Showing papers by "Michael Molls published in 2012"

Induction and repair of DNA double-strand breaks assessed by gamma-H2AX foci after irradiation with pulsed or continuous proton beams.

Abstract: In particle tumor therapy including beam scanning at accelerators, the dose per voxel is delivered within about 100 ms. In contrast, the new technology of laser plasma acceleration will produce ultimately shorter particle packages that deliver the dose within a nanosecond. Here, possible differences for relative biological effectiveness in creating DNA double-strand breaks in pulsed or continuous irradiation mode are studied. HeLa cells were irradiated with 1 or 5 Gy of 20-MeV protons at the Munich tandem accelerator, either at continuous mode (100 ms), or applying a single pulse of 1-ns duration. Cells were fixed 1 h after 1-Gy irradiation and 24 h after 5-Gy irradiation, respectively. A dose-effect curve based on five doses of X-rays was taken as reference. The total number of phosphorylated histone H2AX (gamma-H2AX) foci per cell was determined using a custom-made software macro for gamma-H2AX foci counting. For 1 h after 1-Gy 20-MeV proton exposures, values for the relative biological effectiveness (RBE) of 0.97 ± 0.19 for pulsed and 1.13 ± 0.21 for continuous irradiations were obtained in the first experiment 1.13 ± 0.09 and 1.16 ± 0.09 in the second experiment. After 5 Gy and 24 h, RBE values of 0.99 ± 0.29 and 0.91 ± 0.23 were calculated, respectively. Based on the gamma-H2AX foci numbers obtained, no significant differences in RBE between pulsed and continuous proton irradiation in HeLa cells were detected. These results are well in line with our data on micronucleus induction in HeLa cells.

Respiratory gated [18F]FDG PET/CT for target volume delineation in stereotactic radiation treatment of liver metastases.

Abstract: Purpose The use of 4D-[18F]fluorodeoxyglucose (FDG) PET/CT in combination with respiratory gated magnet resonance imaging (MRI) in target volume definition for stereotactic radiation of liver metastases was investigated.

Outcome After Conformal Salvage Radiotherapy in Patients With Rising Prostate-Specific Antigen Levels After Radical Prostatectomy

Abstract: Purpose This study attempts to improve our understanding of the role of salvage radiotherapy (SRT) in patients with prostate-specific antigen (PSA) relapse after radical prostatectomy with regard to biochemical control, rate of distant metastasis, and survival. Methods and Materials We performed a retrospective analysis of 96 men treated with conformal prostate bed SRT (median, 64.8 Gy) at a single institution (median follow-up, 70 months). The majority had intermediate- or high-risk prostate cancer. Fifty-four percent underwent a resection with positive margins (R1 resection). The median time interval between surgery and SRT was 22 months. Results After SRT, 66% of patients reached a PSA nadir of less than 0.2 ng/mL. However, the 5-year biochemical no evidence of disease rate was 35%. Seminal vesicle involvement was predictive for a significantly lower biochemical no evidence of disease rate. All patients with a preoperative PSA level greater than 50 ng/mL relapsed biochemically within 2 years. The 5-year distant metastasis rate was 18%, the 5-year prostate cancer–specific survival rate was 90%, and the 5-year overall survival rate was 88%. Significantly more distant metastases developed in patients with a PSA nadir greater than 0.05 ng/mL after SRT, and they had significantly inferior prostate cancer–specific and overall survival rates. Resection status (R1 vs. R0) was not predictive for any of the endpoints. Conclusions Men with postoperative PSA relapse can undergo salvage treatment by prostate bed radiotherapy, but durable PSA control is maintained only in about one-third of the patients. Despite a high biochemical failure rate after SRT, prostate cancer–specific survival does not decrease rapidly.

Monitoring PAI-1 and VEGF levels in 6 human squamous cell carcinoma xenografts during fractionated irradiation.

Abstract: Purpose Previous studies have shown that the plasminogen activator inhibitor type-1 (PAI-1) and vascular endothelial growth factor (VEGF) are regulated by hypoxia and irradiation and are involved in neoangiogenesis. The aim of this study was to determine in vivo whether changes in PAI-1 and VEGF during fractionated irradiation could predict for radiation resistance. Methods and Materials Six xenografted tumor lines from human squamous cell carcinomas (HSCC) of the head and neck were irradiated with 0, 3, 5, 10, and 15 daily fractions of 2 Gy. The PAI-1 and VEGF antigen levels in tumor lysates were determined by enzyme-linked immunosorbent assay kits. The amounts of PAI-1 and VEGF were compared with the dose to cure 50% of tumors (TCD 50 ). Colocalization of PAI-1, pimonidazole (hypoxia), CD31 (endothelium), and Hoechst 33342 (perfusion) was examined by immunofluorescence. Results Human PAI-1 and VEGF (hVEGF) expression levels were induced by fractionated irradiation in UT-SCC-15, UT-SCC-14, and UT-SCC-5 tumors, and mouse VEGF (msVEGF) was induced only in UT-SCC-5 tumors. High hVEGF levels were significantly associated with radiation sensitivity after 5 fractions ( P =.021), and high msVEGF levels were significantly associated with radiation resistance after 10 fractions ( P =.007). PAI-1 staining was observed in the extracellular matrix, the cytoplasm of fibroblast-like stroma cells, and individual tumor cells at all doses of irradiation. Colocalization studies showed PAI-1 staining close to microvessels. Conclusions These results indicate that the concentration of tumor-specific and host-specific VEGF during fractionated irradiation could provide considerably divergent information for the outcome of radiation therapy.