Experimental dosimetry in conformal breast teletherapy compared with the planning system.

The objective of this study was to compare and analyse the absorbed dose profiles from the conformal radiotherapy planning and experimental dosimetry taken in a breast anthropomorphic and anthropometric phantom. Conformal radiotherapy planning was elaborated in the Treatment Planning System (TPS). EBT2 Gafchromic radiochromic films were applied as dosimeters, positioned internally and superficially in the breast phantom. The standard radiation protocol was applied in the breast phantom. The films were digitalised, and their responses were analysed in RGB. The optical densities were processed, reproducing the spatial dose distribution.

Pattern of oncologic emergencies seen in adult cancer patients attending the Radiotherapy and Oncology Centre, Ahmadu Bello University Teaching Hospital, Zaria - Nigeria.

AIMS AND OBJECTIVES: To evaluate the Pattern of Oncologic Emergencies seen in Adult cancer patients and the treatment modalities used. MATERIALS AND METHODS: Between January 2004 and December 2008, a total of 1824 (M:F = 1:1.8) new patients were seen. 196 (M:F = 1:1.4) consecutive patients with histologically confirmed malignancies presenting with or having oncologic emergencies were treated and have been reviewed. Patients' folders were reviewed retrospectively with a structured pro forma. Results were analysed using Epi Info soft ware Version 3.4.1; 2007 Edition. RESULTS: The median age was 49 years and mean age of 42 years (range, 15 - 82 years). M: F = 1:1.4. 162 patients had oncologic emergencies at presentation while 21 during treatments and 13 during follow up. At the time of diagnosis of oncologic emergency, 126 were not on any treatment, 42 patients on hormonal therapy and 28 patients were on diverse chemotherapy. All the patients presented late with 108 patients presenting with metastatic disease and 88 patients with locally advanced disease. Only 35 patients were treated within 1 week of onset of emergency. 59 patients had cervical cancer, 31 patients with breast cancer and 28 patients with prostate cancer. Tumour haemorrhage wass the commonest oncologic emergency seen in 107 patients followed by bone pain with imminent cord compression from bone metastases in 59 patients. Of 107 patients with tumour haemorrhage, 54 patients had cardiovascular collapse with 7 having acute renal failure. Similarly, of the 107 with tumour haemorrhage, 56 patients bled from cervical cancer, 12 patients from breast cancer and 8 patients from urinary bladder. 129 patients were treated with teletherapy, 31 patients had chemotherapy, 27 patients had emergency surgery and 5 patients had chemoradiation. Oncologic emergencies were corrected in 126 patients. CONCLUSION: Tumour haemorrhage is the commonest oncologic emergency in this environment and teletherapy is the commonest therapy used. More radiotherapy centres are needed for prompt treatment and their usefulness in managing emergencies should be made known. Oncologic emergencies are commonly seen in metastatic and locally advanced disease.

Workload modeling for teletherapy unit.

AIMS: This study aims to derive a radiotherapy workload model using a prospectively collected dataset of patient and treatment information from a teletherapy treatment unit. MATERIALS AND METHODS: Information about all individual radiotherapy treatment was collected for two weeks from the Phoenix unit in our department. This information included diagnosis, treatment site, treatment time, fields per fraction, technique, use of blocks and wedges. Data were collected for two weeks (10 working days) in January 2008. During this time, 45 patients were treated with 450 fractions of external beam radiotherapy in Phoenix unit. RESULTS: The mean fraction duration, irradiation time and setup time were 9.55 minutes, 1.84 minutes and 7.66 minutes respectively. A mathematical workload model was derived using the average fraction duration time, total irradiation time and setup time of different types of treatment. A simple software program (Workload Calculation Chart) was also constructed in Microsoft Excel using the derived algorithm. The model based software program was tested and applied for one year and found that it can be used effectively to describe workload of teletherapy unit. CONCLUSION: Proposed methodology for workload modeling of teletherapy unit and the workload calculation software is very effective to quantitatively plan/calculate the optimal workload which will satisfy both the patient care administrator and radiation therapy technologists.

Clinic based transfer of the N(D,W)(60Co) calibration coefficient using a linear accelerator.

Ionization chambers used for reference dosimetry require a local secondary standard ionization chamber with a 60Co absorbed dose to water calibration coefficient N(D,W)(60Co) traceable to a national primary standards dosimetry laboratory or an accredited secondary dosimetry calibration laboratory. Clinic based (in-house) transfer of this coefficient to tertiary reference ionization chambers has traditionally been accomplished with chamber cross calibration in water using a 60Co beam; however, access to 60Co teletherapy machines has become increasingly limited for clinic based physicists. In this work, the accuracy of alternative methods of transferring the N(D,W)(60Co) calibration coefficient using 6 and 18 MV photon beams from a linear accelerator in lieu of 60Co has been investigated for five different setups and four commonly used chamber types.

[Choroidal metastases of malignancies. Review of treatment methods with special regard to application of radiotherapy]. / Przerzuty nowotworowe do naczyniówki galki ocznej. Przeglad metod leczenia ze szczególnym uwzglednieniem radioterapii.

Choroidal metastases are developed in 4 - 12% of patients with solid malignancies. Typical symptoms are loss of visual acuity or visual field, photophobia and floaters. In therapy of choroidal metastases are used following methods: surgery, laser photocoagulation, radiotherapy, and systemic treatment (anti-neoplastic chemotherapy or hormonotherapy). At choice of method of treatment it is taking not only features associate with choroidal metastases (as size, shape, number of changes and localization) but also: performance status of patient and the presence of metastases in any sites. The purpose of this paper is the review of treatment methods of choroidal metastases with special regard to application of radiotherapy. Radiotherapy is a conservative method of treatment, and it is used as brachytherapy or external beam irradiation (teleradiotherapy). Brachytherapy is recommended in case of single change, with base diameter below 18 mm. The positive results are observed in 90% cases. Teleradiotherapy is used in metastatic tumours which size exceed possibility successfully using of brachytherapy, and in case of multiple foci of choroidal changes, and metastases bilaterally localized. 70 - 89% patients developed regression of choroidal metastases after external beam irradiation. The preservation of bulbus oculi is observed in 98% patients. Presented paper showed application of methods of brachytherapy used in Ophthalmological Department of Jagiellonian University, and technique of teleradiotherapy used in Radiotherapy Department of Oncology Centre in Krakow, which are used in treatment of choroidal metastases.

Current status of radiotherapy in Vietnam, 2002.

PURPOSE: Resources for radiation therapy in Vietnam were analyzed to obtain an understanding of the current status of radiation oncological practice in Vietnam. MATERIALS AND METHODS: Data were obtained through a report on the locations of major equipment and personnel. RESULTS: The availability of both teletherapy and brachytherapy was related to the economic status of the country. Most departments were found to treat patients without simulator or treatment planning systems. CONCLUSIONS: The information in the report is currently available for radiation oncological practices in Vietnam and provides for planning of development programs on radiation oncology.

Radiotherapy services in countries in transition: gross national income per capita as a significant factor.

BACKGROUND AND PURPOSE: The acquisition of radiotherapy by countries in transition (CITs) is an evolutionary process from having no resources whatsoever, to meeting the standards adopted by well-developed countries. The influence of the economic ability of a country to acquire and sustain this technology has intuitively been accepted as a major factor but has not before been subjected to analysis for a large group of countries. This information has been analysed to provide guidance to countries commencing and expanding radiotherapy services. MATERIAL AND METHODS: The number of linear accelerators and (60)Co megavoltage teletherapy machines in 72 CITs, those with gross national income per capita (GNI/cap)<$12000 per annum (pa) and a sample of 12 countries with GNI/cap>$12000 pa were expressed as machines per million population (MEV/mil) and used as an index of the ability of the country to provide a service. This figure was related to GNI/cap. The average populations of 24 further countries without radiotherapy were compared with 21 countries with radiotherapy facilities having the same range of GNI/cap. RESULTS: The relationship log(10) MEV/mil=-2.90+0.85 log(10) GNI/cap was identified between the machines and income. Also verified was that small low income countries were less likely to have the technology than those with large populations. CONCLUSIONS: The increase in the number of teletherapy machines is closely linked to the GNI/cap of a country. Our sample of well developed countries failed to demonstrate a levelling off of equipment acquisition with income. In the lower income group, smaller countries were less likely to have radiotherapy services than those with large populations.

[The calculation of the dose from a 60Co source using 3-dimensional Fourier transform]. / Raschet dozy ot istochnika 60Co s pomoshch'iu trekhmernogo preobrazovaniia Fur'ee.

The distribution of a dose in tissue-equivalent phantoms was calculated through convolution of scattered photon flux by using three-dimensional Fourier transform. A simplified model of a scattering kernel is presented, wherein multiple scattering radiation is taken into account by a water point source accumulation factor. A 64 x 64 x 64 grid calculation lasts about 2 sec on a routine personal computer (three-dimensional Fourier transform and convolution). The dose were calculated in the cube, 32 x 32 x 32 cm in size and in the cylinder, 12 cm in diameter for 4 x 4-to-20 x 20-cm radiation fields. The results are in good agreement with the reference data and Monte Carlo simulation results.

[The effects of low-dose Co-60 irradiation on the course of aseptic arthritis in a rabbit knee joint]. / Effekte einer niedrig dosierten Co-60-Bestrahlung auf den Verlauf einer aseptischen Arthritis am Kniegelenk des Kaninchens.

PURPOSE: Numerous clinical observations demonstrate the efficacy of low radiation doses in the treatment of painful osteoarthritis. Experimental investigations remain scarce. We investigated the effects of locally daily 5 times 1.0 Gy 60-Co irradiation on an artificially induced aseptic gonarthritis in rabbits. MATERIAL AND METHODS: Three separate experiments (EV) were performed (10 rabbits per experiment, 5 treated/5 controls; duration: EV1: 18 days; EV2: 6 days; EV3: 29 days). An aseptic arthritis in the right knee joint of rabbits was induced by intraarticular injection of 0.5 ml papain solution (3%, 30,000 USP/mg) on day 0. The arthritic knee joint of the anesthesized animals was irradiated daily from day 1 to 5 with 5 times 1.0 Gy. The controls were sham-irradiated under the same conditions. The time course of arthritis in treated animals and sham-treated controls was evaluated by clinical, laboratory-chemical and histological criteria. The clinical investigation was performed daily, the puncture of the knee-joints was carried out several times in EV1, and at the end of experiments in EV2 and EV3. At the end of the observation period, animals were killed and the knee joints excised for histological analysis. RESULTS: The intraarticular injection of papain caused a peracute inflammatory response in all animals. After 1 week the chronic stage was reached, and the experimental arthritis resolved slowly within several weeks. Local irradiation accelerated the decrease of inflammatory joint swelling, being significant by day 4. On day 6 the volume of synovial fluid in irradiated knee-joints was significantly smaller. The morphometric data indicated a reduction in thickness of synovial membrane, a decrease in number of synovial cell layers, and a decrease in distance between capillaries and the synovial membrane surface following irradiation of arthritic joints. Due to considerable individual variability, the morphometric data partially did not reach statistically significance. CONCLUSION: The experiments provide evidence for an antiphlogistic effect of irradiation with 5 times 1.0 Gy in vivo. They support the clinical observations of the efficacy of anti-inflammatory radiotherapy.

[Which factors modify the reproducibility of patient positioning in the daily irradiation routine?]. / Welche Faktoren beeinflussen die Reproduzierbarkeit der Patientenlagerung in der täglichen Bestrahlungsroutine?

AIM: Factors which influence the accuracy of the field application during daily irradiation routine are not well known. The aim of this prospective analysis was to determine the significance of these factors on the occurrence of field misadjustments in irradiation without immobilization and to evaluate their clinical relevance. PATIENTS AND METHODS: Fifty-three patients received external cobalt-60 beam irradiation without fixation. Once weekly portal images of all treatment fields were carried out. In addition to objective patient data (age, weight, height, general condition, irradiation indication), the psychological situation of the patient during treatment (anxiety, restlessness, pain) and work circumstances of the medical staff during treatment were evaluated once weekly. The distance of clearly visible anatomic structures to the field borders of the portal images were measured and the deviation to the corresponding simulator images was calculated. Patient data were correlated to the number of field misadjustments (deviation larger than 1 cm). RESULTS: Patients whose condition is generally poor and patients being treated palliatively, patients with feeling of anxiety, restlessness or pain during simulation or irradiation and heavy patients (90 kg and more) were more often misadjusted. The number of field misadjustments increased with the stress of the medical staff. CONCLUSIONS: The problem of reproducibility of external beam irradiation without fixation in palliative treatment is of clinical relevance. Effective analgesic therapy and a comfortable and painfree patient set-up reduce misadjustments. In curative treatment, immobilization techniques should be used.

[Volume changes to the neck lymph node metastases in head-neck tumors. The evaluation of radiotherapeutic treatment success]. / Volumenveränderung der Halslymphknotenmetastasen bei Kopf-Hals-Tumoren. Bewertung des strahlentherapeutischen Behandlungserfolges.

AIM: This work is engaged with the volume change of neck lymph node metastasis of malignant tumors in the head-neck region during radiotherapy. PATIENTS AND METHOD: In 54 patients with head and neck tumors, the volume of neck lymph nodes before and after radiation was measured. The volumetry was done with CT planimetry. The total dose was 66 Gy (2 Gy/d) telecobalt from 2 lateral opponated fields. The time of volume change could be defined with measuring of the half-time and the doubling-time by the help of Schwartz formula. RESULTS: After 10 Gy the volume diminution was about 20% and half-time 24 to 26 days. Afterwards the time of volume diminution picked up speed and finally achieved 60 to 72%. Meanwhile the half-time decreased to the half value. The result was independent of the site of primary tumor, the patient's sex and age. CONCLUSION: In our opinion the effectivity of radiotherapy can best be judged with defining of the volume change of lymph nodes of the neck.

Off-axis primary-dose measurements using a mini-phantom.

The characterization of the incident photon beam is usually divided into its dependence on collimator setting (head-scatter factor) and off-axis position (primary off-axis ratio). These parameters are normally measured "in air" with a build-up cap thick enough to generate full dose build-up at the depth of dose maximum. In order to prevent any influence from contaminating electrons, it has been recommended that head-scatter measurements are carried out using a mini-phantom rather than a conventional build-up cap. Due to the volume of the mini-phantom, the effects from attenuation and scatter are not negligible. In relative head-scatter measurements these effects cancel and the head scatter is thus a good representation of the variation of the incident photon beam with collimator setting. However, in off-axis measurements, attenuation and scatter conditions vary due to beam softening and do not cancel in the calculation of the primary off-axis ratio. The purpose of the present work was to estimate the effects from attenuation and phantom scatter in order to determine their influence on primary off-axis ratio measurements. We have characterized the off-axis beam-softening effect by means of narrow-beam transmission measurements to obtain the effective attenuation coefficient as a function of off-axis position. We then used a semi-analytical expression for the phantom-scatter calculation that depends solely on this attenuation coefficient. The derived formalism for relative "in air" measurements using a mini-phantom is clear and consistent, which enables the user to separately calculate the effects from scatter and attenuation. For the investigated beam qualities, 6 and 18 MV, our results indicate that the effects from attenuation and scatter in the mini-phantom nearly cancel (the combined effect is less than 1%) within 12.5 cm from the central beam axis. Thus, no correction is needed when the primary off-axis ratio is measured with a mini-phantom.

[The results of primary radiotherapy in vaginal carcinoma]. / Ergebnisse der primären Strahlentherapie beim Vaginalkarzinom.

BACKGROUND: Cancer of the vagina is the least frequent primary malignant tumor of the female genital tract except carcinoma of the fallopian tube. Radiation therapy is the preferred treatment in most cases. PATIENTS AND METHOD: Between 1965 and 1991, 39 patients (median age 66 years) with primary carcinoma of the vagina were treated with radiation therapy at our clinic. The mean observation period was 37 months. Classification according to the FIGO yielded a stage I in 43%, stage II in 24%, stage III in 22% and stage IV in 11%. Histological differentiation resulted in 35 squamous cell carcinomas and 4 adenocarcinomas. In 69%, the tumor was found on the posterior or lateral wall of the vagina, in 43% it arose from the upper third of the vagina. Standard therapy consisted of combined brachy- and teletherapy. Most of the brachytherapy applications were performed with a radium source. RESULTS: Median survival was 37 months, calculated according to the Kaplan-Meier method. The 5-year actuarial survival rate for all stages was 41% (stage 1: 62%, stage II: 44%, stage III: 25%). Sixty-eight percent of all patients achieved a complete remission, 19% a partial response. Significant prognostic factors were stage of disease and histological grading. CONCLUSION: Our results demonstrate the value of radiation therapy for the treatment of primary carcinoma of the vagina. Combined treatment with both external beam radiation and brachytherapy should be preferred.

Design and comparison of wedge shaped midline block with rectangular block used in early stage cervical cancers.

PURPOSE: Design of an universal wedge shaped midline block for early stage cervical cancers to get uniform dose distribution around the target volume. MATERIAL AND METHODS: The method of fabrication of wedge shaped midline block is discussed for treatment of early stage cervical cancers based on the configuration of 137Cs pellets used in intracavitary applications and along with external photon beams obtained by using 60Co teletherapy machine and 6 and 10 MV linear accelerators. RESULTS: The dosimetric measurements are carried out to confirm the adequacy of thickness and shape of the block using radiation field analyzer for all the 3 energies. DISCUSSION: The dose distribution comparison has been made with wedge shaped midline block and conventional rectangular shields to show its superiority in getting homogeneous dose distribution around target volume. The shift in 184 intracavitary applications is analyzed in actual clinical applications with respect to central axis of external beams and its comparison is made with both types of blocks. With the shift of 1 cm towards lateral from midline an overdose can occur upto 12 Gy at certain points with rectangular block compared to wedge shaped midline block. CONCLUSION: Since the preparation of individual wedge shaped midline block for every application will be a difficult process for busy centers, the single wedge shaped midline block for each energy is more convenient to handle for busy centers instead of individualized compensating blocks for every intracavitary application.

A simple and generally applicable method to estimate the peripheral dose in radiation teletherapy with high energy x-rays or gamma radiation.

PURPOSE: Many articles have been published on the measurement of the dose to points outside the primary beam, often called the peripheral dose (PD), for instance, to the gonads, for specific treatment machines and/or techniques. We investigated the possibilities for developing a generalized method based on the data from several publications. METHODS AND MATERIALS: The data from several publications were recalculated for a reference situation, then averaged, and the frequency distributions around the mean were determined. Published data were available for 60Co, 4, 6, 8, and 10 MV, and 18 to 25 MV for a large variety of treatment machines. Furthermore, an analysis of possible corrections for depth dependence, field elongation, irregularly shaped fields, wedges, and shielding blocks was carried out. RESULTS: The frequency distributions of all published PD values for square fields for photon energies of 4 MV to 25 MV showed a standard deviation of 33%. The PD values of 60Co are significantly different with a standard deviation of 25%. A difference in the leakage radiation between cobalt machines and linear accelerators can possibly explain this difference, especially for large distances, where leakage radiation predominates. Taking the uncertainty of the risk factors into consideration, we conclude that the use of average values is justified. Although statistically not significant, the peripheral dose appears to be dependent on photon energy with a minimum around 6 MV. CONCLUSIONS: It is possible to estimate the peripheral dose for photon energies of 4 MV to 25 MV with an accuracy of +/- 33%; for 60Co, the accuracy is even better. The variation of the PD between different treatment machines is so small that it is justified to use average PD values, irrespective of the treatment machine.

[Primary cerebral non-Hodgkin's lymphomas. The results of radiotherapy]. / Primär zerebrale Non-Hodgkin-Lymphome. Ergebnisse der Strahlentherapie.

BACKGROUND: In the last years many therapeutic attempts were made to improve the poor prognosis of primary cerebral non Hodgkin's lymphoma. The aim of this study was to report on own experiences concerning this rare disease. PATIENTS AND METHODS: In 1986 to 1994 26 patients were treated for primary cerebral non Hodgkin's lymphoma. 15% were HIV-positive. High-grade non-Hodgkin's lymphomas were diagnosed in 62%. 46% of all cases showed multiple lesions. 23% of our patients received a dose less than 25.5 Gy, 27% received 37.5 Gy (whole brain) and 39% were treated with 51 Gy (37.5 Gy whole brain and 13.5 Gy boost dose). Radiation technique included regular and irregular fields (single dose: 1.5 Gy). RESULTS: 62% of patients achieved a complete or partial remission directly after irradiation, in 4% no change or progression was seen. 31% could not be examined due to their bad status or death. The mean follow-up time for all patients was 19.6 months, the median survival was 3.6 months. The 1-year-survival rate was 41%, 3-year survival rate was 28%. Patients who received a tumor dose of 51 Gy had better survival times in comparison to patients who received less (p = 0.01). Prognostic parameters (Cox regression analysis) were: tumor dose, grading and local result after irradiation. The Karnofsky performance status was not an independent parameter (p = 0.12). Side effects were low. Long-term survivors had relatively good quality of life. CONCLUSION: Taking into consideration the small numbers of patients in all studies all results or conclusions have to be made with great reservations. Despite the high proportion of HIV-positive patients our results are in compliance with other authors using similar therapy protocols. Reports dealing with combined radio-chemotherapy have published good results concerning survival time. But long-term morbidity due to these protocols needs further investigation and has to be awaited.

On the measurement of the effective linear attenuation coefficient mueff in 60Co wedge fields.

PURPOSE: It is difficult to obtain a correct measurement of mueff. Moreover, wedge calculations using a single mueff value are not correct. We present a program for the analysis of wedge measurements. MATERIALS AND METHODS: The program employs parameters of an open field to correct the dosimetry of a wedge field. For this the ASCII export files of an MP3 (PTW) system are automatically imported into our program. The principle is illustrated for ionization measurements from a Chisobalt 2B75 cobalt unit. The wedge field dose profiles are corrected by the off-centre ratio of the open field and mueff is analysed as well as its dependents on geometry. RESULTS: We found that the dose attenuation by a wedge can be described by the product of wedge thickness and the effective linear attenuation coefficient mueff. However, mueff values for a given field size decrease with depth. This is interpreted as an effect of beam hardening. For the usual fields in radiotherapy this effect is independent of field size and can be described as an exponential function of wedge thickness. CONCLUSION: The effective linear attenuation coefficient mu(eff) is depth-dependent. A correction could be added to planning programmes, i.e.: exp. (delta mu.tw.[d-dmax]).

[Spiral computed tomography for treatment planning and quality assurance in radiotherapy]. / Spiralcomputertomographie zur Bestrahlungsplanung und Qualitätssicherung in der Strahlentherapie.

BACKGROUND: The possibilities of spiral CT for radiotherapeutic treatment planning and quality assurance have been systematically investigated. PATIENTS AND METHODS: The influence of parameters such as slice thickness, table speed and increment on geometric accuracy was studied. Ring-, spheric-, PMMA- and humanoid Alderson phantoms were used. Furthermore, patients with infradiaphragmatic irradiation of Hodgkin's disease or with mediastinal irradiation were studied using CT-angiography. Patients with carcinomas of the head and neck before HDR- and PDR-brachytherapy were examined as well. RESULTS: Spiral CT offers 3D volume data information with excellent reduction of breath and motion artefacts for virtual simulation. 2D multiplanar reconstructions with excellent local resolution may be obtained. 3D MIP (Maximum Intensity Projection), based on CT-angiographic imaging, is a good tool for infradiaphragmatic treatment planning of Hodgkin's disease, if small numbers for slice thickness, table speed and increment are used. SSD (Surface Shaded Display) offers good 3D visualization and good geometric control of intracavitary and interstitial brachytherapy applicators. High qualitative multiplanar reconstructions are useful for CT-based brachytherapy planning. CONCLUSIONS: Spiral CT is a precious tool for 3D treatment planning and virtual simulation in radiotherapy and superior to conventional CT data acquisition. Quality assurance is improved for dose-volume-histograms and for brachytherapy.

Overall time in telecobalt therapy for T1 glottic carcinoma treated with 2 Gy per day.

BACKGROUND/AIM: We already reported the tumor response during radiotherapy as a prognostic factor for T1 glottic carcinoma. In these reports, we did not evaluate the overall treatment time. There were many reports of correlation between local control and overall treatment time of radiation for head and neck cancer. Our aim was to evaluate the overall treatment time as a prognostic factor of the local control for T1 glottic carcinoma or not. PATIENTS AND METHODS: From 1967 through 1985, 295 patients of T1 glottic carcinoma were treated with telecobalt therapy at the Department of Radiology, Osaka University Medical School. Of 295 patients, 219 patients treated with 2 Gy per day were evaluated. The median of total doses was 60 Gy (42 to 72 Gy). Overall treatment times of patients with tumor clearance at 40 Gy were significantly shorter than those with tumor persistence at 40 Gy. RESULTS: According to the univariate analysis, there were no statistically significant factors for local control except tumor response during treatment. Of 124 patients treated with a total dose of 60 Gy and the overall treatment time of 40 to 46 days, local control rates of patients treated with the overall treatment time of 40 to 42 days and 43 to 46 days were 88% and 78%, respectively (p = 0.3072). For 91 patients with tumor clearance at 40 Gy, local control rates of patients treated with the overall treatment time of 40 to 42 days and 43 to 46 days were 96% and 82%, respectively (p = 0.1645). Corresponding figures for 31 patients with tumor persistence at 40 Gy were 63% and 65%, respectively (p = 0.4227). CONCLUSION: We compare the treatment results of patients treated with the same total dose and the same tumor response during radiotherapy. We concluded that the overall treatment time was not a prognostic factor for T1 glottic tumor treated with overall time of 40 to 46 days.

Clinical assessment of tumor clearance during radiotherapy as a prognostic factor of early glottic carcinoma.

From 1967 through 1985, 358 cases of early glottic carcinoma were treated with telecobalt therapy at the Department of Radiology, Osaka University Medical School. Among 278 cases treated with 2 Gy a day, the tumor response of 262 cases at 40, 50 and 60 Gy were evaluated by direct or indirect laryngoscope. The five-year local control rates of these evaluable cases of T1 and T2 glottic carcinoma were 79% and 70%, respectively. The local control rates of T1 glottic carcinoma with tumor clearance and persistence at 40 Gy were 83% (119/143) and 64% (43/67), and those of T2 cases were 86% (18/21) and 58% (18/31), respectively. The local control rates of the cases with tumor clearance and persistence at 40 Gy were same between T1 and T2 cases. The tumor clearance rates of T1 cases were significantly higher than those of T2 cases (p < 0.005). T2 glottic carcinoma had larger tumor volumes and slower tumor regression and resulted in lower control rates compared with T1 glottic carcinoma. The difference in the radiation dose of T1 and T2 glottic carcinoma with the same clearance rate was estimated as 15 Gy using logit analysis.