Potential benefits of using non coplanar field and intensity modulated radiation therapy to preserve the heart in irradiation of lung tumors in the middle and lower lobes

PurposeInvestigate whether the use of non coplanar fields and intensity modulated radiation therapy (IMRT) reduces the dose to the heart, in irradiation of middle and lower lung tumors.Materials and methodsFour plans are compared on 10 CT scans: (1) a reference plan, corresponding to coplanar plan of 3D conformal radiotherapy (3DCRT); (2) a 3DCRTnoncopl plan, differing from reference plan by the change of one field in non coplanar fields; (3) an IMRTcopl plan optimized on the same coplanar plan as reference plan; and (4) an IMRTnoncopl plan optimized on the same non coplanar beams as 3DCRTnoncopl plan. The equivalent uniform dose (EUD) for PTV was 74 Gy in 37 fractions.ResultsIn all plans, the 95% isodose surface covers at least 99% of the PTV with very similar conformity index values. A significant reduction in EUD, V30, V40 and V50 is observed for heart when either non coplanar fields or IMRT is used. IMRT also reduces the lung NTCP, V5, V13, V20 and V30 values and esophagus NTCP.ConclusionBoth the use of non coplanar fields and IMRT dramatically reduces the dose received by the heart. The largest benefit is seen when the two techniques are combined.