Background A growing number of studies worldwide have advocated the replacement of whole-breast irradiation with accelerated partial breast irradiation using three-dimensional conformal external-beam radiation (APBI-3DCRr) for early-stage breast cancer. But APBI can be only used in selected population of patients with early-staged breast cancer. It is not replacing the whole breast radiotherapy. This study aimed to examine the feasibility and acute normal tissue toxicity of the APBI-3DCRT technique in Chinese female patients who generally have smaller breasts compared to their Western counterparts.Methods From May 2006 to December 2009, a total of 48 Chinese female patients (with early-stage breast cancer who met the inclusion criteria) received APBI-3DCRT after breast-conserving surgery at Sun Yat-sen University Cancer Center. The total dosage from APBI-3DCRT was 34 Gy, delivered in 3.4 Gy per fractions, twice per day at intervals of at least six hours. The radiation dose, volume of the target area and volume of irradiated normal tissues were calculated.Acute toxicity was evaluated according to the Common Toxicity Criteria (CTC) 3.0.Results Among the 48 patients, the planning target volume for evaluation (PTVE) was (90.42±9.26) cm3, the ipsilateral breast volume (IBV) was (421.74±28.53) cm3, and the ratio between the two was (20.74±5.86)%. Evaluation of the dosimetric characteristics of the PTVE revealed excellent dosimetric results in 14 patients and acceptable results in 34 patients. The dose delivered to the PTVE ranged from 93% to 110% of the prescribed dose. The average ratio of the volume of PTVE receiving 95% of the prescription dose (V95) was (99.26±0.37)%. The habituation index (HI) and the conformity index (CI) were 1.08±0.01 and 0.72±0.02, respectively, suggesting good homogeneity and conformity of the dose delivered to the target field. The radiation dose to normal tissues and organs was within the dose limitation.Subjects experienced mild acute toxicity. The main manifestations were breast edema in 22 patients, breast pain in 7,skin erythema in 25, general malaise in 22 and cytopenia in 8. No acute radiological cardiac or pulmonary injury was found.Conclusions The results of our short-term follow-up showed that it is feasible to perform APBI-3DCRT for early-stage breast cancer after breast-conserving surgery in Chinese female patients with smaller breasts. However, further studies are required to elucidate its efficacy and long-term side effects.