delivered 4–5% higher dose to central skin region than bilateral regions, while skin dose distribution of HT was relatively homogeneous. In PMRT group, IMRT delivered higher surface dose than HT did (107.34% and 100.28% of prescribed dose, respectively, P<0.0001).
Conclusions: For WBRT, HT plus virtual bolus leads to homogeneous skin dose distribution and 7% lower skin dose than IMRT does. For PMRT, HT plus 10 mm bolus provides adequate surface dose which is close to 100% of prescribed dose; while IMRT plus 5 mm bolus and skin flash results in overdose with 7% more than prescribed dose. HT should be considered to be an option of breast RT.
Methods: Women who received whole breast RT (WBRT) or post-mastectomy RT (PMRT) were included. Treatment machines included Synergy® (Elekta, Stockholm, Sweden) and TomoTherapy Hi-ART® (Accuray, Sunnyvale, CA, USA). For WBRT, 20 mm “skin flash” was used in IMRT, and 10 mm “virtual bolus” was used in HT. For PMRT, 5 mm bolus plus skin flash was used in IMRT and 10 mm bolus was used in HT. GafChromic EBT3 (International Specialty Products, Wayne, NJ, USA) films were placed on patient’s skin for measurement.
Results: Between July 2012 and December 2013, 17 patients in WBRT group and 13 patients in PMRT group were included. In WBRT group, patients received higher skin dose with IMRT than with HT (86.57% and 79.69% of prescribed dose, respectively, P<0.0001). IMRT delivered 4–5% higher dose to central skin region than bilateral regions, while skin dose distribution of HT was relatively homogeneous. In PMRT group, IMRT delivered higher surface dose than HT did (107.34% and 100.28% of prescribed dose, respectively, P<0.0001).
Conclusions: For WBRT, HT plus virtual bolus leads to homogeneous skin dose distribution and 7% lower skin dose than IMRT does. For PMRT, HT plus 10 mm bolus provides adequate surface dose which is close to 100% of prescribed dose; while IMRT plus 5 mm bolus and skin flash results in overdose with 7% more than prescribed dose. HT should be considered to be an option of breast RT.
