Abstract

Purpose : In spite of recent remarkable improvement of diagnostic imaging modalities such as CT, MRI, and PET and radiation therapy planing systems, ICR plan of uterine cervix cancer, based on recommendation of ICRU38(2D film-based) such as Point A, is still used widely. A 3-dimensional ICR plan based on CT image provides dose-volume histogram(DVH) information of the tumor and normal tissue. In this study, we compared tumor-dose, rectal-dose and bladder-dose through an analysis of DVH between CTV plan and ICRU38 plan based on CT image. Method and Material : We analyzed 11 patients with a cervix cancer who received the ICR of Ir-192 HDR. After 40Gy of external beam radiation therapy, ICR plan was established using PLATO(Nucletron) v.14.2 planing system. CT scan was done to all the patients using CT-simulator(Ultra Z, Philips). We contoured CTV, rectum and bladder on the CT image and established CTV plan which delivers the 100% dose to CTV and ICRU plan which delivers the 100% dose to the point A. Result : The volume$(average{\pm}SD)$ of CTV, rectum and bladder in all of 11 patients is $21.8{\pm}6.6cm^3,\;60.9{\pm}25.0cm^3,\;111.6{\pm}40.1cm^3$ respectively. The volume covered by 100% isodose curve is $126.7{\pm}18.9cm^3$ in ICRU plan and $98.2{\pm}74.5cm^3$ in CTV plan(p=0.0001), respectively. In (On) ICRU planning, $22.0cm^3$ of CTV volume was not covered by 100% isodose curve in one patient whose residual tumor size is greater than 4cm, while more than 100% dose was irradiated unnecessarily to the normal organ of $62.2{\pm}4.8cm^3$ other than the tumor in the remaining 10 patients with a residual tumor less than 4cm in size. Bladder dose recommended by ICRU 38 was $90.1{\pm}21.3%$ and $68.7{\pm}26.6%$ in ICRU plan and in CTV plan respectively(p=0.001) while rectal dose recommended by ICRU 38 was $86.4{\pm}18.3%$ and $76.9{\pm}15.6%$ in ICRU plan and in CTV plan, respectively(p=0.08). Bladder and rectum maximum dose was $137.2{\pm}50.1%,\;101.1{\pm}41.8%$ in ICRU plan and $107.6{\pm}47.9%,\;86.9{\pm}30.8%$ in CTV plan, respectively. Therefore, the radiation dose to normal organ was lower in CTV plan than in ICRU plan. But the normal tissue dose was remarkably higher than a recommended dose in CTV plan in one patient whose residual tumor size was greater than 4cm. The volume of rectum receiving more than 80% isodose (V80rec) was $1.8{\pm}2.4cm^3$ in ICRU plan and $0.7{\pm}1.0cm^3$ in CTV plan(p=0.02). The volume of bladder receiving more than 80% isodose(V80bla) was $12.2{\pm}8.9cm^3$ in ICRU plan and $3.5{\pm}4.1cm^3$ in CTV plan(p=0.005). According to these parameters, CTV plan could also save more normal tissue compared to ICRU38 plan. Conclusion : An unnecessary excessive radiation dose is irradiated to normal tissues within 100% isodose area in the traditional ICRU plan in case of a small size of cervix cancer, but if we use CTV plan based on CT image, the normal tissue dose could be reduced remarkably without a compromise of tumor dose. However, in a large tumor case, we need more research on an effective 3D-planing to reduce the normal tissue dose.

Keywords

• Uterine cervix cancer;
• Intracavitary radiotherapy;
• Clinical target volume

• 자궁경부암;
• 강내조사;
• 표적용적;

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References

1. Kottmeier HL. Classification and staging of malignant tumors in the female pelvis. J. Int. Fed. Gynecol. Obstet. 1971:172-179
2. Chassagne D. Dutreix A. Almond P. Burgers J. Busch M. Joslin C. ICRU report No. 38. and volume specification for reporting intracavitary therapy in gynecology. International Commissioning on Radiation Units and Measurements. Bethesda. 1985
3. Wachter-Gerstner N, Wachter S, Reinstadler E, et al. : Bladder and rectum dose defined from MRI based treatment planning for cervix cancer brachytherapy : comparison of dose-volume histograms for organ contours and organ wall, comparison with ICRU rectum and bladder reference point. Radiother Oncol. 2003 Sep:68(3):269-76 https://doi.org/10.1016/S0167-8140(03)00189-0
4. Malyapa RS, Mutic S, Low DA, et al. Physiologic FDG-PET three-dimensional brachytherapy treatment planning for cervical cancer. Int. J. Radiat. Oncol. Biol. Phys. 2002:54:1140-1146 https://doi.org/10.1016/S0360-3016(02)03043-2
5. Schoeppel SL, Ellis JH, LaVigne ML, et al. Magnetic resonance imaging during intracavitary gynecologic brachytherapy. Int. J. Radiat. Oncol. Biol. Phys. 1992 :23:169-174 https://doi.org/10.1016/0360-3016(92)90557-X
6. Ling CC, Schell MC, Working KR, et al. CT-assisted assessment of bladder and rectum dose in gynecological implants. Int. J. Radiat. Oncol. Biol. Phys. 1987 :13:1577- 1582 https://doi.org/10.1016/0360-3016(87)90327-0
7. Fellner C, Potter R, Knocke TH, et al. Comparison of radiography and computed tomography-based treatment planning in cervix cancer in brachytherapy with specific attention to some quality assurance aspects. Radiother. Oncol. 2001 :58:53-62 https://doi.org/10.1016/S0167-8140(00)00282-6
8. Kim RY, Caranto JF, Pareek PN, Virost LJ. Dynamics of pear-shaped dimensions and volume of intracavitary brachytherapy in cancer of the cervix: a desirable pear shape in the era of three-dimensional treatment planning. Int. J. Radiat. Oncol. Biol. Phys. 1997:37(5):1193-1199 https://doi.org/10.1016/S0360-3016(96)00630-X
9. Wachter-Gerstner N, Wachter S, Reinstadler E, Fellner C, Knocke TH, Potter R. The impact of sectional imaging on dose escalation in endocavitary HDR-brachytherapy of cervical cancer : results of a prospective comparative trial. Radiother. Oncol. 2003:68(1):51-59 https://doi.org/10.1016/S0167-8140(03)00083-5
10. Kim RY. CT-based intracavitary brachytherapy for cancer of the cervix: analysis of dose-volume histogram. Int. J. Radiat. Oncol. Biol. Phys. 1998 :40:515-524 https://doi.org/10.1016/S0360-3016(97)00732-3
11. Eich HT, Haverkamp U, Micke O, Prott FJ, Muller RP. Dosimetric analysis at ICRU reference points in HDRbrachytherapy of cervical carcinoma. Rontgenpraxis. 2002:53(2):62-69
12. Hellebust TP, Dale E, Skjonsberg A, Olsen DR. Inter fraction variations in rectum and bladder volumes and dose distributions during high dose rate brachytherapy treatment of the uterine cervix investigated by repetitive CTexaminations. Radiother. Oncol. 2001 Sep:60(3):273-280 https://doi.org/10.1016/S0167-8140(01)00386-3
13. Barillot I, Horiot JC, Maingon P, Bone-Lepinoy MC, et al. Maximum and mean bladder dose defined from ultrasonography Comparison with the ICRU reference in gynecological brachytherapy. Radiother. Oncol. 1994 Mar:30(3):231-238 https://doi.org/10.1016/0167-8140(94)90463-4