Telecobalt Therapy Research Articles

Comparative study of concurrent chemo-radiation in locally advanced head and neck carcinoma treated with 3DCRT versus telecobalt (2D) therapy in relation to toxicity and response

Background: Radiotherapy techniques in Head and neck cancers have evolved over years from 2D RT to conformal techniques. As conformal radiotherapy planning is more time consuming, costly and not available in every radiotherapy centre in India, we can consider Conventional 2D radiotherapy for patients in a country like India where we get large number of patients with low economic profile and with locally advanced stages. Aims: To compare the clinical response along with acute and late treatment related toxicity between two treatment modalities namely 3DCRT versus Telecobalt therapy during and after completion of Radiotherapy. Materials and Methods: 50 patients of Head and Neck cancer were enrolled in the study and were divided into two arms. Arm A consists of the patients planned for conventional EBRT and Arm B consists of the patients planned for 3DCRT. Statistically analysis was performed with the help of Epi Info (TM) 3.5.3. Chi Square(X2) test was used to test the association of different study variables with the study groups. T-test was used to compare the means. z-test was used to test the significant difference between the two proportions.

Validation of Leaf Design Characteristics of an Add-on Automated Multi Leaf Collimator for Telecobalt Therapy Machine.

Background: In developing countries like India, cobalt-60 machines still find their applicability, considering the cost and maintenance issues. With a view to deliver conformal treatment plans using teletherapy machines, an automated Multi-Leaf Collimator (MLC) was developed for the existing machines as a retrofit attachment to the collimator assembly without any modifications to the unit. Objective: This study aims to investigate the radiation characteristics of leaf designs incorporated in two add-on prototype MLC systems with respect to the shape of leaf projected at the isocenter plane and the isodose distribution around the target. Besides, the dosimetric characteristics of prototype MLC with divergent leaf design are validated through simulation and experimental measurements.Material and Methods: In this experimental study, two add-on prototype MLC systems were designed and fabricated. The characteristic measurements of leaf designs incorporated in both the prototypes were carried out using Gafchromic films (GAF) and compared with Monte Carlo (MC) simulations. For divergent leaf design, beam profiles were obtained using Monte Carlo simulations which are complemented with the results obtained from measurements of radiochromic films and ionization chamber (IC) profiler. Dosimetric characteristics like radiation field width and beam penumbra were evaluated.Results: The Monte Carlo simulated data are in agreement with experimental data from IC profiler as well as from Radiochromic films. The results of this study are well within acceptable tolerance limits. Conclusion: The prototype MLC system designed for existing telecobalt machines supports its clinical applicability for conformal therapy to better manage treatment in rural areas, which can provide superior cost effective treatments.

Estimation of Skin doses for Retrofit Prototype Multileaf Collimators Designed for Telecobalt Therapy Machine.

Aim:The objective of this study was to evaluate skin dose based on retrofit prototype multileaf collimators (MLCs), designed for cobalt-60 teletherapy machine. Since patient's skin is sensitive to radiation, evaluation of skin dose is of utmost importance for investigating the risk of late effects.Materials and Methods:Measurements were performed with a Phoenix cobalt-60 teletherapy machine and the detector used was EBT3 radiochromic film. The experiments were performed in a solid water phantom with two prototype MLCs mounted to the machine. Dose readings were taken by placing the films at source-to-surface distance (SSD) of 60 cm, 65 cm, 70 cm, 75 cm, 80 cm, 85 cm, and 90 cm for various MLC-generated field sizes starting from 2 cm × 2 cm to 14 cm × 14 cm. The films were analyzed using custom made programs. The measured doses were normalized to the dose at dmax for that particular measurement of SSD.Results:The skin dose is expressed as a percentage of dose at dose maximum. In general, the skin dose increases with field size and decreases with SSD. The measurements indicate surface doses within 20%–60% for the investigated SSD range. Furthermore, there is no significant difference between the surface doses of two prototype MLCs studied.Conclusions:From the measurements, it can be concluded that there is good skin sparing even at close distance to the MLCs. The skin dose is <50% for SSDs >65 cm. A minimum gap of 5 cm is required to produce acceptable skin dose.

Design and development of an add-on automated multi-leaf collimator for telecobalt therapy machine and study of its characteristics

Purpose: The purpose of the paper is to present the design, development and dosimetric characteristics of an automated Multi-leaf collimator (MLC) integrated along with an inexpensive Treatment Planning System (ROPS), developed for existing telecobalt units as an add-on without making any modifications to the treatment machine. Method: The prototype MLC design consists of 28 tungsten alloy leaves (14 leaf pairs) having a mass density of 18 g cm -3 . Each of the leaves projects 10 mm width at the isocenter, which is at 80 cm from the source. The automation has been achieved with a dedicated linear actuator for each leaf. Radiochromic films and IC PROFILER™ (Sun Nuclear Corporation, Melbourne, FL) were used for the measurement of beam profiles and the profiles were analyzed to arrive at radiation field width, beam flatness, symmetry and beam penumbra. Results: The prototype MLC can define radiation fields of up to 14 × 14 cm² within the prescribed tolerance values of 2 mm. The flatness and symmetry were found to be within the prescribed tolerance value of 3%. The penumbra for a 10 × 10 cm² field size is 9.5 mm which is less than the generally acceptable value of 12 mm for a telecobalt machine. The maximum leakage through the leaf ends in closed condition was observed to be 7.3% which is less than the values reported for other MLCs designed for medical linear accelerators. Conclusion: It is concluded that dosimetric parameters and the leakage radiation of the prototype MLC are well below their recommended tolerance values. The MLC can be used for carrying out conformal radiotherapy with existing telecobalt machines.

Hypothyroidism in patients treated with radiotherapy for head and neck carcinoma: standardised long-term follow-up study.

Hypothyroidism is a common complication when radiotherapy is part of the treatment for head and neck tumours. This study aimed to show the incidence of hypothyroidism and possible risk factors in these patients. Factors related to the population, tumour, treatment and occurrence of hypothyroidism were analysed in 241 patients diagnosed with head and neck carcinoma. Approximately 53 per cent of patients were diagnosed with radiation-induced hypothyroidism. Its occurrence was related to: tumour location, laryngeal surgery type, neck dissection type, post-operative complications, cervical radiotherapy and radiotherapy unit type (linear particle accelerator or telecobalt therapy technology). Control of thyroid function should be standardised for several years after treatment, particularly in patients with risk factors, such as those treated with telecobalt therapy, those with post-operative complications and for whom the thyroid parenchyma is included in the irradiated area (laryngeal or pharyngeal location and bilateral cervical radiation).

Hypofractionated Radiotherapy for T1N0M0 Glottic Cancer: Retrospective Analysis of Two Different Cohorts of Dose-fractionation Schedules from a Single Institution

AimsTo determine the influence of dose and fractionation on tumour characteristics, toxicity, disease control and survival outcomes in T1 glottic carcinoma. Materials and methodsBetween 1975 and 2000, treatment charts of 652 patients with T1 glottic carcinoma who received curative radiation with four hypofractionated schedules (50 Gy/15 fractions [3.3 Gy/fraction] or 55 Gy/16 fractions [3.43 Gy/fraction] or 60 Gy/24 fractions or 62.5 Gy/25 fractions [2.5 Gy/fraction]) were analysed. The patients were divided into two groups based on fraction size <3 Gy and >3 Gy. Local control and overall survival were calculated. Patient- and tumour-related factors affecting local control were analysed using univariate and multivariate analysis. Factors affecting late toxicity were also analysed. ResultsThe local control and overall survival at 10 years were 84 and 86.1%, respectively, for T1 glottic carcinoma. The response to radiation had a significant effect on local control with univariate analysis (P = 0.001). Other factors, such as beam energy, anterior commissure involvement and fractionation, did not affect local control. Persistent radiation oedema was seen in 123 patients (23.4%) and was significantly worse in patients who received radiation with a larger field size (>36 cm2) on a telecobalt machine (P < 0.001). ConclusionsRadical radiotherapy schedules incorporating a higher dose per fraction yield acceptable local control rates and late toxicity. Telecobalt therapy for early glottic cancer is a safe alternative to treatment with 6 MV photons on a linear accelerator in terms of local control and late toxicity as long as field sizes smaller than 36 cm2 are used.

Radiotherapy for esophageal cancer in Japan

Currently, surgery is the most popular treatment method for esophageal cancer. Radiation is not main treatment but only a supporting one. This situation is now changing because of chemoradiotherapy (CRT). In the 1980s, although most patients treated with radiotherapy were inoperable for extremely advanced or some medical reasons, treatment outcome of surgery was undoubtedly superior to that of radiotherapy. Low-dose rate radiotherapy has many biological benefits. We tried low-dose rate telecobalt therapy (LDRT) as a boost to improve the outcome of radiotherapy for esophageal cancer. However, the LDRT did not improve survival. Since 1990s, studies have demonstrated the effectiveness of CRT using cisplatin and 5-fluorouracil. We made a prospective comparison of surgery and CRT with salvage surgery after recurrence for operable esophageal cancer. Five-year survival rates of 75 CRT patients and 76 surgery ones were 67.5 and 57.7 %, respectively. Twenty-eight patients in the CRT group underwent salvage surgery and 14 survived. Thirty-nine patients in the CRT group (52 %) survived, preserving their esophagus and their QOL was excellent. CRT with salvage surgery should be offered to all operable patients. After CRT, some patients complained severe radiation pneumonitis and myocardial disease. Radiation field should be as small as possible, including the low-dose area. Dose distribution of proton and heavy particle therapies is superior to ordinary radiotherapy. In future, particle beam therapy alone or in combination with photon beam therapy will become widespread as a radiotherapy method during CRT for esophageal cancer.

Effect of low-density heterogeneities in telecobalt therapy and validation of dose calculation algorithm of a treatment planning system.

Telecobalt machines are still prominently used for the treatment of a variety of cancer cases in developing countries. The human body is a heterogeneous composition of variety of tissues and cavities which vary widely in their physical and radiological properties. The presence of heterogeneities in the path of telecobalt beam presents an altered dose distribution in the region of clinical interests. A computerized treatment planning system (TPS) is generally used for calculating the dose distribution in the patient. Experimental measurements were carried out in a telecobalt beam with the objectives to study the effects of low-density heterogeneities and to verify the ability of the ASHA radiotherapy TPS in predicting the altered dose distribution along the central axis and off-axis of the beam. Locally available kailwood was tested for its lung equivalence and measurements were carried out in a polymethyl methacrylate phantom by introducing lung equivalent and air gap heterogeneities. A comparison of experimentally measured and TPS calculated dose values indicates that the TPS overestimates the dose by 11.6% in lung equivalent (kailwood) heterogeneity along the central axis. Similarly, it was found that the TPS overestimates the dose by 3.9% and 5.9%, respectively, with air heterogeneity of 1.0 and 2.0 cm. While testing the adequacy of TPS in off-axis region, it was found that the TPS calculation does not indicate the widening of the beam profile in the low-density heterogeneity region. This study suggests that the effective path length based algorithm of the ASHA radiotherapy TPS is unable to achieve the recommended 3% accuracy of clinical dose calculation in heterogeneous media.

Value of panendoscopy in metastases of unknown origin

Neck metastases of unknown origin are metastatic solid tumors wth primary undetactable by physical examination, chest x-ray, rutine blood and urine studies and histologic evaluation. This study included 77 patients of both sexes, average age 57 years, undergoing a diagnostic procedure at ENT clinic, Clinical Center Novi Sad, in the period from 1992 to 2001. The prymary tumor was detected in 51% of all cases by panendoscopy and bilateral tonsillectomy. In 14 of 26 patients (54%), in whom the site of the primary tumor was not detected, after telecobalt therapy and radical neck dissection, no relapses occurred. Pathohistological examination revealed planocellular carcinoma in 50 (65%) cases, transitional cell carcinoma in 9 (11.7%) cases and lymphoma in 7 (9.1%) cases. Cervical metastases with unknown primary tumor are the first sign of head and neck malignant disease. Panendoscopy with bilateral tonsillectomy and multiple mucosal biopsies are necessary procedures in detecting the primary tumor site.

Timescale of evolution of late radiation injury after postoperative radiotherapy of breast cancer patients

Purpose: To evaluate the incidence and prevalence of various signs of late morbidity, their time of appearance and pattern of progression during an observation period up to 34 years in breast cancer patients treated with postoperative radiation therapy after radical mastectomy. Methods and Materials: A group of 71 breast cancer patients received in 1963–1965 aggressive postoperative telecobalt therapy to the parasternal, axillary, and supraclavicular lymph node regions after total mastectomy and axillary clearance. None of the patients received chemotherapy either prior to, or after the irradiation as part of their primary treatment. The prescribed dose to the three lymph node regions was 44 Gy in 11 fractions. Only two of the three fields were treated per day. This total dose was given in 16–17 fractions over 3–4 weeks. Because of the overlap of the supraclavicular and axillary fields, the dose received by the brachial plexus was not the dose that was prescribed. A retrospective dose calculation showed that the total dose to the brachial plexus was 57 Gy, delivered as a complex combination of 1.8 Gy, 3.4 Gy, and 5.2 Gy fractions. This cohort of patients has now been followed to 34 years and the late side effects of the treatment evaluated and scored. Results: This series is unique in the literature. There is no comparable report of a detailed long-term follow-up in a homogeneously treated group of patients with such a high survival, especially among the younger women, where it is almost 50% at 30 years. This is the reason that they were able to develop some of the very slowly evolving injuries. There was progression of many of the late effects in the period between 5 and 34 years. The more serious morbidities have increased progressively over the whole 34-year follow-up period. Ninety-two percent of the long-term survivors have paralysis of their arm. Other neurological findings included unilateral vocal cord paralysis among 5% of the patients, who developed the disease after a median time of 19 years. All of them were left-sided, indicating a mediastinal involvement of the recurrent nerve. Local recurrence or the appearance of a new primary tumor infiltrating or causing pressure on the recurrent nerve were vigorously investigated and excluded as possible causes of these symptoms. Conclusion: The greatest risk for all cancer patients is the inadequate treatment of their disease, because this is inevitably lethal. The aggressiveness of the therapy and the acceptable risk of complications must therefore be balanced against the risk of recurrence. The neuropathy seems to be closely linked to the development of fibrosis around the nerve trunks. The use of large daily fractions, combined with hot spots from overlapping fields contributed to the severity of the complications.

Brachial Plexopathy After Postoperative Radiotherapy of Breast Cancer Patients: A Long-Term Follow-up

In 1963-1965 a group of 71 patients operated on for breast cancer with total mastectomy and axillary clearance were given aggressive postoperative telecobalt therapy to the axillary, supraclavicular and parasternal lymph node regions. The prescribed dose to these lymph node regions was 44 Gy in 11 fractions. Only two of the three fields were treated per day. Retrospective dose calculations showed that the total dose in the brachial plexus from the axillary and supraclavicular fields was c. 57 Gy in 16-17 fractions over 3-4 weeks. After a few years, symptoms and signs of brachial plexus injury appeared in many patients, which was reported in some early papers. The cohort has now been followed-up to 34 years. As expected, there was progression of both prevalence and severity of the late effects between 5 and 34 years and 11 of 12 patients who are still alive have paralysis of their arms. The neuropathy seems to be closely linked to fibrosis around the nerve trunks. The use of large daily fractions, in some cases combined with hot spots from overlapping fields, was certainly the cause of the complication.

Brachial plexopathy after postoperative radiotherapy of breast cancer patients. A long term follow-up

In 1963-1965 a group of 71 patients operated on for breast cancer with total mastectomy and axillary clearance were given aggressive postoperative telecobalt therapy to the axillary, supraclavicular and parasternal lymph node regions. The prescribed dose to these lymph node regions was 44 Gy in 11 fractions. Only two of the three fields were treated per day. Retrospective dose calculations showed that the total dose in the brachial plexus from the axillary and supraclavicular fields was c. 57 Gy in 16-17 fractions over 3-4 weeks. After a few years, symptoms and signs of brachial plexus injury appeared in many patients, which was reported in some early papers. The cohort has now been followed-up to 34 years. As expected, there was progression of both prevalence and severity of the late effects between 5 and 34 years and 11 of 12 patients who are still alive have paralysis of their arms. The neuropathy seems to be closely linked to fibrosis around the nerve trunks. The use of large daily fractions, in some cases combined with hot spots from overlapping fields, was certainly the cause of the complication.

Pathological fracture of the mandible, secondary to eosinophilic granuloma in a medically compromised patient.

A case of eosinophilic granuloma of the mandible with submandibular lymph node involvement in a medically compromised patient is presented. The lesion caused the pathologic fracture of the. mandible. It was treated radically with the resection of the mandible between the angle posteriorly and the midline anteriorly and immediate reconstruction with a 3DBDB AO reconstruction plate. This was followed by telecobalt therapy of 2000 cGys in 10 fractions over 20 days.The combined surgical and radiation therapy should be reserved for patients having: (1) unremitting pain following currettage (2) Limitation of activity (3) a medically compromised patient or (3) in whom radiographic findings suggest an aggressive lesion involving adjacent tissues and/or causing pathologic fractures.

The development of radiotherapy in cervical carcinoma at the University Clinic of Rostock

Doubtlessly modern high voltage radiation treatment has less side effects than former techniques. It may be better than conventional methods with respect to 5-year survival rates, but that has to be proven using a large number of cases. Retrospective study using the material of one department of gynecology and obstetrics, practicing both operation and irradiation. 1830 cervical carcinomas are differentiated in stages and then divided in 3 historical collectives. From 1959 to 1968 there was a combination of traditional contact therapy with conventional X-ray irradiation. The period from 1969 to 1972 is characterized as a changing one with partly therapy as described above, partly traditional contact therapy was combined with biaxial telecobalt therapy. From 1973 to 1986 a reduced contact therapy doses was applied to pelvic high voltage irradiation. Five-year survival rate in stage I was 79% in conventional treatment and with ultra high energy 77%. The corresponding figures in stage II are 56% respectively 52%, in stage III 26% respectively 25% (Table 1) of gynecology and obstetrics, practicing both operation and irradiation. Application of ultra high energy radiation in higher doses in Rostock had not the consequence of elevating the 5-year survival rate, but the quality of life is much better.

ラジオアイソトープの治療への応用 ＶＩ．新しい遠隔照射治療 ガンマナイフを中心に

ラジオアイソトープの治療への応用 ＶＩ．新しい遠隔照射治療 ガンマナイフを中心に

The race for megavoltage. X-rays versus telegamma.

Roentgen's discovery was announced in January, 1896, and x-ray therapy trials followed in 1897. Becquerel rays and radioactive minerals were identified during 1896 through 1898. Radium was used for therapy by 1901, even though a pure standard was not achieved until 1910-1912. Quantities of radium finally became available after 1919, and for 20 years telegamma therapy machines underwent progressive development. Their megavoltage beam was much preferred over the standard 200-250 KV x-ray units of that time. Nuclear physicists during the Great Depression modified electron accelerators into giant 600-900 KV medical x-ray therapy machines and achieved one MV by 1937-1939. These were huge, complex, expensive, and unique to major academic and/or metropolitan centers. During World War II nuclear reactors superseded cyclotrons as efficient factories for few new radioisotopes, including "artificial radium". Few seemed interested in the latter for use in telegamma therapy until 1949-1951, when three competing teams from Canada and the USA designed telecobalt machines. From this competition, among then unknown innovators, emerged three future giants in radiation therapy: A.E.C.L., H. Johns, and G.H. Fletcher. The clinical application of telecobalt therapy was to revolutionize cancer care in community hospitals worldwide.

Auswirkungen der Therapie von Larynx- und Hypopharynxkarzinomen auf die Funktion der Tuba Eustachii*

In a prospective investigation Eustachian tube function was tested before and after surgery and irradiation of patients suffering from carcinoma of the larynx or hypopharynx. Passive and active tubal parameters were determined using the dual-impedance method in a pressure chamber. In this test, passive tubal function is described by the spontaneous opening and closing characteristics of the tube by an overpressure in the middle ear. Active tubal parameters are determined by the facility of the tube to equalize an over- and underpressure in the middle ear by swallowing. Statistic evaluation was performed with Student's t-test. There were no significant alterations of passive or active tubal function after neck dissection with or without surgery of the primary tumour. On the other hand we observed significant deterioration of all tubal parameters immediately after a series of fractionated percutaneous telecobalt therapy (60 Gy). 2 out of 18 patients developed unilateral middle ear effusion during irradiation which was reversible within 6 months. In most patients we observed a total or at least partial restitution of passive tubal parameters during this time, which was statistically significant. The active tubal function was of minor reversibility. Whereas the facility to equalize a positive pressure in the middle ear was quite good after 6 months, only few patients were able to equalize a negative pressure. The temporary deterioration of passive tubal function may be caused by a marginal implication of the tube at the edge of the irradiation field and by increased lymphatic pressure in tubal tissue following a radiogenic swelling of the lymphatic vessels of the neck.(ABSTRACT TRUNCATED AT 250 WORDS)

LOW-DOSE RATE TELECOBALT-THERAPY AS A BOOST AGAINST BRAIN-TUMORS

We applied low-dose rate telecobalt therapy (LDRT) as a boost for 26 brain tumors (17 malignant gliomas, 4 pontine gliomas and 5 others). Eleven of those cases were recurrent. The LDRT; 1 Gy per hour, 7 Gy per day, a total dose of 14 Gy in two successive days, was boosted after a conventional irradiation. In malignant glioma, the local control rate and the survival rate were not improved, compared with those of the control group. The treatment results of other brain tumors were also unsatisfactory. The incidence of brain necrosis was higher in the LDRT group. The benefits of the LDRT as a boost for radioresistant brain tumors seem to be small.

Prognostic factors in telecobalt therapy for early supraglottic carcinoma

The local control rates of T1 and T2 supraglottic carcinoma treated with radiation alone were reported as 71% to 92% and 59% to 83%, respectively. The factors that affect the local control rate for early supraglottic carcinoma were investigated. From 1967 through 1985, 100 cases with early supraglottic carcinoma (T1N0, 51; T2N0, 49) were treated with telecobalt therapy at the Department of Radiology, Osaka University Hospital. The 5-year actuarial survival rates of cases with T1 and T2 were 69% and 74%, respectively. The 5-year local control rates of cases with T1 and T2 were 77% and 62%, respectively. The local control rate for the epilarynx (94%) was significantly better than that for the lower supraglottis (66%; P < 0.05). For the lower supraglottis, the local control rates of 24 tumors that disappeared at 40 Gy and 58 tumors that persisted at 40 Gy were 88% and 55%, respectively (P < 0.05). The tumor site was an important prognostic factor in radiation therapy for the supraglottis, as was the tumor response at 40 Gy for the lower supraglottis.

The radiotherapy of advanced breast cancer

The authors discuss the indications for radiotherapy in late breast cancer, retrospectively analysing the experience of the Radiotherapy Department of the Portuguese Institute of Oncology in Lisbon. Treatment results of locally advanced cancer (T4a-b-c) with megavoltage machines (telecobalt therapy) using two different types of fractionation regimes are discussed. They conclude that conventional fractionation remains the best option. In elderly patients, those with ulcerated and bleeding lesions and those with socio-economic problems, it is acceptable to use non-conventional fractionation regimes with a high dose per fraction for the first part of the treatment. Advantages are overall shortening of treatment time without an increase in morbidity although survival is somewhat lower (30% versus 40% at 5 years). The authors also discuss the role of radiotherapy in disseminated disease which, in combination with systemic treatment, may be extremely useful in improving the patient's quality of life--as a way of stopping haemorrhage in bleeding lesions, for pain relief in secondary deposits, to treat superior vena cava syndrome and spinal cord compression, to prevent pathological fractures and last, but not least, to relieve or prevent symptoms such as those caused by brain metastases. The results presented in this paper are in agreement with current literature. Finally, the authors mention the most frequent complications of radiotherapy in late breast cancer as well as the guidelines for supportive care of the irradiated patient with the aim of a complete re-habilitation.