Dosimetric Analysis Of Target Dose In Postoperative Breast Cancer Patients With Different Bolus Times

Background and ObjectiveWith the development of social economy,people’s life and work pressure is increasing.The incidence rate of breast cancer is increasing.Breast cancer has become one of the culprits that endanger women’s health.Radiotherapy after radical mastectomy is one of the main means of comprehensive treatment for breast cancer.Due to the objective existence of built-up effect,during radiotherapy of skin and superficial organs,It is often necessary to add tissue compensation on the skin surface to increase the local exposure dose,and it is often necessary to add tissue compensation on the skin surface to increase the local exposure dose.Therefore,based on prescription dose requirements and X-ray physical construction theory.During planning and radiotherapy,tissue compensators may be applied to the skin surface to increase the dose in the local area while ensuring that the dose is uniform.General silicone bolus is commonly used as tissue compensator to increase chest wall dose in patients receiving radiotherapy after modified radical mastectomy for breast cancer.However,the quality of life of patients must be fully considered while the dosage of tumor target is satisfied.That is to ensure that the tumor target area and skin overlapping area to get enough dose to prevent local recurrence,at the same time,reasonable control of the dose to prevent skin necrosis,ulcer and other side reactions.At present,there have been many studies on the method of tissue compensator addition,and it is relatively consistent to reflect the advantages of the whole process of tissue compensator addition.Some studies have shown that there is no significant difference between the addition of tissue compensation in half and in full.In most studies,dose evaluation parameters were taken as the object of the whole target area,and this method could not fully reflect the dose distribution mode of the surface built-up area.Based on this,in order to provide evidence for the coverage times of tissue compensators in the course of radiotherapy after modified radical mastectomy for breast cancer.The new evaluation parameters of radiotherapy after modified radical mastectomy for breast cancer were proposed.This paper mainly analyzed the effect of chest wall tissue compensation on chest wall dose after radical mastectomy.Material and methodsCT images of breast cancer patients who received radiotherapy after radical breast cancer surgery from February 2017 to December 2019 were obtained.Target volume of Tumor and organs at risk are delineated by qualified physicians.Tissue compensators were added to all the acquired cases during the actual treatment.Twenty patients who had received radiotherapy after radical resection of breast cancer and 11 groups of radiotherapy plan with progressive reduction of bolus were adopted and the results were statistically analyzed.Using human simulators and thermoluminescence dosimeters,Simulated radiation therapy plan with tissue compensator after radical mastectomy,and measure the dose in the chest wal.ResultThe study result shows that the D95 of PTV for every patients will decrease with the decrease of bolus times.The D95 of PTV has shrunk to less than 4700cGy,when the patients with the preceding 21 times of radiotherapy with boluses and the following 4 times of ones with no boluses.The D95 of PTV is still greater than 4500cGy,when the patients with the preceding 16 times of radiotherapy with boluses and the following 9 times of ones with no boluses.When the number of times of coating tissue compensation film on the human simulation phantom is less than or equal to 22 times,The total dose at three reference points A,B and C were all less than 4500cGy.When covering 23 times,the dose at points A and B was less than 4500cGy.When the tissue compensation membrane was covered 24 times,the total dose of A,B and C were all greater than 4500cGy.When the tissue compensation membrane was covered 25 times,the total dose of A,B and C were all greater than 4500cGy.ConclusionThe radiation therapy plans of postoperative patients with breast cancer should with boluses all the way.The doses of target lies under the skin 5mm should be evaluated as a separate parameter.