2015年 · 第24卷第04期

At present, most of the built-in dose algorithms of radiotherapy planning system are based on pencil beam iterative convolution technology. Several studies have shown that the pencil beam algorithm has limitations in heterogeneous media, mainly because the pencil beam algorithm cannot accurately simulate the dose distribution of secondary electrons in heterogeneous media by applying one-dimensional density correction^[1,2]。 Monte Carlo simulation algorithm is recognized as the "gold standard" of dose calculation at present^[3,4]。 The aim of this study was to compare the difference of dose distribution between pencil beam and Monte Carlo algorithms in clinical dose calculation.

In order to reduce the positioning error, many scholars improve the accuracy of radiotherapy by improving patient fixation^[1,2]。 However, for patients with pelvic tumor, due to the influence of skin looseness, abdominal fat, lower limb rotation and leg separation angle, the position of selected marker points changes greatly, which increases the positioning error^[3]。 Therefore, according to the positioning requirements of pelvic tumor radiotherapy and the fixation characteristics of thermoplastic membrane and body frame, the author made a self-made auxiliary fixation device for both lower limbs (patent number: zl 2013 2 0222024.2) and applied it in clinic.

The HT system represents a completely new technique for radiotherapy, whose therapeutic principle is similar to computed spiral tomography CT, which can achieve a high conformal dose distribution^[1]。 In order to ensure accurate irradiation dose and successful implementation of treatment plan, patient pre-treatment dose verification has become a key link in quality assurance. The results of HT dose verification of pancreatic cancer patients using ArcCHECK motif in 2012 are analyzed as follows, in order to more strictly implement QA in future clinical work.

Lung cancer is the first malignant tumor in both morbidity and mortality^[1]。 Radiotherapy is the main treatment for intermediate and advanced lung cancer, and at least 60% of lung cancer patients need radiotherapy^[2]。 The primary dose limiting factor for lung cancer radiotherapy is RP. RP is a common complication of thoracic radiotherapy, which is a sterile inflammatory reaction caused by radiation damage to normal lung tissue after radiotherapy of thoracic malignant tumor. The main clinical manifestations of RP are fever, cough, chest pain, tightness of air and dyspnea, etc. Severe patients often die due to respiratory distress and high fever, and some patients only have imaging changes without clinical symptoms. The risk factors affecting RP were sex, age, smoking, KPS score, pathological type, dosimetric parameters, tumor site, other diseases and chemotherapy, etc^[3,4]。 However, under the condition of fully considering the above influencing factors, patients with the same clinical stage and similar lung function are given the same dose and similar volume of irradiation, and the development speed and severity of RP are also different. Some patients develop acute RP symptoms during radiotherapy or within 3 months after radiotherapy, some appear more than 1 year after radiotherapy, showing chronic RP manifestations, and some do not have RP. A large number of clinical observations have found that the incidence of RP has individual differences, suggesting that the occurrence of RP may also be related to genetic factors.

Gastric cancer is one of the fourth most common malignant tumors in the world, and gastric cancer patients in China account for 40% of all gastric cancers in the world^[1]。 According to the data of China Cancer Registry Annual Report in 2012, its incidence rate ranks second among all malignant tumors, and its mortality rate ranks third^[2]。 China is a developing country, the people's awareness of regular physical examination is weak, the cancer screening rate is low, and the initial symptoms of gastric cancer patients are often atypical. Therefore, about 50% of patients are advanced or locally advanced when they see a doctor, and they lose the opportunity of radical surgery. Usually, such patients have a poor prognosis, with a median survival time of only 8 to 13 months^[3,4,5,6]。 Since the publication of the results of the US INT 0116 study^[7,8]The postoperative adjuvant therapy for gastric cancer has basically reached a consensus: concurrent postoperative chemoradiotherapy is considered to undergo radical surgery (R₀) and<D₂Standard treatment for locally advanced gastric cancer with lymph node dissection^[9]； If it is D₂Lymph node dissection, postoperative concurrent radiotherapy and chemotherapy are open to debate. However, the value of simultaneous radiotherapy and chemotherapy for gastric cancer is still unclear. How to transform inoperable gastric cancer into surgically resectable gastric cancer through appropriate preoperative neoadjuvant therapy is an urgent problem to be solved at present. The following is a brief description of the research progress of preoperative chemoradiotherapy for locally advanced gastric cancer.

The first Guangzhou Radiation Oncology Forum, sponsored by the Cancer Prevention and Treatment Center of Sun Yat-sen University, was held in Guangzhou on May 30, 2015. More than 320 experts and colleagues from dozens of brother hospitals across the country, including Affiliated Cancer Hospital of Academy of Medical Sciences, Peking Union Medical College Hospital, Affiliated Cancer Hospital of Fudan University, West China Hospital and Tianjin Cancer Hospital, and various radiotherapy units in Guangdong Province gathered at the Cancer Prevention and Treatment Center of Sun Yat-sen University. Professor Liao Zhongxing, director of radiotherapy department of MD Anderson Cancer Center in the United States, and Professor Anna Simeonova from Mannheim Medical Center of Heidelberg University in Germany attended the appointment and joined them.