Objective  To compare the advantages and disadvantages of forward intensity modulated (f-IMRT) and intensity modulated radiation therapy (IMRT) plans for radiotherapy patients with left breast cancer undergoing breast conserving surgery.

  Methods  Eleven patients with left breast cancer undergoing conserving surgery were selected, Pinnacle³ Treatment Planning System(TPS) was used to design IMRT and f-IMRT planning. Dosimetric analysis was performed by TPS and the passing rate was analyzed using the Compass verification system, the strengths and weaknesses of the two plans were compared.

  Results  The results showed that the Planning Target Volume (PTV) and Argan at Risk (OAR) doses in both groups could meet the clinical requirements. The volume of the heart and the left lung exposed to 5 Gy dose (V₅) and exposed to 30 Gy dose (V₃₀) in the two plans and the values of mean dose (D_mean) of the left lung and the right lung were statistically significant (P < 0.05 orP < 0.01). The results of the passing rate analysis showed that both plans passed the verification under the standard of 3mm/3%, while only f-IMRT plan passed the verification under the standard of 2 mm/2%. The Gamma passing rates of PTV and OAR of the f-IMRT plan were significantly higher than those of the IMRT plan(P < 0.05 orP < 0.01).

  Conclusion  f-IMRT technology improves the plan passing rate while ensuring the clinical dose requirements, and may be considered as the first choice for routine radiotherapy of left breast cancer undergoing conserving surgery.