Feasibility, efficacy, and cosmetic effect of three-dimensional conformal external beam partial breast irradiation for the selected early-stage breast cancer patients after breast-conserving surgery in China.

Abstract

e11520 Background: To explore the feasibility, efficacy and cosmetic effect of three-dimensional conformal external beam partial breast irradiation after breast-conserving surgery for the selected Chinese early stage breast cancer patients Methods: Forty four early stage breast cancer patients undertaken EB-PBI after breast-conserving surgery. Twenty patients undertaken CT simulation scan in the state of moderate deep inspiration breathing hold (mDIBH), and twenty-four patients during free breathing (FB). The surgical cavity marked by silver clips was delineated and defined as gross tumor volume (GTV), and planning target volume (PTV) was defined as the area encompassed GTV with extended margin of 15 mm for the patients treated in the state of mDIBH or 20 mm for the patients treated in the state of FB. EB-PBI was planned and carried out by three-dimensional conformal radiotherapy (3DCRT) , the total prescribed dosage was 34 Gy delivered in 3.4 Gy per fractions in thirty nine patients and 38.5Gy delivered in 3.85 Gy per fractions in five patients, twice per day at intervals of at least six hours, in five consecutive days Results: Grade 1 of acute radiation-induced dermatitis was observed in 38.6% (17/44) of all the patients, no equal or more than grade 2 of radiation-induced dermatitis was observed, and no any grade of acute radiation-induced pneumonitis was observed. Cosmesis scored basing on Harris critieria was good or excellent in all cases at the time of six months after radiotherapy and in 94.9% cases at the time of two years after radiotherapy. The 2-, 3- and 5-year local control rates were 100% (39/39), 98.8% (30/31) and 93.8% (15/16), respectively. The 2-, 3-, and 5-year survival rates were all 100% and no metastases occurred Conclusions: EB-PBI delivered by 3DCRT is feasible for the selected Chinese early stage breast cancer patients after breast-conserving surgery, satisfactory cosmetic effect, local control rate and long-term survival rate are obtained, meanwhile, acute radiation response rate is lower.