Effects of UV radiation exposure on DNA and DNA repair enzymes

Dissertação para obtenção do Grau de Mestre em Biotecnologia

Radiation damage in flexible TFTs and organic detectors

In this thesis was investigated the radiation hardness of the building blocks of a future flexible X-ray sensor system. The characterized building blocks for the pixel addressing and signal amplification electronics are high mobility semiconducting oxide transistors (HMSO-TFTs) and organic transistors (OTFTs), whereas the photonic detection system is based on organic semiconducting single crystals (OSSCs). TFT parameters such as mobility, threshold voltage and subthreshold slope were measured as function of cumulative X-ray dose. Instead for OSSCs conductivity and X-ray sensitivity were analysed after various radiation steps. The results show that ionizing radiation does not lead to degradation in HMSO-TFTs. Instead OTFTs show instability in mobility which is reduced up to 73% for doses of 1 kGy. OSSC demonstrate stable detector properties for the tested total dose range. As conclusion, HMSO-TFTs and OSSCs can be readily employed in the X-ray detector system allowing operation for total doses exceeding 1 kGy of ionizing radiation.

Radiation therapy for the solitary plasmacytoma

Plasma-cell neoplasms are classically categorized into four groups as: multiple myeloma (MM), plasma-cell leukemias, solitary plasmacytomas (SP) of the bone (SPB), and extramedullary plasmacytomas (EMP). These tumors may be described as localized or diffuse in presentation. Localized plasma-cell neoplasms are rare, and include SP of the skeletal system, accounting for 2-5% of all plasma-cell neoplasms, and EMP of soft tissue, accounting for approximately 3% of all such neoplasms. SP is defined as a solitary mass of neoplastic plasma cells either in the bone marrow or in various soft tissue sites. There appears to be a continuum in which SP often progresses to MM. The main treatment modality for SP is radiation therapy (RT). However, there are no conclusive data in the literature on the optimal AT dose for SP. This review describes the interrelationship of plasma-cell neoplasms, and attempts to determine the minimal RT dose required to obtain local control.

Successful treatment of trilateral retinoblastoma with conventional and high-dose chemotherapy plus radiotherapy: a case report.

Trilateral retinoblastoma (TRB) is a rare condition characterized by an intracranial neuroblastic tumor associated with bilateral or unilateral retinoblastoma (RB). The outcome is almost always fatal. An 18-month-old patient with familial bilateral RB was referred for a pineal lesion detected on a screening by magnetic resonance imaging. The child, considered inoperable by 2 different neurosurgical teams, was treated with conventional chemotherapy (methotrexate, vincristine, vepeside, cyclophosphamide, and carboplatin) plus tandem transplantation (vepeside/carboplatin and thiotepa/mephalan) followed by local radiotherapy. At 80 months from the diagnosis of TRB, the patient is alive and in complete remission, with no neuropsychologic consequences. An early and aggressive treatment may improve the prognosis of TRB.

How to set up and apply reference levels in fluoroscopy at a national level.

A nationwide survey was launched to investigate the use of fluoroscopy and establish national reference levels (RL) for dose-intensive procedures. The 2-year investigation covered five radiology and nine cardiology departments in public hospitals and private clinics, and focused on 12 examination types: 6 diagnostic and 6 interventional. A total of 1,000 examinations was registered. Information including the fluoroscopy time (T), the number of frames (N) and the dose-area product (DAP) was provided. The data set was used to establish the distributions of T, N and the DAP and the associated RL values. The examinations were pooled to improve the statistics. A wide variation in dose and image quality in fixed geometry was observed. As an example, the skin dose rate for abdominal examinations varied in the range of 10 to 45 mGy/min for comparable image quality. A wide variability was found for several types of examinations, mainly complex ones. DAP RLs of 210, 125, 80, 240, 440 and 110 Gy cm2 were established for lower limb and iliac angiography, cerebral angiography, coronary angiography, biliary drainage and stenting, cerebral embolization and PTCA, respectively. The RL values established are compared to the data published in the literature.

Low doses of ionizing radiation promote tumor growth and metastasis by enhancing angiogenesis.

Radiotherapy is a widely used treatment option in cancer. However, recent evidence suggests that doses of ionizing radiation (IR) delivered inside the tumor target volume, during fractionated radiotherapy, can promote tumor invasion and metastasis. Furthermore, the tissues that surround the tumor area are also exposed to low doses of IR that are lower than those delivered inside the tumor mass, because external radiotherapy is delivered to the tumor through multiple radiation beams, in order to prevent damage of organs at risk. The biological effects of these low doses of IR on the healthy tissue surrounding the tumor area, and in particular on the vasculature remain largely to be determined. We found that doses of IR lower or equal to 0.8 Gy enhance endothelial cell migration without impinging on cell proliferation or survival. Moreover, we show that low-dose IR induces a rapid phosphorylation of several endothelial cell proteins, including the Vascular Endothelial Growth Factor (VEGF) Receptor-2 and induces VEGF production in hypoxia mimicking conditions. By activating the VEGF Receptor-2, low-dose IR enhances endothelial cell migration and prevents endothelial cell death promoted by an anti-angiogenic drug, bevacizumab. In addition, we observed that low-dose IR accelerates embryonic angiogenic sprouting during zebrafish development and promotes adult angiogenesis during zebrafish fin regeneration and in the murine Matrigel assay. Using murine experimental models of leukemia and orthotopic breast cancer, we show that low-dose IR promotes tumor growth and metastasis and that these effects were prevented by the administration of a VEGF receptor-tyrosine kinase inhibitor immediately before IR exposure. These findings demonstrate a new mechanism to the understanding of the potential pro-metastatic effect of IR and may provide a new rationale basis to the improvement of current radiotherapy protocols.

Estimation of the radiation risks in diagnostic procedures to populations and patients

Since 1895, when X-rays were discovered, ionizing radiation became part of our life. Its use in medicine has brought significant health benefits to the population globally. The benefit of any diagnostic procedure is to reduce the uncertainty about the patient's health. However, there are potential detrimental effects of radiation exposure. Therefore, radiation protection authorities have become strict regarding the control of radiation risks.¦There are various situations where the radiation risk needs to be evaluated. International authority bodies point to the increasing number of radiologic procedures and recommend population surveys. These surveys provide valuable data to public health authorities which helps them to prioritize and focus on patient groups in the population that are most highly exposed. On the other hand, physicians need to be aware of radiation risks from diagnostic procedures in order to justify and optimize the procedure and inform the patient.¦The aim of this work was to examine the different aspects of radiation protection and investigate a new method to estimate patient radiation risks.¦The first part of this work concerned radiation risk assessment from the regulatory authority point of view. To do so, a population dose survey was performed to evaluate the annual population exposure. This survey determined the contribution of different imaging modalities to the total collective dose as well as the annual effective dose per caput. It was revealed that although interventional procedures are not so frequent, they significantly contribute to the collective dose. Among the main results of this work, it was shown that interventional cardiological procedures are dose-intensive and therefore more attention should be paid to optimize the exposure.¦The second part of the project was related to the patient and physician oriented risk assessment. In this part, interventional cardiology procedures were studied by means of Monte Carlo simulations. The organ radiation doses as well as effective doses were estimated. Cancer incidence risks for different organs were calculated for different sex and age-at-exposure using the lifetime attributable risks provided by the Biological Effects of Ionizing Radiations Report VII. Advantages and disadvantages of the latter results were examined as an alternative method to estimate radiation risks. The results show that this method is the most accurate, currently available, to estimate radiation risks. The conclusions of this work may guide future studies in the field of radiation protection in medicine.¦-¦Depuis la découverte des rayons X en 1895, ce type de rayonnement a joué un rôle important dans de nombreux domaines. Son utilisation en médecine a bénéficié à la population mondiale puisque l'avantage d'un examen diagnostique est de réduire les incertitudes sur l'état de santé du patient. Cependant, leur utilisation peut conduire à l'apparition de cancers radio-induits. Par conséquent, les autorités sanitaires sont strictes quant au contrôle du risque radiologique.¦Le risque lié aux radiations doit être estimé dans différentes situations pratiques, dont l'utilisation médicale des rayons X. Les autorités internationales de radioprotection indiquent que le nombre d'examens et de procédures radiologiques augmente et elles recommandent des enquêtes visant à déterminer les doses de radiation délivrées à la population. Ces enquêtes assurent que les groupes de patients les plus à risque soient prioritaires. D'un autre côté, les médecins ont également besoin de connaître le risque lié aux radiations afin de justifier et optimiser les procédures et informer les patients.¦Le présent travail a pour objectif d'examiner les différents aspects de la radioprotection et de proposer une manière efficace pour estimer le risque radiologique au patient.¦Premièrement, le risque a été évalué du point de vue des autorités sanitaires. Une enquête nationale a été réalisée pour déterminer la contribution des différentes modalités radiologiques et des divers types d'examens à la dose efficace collective due à l'application médicale des rayons X. Bien que les procédures interventionnelles soient rares, elles contribuent de façon significative à la dose délivrée à la population. Parmi les principaux résultats de ce travail, il a été montré que les procédures de cardiologie interventionnelle délivrent des doses élevées et devraient donc être optimisées en priorité.¦La seconde approche concerne l'évaluation du risque du point de vue du patient et du médecin. Dans cette partie, des procédures interventionnelles cardiaques ont été étudiées au moyen de simulations Monte Carlo. La dose délivrée aux organes ainsi que la dose efficace ont été estimées. Les risques de développer des cancers dans plusieurs organes ont été calculés en fonction du sexe et de l'âge en utilisant la méthode établie dans Biological Effects of Ionizing Radiations Report VII. Les avantages et inconvénients de cette nouvelle technique ont été examinés et comparés à ceux de la dose efficace. Les résultats ont montré que cette méthode est la plus précise actuellement disponible pour estimer le risque lié aux radiations. Les conclusions de ce travail pourront guider de futures études dans le domaine de la radioprotection en médicine.

Feasibility and efficacy of subcutaneous amifostine therapy in patients with head and neck cancer treated with curative accelerated concomitant-boost radiation therapy.

OBJECTIVE: To assess the feasibility and efficacy of subcutaneous amifostine therapy in patients with head and neck cancer treated with curative accelerated radiotherapy (RT). DESIGN: Retrospective study. SETTING: University of Lausanne, Lausanne, Switzerland. PATIENTS: Thirty-three consecutive patients (male-female ratio, 4.5; median age, 54 years [age range, 39-76 years]). INTERVENTIONS: Between November 2000 and January 2003, the 33 patients were treated with curative definitive (n = 19) or postoperative (n = 14) RT with (n = 26) or without (n = 7) chemotherapy. All patients received conformal RT. Fractionation schedule consisted of concomitant-boost (Friday afternoon session) accelerated RT using 70 Gy (2 Gy per fraction) in 6 weeks in patients treated with definitive RT and 66 Gy (2 Gy per fraction) in 5 weeks and 3 days in the postoperative setting. Parotid glands received at least 50 Gy in all patients. Amifostine was administered to a total dose of 500 mg subcutaneously, 15 to 30 minutes before morning RT sessions. RESULTS: All patients received their planned treatment (including chemotherapy). Ten patients received the full schedule of amifostine (at least 25 injections), 9 received 20 to 24 doses, 4 received 10 to 19 doses, 5 received 5 to 9 doses, and 5 received fewer than 5 doses. Fifteen patients (45%) did not show any intolerance related to amifostine use. Amifostine therapy was discontinued because of nausea in 11 patients (33%) and hypotension in 6 patients (18%), and 1 patient refused treatment. No grade 3, amifostine-related, cutaneous toxic effects were observed. Radiotherapy-induced grade 3 acute toxic effects included mucositis in 14 patients (42%), erythema in 14 patients (42%), and dysphagia in 13 patients (39%). Late toxic effects included grade 2 or more xerostomia in 17 patients (51%) and fibrosis in 3 patients (9%). Grade 2 or more xerostomia was observed in 8 (42%) of 19 patients receiving 20 injections or more vs 9 (64%) of 14 patients receiving fewer than 20 injections (P = .15). CONCLUSIONS: Subcutaneous amifostine administration in combination with accelerated concomitant-boost RT with or without chemotherapy is feasible. The major adverse effect of subcutaneous administration was nausea despite prophylactic antiemetic medication, and hypotension was observed in only 6 patients (18%).

Fecundity Changes Induced by Low-Doses of Gamma Radiation on Biomphalaria straminea (Dunker, 1848)

A population of 420 snails Biomphalaria straminea, an intermediate host of Schistosoma mansoni, received gamma-rays obtained from a 60Co source in low-doses (0/2,5/5/7,5/10/15/20 and 25 Gy); half population was kept in colonies (allowing cross fertilization) and the other half was mantained in sexual isolation (allowing self fertilization). Results showed that 15 Gy stimulates the fertility of both groups but the colonies were more sensitive and at this dose its fertility overpasses the control group dose. The possible hormonal role played in the observed phenomena is under investigation

RTOG 0525: Exploratory Subset Analysis from a Randomized Phase III Trial Comparing Standard (std) Adjuvant Temozolomide (TMZ) with a Dose-dense (dd) Schedule for Glioblastoma (GBM)

Purpose/Objective(s): RTwith TMZ is the standard for GBM. dd TMZ causes prolongedMGMTdepletion in mononuclear cells and possibly in tumor. The RTOG 0525 trial (ASCO 2011) did not show an advantage from dd TMZ for survival or progression free survival. We conducted exploratory, hypothesis-generating subset analyses to detect possible benefit from dd TMZ.Materials/Methods: Patients were randomized to std (150-200 mg/m2 x 5 d) or dd TMZ (75-100 mg/m2 x 21 d) q 4 weeks for 6- 12 cycles. Eligibility included age.18, KPS$ 60, and. 1 cm2 tissue for prospective MGMTanalysis for stratification. Furtheranalyses were performed for all randomized patients (''intent-to-treat'', ITT), and for all patients starting protocol therapy (SPT). Subset analyses were performed by RPA class (III, IV, V), KPS (90-100, = 50,\50), resection (partial, total), gender (female, male), and neurologic dysfunction (nf = none, minor, moderate).Results: No significant difference was seen for median OS (16.6 vs. 14.9 months), or PFS (5.5 vs. 6.7 months, p = 0.06). MGMT methylation was linked to improved OS (21.2 vs. 14 months, p\0.0001), and PFS (8.7 vs. 5.7 months, p\0.0001). For the ITT (n = 833), there was no OS benefit from dd TMZ in any subset. Two subsets showed a PFS benefit for dd TMZ: RPA class III (6.2 vs. 12.6 months, HR 0.69, p = 0.03) and nf = minor (HR 0.77, p = 0.01). For RPA III, dd dramatically delayed progression, but post-progression dd patients died more quickly than std. A similar pattern for nf = minor was observed. For the SPT group (n = 714) there was neither PFS nor OS benefit for dd TMZ, overall. For RPA class III and nf = minor, there was a PFS benefit for dd TMZ (HR 0.73, p = 0.08; HR 0.77, p = 0.02). For nf = moderate subset, both ITT and SPT, the std arm showed superior OS (14.4 vs. 10.9 months) compared to dd, without improved PFS (HR 1.46, p = 0.03; and HR 1.74, p = 0.01. In terms of methylation status within this subset, there were more methylated patients in the std arm of the ITT subset (n = 159; 32 vs. 24%). For the SPT subset (n = 124), methylation status was similar between arms.Conclusions: This study did not demonstrate improved OS for dd TMZ for any subgroup, but for 2 highly functional subgroups, PFS was significantly increased. These data generate the testable hypothesis that intensive treatment may selectively improve disease control in those most likely able to tolerate dd therapy. Interpretation of this should be considered carefully due to small sample size, the process of multiple observations, and other confounders.Acknowledgment: This project was supported by RTOG grant U10 CA21661, and CCOP grant U10 CA37422 from the National Cancer Institute (NCI).

Promising survival for patients with newly diagnosed glioblastoma multiforme treated with concomitant radiation plus temozolomide followed by adjuvant temozolomide.

PURPOSE: Temozolomide is a novel oral alkylating agent with demonstrated efficacy as second-line therapy for patients with recurrent anaplastic astrocytoma and glioblastoma multiforme (GBM). This phase II study was performed to determine the safety, tolerability, and efficacy of concomitant radiation plus temozolomide therapy followed by adjuvant temozolomide therapy in patients with newly diagnosed GBM. PATIENTS AND METHODS: Sixty-four patients were enrolled onto this open-label, phase II trial. Temozolomide (75 mg/m(2)/d x 7 d/wk for 6 weeks) was administered orally concomitant with fractionated radiotherapy (60 Gy total dose: 2 Gy x 5 d/wk for 6 weeks) followed by temozolomide monotherapy (200 mg/m(2)/d x 5 days, every 28 days for six cycles). The primary end points were safety and tolerability, and the secondary end point was overall survival. RESULTS: Concomitant radiation plus temozolomide therapy was safe and well tolerated. Nonhematologic toxicities were rare and mild to moderate in severity. During the concomitant treatment phase, grade 3 or 4 neutropenia, thrombocytopenia, or both were observed in 6% of patients, including two severe infections with Pneumocystis carinii. During adjuvant temozolomide, 2% and 6% of cycles were associated with grade 3 and 4 neutropenia or thrombocytopenia, respectively. Median survival was 16 months, and the 1- and 2-year survival rates were 58% and 31%, respectively. Patients younger than 50 years old and patients who underwent debulking surgery had the best survival outcome. CONCLUSION: Continuous daily temozolomide and concomitant radiation is safe. This regimen of concomitant chemoradiotherapy followed by adjuvant chemotherapy may prolong the survival of patients with glioblastoma. Further investigation is warranted, and a randomized trial is ongoing.

Growth changes induced by gamma radiation on Biomphalaria straminea (Dunker, 1848)

Doses of 60Co gamma radiation with 2.5; 5; 7.5; 10; 15; 20; 25; 30; 35; 40; 45; 50; 55; 60; 80; 160; 320 and 640 Gy were applied to 1,080 snails Biomphalaria straminea, an intermediate host of Schistosoma mansoni, divided in groups containing 30 mollusks. In addition, 60 non irradiated snails were kept as control. Fifty percent of the population was kept in colonies (allowing cross fertilization) while the other half was maintained in sexual isolation (allowing self fertilization) and during one month their growth was observed through the daily measurement of the shell diameter. Results showed that after 20 Gy doses the growth in shell diameter of irradiated snails was greater than that of the control group after 30 days. At this dose the snail size was the greatest, among all isolated groups. The 80 Gy doses also induced the final shell diameter of isolated snails to be greater then that observed in the control groups. As this effect was most evident among the isolated snails, a possible hormonal role may have been involved in the observed phenomena, which is under investigation with the objective of identifying any future applications that this could have to schistosomiasis control.

Helical tomotherapy or intensity-modulated radiation therapy in the treatment of anal cancer: experience of Geneva and Lausanne

Background: To assess the early clinical outcomes and toxicities in patients treated with high precision radiation therapy (RT) consisting of helical tomotherapy (HT) or intensity-modulated radiation therapy (IMRT) for anal cancer. Materials and Methods: Since March 2006, 30 patients with stage I-IIIB anal squamous-cell carcinoma were treated curatively by IMRT or HT alone (n = 2) or by concomitant chemotherapy and IMRT or HT (n = 28). Median age was 59 years (range, 36−83 years) and the female/male ratio was 2.3 (21/9). Primary tumor site was anal canal, anal margin, or both in 26, 1, and 3 patients, respectively. Anal tumor, pelvic and inguinal nodes were irradiated with a median dose of 36 Gy using HT, or 5- or 7-field IMRT in 18 and 12 patients, respectively; After a planned gap of 1−2 weeks (median 1 week), a median boost dose of 23.4 Gwas delivered to the tumor and/or involved nodes using 3DRT (n = 24) or HT/IMRT (n = 6). The total delivered dose ranged between 59.4 and 64.8 Gy (median, 59.4 Gy). Concomitant chemotherapy consisted of mitomycin C alone (n = 1), mitomycin C and 5-fluorouracil (n = 17) or capecitabin (n = 10) in 28 patients. Common Terminology Criteria for Adverse Events v3.0 scale was used to score acute and late toxicities. Results: All but one patient, who developed progressive local and distant disease at the end of RT, achieved a complete response. Twelve months following RT, one patient had a recurrence at the primary tumor site, salvaged with brachytherapy. After a median follow-up of 7.5 months (range, 1−35 months), no deaths were observed. The 2-year actuarial locoregional control and probability of disease control without colostomy rates were 82% and 79%, respectively. RT was well tolerated without any unplanned treatment interruptions. Grade 1 or 2 acute adverse events consisted of skin toxicity in 8 and 22 patients, diarrhea in 18 and 3 patients, and cystitis in 9 and 2 patients; respectively. Only one patient developed grade 3 mucosal necrosis at the end of the treatment, requiring diverting colostomy. No difference in terms of acute toxicity was observed between patients treated with HT or IMRT. None of the 22 patients with a follow-up of more than 3 months developed grade 3 or more late toxicity. Conclusions: Our preliminary results suggest that HT or IMRT combined with concomitant chemotherapy for anal cancer is effective, and associated with favorable rates of toxicity compared with historical series. Further follow-up is warranted to assess late toxicity.

Copper filtration in pediatric digital X-ray imaging: its impact on image quality and dose.

The effect of copper (Cu) filtration on image quality and dose in different digital X-ray systems was investigated. Two computed radiography systems and one digital radiography detector were used. Three different polymethylmethacrylate blocks simulated the pediatric body. The effect of Cu filters of 0.1, 0.2, and 0.3 mm thickness on the entrance surface dose (ESD) and the corresponding effective doses (EDs) were measured at tube voltages of 60, 66, and 73 kV. Image quality was evaluated in a contrast-detail phantom with an automated analyzer software. Cu filters of 0.1, 0.2, and 0.3 mm thickness decreased the ESD by 25-32%, 32-39%, and 40-44%, respectively, the ranges depending on the respective tube voltages. There was no consistent decline in image quality due to increasing Cu filtration. The estimated ED of anterior-posterior (AP) chest projections was reduced by up to 23%. No relevant reduction in the ED was noted in AP radiographs of the abdomen and pelvis or in posterior-anterior radiographs of the chest. Cu filtration reduces the ESD, but generally does not reduce the effective dose. Cu filters can help protect radiosensitive superficial organs, such as the mammary glands in AP chest projections.