Tomotherapy for Advanced Cervical Cancer: A Comparison of Dosimetric and Clinical Outcomes With Intensity Modulated Radiation Therapy
Authors: Yin Yueju , Wang Dandan , Li Dapeng , Zhu Jian , Chen Quancai , Sheng Xiugui , Feng Shuai , Jia Jue , Yu Hao 
Published: September 2020

Abstract
Purpose: The aim of this study was to investigate the therapeutic response (loco-regional control, disease-free, overall survival), toxicities (acute and long-term toxicities) and dosimetric parameters between intensity-modulated radiation therapy (IMRT) and tomotherapy (TOMO) in patients with advanced cervical cancer.Materials and Methods: This study included 310 patients with advanced cervical cancer and who received concurrent chemoradiation (CCRT) from August 2015 to March 2018. All patients were initially diagnosed with International Federation of Gynecology and Obstetrics (FIGO 2009) stage ⅡB–ⅢB cervical cancer. A total of 155 patients were treated with TOMO, whereas the remaining 155 patients underwent IMRT. Intracavitary brachytherapy and concurrent chemotherapy were performed during external irradiation.Results: A total of 310 patients were included in the present study. There was no statistical difference in age, FIGO stage, histologictype, tumor size, tumor grade, pathologic morphology type, between the 2 groups (P=0.924, 0.352,0.954, 0.36, 0.11, and 0.123, respectively). In comparing TOMO with IMRT, better dose conformity (0.82±0.033 vs. 0.75±0.064, P= 0.006) and dose homogeneity (1.03±0.006 vs. 1.09±0.076, p＜0.001) were observed by TOMO planning. TOMO provided better critical organ sparing than IMRT in the lower bladder V20 (p=0.001), femoral head V40 (p=0.014), and lower rectum V40 (p=0.035), V20 (p=0.005) were observed in the planning by TOMO compared to IMRT for patients with advanced cervical cancer. TOMO demonstrated a superior ability to protect the ovary (Dmax: 4.61Gy versus 5.81Gy, P=0.026; Dmean: 2.99Gy versus 3.97Gy, P=0.017). A few OARs and dosimetric parameters, including bladder V40 (p=0.113), and femoral head V20 (p=0.066), exhibited a tendency toward more favorable values in TOMO than IMRT. There were no statistically signifcant diferences in small bowel V20 (p=0.251), V40 (p=0.575) or bone marrow protection V20 (p=0.917), V40 (p=0.53) between the IMRT plan and the TOMO plan. But it gave significantly better values for Dmax parameters for bone marrow and small bowel with a statistically significant level (P= 0.004, and 0.002, respectively). Acute major toxic effects included cystitis, proctitis, leukopenia, dermatitis, and enteritis. Seventeen (11%) patients in the IMRT group and 5(3.22%) in the TOMO group experienced grade 3/4 acute proctitis. Grade 3/4 leukopenia occurred in 71 (45.81%) patients in the IMRT group and 60 (38.71%) patients in TOMO group. Eleven (7.1%) patients in the IMRT group experienced grade 3/4 late radiation cystitis. And grade 3/4 late radiation enterocolitis occurred in 10 (6.45%) patients in the IMRT group. The incidence of chronic radiation cystitis and enterocolitis in the TOMO group was 3.87% (6/155). The acute radiation toxicity of proctitis, and leukopenia was significantly lower in TOMO group than IMRT group (P=0.034, and 0.025, respectively). There was no statistical difference in the acute radiation toxicity of cystitis, enteritis, and dermatitis between the 2 groups (P= 0.084, 0.082 and 0.616, respectively). The chronic radiation toxicity of radiation enterocolitis and cystitis was lower in the IMRT group (P= 0.032 and 0.048, respectively). But there was no statistical difference for 1- and 3-year OS between the TOMO and IMRT groups (98.7% vs 98.5%, P= 0.149；91.3% vs 96.3%, P= 0.142). No obvious difference was found in 1- and3-year PFS rates between 2 groups (1-year: 91.4% vs 91.6%, P= 0.82; 3-year: 86.8% vs 88.3%, P= 0.751). Conclusions: This study has shown that TOMO and IMRT are comparable in dose conformity, dose homogeneity, and protection of the ovary. TOMO provided better critical organ sparing than IMRT in lower bladder, femoral head, ovary sparing and lower rectum were observed in the planning. The acute and chronic toxicities were acceptable. So TOMO is a good option for adjuvant treatment of FIGO stage ⅡB–ⅢB cervical cancer, especially to young patients. Further prospective randomized multicenter studies are needed to confirm the benefits of TOMO.