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Utility of Three-Dimensional Conformal Radiation Therapy Using Helical Tomotherapy for Anal Cancer

J Baek*, D Jung , S Kim , K Park , T Jeong , R Park , M Kim , J Kim , J Cho , Yonsei Cancer Center, Seoul, Republic Of Korea, seoul/Republic of Korea


(Sunday, 7/29/2018) 3:00 PM - 6:00 PM

Room: Exhibit Hall

Purpose: To access the usefulness of three-dimensional conformal radiation therapy (3D-CRT) using helical tomotherapy (tomo-3D) in anal cancer by comparing the target coverage and organ-at-risk (OAR) sparing of 3D-CRT techniques and intensity-modulated radiaton therapy (IMRT) using tomotherapy (tomo-IMRT).

Methods: We selected a 44-year-old female cT2N0 anal cancer patient treated with concurrent chemoradiotherapy with 5-fluorouracil and mitomycin C. The clinical target volume (CTV) targets were contoured according to the RTOG protocol, and the prescription doses were 30.6 Gy, 45 Gy, and 50.4 Gy in 1.8 Gy daily fractions (CTV 30.6Gy, CTV 45Gy, and CTV 50.4Gy, respectively). OARs included the iliac, low pelvic, lumbosacral bone marrow (BM), external genitalia, small bowel, and bladder. The tomo-3D was compared with two different 3D-CRT plans (photon-electron combination, thunderbird) and the tomo-IMRT plan.

Results: Tomo-3D achieved better target coverage and homogeneity (especially in CTV 30.6Gy) than 3D-CRT. Target coverage was similar to that of tomo-IMRT and homogeneity was better than that of tomo-IMRT. The results for healthy tissue conformity indices in CTV 50.4Gy were as follows: tomo-IMRT, 0.51; tomo-3D, 0.45; thunderbird, 0.34; and photon-electron, 0.40. Tomo-3D showed better results than 3D-CRTs in V20, V30, V40, and Dmean of low pelvic BM and V30, V40, and Dmean of lumbosacral BM, but not better than tomo-IMRT. The Dmean of external genitalia and bladder in tomo-3D was lower than that of thunderbird.

Conclusion: Tomo-3D achieves better target coverage, homogeneity, conformity and OAR sparing than 3D-CRT. Although tomo-IMRT is the most effective treatment approach, tomo-3D could be an alternative treatment in anal cancer.


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