| The incidence of breast cancer is on the top of the female malignantcarcinoma, and the disease rate increases with the speed of about2%per year.About1.2million women were diagnosed with new breast cancer and500,000women died of it each year in the world. In North America and NorthernEuropean, the incidence of breast cancer is higher than other area. In recentyears, new breast cancer incidence rate increases of3-4%progressively inChina. In Beijing, Shanghai and other major cities, breast cancer has becomethe most dangerous malignant tumor instead of cervical cancer.The breast is a secondary sex character for women and importantembodiment of female beauty. The traditional operations not only damagebreast physiological function, but also affect women’s mental health seriously.Some randomized clinical trials proved that the breast-conserving surgerycombined with postoperative radiation therapy could have the same curativeeffect with the Halsted radical mastectomy. The breast cancer treatment hasbecome systemic comprehensive one dominated by surgery, combined withradiotherapy, chemotherapy, immunotherapy and endocrine treatment.Radiotherapy for breast cancer patients could reduce postoperative localrecurrence rate. The radiation technology after conservative surgery for breast cancerwith early stage is including:3-dimensional conformal radiotherapy(3D-CRT),4-beam intensity-modulated radiotherapy (4B-IMRT) andvolumetric modulated arc therapy (VMAT).The dose distributions on the targets and organs at risk (OAR) in3D-CRT,4B-IMRT and VMAT were observed on breast patients afterconservative surgery. The dose-volume histograms of targets and OAR indifferent irradiation technologies were detected in this paper.A total of53patients with breast cancer after conserving surgery wererecruited for this research. Of53patients,30were left breast cancer and23were right breast cancer. These participants were all Chinese of Han originand came from the Northeast area of China. The radiotherapy targets includedlacteal gland and OAR included lung, heart and liver. They were contouredafter CT simulation. The dose distributions of targets and OAR, therapeutictime and monitor unit were analyzed in3D-CRT,4B-IMRT and VMAT.The results of target V40(%), V45(%) and V50(%) showed that VMATgroup (99.8±0.23，98.5±0.37，95.2±0.12) was higher than4B-IMRT group(91.79±1.4，83.2±2.23，45.1±14.6) and3D-CRT group (88.5±3.7，78.1±5.7，25.9±13.9)(P <0.05). As compared with4B-IMRT group (5839±144.3), thetarget maximum dose (cGy) of VMAT group (5976±42.9) was increasedsignificantly (P <0.05). The treatment time (s) of VMAT group (295±37.5)was shorter than4B-IMRT group (713±125.1)(P <0.05). The monitor unit (MU) of3D-CRT group (230±17.2) was decreased significantly comparedwith4B-IMRT group (620±51.3) and VMAT group (570±37.0)(P <0.05).The VMAT group (637.1±432.1) had higher average dose of liver than3D-CRT group (268.4±167.3). The analysis showed that average dose of heartin the right side of breast cancer in VMAT group (425±236) was increasedsignificantly compared with3D-CRT group (110±29.32) and4B-IMRT group(131±39.5)(P <0.05).VMAT is feasible for patients with early stage breast cancer afterconservative surgery and improves technical characteristics of the target dosedistribution, especially for the irregular target. It could reduce the high dosevolume during irradiation of heart, lungs, liver and other OAR, but probablyincrease the low-dose irradiation volume at the same time. VMAT coulddecrease the time of radiotherapy significantly, improve equipment utilizationefficiency，and increase the therapy rate of patients with intolerable positionfixation. |
