Neoadjuvant hyperfractionated accelerated radiotherapy plus concomitant 5-fluorouracil infusion in locally advanced rectal cancer: A phase II study.

AIM: To evaluate the efficacy and tolerability of neoadjuvant hyperfractionated accelerated radiotherapy (HART) and concurrent chemotherapy in patients with locally advanced infraperitoneal rectal cancer. METHODS: A total of 30 patients with histopathologically confirmed T2-3/N0+ infraperitoneal adenocarcinoma of rectum cancer patients received preoperative 42 Gy/1.5 Gy/18 days/bid radiotherapy and continuous infusion of 5-fluorouracil (325 mg/m2). All patients were operated 4-8 wk after neoadjuvant concomitant therapy. RESULTS: In the early phase of treatment, 6 patients had grade III-IV gastrointestinal toxicity, 2 patients had grade III-IV hematologic toxicity, and 1 patient had grade V toxicity due to postoperative sepsis during chemotherapy. Only 1 patient had radiotherapy-related late side effects, i.e., grade IV tenesmus. Complete pathological response was achieved in 6 patients (21%), while near-complete pathological response was obtained in 9 (31%). After a median follow-up period of 60 mo, the local tumor control rate was 96.6%. In 13 patients, distant metastasis occurred. Disease-free survival rates at 2 and 5 years were 63.3% and 53%, and corresponding overall survival rates were 70% and 53.1%, respectively. CONCLUSION: Although it has excellent local control and complete pathological response rates, neoadjuvant HART concurrent chemotherapy appears to not be a feasible treatment regimen in locally advanced rectal cancer, having high perioperative complication and intolerable side effects. Effects of reduced 5-fluorouracil dose or omission of chemotherapy with the aim of reducing toxicity may be examined in further studies.

A comparative study of the peripheral doses from a linear accelerator with a multileaf collimator system.

This study presents a comparison of peripheral doses (PDs) measured using an ionisation chamber with treatment planning system (TPS) data and a Monte Carlo (MC) simulation of a 6-MV photon beam. The ion chamber measurements and MC simulation produced similar results for all out-of-field distances and field sizes considered in this study. For the 0° and 90° collimation angles, the average local per cent dose differences between the MC and TPS calculations were 2.7 % (range: -2.4, +22.6) and -1.7 % (range: -12.2, +10.8), respectively. The corresponding differences between the MC calculations and the ion chamber measurements were 2.2 % (range: -2.4, 24.7) and -1.8 % (range: -17, 15.2) for all field sizes and depths, respectively. Whereas the PDs increased with field sizes, the variations with depth were negligible at large distances. The TPS calculations usually yielded higher PDs than ion chamber measurements at distances close to the field edge. In contrast, at the farther distances, the TPS results indicated lower doses than both the ion chamber and the MC data. TPS data are not sufficient for use in calculating the out-of-field doses. These results can be used to estimate non-target organ doses to patients.

Dosimetric investigation of LDR brachytherapy ¹9²Ir wires by Monte Carlo and TPS calculations.

PURPOSE: The aim of this study was to investigate the dose rate distribution around (192)Ir wires used as radioactive sources in low-dose-rate brachytherapy applications. MATERIALS AND METHODS: Monte Carlo modeling of a 0.3-mm diameter source and its surrounding water medium was performed for five different wire lengths (1-5 cm) using the MCNP software package. RESULTS: The computed dose rates per unit of air kerma at distances from 0.1 up to 10 cm away from the source were first verified with literature data sets. Then, the simulation results were compared with the calculations from the XiO CMS commercial treatment planning system. CONCLUSION: The study results were found to be in concordance with the treatment planning system calculations except for the shorter wires at close distances.