Research on Using IMRT Plan for Preoperative Rectal Cancer Patients

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.