Study On Dosimetry And Efficacy Of Modified Field Radiotherapy During Neoadjuvant Therapy For Advanced Rectal Cancer

Part I:The dosimetry study of the modified irradiation field foradvanced rectal cancer before surgery ObjectiveWe changed conventional neoadjuvant radiotherapy target range for advanced rectal cancer. Futhermore, evaluation the dosimetric advantage of modified target was performed. It will provide basis for choosing radiation ranges for neoadjuvant radiotherapy of rectal cancer. Materials and MethodsFrom September 2013 to December 2014, 23 cases of patients with rectal cancer in our department who had received neoadjuvant chemoradiotherapy were selected. All patients must be diagnosed as rectal adenocarcinoma. The simulation CT-scan images of 23 patients were tranferred to 3D-TPS workstation. Physicians were required to outline treatment group and control group on the CT images. 5 fields IMRT plans was designed for two groups of radiation field respectively.Their prescription dose are 50Gy/25Fx/5W. The dosimetry of the radiation target and normal organ was evaluated respectively. Results1、Both groups of 10X-IMRT treatment plans can meet the requirements of the prescribed dose. There was no significance difference(p=0.061) between the conformal index(CI) values of the treatment group(0.82±0.02) and control group(0.82±0.02). Meanwhile, there was no statistically significant difference between the uniformity index(HI) of the treatment group(1.05±0.06) and control group(1.06±0.08). Results showed that both treatment plannings can meet the requirement in CI and HI. DVH diagram showed that the iso-dose lines were steeper in the treatment group, but the difference was not significant.2、 The treatment group can significantly reduce the volume and radiation dose of normal tissues and organs. There were significant differences between the absolute volume of small intestine and colon irradiated(V10 ~ 50Gy). V15 Gy of treatment group was reduced to a mean of approximate 69.9% and the average radiation dose of the small intestine was reduced by about 63.0% in the treament group. There are significant differences in the volume of irradiated pelvis(V10Gy~50Gy).The average radiation dose to the pelvis was reduced by approximately 28.2% in the treament group. The irradiation dose of the bladder and colon were also significantly reduced. But there was no statistically significant difference on the irriation dose of femoral head. ConclusionsBoth groups of treament plans can meet the requirements of prescribed dose of patients with advanced rectal cancer who receive neoadjuvant chemoradiotherapy. It is safe and feasible for them. The modified small target irradiation field can significantly reduce radiation dose and volume of surrounding normal tissues and organs, In particular, the role of the protection of the small intestine and pelvis has significant meaning.Part II:Study on the short-term clinical efficacy of the modifiedirradiation field for advanced rectal cancer before surgery ObjectiveThe aim of this study was to evaluate the difference of short-term clinical efficacy and acute adverse reactions of advanced rectal cancer patients treated by different irradiation range before the surgery. Furthermore, it will provide basis for modified target irradiation field for neoadjuvant radiotherapy of rectal cancer. Materials and MethodsFrom July 2013 to November 2014, advanced rectal cancer patients treated in our department treatment were included as research objects and 54 cases with complete data were included to this study. Patients were randomly divided into two groups, Both groups received neoadjuvant chemoradiotherapy. Their prescription dose are 50Gy/25 Fx. The method of concurrent chemotherapy was as follows: Capecitabine 625 mg/m2, 2 times/day, oral, lasting 14 days and then taking a rest for 7 days. This method will continue to the end of radiotherapy. Depending on the reaction of the patient to neoadjuvant therapy, rectal cancer patients chose to receive surgery at the end of 6 to 8 weeks in accordance with the principles of TME. The efficacy of neoadjuvant therapy was evaluated by RECIST1.1 standard system, Acute adverse reactions were assessed y CTC3.0 standard. ResultsAll patients completed neoadjuvant chemoradiatherapy. Total effective rate(RR) were 70.4% and 74.1% in the treatment and control group(P>0.05),respectively., Disease control rates(DR) were 96.3% and 92.6% in the treatment and control group(P>0.05),respectively. Differences between the two groups had no statistical significance in RR and DR. So there was no statistical significance in the recent therapeutic effects between two groups. Myelosuppression in both groups were mainly leukopenia and neutropenia. The occurence of leukopenia in treatment group and control group were 48.1% and 77.8%, respectively(P < 0.05). The occurence of leukopenia in treatment group and control group were 22.2% and 55.6%, respectively(P<0.05). So there was no statistical significance between the two groups. In addition, there is no significant difference in the indidence of fatigue and mucocutaneous reactions in two groups. Digestive system reaction mainly contained diarrhea, malignant and vomiting. Serious vomiting rates were 40.7% and 70.4% in the treatment and control group(P <0.05), The difference was statistically significant in both groups. Conclusionshere are no significant difference in the response rate and disease control rate between both groups of patients after neoadjuvant chemotherapy. But modified field target radiation group can significantly reduce adverse reaction(e.g. blood and digestive system toxicity). Furthermore, and compliance of the patients in the treatment process is better.