Background   

Evidence shows that IMRT leads to better dose distribution than 3DCRT for  whole breast radiotherapy  and for post mastectomy chest wall irradiation with internal mammary nodes . Data on the effect of IMRT of chest wall in post mastectomy breast cancer patients without IMN are scarce in literature.

Methods and Material:

For 30 Postmastectomy  breast cancer patients, 7 field IMRT plan and  tangential beam 3D–CRT plan were generated. The dose  prescribed to PTV was 50 Gy in 25 fractions. The average values of the PTV parameters namely D_mean, HI, CI, D₂, D₅₀, D₉₈ obtained by the two techniques (3DCRT and IMRT) are compared.

Results

 On comparison, D_95(%) of  PTV (3D–CRT 47.26 Gy; IMRT  48.37 Gy (p<0.01),HI and CI were significantly improved with IMRT. In Left chest wall irradiation, with IMRT V₃₀ of heart was decreased from 23.31% to 18.99% ( p=0.075) and D_mean (14.05Gy 3D–CRT, 19.06Gy  IMRT) was increased (p<0.01). V₅ of heart was increased from 6.55% (3D–CRT) to 92.35% (IMRT) (p<0.001). Ipsilateral lung Dmean (21.13Gy 3D–CRT, 18.08Gy IMRT, p=0.07) and V20 (38.22% 3D–CRT, 35.14%  IMRT p=0.006) decreased with IMRT. Low dose volumes of lung is increased with IMRT.

Conclusions:

The benefit is marginal in sparing OAR in post mastectomy chest wall without IMN radiation,  which is achieved at a cost of increase in low dose volumes of lungs and heart. IMRT can be used in situations where strict constraints to the heart and lungs are not satisfied.