Abstract
Aims: Research the possibility of using IMRT for rectal cancer patients in preoperative radiotherapy. Methods and Material: The research object is the preoperative radiotherapy plan for rectal cancer patients. The research group made two plans (IMRT, 3DCRT) for each image series of 34 rectal cancer patients who have received preoperative radiotherapy in Hanoi Oncology Hospital; and then compared the dose distribution on PTV, bladder, intestine, femoral bones, the average MU, and QA results of two types of plan. Results: The 95% isodose line and 50% isodose of IMRT plan are closer than those of 3DCRT plan. The average dose of PTV in IMRT plan and 3DCRT plan are 5006 ± 23 cGy and 5036 ± 42 cGy, respectively. The HTCI and HI values of IMRT and 3D plan are 0.97 ± 0.026 and 5.37 ± 1.32; 1.00 ± 0.003 and 7.08 ± 0.88. About the dose of organ at risk: The maximum dose, average dose on the right, left femoral head in the IMRT plan are less than those values in the 3DCRT plan (6.2 Gy, 6 Gy, 7.4 Gy, 9 Gy, respectively). The maximum dose and average dose on the bladder of the IMRT plan are smaller than those values of the 3DCRT plan (5.3 Gy, 1.5 times, respectively). The maximum dose and average dose of intestine in the IMRT plan was less than those values in the 3DCRT plan (4.3 Gy, 1.54 times, respectively). The MU number of IMRT plan is 1.5 times bigger than that of 3DCRT plan. Gamma index of IMRT plan is better than that of 3DCRT plan (99% compared with 97%). Conclusions: Using IMRT plan in preoperative radiotherapy for rectal cancer patients can still ensure covered PTV as well as the 3D PLAN. Furthermore, the dose of PTV in the IMRT plan is more uniform than those in the 3D plan, and the dose effect on the OAR surrounding PTV is much lower than when using the 3D plan. When IMRT plan were used to treat the preoperative rectal cancer patients, the LINAC took more time than when using 3DCRT plan.
Highlights
According to the study of global cancer statistics 2018 by Freddie Bray et al, based on data from 185 countries, in the New Cases and Deaths for 36 Cancers and All Cancers Combined in 2018 Report, rectal cancer ranked the 9th with 704,376 new cases and 31,394 deaths [1].Generally, there have been many studies on Intensity Modulated Radiation Therapy (IMRT) radiation therapy for rectal cancer or cancer of pelvis region, such as the study of Yevgeniya Jane Mikhailovna Ioffe et al In this research, eighty-three patients registered to be treated with IMRT
1) Comparison of dose distribution on the transverse CT slice In Figure 1, observing the 95% isodose line, that is the green line, in pairs of the sections of CT images of both IMRT and 3D-conformal radiation therapy (3DCRT) plans, the results showed that the isodose line of the IMRT plan bends and circles around the PTV line, and avoids the intestines
Observing the lower isodose line, the 50% isodose line in the IMRT plan bends in PTV shape, and evades the intestine
Summary
According to the study of global cancer statistics 2018 by Freddie Bray et al, based on data from 185 countries, in the New Cases and Deaths for 36 Cancers and All Cancers Combined in 2018 Report, rectal cancer ranked the 9th with 704,376 new cases and 31,394 deaths [1].Generally, there have been many studies on IMRT radiation therapy for rectal cancer or cancer of pelvis region, such as the study of Yevgeniya Jane Mikhailovna Ioffe et al In this research, eighty-three patients registered to be treated with IMRT. This study has shown the possible advantage of IMRT in improving long-term functioning of cervical cancer survivors, and in decreasing in pelvic girdle complications, which are likely to reduce pain levels and chronic morbidity and contribute to a higher psychosocial and sexual function. The vast majority of the patients in our study who experienced pelvic girdle complications post-RT were symptomatic with pain that became chronic or required the use of narcotic medications [2]-[16]. Howell et al found that Effective doses were higher for conventional radiotherapy compared to IMRT for all beam energies. Jabbour et al compared the acute toxicities of IMRT to 3D-conformal radiation therapy (3DCRT) in the treatment of rectal cancer, the research showed that IMRT reduces doses of the irradiated small bowel and IMRT can reduce median charges to small bowel by 5.1 Gy for rectal cancer [6]
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