Dosimetric comparison of IMRT vs. 3D conformal radiotherapy in the treatment of cancer of the cervical esophagus

Background and PurposeRadiotherapy planning for cervical esophageal cancer is challenging. We compared IMRT and 3D conformal radiotherapy (CRT) with respect to conformality of target coverage and normal tissue sparing.Materials and methodsWe selected five patients with cervical esophagus cancer, who represented the heterogeneity of clinical cases, treated to radical dose and planned with Pinnacle v6.2. Target doses for CRT plans were 50, 60, and 70 Gy (single-phase IMRT 56, 63, and 70). We compared PTV coverage by the 95% isodose (PTV95), conformality ratio (CR), conformation number (CN), and maximum or mean doses (Dmax, Dmean) to normal structures.ResultsMedian PTV95 for IMRT plans for PTV70, PTV63, and PTV56 were 97%, 99%, and 98% (CRT 91%, 98%, and 85%). IMRT plans demonstrated lower Dmax to the spinal cord and brainstem (42 and 36 Gy) compared to CRT (46 and 39 Gy). Median left parotid Dmean was 35 Gy (IMRT) vs. 53 Gy (CRT). Median right parotid Dmean was 35 Gy (IMRT) vs. 36 Gy (CRT). The median CR50/56 Gy was 1.4 (CRT) vs. 1.2 (IMRT), CR70 Gy 1.7 (CRT) vs. 1.1 (IMRT). CN50/56 and CN70 values were 0.80 and 0.85 (IMRT) vs. 0.56 and 0.5 (CRT).ConclusionsIMRT provides superior target volume coverage and conformality, with decreased dose to normal structures.