[Comparison of the application among intensity-modulated radiotherapy, 3D-conformal radiotherapy and conventional radiotherapy for locally advanced middle-low rectal cancer].

OBJECTIVE

To compare the application among intensity-modulated radiotherapy (IMRT), three-dimensional conformal radiotherapy(3D-CRT) and conventional radiotherapy (CRT) for locally advanced middle-low rectal cancer.

METHODS

From January 2015 to December 2016, 93 locally advanced middle-low rectal cancer patients with clinical stage cT3N+M0 or cT4N0/+M0 who underwent preoperative concurrent chemoradiotherapy at Department of Colorectal Surgery, the Third Affiliated Hospital of Kunming Medical University and had complete data were enrolled in this retrospective cohort study. Patients were divided into IMRT group (17 cases), 3D-CRT group (28 cases) and CRT group (48 cases) according to different radiotherapy methods. The frequency and dose of CRT were 1 time/day, 5 times/week, for a total of 5 weeks, with a single dose of 2.0 Gy, the total dose was 50 Gy. Frequency and dose of 3D-CRT and IMRT were 1 time/day, 5 times/week, for a total of 23 to 28 times, with a single dose of 1.8 to 2.0 Gy, and a total dose of 45.0 to 50.4 Gy. The chemotherapy regimen was performed with capecitabine tablets at a dose of 825 mg/m twice a day for 5 days every week, at the same time during radiotherapy. The efficacy, chemotherapy adverse reactions and immune function of the three groups were compared.

RESULTS

There was no significant difference in the baseline data among the three groups (all P>0.05). The proportion of patients receiving permanent ostomy in the IMRT group and the 3D-CRT group was 29.4%(5/17) and 32.1%(9/28) respectively, which was lower than 58.3%(28/48) in CRT group, and the difference was statistically significant (χ²=7.982, P=0.030), while this proportion was not significantly different between IMRT and 3D-CRT group(χ²=0.037, P=0.848). The pathologic complete response(pCR) rate was 23.7%(22/93) in the whole study, and the pCR rate was 39.3%(11/28) in the 3D-CRT group, which was higher than that of CRT group and IMRT group [12.5%(6/48) and 29.4%(5/17)], and the difference was statistically significant (χ²=7.407, P=0.025), while there was no significant difference in pCR rate between CRT group and IMRT group (χ²=2.554, P=0.110). There was no adverse reaction of grade 3 or above in all three groups. No significant difference in the incidence of bone marrow suppression, abnormal liver and kidney function markers, digestive tract reaction or radiation dermatitis was found(all P>0.05). After receiving concurrent chemoradiotherapy, the proportion of CD3/CD4 cells in the IMRT group and the CRT group decreased compared with that before treatment(23.1±9.3 vs. 31.1±10.9, 27.4±10.7 vs. 33.6±7.2, respectively); the proportion of CD3/CD8 cells was up-regulated (36.1±15.2 vs. 24.8±10.9, 30.9±14.4 vs. 24.0±8.3,respectively), and the differences were statistically significant (both P<0.05), while the above indexes before and after treatment were not significantly different in the 3D-CRT group(all P>0.05). After treatment, the proportion of CD4/CD8 cells in IMRT group decreased (0.8±0.6 vs. 1.6±1.0, t=3.838, P=0.003), while this proportion was not significantly different in CRT group and 3D-CRT group(all P>0.05).

CONCLUSIONS

IMRT and 3D-CRT can reduce the rate of permanent stoma. 3D-CRT can increase pCR rate. No obvious advantage is shown in IMRT as compared with 3D-CRT in the short-term efficacy. On the contrary, an immunosuppressive status may occur. Therefore, 3D-CRT is recommended as the best preoperative treatment strategy for patients with locally advanced middle-low rectal cancer, especially for those with immunosuppression status.