Chromosomal aberrations in peripheral blood lymphocytes exposed to a mixed beam of low energy neutrons and gamma radiation

Cells exposed to thermal neutrons are simultaneously damaged by radiations with high and low linear energy transfer (LET). A question relevant for the assessment of risk of exposure to a mixed beam is whether the biological effect of both radiation types is additive or synergistic. The aim of the present investigation was to calculate whether the high and low LET components of a thermal neutron field interact when damaging cells. Human peripheral blood lymphocytes were exposed to neutrons from the HB11 beam at the Institute for Energy and Transport, Petten, Netherlands, in a 37 °C water phantom at varying depths, where the mix of high and low LET beam components differs. Chromosomal aberrations were analysed and the relative biological effectiveness (RBE) values as well as the expected contributions of protons and photons to the aberration yield were calculated based on a dose response of aberrations in lymphocytes exposed to (60)Co gamma radiation. The RBE for 10 dicentrics per 100 cells was 3 for mixed beam and 7.2 for protons. For 20 dicentrics per 100 cells the respective values were 2.4 and 5.8. Within the limitations of the experimental setup the results indicate that for this endpoint there is no synergism between the high and low LET radiations.

Effect of temperature during irradiation on the level of micronuclei in human peripheral blood lymphocytes exposed to X-rays and neutrons

OBJECTIVES

It has been reported that the level of cytogenetic damage in human peripheral blood lymphocytes (PBL) is higher following irradiation at 37 degrees C than at 0-4 degrees C. The mechanisms of this cytogenetic temperature effect are not fully known. The aim of our study was to check whether the effect was related to the indirect or direct action of radiation.

MATERIALS AND METHODS

PBL were kept at 37 degrees C and 0 degree C for 20 min and exposed to 2 Gy of X-rays. In some experiments PBL were isolated and 0.5 M dimethyl sulfoxide (DMSO) was added for 5 min before exposure. PBL were also irradiated at 37 degrees C and 0 degree C with 1 Gy of 6 MeV neutrons. Micronuclei were scored as the endpoint. Following exposure to X-rays the level of initial DNA damage was also measured by the alkaline and neutral comet assay.

RESULTS

The frequency of micronuclei in cells exposed at 37 degrees C to X-rays or neutrons was higher than that after exposure at 0 degree C. No effect of temperature was seen when PBL were exposed to X-rays in the presence of DMSO. No effect of temperature was observed on the level of DNA damage measured with the alkaline or neutral comet assay.

CONCLUSIONS

The results of experiments with DMSO indicate that the temperature effect is due to the indirect action of radiation, i.e., via reactive oxygen species. However, this is not supported by the results with neutrons and the comet assay. Possible reasons for the discrepancies are discussed.

Comparison between PENELOPE and electron Monte Carlo simulations of electron fields used in the treatment of conjunctival lymphoma

For the treatment of conjunctival lymphoma in the early stages, external beam radiotherapy offers a curative approach. Such treatment requires the use of highly conformed small radiation beams. The beam size is so small that even advanced treatment planning systems have difficulties in calculating dose distributions. One possible approach for optimizing the treatment technique and later performing treatment planning is by means of full Monte Carlo (MC) simulations. In this paper, we compare experimental absorbed dose profiles obtained with a collimator used at the University Hospital Essen, with MC simulations done with the general-purpose radiation transport code PENELOPE. The collimator is also simulated with the hybrid MC code electron Monte Carlo (eMC) implemented in the commercial treatment planning system Eclipse (Varian). The results obtained with PENELOPE have a maximum difference with experimental data of 2.3%, whereas the eMC code differs systematically from the experimental data about 7% in the penumbra tails. We also show that PENELOPE simulations are able to obtain absorbed dose maps with an equivalent statistical uncertainty to the one found with eMC in similar CPU times.

Metabolism of borono-phenylalanine-fructose complex (BPA-fr) and borocaptate sodium (BSH) in cancer patients--results from EORTC trial 11001

Within the clinical trial EORTC 11001, patients were infused with (10)B-enriched borono-phenylalanine-fructose complex (BPA-fr), or borocaptate sodium (BSH) solutions, which are used as boron carriers for boron neutron capture therapy. Urine samples were periodically collected and analyzed by (10)B NMR spectroscopy. The results revealed time-dependent metabolic changes of the administered compounds. BPA-fr dissociated to the constituents BPA and fructose, and the borate group was partly cleaved from BPA. BSH was partly aggregated to a dimer form, BSSB. These observations were previously reported for cultured cells and animal models, and are confirmed here in human cancer patients.

Positive interaction between light iris color and ultraviolet radiation in relation to the risk of uveal melanoma: a case-control study

PURPOSE

To examine the association among phenotypic characteristics, chronic and intermittent ultraviolet (UV) radiation, and the risk of uveal melanoma.

DESIGN

Case-control study.

PARTICIPANTS

Overall, between September of 2002 and March of 2005, 1677 eligible subjects (age range: 20-74 years, living in Germany) participated. Interviews were conducted with 459 incident uveal melanoma cases (response proportion 94%), 827 population controls (55%), 180 ophthalmologist controls (52%), and 187 sibling controls (57%).

METHODS

Data on phenotypic characteristics and chronic and intermittent UV radiation exposure were obtained from a self-administered postal questionnaire and computer-assisted telephone interview. We used conditional logistic regression to estimate odds ratios adjusting for the matching factors. Furthermore, we studied the presence of synergy (super additive of risk or relative excess risk due to interaction) between light iris color and several UV radiation exposures.

MAIN OUTCOME MEASURES

Hair color at age 20 years, eye color, untanned skin color, ability to tan, propensity to burn on exposure, freckling, occupational sun exposure, artificial UV radiation, burns to the eyes.

RESULTS

In all 3 control groups, fair skin color, freckling as a child, nevi on the upper arms, burns to the eyes, use of sunlamps, and ever worked outside for 4 or more hours per day were positively associated with uveal melanoma. The association with eye color was apparent only in population controls (odds ratio = 1.9; 95% confidence interval [CI], 1.4-5.2), resulting in a relative excess risk due to interaction of 0.9 (95% CI, -0.6-2.3) for light iris color and more than 5 eye burns (UV-related keratitis) and 0.6 (95% CI, -0.3 to 1.5) for light iris color and eye protection.

CONCLUSIONS

Our interaction analyses suggest that there is an etiologic synergism between light iris color and the exposure of UV radiation. People with light iris color may have an especially increased risk for uveal melanoma if they are exposed to UV radiation.

FINANCIAL DISCLOSURE(S)

The author(s) have no proprietary or commercial interest in any materials discussed in this article.

Impact of intraoperative radiotherapy (IORT) on survival of patients with unresectable hilar cholangiocarcinoma

BACKGROUND/AIMS

The cure or long-term survival of hilar cholangiocarcinoma patients can only be achieved after complete tumor resection. Many patients though suffer from unresectable hilar cholangiocarcinoma, and palliative treatment is therefore the only therapeutic option. In cases of unresectable bile duct cancer, intraoperative radiotherapy (IORT) is an additional option during surgery. The aim of this study was to compare the efficacy of IORT to surgery alone in patients with unresectable hilar cholangiocarcinoma.

METHODOLOGY

Palliative IORT (group 1) was performed on 9 patients (4 female/5 male); surgery alone (group 2) was performed in a case-matched group of 9 patients (4 female, 5 male) with unresectable hilar cholangiocarcinoma. The mean ages were 52.9 years (group 1) and 57.2 years (group 2). The two groups had comparable local tumor extension and stages of tumor disease according to UICC 6th edition. Group 1 was also compared to all 36 patients (n=36) suffering from unresectable cholangiocarcinoma treated without IORT (Group 3).

RESULTS

The survival of patients after IORT was significantly improved compared to surgery alone in this study. The median survival time was 23.3 months (group 1) versus 9.4 months (group 2) and 5.7 month (group 3). The one year and two year actuarial survival rates are: 56% and 42% (group 1), 33% and 0% (group 2), 25% and 8% (group 3).

CONCLUSIONS

Palliative surgery including IORT is safe for patients with unresectable hilar cholangiocarcinoma. The benefit shown by this investigation is a significant improvement of survival time after application of IORT in the palliative situation. A prospective study with randomization is needed to confirm these first results in a larger cohort.

Confidence limits for Neyman type A-distributed events

The Neyman type A distribution, a generalised, 'contagious' Poisson distribution, finds application in a number of disciplines such as biology, physics and economy. In radiation biology, it best describes the distribution of chromosomal aberrations in cells that were exposed to neutrons, alpha radiations or heavy ions. Intriguingly, no method has been developed for the calculation of confidence limits (CLs) of Neyman type A-distributed events. Here, an algorithm to calculate the 95% CL of Neyman type A-distributed events is presented. Although it has been developed in response to the requirements of radiation biology, it can find application in other fields of research. The algorithm has been implemented in a PC-based computer program that can be downloaded, free of charge, from www.pu.kielce.pl/ibiol/neta.

Design of a rotating facility for extracorporal treatment of an explanted liver with disseminated metastases by boron neutron capture therapy with an epithermal neutron beam

In 2001, at the TRIGA reactor of the University of Pavia (Italy), a patient suffering from diffuse liver metastases from an adenocarcinoma of the sigmoid was successfully treated by boron neutron capture therapy (BNCT). The procedure involved boron infusion prior to hepatectomy, irradiation of the explanted liver at the thermal column of the reactor, and subsequent reimplantation. A complete response was observed. This encouraging outcome stimulated the Essen/Petten BNCT group to investigate whether such an extracorporal irradiation could be performed at the BNCT irradiation facility at the HFR Petten (The Netherlands), which has very different irradiation characteristics than the Pavia facility. A computational study has been carried out. A rotating PMMA container with a liver, surrounded by PMMA and graphite, is simulated using the Monte Carlo code MCNP. Due to the rotation and neutron moderation of the PMMA container, the initial epithermal neutron beam provides a nearly homogeneous thermal neutron field in the liver. The main conditions for treatment as reported from the Pavia experiment, i.e. a thermal neutron fluence of 4 x 10(12) +/- 20% cm(-2), can be closely met at the HFR in an acceptable time, which, depending on the defined conditions, is between 140 and 180 min.

Analyse der okulären Oberfläche nach Protonenbestrahlung bei malignem Melanom der Bindehaut

BACKGROUND

In cases of large, diffuse or multilocular growth pattern of conjunctival melanoma, proton beam irradiation can serve as an alternative therapy to exenteration. In extended tumours, ocular surface problems can result after therapy. In this study we examined ocular surface integrity of ten patients who underwent proton beam radiation between 1996 and 2002.

METHODS

The patients were examined during their follow-up. Eight of the ten cases who underwent proton radiotherapy were recurrent tumours, which were previously treated with other adjuvant therapies. We performed a standard ophthalmological examination and detailed tear film diagnostics.

RESULTS

The follow-up was 17-87 months (mean: 40.9+/-20.1). In six cases more than 50% of the upper and lower eyelids were included in the radiation field. All of these cases showed moderate to severe sicca symptoms. The impression cytology revealed squamous metaplasia of conjunctival cells in nine of ten cases.

CONCLUSIONS

Squamous metaplasia of conjunctival epithelia indicates a radiogenic, persisting disturbance of differentiation of the conjunctival epithelial cells. The tear film instability correlates with the loss of mucin-secreting goblet cells and meibomian gland dysfunction.