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Preview: Radiation Oncology Investigations

Radiation Oncology Investigations

Wiley Online Library : Radiation Oncology Investigations

Published: 1999-01-01T00:00:00-05:00


Acknowledgment to reviewers


Overexpression of the human manganese superoxide dismutase (MnSOD) transgene in subclones of murine hematopoietic progenitor cell line 32D cl 3 decreases irradiation-induced apoptosis but does not alter G2/M or G1/S phase cell cycle arrest


To determine whether overexpression of the human MnSOD transgene protected 32D cl 3 hematopoietic progenitor cells from ionizing irradiation, 32D cl 3 cells were co-electroporated with the pRK5 plasmid containing the human MnSOD transgene and SV2-neo plasmid with G418-resistant colonies selected. Two clones (1F2 and 2C6) were identified to overexpress the human MnSOD transgene by nested reverse transcriptase-polymerase chain reaction (RT-PCR) and increased biochemical activity. Measurement of irradiation-induced damage was determined in cells removed from G418 for 1 week before irradiation. Irradiation survival curves, apoptosis tunnel assay, and Comet assay was performed. Cell cycle distribution was determined for each line at 0, 1, 3, 6, 24, and 48 hr after 500 cGy by fixing the cells in 70% ethanol, staining with propidium iodide, and analysis by flow cytometer. Biochemical MnSOD activity in U/mg protein was 2.6 for 32D cl 3 and significantly elevated to 8.4 and 6.6 (P < 0.001) U/mg protein for subclones 1F2 and 2C6, respectively. Irradiation survival curves demonstrated an increased shoulder on the irradiation survival curve for 1F2 and 2C6 cells with an n of 4.95 ± 0.48 (P = 0.042) and 4.95 ± 0.13 (P = 0.011), compared with 2.77 ± 0.20 for 32D cl 3. A higher percent of 32D cl 3 cells demonstrated apoptosis at 24 and 48 hr after 1,000 cGy irradiation, compared with 1F2 and 2C6 cells (at 24 hr, 29.37% ± 2.01% of 32D cl 3 cells were apoptotic compared with 5.21 ± 2.61 (P = 0.018) and 5.27 ± 2.58 (P = 0.004) for 1F2 and 2C6, respectively). Significantly more DNA strand breaks were detected by Comet assay in 32D cl 3 cells (Comet length at 600 cGy of 103.4 ± 50.3 units, compared with 69.7 ± 36.3 (P < 0.001) and 48.9 ± 27.5 (P < 0.001) for 1F2 and 2C6, respectively). In contrast, irradiation-induced cell cycle arrest was similar between the cell lines with a G2/M phase arrest at 6 hr and a G1/S phase arrest at 24 and 48 hr after irradiation. While overexpression of MnSOD increases the shoulder on the irradiation survival curve of 32D cl 3 cells, decreases irradiation-induced apoptosis, and DNA strand breaks by Comet assay, irradiation-induced alterations in cell cycle distribution were not significantly altered. These 32D cl 3 subclonal lines overexpressing MnSOD provide a potentially valuable system with which to study the mechanism of irradiation-induced cell cycle arrest separate from irradiation-induced apoptosis. Radiat. Oncol. Invest. 7:331–342, 1999. © 1999 Wiley-Liss, Inc.

Enhancement of radiation effects by combined docetaxel and carboplatin treatment in vitro


This study was designed to evaluate the combination of docetaxel (Taxotere) and carboplatin for radiopotentiation in vitro. H460 human lung carcinoma cells were treated with docetaxel (or paclitaxel) for 1 h and rinsed. After 24 h, the cells were treated with carboplatin for 1 h, irradiated, and colony forming ability was assesed. Using various doses of docetaxel with 100 μM carboplatin, the dose enhancement ratio (D.E.R.) for drugs only was 1.26. When 25 nM docetaxel was used with various doses of radiation, the radiation D.E.R. was 1.41. With all three agents combined, and after normalization for combined drug effects, the radiation D.E.R. was 1.55. Similar values were obtained using paclitaxel with these agents. Significant redistribution of cells into the radiosensitive G2/M phase was observed using a dose of paclitaxel (750 nM), which also caused radiation enhancement. However, an equally cytotoxic dose of docetaxel (25 nM) did not result in any cell cycle redistribution; this phenomenon was only observed at higher doses. This study shows that the combination of docetaxel and carboplatin enhance the effects of radiation in vitro more effectively than either drug seperately. In addition, our data show that the mechanism of radiopotentiation by docetaxel probably does not involve a G2/M block in H460 cells. Radiat. Oncol. Invest. 7:343–352, 1999. © 1999 Wiley-Liss, Inc.

What is the optimal treatment volume in Hodgkin's disease patients undergoing high-dose chemotherapy and adjuvant radiation therapy?


To determine the optimal treatment volume in Hodgkin's disease patients undergoing high-dose chemotherapy (HDCT) and radiation therapy (RT), failure sites were reviewed in 56 patients. Twenty-one (38%) received involved-field RT (IFRT) before or after HDCT encompassing sites of prior disease. Failure sites were designated as previously involved (old) or uninvolved (new) sites. Seven patients (12%) died in the immediate post-HDCT period, leaving 49 evaluable (median follow-up, 41 months). Twenty-five patients (51%) relapsed (14 HDCT, 11 HDCT + IFRT): seven (28%) in old, eight (32%) in new, and ten (40%) in old and new sites. Six of the seven who relapsed in old sites received HDCT alone, whereas seven of the eight who relapsed in new sites received IFRT. Relapse in old sites was particularly common in patients failing to achieve a complete response. The most common new failure site was nodal, occurring in 11 patients and was primarily (10/11) adjacent to an old site. Although it controls prior disease, IFRT is insufficient in Hodgkin's disease patients undergoing HDCT. Relapse is common in new nodal sites and is primarily adjacent to prior sites. These results suggest that extended-field RT encompassing old and adjacent uninvolved nodal sites may be the optimal treatment volume in these patients. Radiat. Oncol. Invest. 7:353–359, 1999. © 1999 Wiley-Liss, Inc.

Anticipating prostatic volume changes due to prostate brachytherapy


The purpose of the study was to determine which clinical parameters might predict individual prostate volume changes from prostate brachytherapy. Fifty consecutive, unselected patients treated at the University of Washington by I-125 or Pd-103 implantation for prostatic carcinoma in 1998 were analyzed. The prostate contours on preimplant transrectal ultrasound (TRUS) images were digitized and the prostate volumes calculated. Postimplant axial CT images of the prostate was obtained at 0.5 cm intervals with patients in the supine position the morning after the implant. The postimplant prostate volume increased by an average factor of 1.7 (±0.34) compared with the preimplant volume, the size increase being primarily in the anterior–posterior dimension. The absolute volume change was similar in patients with small vs. large preimplant prostate volume (r = −0.39), but the proportional change was less in patients with a larger prostate volume (r = −0.71). Because patients with a small preimplant prostate had proportionately greater volume increase, their postimplant target coverage was generally less. No single parameter, including preimplant prostate volume, preimplant hormonal deprivation, or supplemental external beam radiation therapy (EBRT) can accurately predict the degree of swelling. The precise significance of and practical solution to implant-related prostate volume changes remains to be determined. Radiat. Oncol. Invest. 7:360–364, 1999. © 1999 Wiley-Liss, Inc.

Treatment of pediatric Hodgkin's disease with chemotherapy alone or combined modality therapy


Optimal treatment for Hodgkin's disease during childhood is unknown. We report the treatment outcome of patients with Hodgkin's disease ≤13 years of age seen at the American University of Beirut Medical Center (AUBMC) between 1980 and 1996. A retrospective review of the medical records of 24 children treated for HD at AUBMC was performed. Treatment consisted of chemotherapy alone (n = 15) or chemotherapy plus involved field radiotherapy (n = 9). Chemotherapy consisted of COPP, ABVD, or alternating cycles of each for a total of 6 to 12 cycles, depending on clinical and radiological response; three patients received MOPP. Five patients in the chemotherapy group had clinical stage (CS) I and II and 10 had CS III disease. In the combined modality group, eight patients had CS I and II and one had CS IV disease. At a median follow-up of 5 years, the event-free survival (EFS) for the combined modality group was 100% and the overall survival (OS) 100%. For the chemotherapy alone group, the EFS was 56% and the OS was 79%. Four patients (27%) in the chemotherapy alone group who had Stage IIIB disease relapsed. Mean time to relapse was 4.3 years. In our experience, six cycles of COPP or (COPP plus ABVD) alone were suboptimal for the treatment of Stage IIIB Hodgkin's disease patients, especially those with involvement of lower abdominal nodes (III2B), extensive pulmonary disease, or mixed cellularity histology. Radiation therapy or additional chemotherapy courses are required for these patients. Radiat. Oncol. Invest. 7:365–373, 1999. © 1999 Wiley-Liss, Inc.

Comparisons of a proposed five-seed assay method with the single-seed and batch assay methods for I-125 seeds in ultrasound-guided prostate implants


A simple five-seed assay method was proposed and investigated. A commercial well ion chamber system with an NIST-traceable single-seed calibration constant was used for the single-seed assays. A batch seed holder was used for batch assays. For the five-seed assays, a second single-seed holder was modified such that all five seeds were loaded in a central region of the well ion chamber. Compared with the same seed in the standard single-seed holder, the relative chamber responses for the five seed positions were 0.993, 0.993, 1.000, 1.001, and 0.977, respectively, indicating little or no position-dependent chamber response and no self-attenuation among seeds. Subsequent comparison of assays with the single-seed and five-seed methods indicated only 0.4% difference in charge collection. The five-seed calibration constant was therefore taken to be the same as the single-seed calibration constant. The reproducibility of the five-seed assay method was found to be better than 0.8%. When a dummy seed replaced an active seed, a nearly 20% reduction in charge was found, indicating that the proposed five-seed assay method can detect a dead seed. Clinical comparison of all three assay methods showed that they produced qualitatively the same assay results when the batch assay method was performed with extra care. Compared with the single-seed assay method, the five-seed method is equally simple, rigid, and reproducible, but it demands much less assay time. Compared with the batch assay method, the five-seed method is much more reproducible and reliable because of its rigid assay geometry; it only demands a moderate amount of assay time and can detect dead seeds. The American Association of Physicists in Medicine Task Group 40 (AAPM TG40) states that, for brachytherapy, ideally every (i.e., 100%) loose seed should be calibrated. For procedures involving large number of loose seeds, it then recommends that 10% of seeds be calibrated. The proposed five-seed assay is very simple to implement. It will facilitate the compliance of the “10%” recommendation from the AAPM TG40; it will make the “ideally 100%” statement from AAPM TG40 a more realistic and practical QA procedure in seed assaying. Radiat. Oncol. Invest. 7:374–381, 1999. © 1999 Wiley-Liss, Inc.

Improvement of X-ray beam quality for treating cancer using double focus electric field strings


Accurate knowledge of the distribution and amount of contamination electrons arising from the gantry head at the surface and in the first few centimeters of tissue is essential for the clinical practice of radiation oncology. These electrons tend to increase the surface dose and deteriorate the buildup in the radiation field compared with a pure photon field. In this study, the relative quantity and reduction of contamination electrons in a therapeutic radiation photon beam (15 MV) was investigated. The contamination electrons can be separated out by a special device. This device, consisting of a double-focus electric field (8 × 105 V/m) made by a large number of strings 2 × 10−4 m in diameter, removes contamination electrons and positrons without affecting the photon beam. It is located under the tray holder. In clinical practice, the device can decrease the relative surface charge and relative surface dose due to contamination electrons in the photon beam used in radiation therapy. Radiat. Oncol. Invest. 7:382–389, 1999. © 1999 Wiley-Liss, Inc.