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Prospective Investigation of Feasibility of Three-Dimensional Treatment Planning of Intracavitary Brachytherapy for Cervical Cancer Based On Computed Tomography Images

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O Yoshifumi

O Yoshifumi1*, A Hidetaka2, H Yoshiyuki3, S Yasumasa4, T Masahiko5, I Mutsumi6, F Noboru7, N Masayuki8, H Hideki9, (1) Kagoshima University Hospital, Kagoshima-shi, Kagoshima-ken, (2) Kyushu University, Fukuoka-city, Fukuoka-ken, (3) Kagoshima University Hospital, Kagoshima-shi, Kagoshima-ken, (4) Kagoshima University Hospital, Kagoshima-shi, Kagoshima-ken, (5) Kagoshima University Hospital, Kagoshima-shi, Kagoshima-ken, (6) Kagoshima University Hospital, Kagoshima-shi, Kagoshima-ken, (7) Kagoshima University Hospital, Kagoshima-shi, Kagoshima-ken, (8) Kagoshima University Kagoshima-shi, Kagoshima-ken, (9) Kyushu University, Fukuoka-city, Fukuoka-ken

SU-E-T-456 Sunday 3:00PM - 6:00PM Room: Exhibit Hall

Purpose:Our aim of this study was to prospectively investigate the feasibility of three-dimensional (3D) treatment planning of intracavitary brachytherapy for cervical cancer based on computed tomography (CT) images. Two-dimensional (2D) treatment planning based on Manchester method and the 3D treatment planning based on Groupe Europeen de Curietherapie-European Society for Therapeutic Radiology and Oncology recommendations were compared using 2D and 3D-based dose evaluation indices.

Methods:The 2D and 3D treatment plans were made on Oncentra for six patients with stage IB-IIB cervical cancer, who had undergone intracavitary brachytherapy (five fractions at 6Gy/fraction). Planning CT images were acquired on a 20-slice CT scanner at the lithotomy position after inserting the applicator. Point A-based and D90 dose prescriptions were employed for 2D and 3D treatment planning, respectively. The GTV plus 1-cm margin was defined as a CTV in 3D treatment planning. The two kinds of treatment plans were evaluated by a conformity index (CI), homogeneity index (HI), and tumor control probability (TCP) for CTV, and doses at bladder and rectum evaluation points, D2cc, and normal tissue complication probability (NTCP) for organs at risk (OAR).

Results:The CIs for 2D and 3D plans were 2.59 ± 0.59 and 1.12 ± 0.18 (p < 0.05), respectively, and the HIs were 2.18 ± 0.28 (2D) and 1.34 ± 0.27 (3D) (p < 0.05). The bladder D2cc for 2D and 3D plans were 378 ± 58.2 cGy and 504 ±47.2 cGy (p < 0.05), respectively, and the rectum D2cc were 316 ± 58.3 cGy (2D) and 455 ± 36.1 cGy (3D) (p < 0.05). There were no statistical significant differences for the TCP and NTCP.

Conclusion:The 3D treatment planning could provide better dose conformity and uniformity in CTVs. The results suggested that the doses for OAR with 2D treatment planning may be underestimated.

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