The study for biological effect dose of spinal cord in thoracic tumors with the model of conformal and intensity modulated technique and conventional fractionation

Abstract

Objective To investigate the necessity and feasibility of evaluation for spinal cord biological effect dose (BED) in clinical radiotherapy on thoracic tumors in the model of conformal or intensity modulated technique and conventional fractionation. Methods From 16 May 2016 to 31 December 2016, 30 patients accepting thoracic radiotherapy were selected in the Radio-chemotherapy department of Tangshan City People's Hospital. Radiotherapy plans of these patients were evaluated by the evaluation module of the RTIS treatment plan system, and then the physical dose (PhD) and BED were compared, respectively. After that, the PhD and BED of the spinal cord in different dose curves for 2.0 Gy irradiation 1 and 30 times were calculated by the linear quadratic equation (L-Q model) . T test was used for all comparison between groups in statistics. Results The BED curve of the spinal cord was on the left of the PhD curve, and the BED curve of planning target volume(PTV) was on the right of the PhD curve. In the radiotherapy plans of the 30 patients, for the spinal cord, the minimum maximum, average doses of PhD and BED were (80.41±274.75), (3398.00±1200.95), (1265.79±762.49) cGy and (74.71±249.34), (3118.93±1181.96), (1181.44±742.18) cGy, separately, the differences of them were significantly (t=0.826, 6.143, 5.234, all P 0.05) . With the decline of the dose curve, the PhD and BED were reducing, and the BED were lower than the PhD in the curve for corresponding dose. Conclusions In the radiotherapy of thoracic tumors, considering potential enhancement of local target control and better spinal cord protection, it is necessary to evaluate the BED of the spinal cord. Key words: Thoracic neoplasms; Radiotherapy, intensity-modulated; Spinal cord; Conventional fractionation; Biological effect dose