Cobalt Machines Research Articles

Impact of adjuvant radiation therapy photon energy on quality of life after breast conservation therapy: Linear accelerator versus the cobalt machine

Breast conservative therapy (BCT) is a standard treatment option in early operable breast cancers (OBC) and a select group of large or locally advanced tumors. The present study deals with prospective evaluation of quality of life (QOL) score in consecutive patients treated with BCT employing adjuvant RT treated with either a cobalt machine or a linear accelerator (LA). Patients of carcinoma breast who underwent BCT were taken into the study. Patients with larger breasts (inter-field separation >18-20 cm) were treated on LA and those with smaller breasts were treated on cobalt machine. All patients received a uniform RT dose (45-50 Gy/25#/5 weeks) to whole breast followed by tumor bed boost with suitable energy electrons. Prospective evaluation of QOL was done using EORTC QLQ C30 and breast cancer-specific EORTC QLQ BR23. QOL evaluation was done at pre-RT, at half completion of RT treatment (at 20-23 fractions) and at completion of RT. Pre-RT evaluation GQOL scores in patients treated with cobalt and LA were 71.6 and 71.7, respectively (P = 0.8). QLQ C30 functional and symptom domain scores were also similar in the groups. At RT completion, Global quality of life (GQOL) scores were 67.7 in patients treated with cobalt as compared to 77.7 in patients treated with LA (P = 0.75). Physical function domain scores in cobalt and LA patients were 70.8 and 80.3, respectively (P = 0.26). Fatigue score was higher in patients treated with cobalt (39.1 versus 29.7; P = 0.9). However, there was no difference in other functional and symptom domains. There was no significant change in any of the EORTC QLQ C30 domains at RT completion as compared to the pre-RT scores. There is no significant difference in QOL domains between appropriately selected patients treated with cobalt and LA. There are no significant changes in QOL domain scores at RT conclusion as compared to pre-RT baseline in patients treated with cobalt or LA source. A cobalt machine may be effectively used to deliver adjuvant RT in appropriately selected BCT patients especially in developing countries with limited resources.

P260 Impact of adjuvant radiation therapy photon energy on quality of life after breast conservation therapy: Linear accelerator versus the Cobalt machine

P260 Impact of adjuvant radiation therapy photon energy on quality of life after breast conservation therapy: Linear accelerator versus the Cobalt machine

Management of GIST: Perspective of Rajshahi Medical College Hospital

A prospective study had been carried out between July 2003 and June 2010 in Radiotherapy Department of Rajshahi Medical College Hospital on the patients diagnosed as Gastrointestinal Stromal Tumor (GIST). A total of 32 patients were enrolled. Males 24(75%) Predominated over the females 8(25%) with male female ratio 3:1. The patients were between 25 and 65 years with the mean age 45 years and majority (75%) belonged to age above 40 years. Common sites of involvement were ileum 14 (40.5%), Stomach 12 (32.5%) followed by duodenum 4 (15.25%) and jejunum 2(11.75%) in descending order. All patients attended after surgery except two who was inoperable. Patients with gross residual disease were planned for oral Imatinib mesylate (400-600mg / day) as adjuvant therapy. The two inoperable cases and those with gross residual disease at primary or metastatic site were planned for palliative treatment. Imatinib mesylate 400mg/day was planned for few cases. 3 cases with gross post operative residue were treated by 50Gys radiotherapy by conventional fractions from cobalt machine. Among 20 cases who were planned for adjuvant therapy 4 completed their course of targeted therapy after four years and are on 2-3 monthly follow up are in disease free state – clinically and by investigation . Among the remaining-16 cases, two patients faced progression of the disease and died and two patients presented with liver metastasis and rest are on oral Imatinib therapy in escalating dose, now gradually improving. Among the 12 cases, who were planned for palliative therapy, 4 post operative cases with gross residual mass, died due to disease progression. 2 post operative cases with gross residual disease, who received radiotherapy, did not come for subsequent follow up. Other 6 cases are yet on Imatinib and the tumor masses are regressing gradually.
 TAJ 2010; 23(1): 1-5

Estimation of organs doses and radiation-induced secondary cancer risk from scattered photons for conventional radiation therapy of nasopharynx: a Monte Carlo study

We used Monte Carlo modeling to calculate the organs doses due to out-of field photons during radiation therapy of the nasopharynx. A medical internal radiation dose (MIRD)-based mathematical phantom resembling an adult man was modeled by MCNP4C MC code. Three validated models of a cobalt-60 machine, a 6-MV photon beam of a Varian 2300 C/D linac, and a 9-MV photon beam of a Neptun linac were used to simulate the isocentric irradiation of a mathematical phantom with two lateral fields of the nasopharynx. The organspecific dose, effective dose, and cancer risk estimates were obtained. The effective doses for out-of-field radiation were 320, 295, and 248 mSv for the (60)Co beam, 6-MV beam, and 9-MV beam devices, respectively, for a 70-Gy tumor dose. The fatal cancer risks of 1.6%, 1.5%, and 1.2% were estimated for a 70-Gy tumor dose of (60)Co and the 6- and 9-MV photon beams, respectively. Our results regarding the effective dose and cancer risk are in agreement with previously published experimental results on conventional radiation therapy. Further investigation on patients' out-of-field dose to provide more knowledge on various radiotherapy techniques is suggested.

Monte Carlo simulation of a multi-leaf collimator design for telecobalt machine using BEAMnrc code.

This investigation aims to design a practical multi-leaf collimator (MLC) system for the cobalt teletherapy machine and check its radiation properties using the Monte Carlo (MC) method. The cobalt machine was modeled using the BEAMnrc Omega-Beam MC system, which could be freely downloaded from the website of the National Research Council (NRC), Canada. Comparison with standard depth dose data tables and the theoretically modeled beam showed good agreement within 2%. An MLC design with low melting point alloy (LMPA) was tested for leakage properties of leaves. The LMPA leaves with a width of 7 mm and height of 6 cm, with tongue and groove of size 2 mm wide by 4 cm height, produced only 4% extra leakage compared to 10 cm height tungsten leaves. With finite 60Co source size, the interleaf leakage was insignificant. This analysis helped to design a prototype MLC as an accessory mount on a cobalt machine. The complete details of the simulation process and analysis of results are discussed.

The measurement of photoneutron dose in the vicinity of clinical linear accelerators

In Brazil, the replacement of rather old cobalt and cesium teletherapy machines with high-energy (E > 10 MV) medical linear accelerators (linacs) started in the year 2000, as part of an effort by the Ministry of Health to update radiotherapy installations. Since then, the contamination of undesirable neutrons in the therapeutic beam generated by these high-energy photons has become an issue of concern when considering patient and occupational doses. The walls of the treatment room are shielded to attenuate the primary and secondary X-ray fluence, and this shielding is generally considered adequate also to attenuate neutrons. However, these neutrons are scattered through the treatment room maze and might result in a radiological problem at the door entrance, an area of high occupancy by the workers of a radiotherapy facility. This paper presents and discusses the results of ambient dose equivalent measurements of neutron using bubble detectors. The measurements were made at different points inside the treatment rooms, including the isocentre and the maze. Several radiation oncology centres, which are users of Varian Clinac or Siemens machines, have agreed to allow measurements to be taken at their facilities. The measured values were compared with the results obtained through the semi-empirical Kersey method of neutron dose equivalent calculation at maze entrances, with reported values provided by the manufacturers as well as values published in the literature. It was found that the measured values were below the dose limits adopted by the Brazilian Regulatory Agency (CNEN), requiring no additional shielding in any of the points measured.

Pattern of local relapse of maxillary sinus carcinoma

Maxillary sinus carcinoma (MSC) is a rare disease with a variety of treatment options. The present study was undertaken to review the outcome of patients with treated MSC in order to clarify the factors related to local recurrence by analyzing CT findings. The study group comprised of 47 cases, 40 males and 7 females with a median age of 61 years (range, 40- 84 years) treated between 1988 to 1996 at the department of radiotherapy. CT was taken with a slice thickness of 5 mm and contrast material was routinely used. The mean follow-up period for the group was 45.0 months (range, 3-125 months). The treatment policy was either preoperative radiotherapy of 40Gy/16fr followed by maxillectomy or radical radiotherapy of 65Gy/26fr with partial maxillectomy during the course of radiotherapy. By using CT-simulation, wedge pair techniques were used in most patients with Cobalt or 6MV X-ray machines as treatment sources. Tumor extension was categorized into the following anatomical sites: orbital contents, other paranasal sinuses, posterior wall of the maxillary sinus, pterygoid plate/muscle, nasopharynx, infra-temporal fossa, base of the skull, anterior wall of the maxillary sinus, subcutaneous tissue, cheek mucosa, hard palate and alveolar bone. Local control was computed by using the Kaplan-Meier method and p value was measured by using Chi-squared test. The 5-year overall local control rates for all patients were 56%. The local recurrence was found in 19 of 47 patients (40.4%). Tumors extending to pterygoid plates (n=13) and pterygoid muscles (n=10) showed higher rate of local recurrences as compared to those without extensions (9/13 [69%] vs 10/34 [29%], p<0.02 and 7/10 [70%] vs 12/37 [32%], p<0.05, respectively). Extensions to nasopharynx (6/9, 66%) and base of skull (4/6, 66%) also showed higher rates of recurrence; however, those were not statistically significant. More than 80% of the relapse became manifest within 12 months of diagnosis and isolated local failure was the most common pattern. This analysis indicates that tumor extension to pterygoid plate/muscles, results in higher rates of recurrences. This may due to the difficult surgical accessibility of the tumor. During radiotherapy planning, special emphasis should be given to this sites of tumor extension to avoid possible local recurrence.

Salvage abdominal irradiation for refractory non-Hodgkin′s lymphoma

Abdominal irradiation, as a part of treatment, is often ignored in the management of refractory non-Hodgkin's lymphoma (NHL). To evaluate the efficacy and the toxicity of this approach after failure of chemotherapy. 27 patients with intraabdominal lymphoma underwent salvage irradiation between 1982 and 2001. All patients were treated with a Cobalt-60 machine. The total dose administered to the abdomen was 18-20 Gy at the rate of 1.5-1.8 Gy per daily fraction, followed by a boost to gross disease up to 20 Gy. All patients had previously been heavily pretreated with chemotherapy. Fourteen patients, nine with follicular and five with diffuse lymphomas, had primary refractory tumors that had never achieved remission. Thirteen patients, six with follicular and seven with aggressive tumors, had refractory relapsed tumors after achieving one or more complete remissions. The response rate was 77%. The median follow-up was 53 months. The 5-year and 10-year survival rates were 25 and 17%, respectively. The in-field and out-of-field recurrence rates were 22 and 33%, respectively. Survival rates were significantly better for patients with refractory relapse compared to those with primary refractory lymphoma (P < 0.01). There was no significant difference in terms of response, recurrence, or survival rates between follicular and aggressive types. Out-of-field recurrence occurred more frequently in initial stage III and IV disease. Toxic deaths occurred in three patients (11%). Salvage radiotherapy for refractory abdominal NHL is a feasible alternative for both follicular and diffuse subtypes and may provide significant palliation and prolongation of survival. It is less effective in patients with primary refractory NHL than in those with refractory relapsed NHL.

Chemoradiotherapy in multicentric glioblastoma multiforme—A clinical study

11525 Background: Glioblastoma multiforme constitutes 40% of primary brain tumors. Multicentric Glioblastoma multiforme is rare about 3%.No definite guidelines is available in literature for management of these tumors. Methods: All Multicentric Glioblastoma multiforme were analyzed retrospectively from Jan 2003 to July 2005 for clinical behavior and response to chemoradiotharpy. Either Temozolamide or Carboplatin or Paclitaxel is used concurrently with radiation. Radiation dose 60 Gy/30 fractions over 6 weeks by bilateral parallel opposed fields was delivered using Cobalt-60 machine. Results: 27 cases were found, Male: Female 24:3, KPS 60 [40–70], Majority of them are symptomatic for 4 months, main symptoms were seizures, headache, vomiting, neurological deficite. 89% of them underwent one form of other surgical intervention. 11% were diagnosed on basis of radiological findings. 85% were supratentorial, 15% were both supra and infratentorial, one of which had spinal cord lesion. 6 [22%] patients did not receive any treatment. Among 21 patients 4 were treated only with radiotherapy, 17 with concurrent Chemoradiotherapy [Paclitaxel-8, Temozolamide-7 and Carboplatin-2]. 5 patients did not complete treatment. Among 16 patients only 6 came for first follow up, 5 of were concurrent Chemoradiotherapy [Temozolamide-4, Paclitaxel-l and RT alone 1]. At the end of 3 months only 2 patients with Temozolamide were alive. Conclusions: Multicentric Glioblastoma multiforme is an aggressive disease. Concurrent Chemoradiotherapy with Temozolamide has better role. No significant financial relationships to disclose.

Postoperative Radiotherapy in Non—Small-Cell Lung Cancer Warrants Further Exploration in the Era of Adjuvant Chemotherapy and Conformal Radiotherapy

that PORT was not associated with an overall improvement in survival and was associated with a detrimental effect on survival for the subgroup of patients with stage I and II disease. Numerous authors have examined the trials that were included in the metaanalysis. These analyses have concluded that many trials lacked appropriate methodology for randomized trials or appropriate treatment regarding recent standards for care. 2,5,7-11 The PORT meta-analysis included trials in which a majority of patients received treatment with cobalt machines, and some groups of patients were treated with just one radiotherapy field each day (an anterior field one day and a posterior field the next). It has been shown that these treatments result in suboptimal dose distributions, which may potentially increase toxicity. 2,4,7 Additionally, a large proportion of the patients who were included in the meta-analysis (more than 30%) were participants in one randomized trial of Dautzenberg et al. 12 This trial allowed physicians to treat patients with daily fractions of 2.50 Gy and total doses of 60 Gy. These doses exceed the doses that have been considered the standard of care in North America for many years. 5,8-10 These high doses do not comply with recent practices because physicians have had concerns about dose-related toxicity and the potential for treatment-related deaths. Both of these suboptimal outcomes were augmented by PORT in the study of Dautzenberg et al. Additionally, a majority of patients who were entered onto the randomized trial of Dautzenberg et al were part of an effort to increase accrual by relaxing the protocol requirements (simplified protocol). It is possible that this simplification detracted from the balance that was sought with the randomization procedure. The analysis of the Surveillance, Epidemiology, and End Results (SEER) database, as highlighted in this issue, demonstrated several similar findings compared with the meta-analysis, with the striking exception of the results for patients with involvement of N2 lymph nodes (N2 disease). Overall, PORT did not have a significant effect on survival and was associated with a survival decrement for patients with N0 or N1 disease. However, PORT was associated with an improvement in survival for patients with N2 disease, unlike the metaanalysis. Therefore, how does the clinician assess the available literature regarding PORT in resected NSCLC and make rational treatment recommendations for patients?

Evaluation of Late Toxicities of Patients with Carcinoma of the Cervix Treated with Radical Radiotherapy: An Audit from India

To evaluate the incidence of, and factors affecting, late toxicities of women with carcinoma of the cervix treated with radical radiotherapy. Between 1996 and 2001, 1069 women with carcinoma of the cervix (stage I-IVA) were treated at our centre with external-beam radiotherapy (EBRT) and intra-cavitary radiotherapy (ICRT) (n = 871) or EBRT alone (n = 198). Median follow-up was 34 months. Median dose to point A was 81 Gy. Five-year actuarial incidence of overall (all grades) and severe (grade 3/4) late toxicities in the rectum, bladder, small intestine and subcutaneous tissue were 12.3% and 1.1%, 11.2% and 1.2%, 9.2% and 0.2%, and 23.1% and 1.2%, respectively. Vaginal adhesions were seen in 29.6% of cases and stenosis in 33.9% of cases. On multivariate analysis, factors adversely affecting overall incidence of proctitis were anterior-posterior (AP) separation of patient more than 18 cm and presence of comorbid diseases. Presence of comorbid diseases was the only factor affecting the incidence of severe proctitis (grade 3/4). AP separation more than 18 cm adversely affected the incidence of cystitis, both overall and severe. Late toxicities (all grades) in small bowel were increased in subsets, like women younger than 50 years and women with comorbid diseases, but no factor emerged as significant for incidence of severe toxicities. Subcutaneous fibrosis was significantly higher in patients with AP separation over 18 cm, those treated by cobalt machines and those who received EBRT only. Severe subcutaneous fibrosis was influenced by the use of EBRT alone. Overall incidence of vaginal toxicity was higher in women whose overall treatment time (OTT) was shorter and in women who received ICRT. Vaginal stenosis was higher in elderly women and in women who received ICRT by low dose rate. Even with telecobalt machines, impressive results with acceptable late toxicity can be achieved in the treatment of cancer of the cervix using an ideal combination of EBRT with ICRT.

CALCULATION AND COMPARISON OF HEART INTEGRAL DOSE IN THE TREATMENT OF ESOPHAGUS CANCER WITH THREE PHOTON ENERGIES & USING CT SIMULATION AND TREATMENT PLANNING SYSTEM

Introduction: Esophageal cancer is one of the most frequently occurring cancers in Iran and having a high incidence rate among other countries. Radiotherapy is one of the three methods (surgery, radiotherapy and chemotherapy) for radical or palliative treatment of esophageal cancer. In this method of treatment, the organs such as heart and spinal cord are regarded as organs at risk (OAR) which their dose should be kept below the tolerance level. Different techniques have been used in conventional radiotherapy, among which two parallel opposed fields (POP) is used more often either for the whole course of the treatment or 2/3 of the fractions. In this technique, a great portion of the spinal cord may be involved in the treatment volume. The rate of treatment success may depend on the tolerance dose of heart and cord which act as the limiting factor. Materials and Methods: In this study, 10 patients with S.C.C. of esophagus having indication for external radiotherapy were selected. The CT scan simulations were performed for all the cases and their data were digitized to be used in computerized treatment planning system. Treatment planning for three photon beam energies (Co-60, 6 and 10 MV) are obtained for each individual patient under the same geometry and dose. The integral dose, absorbed dose and dose volume histogram (DVH) of the heart and target were calculated for all the cases. Results: The maximum point dose in the heart is 140, 125 and 115% of the reference point for Co-60, 6 and 10 MV, respectively. The integral dose for the largest A-P patient was found to be 55.33, 54.17 and 51.66 Gy.Kg for Co-60, 6 and 10 MV, respectively. In using 10 MV beam, 7% reduction in the integral dose of the heart was obtained. Alternatively, by using 6 MV beam, a reduction of only 2% was observed. The integral dose of the heart for the 10 MV beam had a 5% reduction in comparison to 6 MV beam. Discussion and Conclusion: Since lower energy beams cause a higher integral dose to the heart and cord, the use of higher energy photon beams in the case of deep seated tumors and large size patients are unavoidable. In spite of the advantages of cobalt machines, its energy is not suitable for deeply suited tumors.

The efficacy of conventional external beam, three-dimensional conformal, intensity-modulated, particle beam radiation, and brachytherapy for localized prostate cancer

Technologic advances in radiation treatment planning and delivery have generated popular interest in the different radiation therapy techniques used in treating patients with localized prostate cancer. Throughout the past decade, high-energy (> 4 MV) linear accelerators have largely replaced Cobalt machines in external beam radiation therapy (EBRT) delivery. Conventional EBRT has been used to treat prostate cancer successfully since the 1950s. By switching to computed tomography-based planning, three-dimensional conformal radiation therapy provides better relative conformality of dose than does conventional EBRT. Intensity-modulated radiation therapy (IMRT) has further refined dose conformality by spreading the low-dose region to a larger volume. However, the potential long-term risks of larger volumes of normal tissues receiving low doses of radiation in IMRT are unknown. Particle-beam radiation therapy offers unique dose distributions and characteristics with higher relative biologic effect and linear energy transfer. Transperineal prostate brachytherapy offers the shortest treatment time with equivalent efficacy without significant risk of radiation exposure. The addition of hormonal therapy to radiation therapy has been shown to improve the outcome of radiation therapy.

Radiation Induced Meningioma

The patient made an uneventful recovery. RADIATION is widely used in the treatment of many malignant as well as benign conditions. Largely the technology of today has made it possible to treat tumors without undue effects to critical structures. Technology has made it possible to change from cobalt machines to linear accelerators and computers have made it possible to carry out inverse planning, intensity modulated radiation therapy, stereotactic radiotherapy, as well as radiosurgery. This is significant advancement but it should not be forgotten that radiation could induce tumors as well as prevent the growth. Many different types of tumors have been postulated to have resulted as a consequence of previously radiation therapy [1,2]. These include tumors such as gliomas sarcomas and meningiomas.

Multinational assessment of some operational costs of teletherapy

Background and purposeDecisions in planning radiotherapy facilities in countries with limited financial resources require information on economic factors to make provision for sustainability. This study aims at acquiring data on some of these factors involved in delivery of teletherapy in 11 countries of different economic status. Patients and methodsRepresentatives of three European, one African, three Latin American and four Asian countries, were identified from radiation oncology institutions that operated both cobalt and linac teletherapy machines. Productivity data were prospectively collected for the year 2002. A detailed log was recorded for each machine over an arbitrary two-week period. Data on quality assurance (QA), maintenance, the capital costs of each machine, and the source replacement costs for the cobalt units were also recorded. ResultsBoth linear accelerators and cobalt machines treat more than 10,000 fractions per year per machine with 2.5 and 2.3 fields per fraction, respectively. The capital costs of the machines vary considerably, with a factor of more than 10 for linear accelerators. Cobalt sources show a huge variation in price. The median costs of QA and maintenance of a linac was US$ 41,000 compared to US$ 6000 for cobalt machines. This results for the economic factors considered in median costs per fraction of US$ 11.02 for linear accelerators and US$ 4.87 for cobalt machines. These figures do not include the costs for physicians. ConclusionsThe variation of the costs per fraction is more due to the result of differences in machine usage and costs of equipment than of national economic status. A treatment fraction on a linac with functionality comparable to cobalt, costs 50% more than cobalt therapy. This project shows that it is possible to collect data on economic factors prospectively as well as retrospectively.

49. Adjuvant treatment to surgery: Is it still a place for radio-or chemotherapy?

The two metaanalysis conducted by the Cambridge group has cent the scene for adjuvant treatment as well as the pattern of failure analysis after surgery. In the pattern of failure analysis performed after a complete resection, local failure is a race event for pathological stage I and II disease (less than 10 %). In opposite, for stage III, local failure remains an issue due to the wide range of tumor extent, from resectable disease to unresectable tumor. In contrast, distant metastasis is a common problem with figures ranging from 20 to 50%. A last issue is certainly the problem of second cancer induced by a long history of tobacco smoking rising the question of chemoprevention. To prevent distant metastasis, a systemic treatment is the logical answer. The metaanalysis suggested a slight nonsignificant benefit for a sequential Cisplatine based chemotherapy. The recent American trial of Keller et al comparing postoperative radiotherapy to a combined chemo-radiotherapy approach did not showed any difference for stage III disease: the only important prognostic factor was the type of mediastinal exploration: sampling vs. radical dissection. Several trials are on going worldwide: Anita, ALPI, and IALT… The main characteristics of those trials are to include a cisplatine based chemotherapy program and a large number of patients. This implies necessary a low efficacy; a small difference is expected. Furthermore, the already published trials showed a low compliance to chemotherapy. Is the page turned for radiotherapy in a combined approach with surgery? In view of the available randomized trials and the recent metaanalysis, a quick answer is yes. Indeed, both observed either no effect or even a detrimental impact on survival. Nevertheless, those trials were performed during the last three decades, a period of many improvements in the knowledge of the disease, in imaging procedure, in surgery and in radiotherapy. Preoperative radiotherapy may increase the resectability rate in well-selected patient: some groups are still advocating this approach for superior sulcus tumor whereas many phase II and some phase III trials are combining radiation with chemotherapy in a preoperative settings. The data available suggested a higher rate of pathological complete response but also a slight increase in morbidity. In contrast, postoperative irradiation improves the local control especially for stage III disease: this was clearly demonstrated by the Lung Cancer Study group trial, the MRC trial and the Feng trial. Furthermore, we should remember that the PORT metaanalysis suggested a differential impact according to the tumor extent: the negative impact of postoperative radiation disappeared for stage III disease (a similar observation was made by Dautzenberg et al). One possible explanation is that the therapeutic effect of postoperative radiotherapy compensated the negative impact due to a poor radiation technique (large volume, high daily dose, and cobalt machines…). Both approaches imply to use a modern radiation technique minimizing the risk of inducing severe life-threatening late effects: this is especially the case for postoperative radiotherapy due to the already loss of lung function due to the surgery and a long history of tobacco abuse. This is probably the place for a conformal radiotherapeutic approach. The last issue concerns the management of patients after induction chemotherapy followed by surgery: the current approach is to reserve postoperative radiotherapy for incomplete resection or for persistent nodal disease. Probably, another important factor may be the presence or not of nodal capsular rupture. We are certainly lacking good data on the postresection management and outcome of those patients. In conclusion, radiation has still its place for stage III disease in a combined approach with surgery and chemotherapy providing the use of an adequate radiation technique.

Dose distribution throughout the body from radiotherapy for Hodgkin’s disease in childhood

Background and purposes: The individual dosimetry performed for a multicentre European cohort study of second malignant neoplasm following radiotherapy for a solid cancer in childhood demonstrated a large variation in the radiation doses estimated to any site. Materials and methods: From this study we have extracted the present work, i.e. estimation of doses for patients who underwent radiotherapy for Hodgkin’s disease in their childhood. These patients were treated using high energy X-rays from linear accelerators (MV group), γ-radiation from Cobalt machines (Cobalt group), soft X-rays from orthovoltage machines (kV group) and electron beams from accelerators (MeV group) at six French and UK centres. All patients started their radiotherapy between 1955 and 1985 and about 12% of them received more than one beam quality. Most of the patients were irradiated with large mantle AP/PA or partial mantle fields. Patients with transdiaphragmatic extension were also irradiated using inverted-Y paraaortic fields. The absorbed doses at the 91 skeleton points are used to calculate the mean dose to the active bone marrow. Results: Estimates of the median and mean doses, standard deviations and ranges to 13 specific sites of the body and to the active bone marrow are reported. Depending upon the size and sex of patients, target volume and position and radiotherapy techniques, the estimated doses are highly spread, attaining 0.19–106.07% of the target dose. This study underscores the need for individual dosimetry in epidemiological studies. Comparison with the available measured and calculated doses to the ovary and testis shows good agreement. Conclusion: This study underscores the neet for individual dosimetry in epidemiological studies.

Adjuvant radiation therapy for low stage testicular seminoma: Diagnosis and therapy in evolution

We performed a retrospective study to evaluate the clinical outcome of patients with early stage testicular seminoma who received adjuvant radiation therapy after orchiectomy over the past 15 years. During the 15 year period, 61 patients were treated with adjuvant radiation therapy for stages I, IIA, and IIB testicular seminoma. Patients received from 2,000 to 4,000 cGy delivered by a Cobalt machine and later by a linear accelerator. Our standard treatment protocol was modified in 13 patients: 7 secondary to abnormal lymphangiography (LAG) parameters and 6 due to abnormal computed tomography findings. We analyzed each patient's outcome for survival, recurrence, and complications. We then compared outcomes, looking for differing trends based on evolving evaluation or treatment techniques. The average follow-up is 75 months, with an overall survival rate of 93%. The cause specific survival is 100%. Four patients died from intercurrent diseases; at time of autopsy, one of these patients was noted to have a small focus of seminoma in a lateral inguinal node. He died from widely disseminated Hodgkin's disease. Three patients, including the aforementioned one, had recurrent disease outside of the radiation field, yielding a recurrence rate of 5%. No significant long term treatment complications were reported, although 24% of patients had one or more complications from LAG. Regardless the various changes in patient evaluation and radiation treatment techniques over the past 15 years, adjuvant radiation therapy remains effective in patients with early stage testicular seminoma.

Collimator-related radiation dose for different cobalt machines and linear accelerators

Purpose : In previous publications (12, 13) measurements are described of the dose outside the primary beam (the peripheral dose (PD)) for 60Co gamma radiation to 25 MV photons. Comparison with data published by other investigators for different treatment machines, showed good agreement. This can only be explained when the contribution to the PD of radiation leaking through and scattering from the collimator does not differ considerably between treatment machines from different manufacturers, and it is the purpose of this article to investigate whether this assumption is valid. Methods and Materials : A request was sent out to all radiotherapy departments in The Netherlands and one in Belgium to measure the dose outside the primary beam for as many machines as possible. The following geometry was given: field sizes of 10 × 10 cm 2 and 20 × 20 cm 2 at distances of 30 and 50 cm, for collimator angles of 0° and 90° at the standard source surface distance. This, therefore, reslted in a dataset of eight measurement per photon energy. Results : Data were collected for four cobalt machines and 37 linear accelerators, from seven different manufacturers. All togetehr 56 datasets were collected for 12 different photon energies. Although the variation of the leakage radiation dose is small, there can be differences of about 50% in the collimator scatter dose between collimator angles of 0° and 90°, depending on the collimator design or on the design of the flattening filter. For dual energy machines with a large gap between the low and the high energy, the values for the high energy are higher by about 40%. Old cobalt machines show higher leakage radiation dose than modern ones. Conclusion : Although there is no large variation in leakage radiation dose between different makes of accelerators, some show higher collimator scatter dose than others. The magnitude of the leakage radiation dose is well within regulatory limits. As the PD not only consists of a contribution from collimator-related radiation, but also of patient scatter, the differences are negligible when estimating the peripheral dose for an individual patient.

Effects of irradiation on the rat middle ear mucosa. A scanning electron microscopic study.

Adult Sprague-Dawley rats (n = 64) were used in this study to replicate in an animal model tissue change formed clinically during radiotherapy for the treatment of head and neck malignancy. Gamma irradiation was administered to both ears of each rat, using a cobalt-60 machine. A total dose of 30 Gy was administered, with 500 cGy/fraction given on 6 consecutive days to a time-dose fractionation value of 81. Animals were then sacrificed at sequential intervals. The tympanic bullae were removed and the mucosa was processed for scanning electron microscopy. Tissue findings indicated that irradiation might initially have no influence on the clearance activity of the middle ear. However, ultrastructural changes showed stagnation of secretion between cilia, falling off and different directions of the cilia, fused or collapsed cilia, and eustachian tube dysfunction (with mucosal edema). These findings possibly account for the occurrence of middle ear effusions in patients during and after radiotherapy for head and neck malignancy. It is our concept that insertion of a ventilation tube is necessary if abnormal mucociliary function appears, in order to clear and prevent the accumulation of any middle ear effusions and prevent further mucociliary dysfunction.