The effect of adjuvant chemotherapy in stage 2 colorectal cancer

Background: Colorectal cancer is the most common malignant gastrointestinal cancer and the fourth most common cancer throughout the world. Disease staging is performed to select the treatment method. In this interventional study we evaluated the effect of adjuvant chemotherapy on local recurrence, distant metastasis and three-year disease free survival in patients with stage 2 colorectal cancer. Materials and Methods: In this research, patients with stage II colorectal cancer from 2001 to 2006 entered the study. After the surgery, FOLFOX4 chemotherapy regimen was performed and every 3 months ultrasound and CT scan and colonoscopy were assessed using tumor markers in terms of local recurrence and metastasis. Finally, at the end of the third year after chemotherapy, local recurrence, metastasis and survival of patients were analyzed. Results: In this study 40 patients (23 males and 17 females) were studied. After 3 years of follow-up, 2 patients had local recurrence and 7 patients had distant metastasis and 31 patients had nor local recurrence nor distant metastases. In other words, the 3-year disease free survival was 77.5%. Conclusions: In this study, adjuvant chemotherapy for stage II colorectal cancer has been led to overall survival and a 3-year disease free survival

Simulation of therapeutic electron beam tracking through a non-uniform magnetic field using finite element method

Introduction: In radiotherapy, megaelectron volt (MeV) electrons are employed for treatment of superficial cancers. Magnetic fields can be used for deflection and deformation of the electron flow. A magnetic field is composed of non-uniform permanent magnets. The primary electrons are not mono-energetic and completely parallel. Calculation of electron beam deflection requires using complex mathematical methods. In this study, a device was made to apply a magnetic field to an electron beam and the path of electrons was simulated in the magnetic field using finite element method. Methods: A mini-applicator equipped with two neodymium permanent magnets was designed that enables tuning the distance between magnets. This device was placed in a standard applicator of Varian 2100 CD linear accelerator. The mini-applicator was simulated in CST Studio finite element software. Deflection angle and displacement of the electron beam was calculated after passing through the magnetic field. By determining a 2 to 5cm distance between two poles, various intensities of transverse magnetic field was created. The accelerator head was turned so that the deflected electrons became vertical to the water surface. To measure the displacement of the electron beam, EBT2 GafChromic films were employed. After being exposed, the films were scanned using HP G3010 reflection scanner and their optical density was extracted using programming in MATLAB environment. Displacement of the electron beam was compared with results of simulation after applying the magnetic field. Results: Simulation results of the magnetic field showed good agreement with measured values. Maximum deflection angle for a 12 MeV beam was 32.9° and minimum deflection for 15 MeV was 12.1°. Measurement with the film showed precision of simulation in predicting the amount of displacement in the electron beam. Conclusion: A magnetic mini-applicator was made and simulated using finite element method. Deflection angle and displacement of electron beam were calculated. With the method used in this study, a good prediction of the path of high-energy electrons was made before they entered the body