Radiotherapy-induced secondary primary cancer risks for early breast cancer: flattening filter versus flattening filter free IMRT radiotherapy / 中华放射医学与防护杂志

ABSTRACT

Objective To evaluate the secondary cancer risk to various organs due to radiation treatment for early left-sided breast cancer using 6 MV X-ray flattening filter free (FFF) and flattening filter (FF) modes.Methods Two techniques,6 MV FFF and 6 MV FF X-rays modes,were used to develop the two tangential fields d-IMRT plans for 20 early left-sided breast cancer patients respectively.For all the patients,the dose to surrounding tissues was minimized as low as possible,the 95％ volume of the planning target volume (PTV) and clinical target volume (CTV) was consistent with the prescribed dose.The beam parameters and the plan optimization parameters of FFF modes were in consonance with FF modes.The radiation doses and volumes of the planning target volumes,organs at risk and normal tissue were detected by dose-volume histogram.And then,the excess absolute risk(EAR) of contralateral breast,ipsilateral lung,contralateral lung,thyroid and liver were calculated using the radiotherapy-induced secondary primary cancer risks models.Results The treatment plans of two groups met the requirements of clinical.The FFF d-IMRT techniques resulted in a systematic reduction of the organ equivalent dose (OED) (t =2.18-9.72,P ＜ 0.05),and the EAR (t =2.11-9.99,P ＜ 0.05) of contralateral breast,ipsilateral lung,contralateral lung,thyroid and liver was compared to the FF IMRT techniques,especially for the contralateral breast.Conclusions Both FFF and FF d-IMRT plans can achieve comparable target dose coverage in patients with early left-sided breast cancer,while the FFF d-IMRT techniques could reduce the excess absolute risk of contralateral breast,ipsilateral lung,contralateral lung,thyroid and liver.These results are of clinical importance,especially for the early-stage patients with an overall good prognosis.