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T Tacev

Publications and source records attributed to T Tacev.

At least 19 recordsLinked to original sources
PubMed2006

[Preoperative radiotherapy in hypoxia in the complex treatment of the rectal carcinoma--complications].

INTRODUCTION: Preoperative radiotherapy is considered to be the standard approach in the treatment of the rectal carcinoma. Acute hypoxia decreases partial pressure of oxygen in healthy tissues immediately, but in the tumor after 30 min of duration. There is a higher radioresistance of healthy tissues in this interval because of lower oxygenation compared with normooxic status and the tumor is still relatively good oxygenated. This fact theoretically enables higher doses of radiotherapy and lower adverse effects. The aim of this study was to evaluate short and long term complications after preoperative radiotherapy of rectal carcinoma in hypoxia. PATIENTS AND METHODS: Between April 1991 and October 2000, 127 patients with the rectal carcinoma were treated preoperatively with locoregional accelerated hypofractionated radiotherapy in hypoxic conditions in Masaryk Memorial Cancer Institute. The dosis was up to 8 x 4 Gy. Acute hypoxia was induced during irradiation by ventilation of a hypoxic gas mixture containing 7.8-8.0% oxygen for totally 7-8 min. Operation was performed till 24 hours. RESULTS: There was no complication concerning with breathing of hypoxic gas mixture. A 30 day postoperative mortality was 0.8%. A 30 day postoperative morbidity was 31.7%. An anastomotic leakage occurred in 6.5%. Chronic gastrointestinal disorders occurred in 16.1% patients. CONCLUSION: Preoperative irradiation in hypoxic conditions is safe and efficient procedure. It permits safe administration of doses higher than those tolerated by normooxic conditions. Type and frequency of complications are comparable with other preoperative regimens.

Adult↗
PubMed2001

Modulation of radioprotective effects of respiratory hypoxia by changing the duration of hypoxia before irradiation and by combining hypoxia and administration of hemopoiesis-stimulating agents.

AIM: Analysis of radioprotective effect of respiratory hypoxia on hemopoietic tissue and enhancement of this effect by hemopoietic activation. MATERIAL AND METHODS: In mice breathing hypoxic gas mixture during total body gamma irradiation the recovery of pluripotent and committed granulocyte-macrophage progenitor cells and animal lethality were determined. RESULTS: In mice forced to breathe 10% O2 and 8% O2 during irradiation, the oxygen tension in the spleen decreased to 40% and 20%, respectively, of control values. Hypoxia mitigated the lethal effect of gamma-rays and improved the recovery of hemopoiesis in compartments of pluripotent and committed progenitor cells. Enhancement of the proliferative activity in hemopoietic tissue by a cytokine (rmGM-CSF) or an immunomodulator (dextran sulfate) increased the effect of hypoxic radioprotection, while elimination of proliferative cells by hydroxyurea decreased the radioprotective effect. Adaptation of experimental animals to hypoxic conditions was found to reduce the radioprotective effect without influencing tissue partial oxygen pressure lowered by hypoxic conditions. CONCLUSION: The data presented confirm the radioprotective effect of 10% and 8% O2 respiratory hypoxia on hemopoiesis. These findings may represent a way out for further experimental and clinical research aimed at considering differential protection of various tissues by hypoxia.

Adaptation, Physiological↗
PubMed1998

Early changes in flow cytometric DNA profiles induced by californium-252 neutron brachytherapy in squamocellular carcinomas of the uterine cervix.

Ninety-five squamocellular carcinomas of the uterine cervix, clinical Stages II and III, were treated by either four schedules combining 252-californium neutron-gamma-radiotherapy with different proportions of a neutron component (9, 6 and 3 Gy) or gamma-irradiation alone. Flow cytometric DNA profiles were obtainable in 72 cases before treatment and 56 cases were monitored for DNA content by flow cytometry (FCM) in weekly intervals by analysis of sequential microbiopsies for one month during and after radiotherapy. DNA aneuploidy was reduced from 40% (25/63) to 19% (9/47) one week within therapy in neutron-treated groups, but not after initial gamma-radiotherapy alone. Extinction of DNA aneuploid subpopulations occurred after neutron therapy in all remaining aneuploid tumors (9/9) during further monitoring, but only in 40% (2/5) of tumors after sole gamma-irradiation. In contrast, proliferation index by more than 50% was more often achieved in groups with a higher gamma-radiation component than after neutrons only. When all therapy-induced DNA flow cytometric events are taken together for evaluation of the effects of various radiotherapy schedules, it appears that the regimen with the maximal neutron dose may not be optimal for all tumors. It is hypothesized that the differences in the early flow cytometric DNA profiles may select the DNA aneuploid squamous cell uterine cervical carcinomas as candidates for combined neutron-brachytherapy, while highly proliferating DNA near-diploid tumors may profit more from treatment with a higher gamma-radiotherapy component. However, these early DNA flow cytometric findings need to be correlated with clinical course of the disease to validate this hypothesis, a process which will be completed at the end of the expected five-year clinical outcome in 2000.

Aneuploidy↗
PubMed1994

[Hypoxic radiotherapy. The radioprotective effect of acute hypoxia in the radiotherapy of tumors in the abdominal area].

AIM: We tested, whether inhalation a of gas mixture containing 8.0 to 8.5% O2 reduces the radiosensitivity of healthy tissue in order to deliver higher tumor doses without increasing the side effects of radiation therapy. PATIENTS AND METHODS: In this study 165 patients were treated in the Clinic of Radiation Oncology Erlangen (Germany) and in the Institute of Oncology in Brno (Czech Republic) in the period of January 1986 to December 1993. In 108 patients external irradiation was applied using acute hypoxia (group A--hypoxyradiotherapy). This group was compared with a conventional therapy group of 57 patients (group B). The majority of the patients had advanced tumor of cervix uteri or of rectum. In 89% of patients of group A and in 61% patients of group B external irradiation was applied with portals > 20 x 15 cm2 (p < 0.01). The mean dose in the group A was increased about 30% compared to the mean dose of group B (55.2 Gy vs. 43.6 Gy; p < 0.01). RESULTS: Despite this increase in dose and large-field irradiation in most cases in group A no differences were found between group A and B concerning acute or late effects of radiation therapy. CONCLUSION: The aerogen acute hypoxia (hypoxyradiotherapy) is so far not only the simplest, but also one of the most effective selective radioprotective methods.

Abdominal Neoplasms↗
PubMed1992

A contribution to the comparison of the efficacy of radiotherapeutic procedures in cervical carcinoma.

This paper presents a new method in which the regression velocity of cervical carcinoma is measured by computer tomography and the results evaluated by two statistical methods: non-linear regression analysis and survival analysis. By means of this approach it was possible to compare the early effect of therapy in patients treated with intracavitary application of 226Ra plus external radiotherapy with those treated with 252Cf, 226Ra and extended radiotherapy. In the latter group a higher efficacy of the therapy was demonstrated by both statistical methods. As the timing between external and intracavitary radiotherapy was different in the two groups and as 252Cf contributed to a rather small part of the total radiation dose it could not be concluded that the difference in efficacy really was due to 252Cf. Of essential interest was, however, that an obvious difference in efficacy could be found between two slightly different treatment techniques. The statistical procedure called survival analysis, used here parallelly with weighed regression analysis seemed to give better results than a classical regression analysis and can thus be recommended for processing of clinical data of the type which is discussed in this paper.

Brachytherapy↗
PubMed1990

Tumor response and treatment complications in radiotherapy of localized prostate cancer.

The response of primary tumor to definitive radiation therapy and treatment related morbidity has been analysed in a group of 35 patients. All of them were treated with 20 MeV photon beam to a total dose of 67 to 71 Gy to the prostate. The effect of radiotherapy to a primary tumor were evaluated by means of repeated CT examination of the tumor volume. A statistically significant tumor regression was found to occur from the sixth month after finishing radiotherapy. The absolute majority of treatment complications was of the first grade. Neither moderate nor severe gastrointestinal or genitourinary complications were recorded. The follow-up data of our patients have confirmed that radiotherapy in localized prostatic carcinoma, when sophisticated techniques are employed, represents highly effective treatment modality which improved the quality of life in patients with prostate cancer.

Adenocarcinoma↗
PubMed1990

Hypoxyradiotherapy of uterine cervix cancer to decrease of acute side-effects and treatment complications.

The authors have reported on preliminary results of hypoxyradiotherapy in the course of external irradiation in patients with uterine cervix cancer from a view-point of the occurrence of acute reactions and treatment complications. A mixture of nitrogen and oxygen containing 8.0 to 8.5% of O2 was used to provoke acute hypoxia during irradiation. The applied doses of external irradiation was simultaneously increased by 40%. On the basis of a randomized study with 120 patients, acute hypoxia was found to protect healthy tissues against post-radiation damage. When the doses of 96 Gy in the paracervical space and that of 75 Gy in the pelvic wall were applied, acute side-effects decreased significantly if compared with a conventional radiotherapeutic procedure (p less than 0.01). Radiological preconditions for using acute hypoxia in radiotherapy are discussed.

Brachytherapy↗
PubMed1990

Calculation of radiation doses in critical organs compared with in vivo dosimetry during brachytherapy of carcinoma of the uterine cervix.

In a group of 38 patients with carcinoma of the uterine cervix, radiation doses were measured by thermoluminiscent dosimeters (TLDs) placed in catheters introduced into the urinary bladder and rectum during a 24 h uterovaginal application of 226Ra. The values of radiation doses registered by the TLDs were compared to those calculated from roentgenograms made after 24 h. To calculate the radiation doses, we used the program Brachy 9.3-C of the planning unit Evados (Siemens, FRG). Using nonparametric comparison tests, no statistically significant differences were found between the values of radiation doses registered by TLDs and those calculated after 24 h of uterovaginal application of 226Ra. Only in the oral part of the rectum, at a distance of 10 cm and above from the anal orifice, there were differences between doses measured by TLDs and those calculated from roentegenograms made after 24 h of brachytherapy. These differences were caused by the movement of the flexible catheters carrying the TLDs.

Brachytherapy↗
PubMed1990

Complications of radiotherapy of uterine cervix carcinoma.

The retrospective analysis of 242 patients treated for uterine cervix cancer at VUKEO Brno within 1977-1982 has been realized. The patients being only treated with radiotherapy alone using the external 42 MeV X-ray betatron beam irradiation of the pelvis, and the vaginal and intrauterine application of 226Ra, were included in this study. The complications of therapy were evaluated in accordance with the grade of severity, location and time of their source. The radiotherapeutical complications of the 2nd stage appeared for 27 patients (11.2%), and the complications of the 3rd stage appeared for 8 patients (3.3%). The total five-years' survival rate is 71%, 92% for 37 patients in the Ib stage, 78% for 105 patients in the IIa, b stages, and 54% for 100 patients in the IIIa, b stages.

Female↗
PubMed1989

Variations in dose distributions by the use of independent asymmetric jaws. A new technique for irradiation of localized carcinoma of the prostate.

The use of independent jaws set asymmetrically in the moving field technique with bilateral arcs allows the entirely new dose distributions be obtained. The basic principle of this technique is that, with the use of moving field technique with bilateral arcs, the independent jaw more proximate to the central ray (axis) of beam must always be on the side of the critical organ. In this area the characteristic deformation of isodoses and the formation of very steep dose slope occur. We consider as optimum technique for the target irradiation of the prostatic carcinoma the moving field technique with bilateral 105 degrees arcs with 20 MeV X-ray beam of linear accelerator and with independent jaws set asymmetrically, when the independent jaw more proximate to the central ray is always + 1.5 cm from the central ray of the beam.

Carcinoma↗
PubMed1989

Effect of small doses of 252Cf on the tumour regression in cervix uteri during combined radiotherapy.

The results of a randomized study on the regression rate of the cervix uteri tumour for a group of 56 patients, investigated during and after radiotherapy with 2 Gy dose of the 252Cf neutron component applied by means of intracavitary therapy at the beginning of the therapeutic cure are presented and compared with the conventional 226Ra therapy. It was found that the tumour regression curve after 252Cf irradiation is significantly steeper than the curve of the control group. The quantitative evaluation of the results regarding the time required for a 50% regression of the original tumour shows that a group of patients treated by 252Cf needs a 27 days' cure in comparison with 40 days' cure for patients treated only by gamma radiation. The regression rate of the irradiated tumours shows a difference of approximately 30% for the treatment using small doses of 252Cf.

Adult↗
PubMed1989

[Radiotherapy of carcinoma of the prostate--5 years' experience].

Forty three patients were treated for cancer of prostate by irradiation at the Radiotherapeutic Ward of the Research Institute of Clinical and Experimental Oncology in the years 1976 to 1981. The five-year period of survival in patients with a localized tumorous disease was 45%. The authors analyzed causes of unsuccessful therapy and evaluated complications of the therapy, the latter being mostly early postirradiation reactions. Possibilities of improving the results of treatment in optimizing the radiotherapy of the localized prostate cancer are outlined.

Carcinoma↗
PubMed1989

[Reoxygenation of tumors of the uterine cervix during combined radiotherapy using low dose gamma-neutron irradiation with californium-252].

A polarographic method was used to follow the changes in oxygenation of a tumour of uterus cervix after intracavital irradiation by 252Cf by a physical dose of 2 Gy, applied at the beginning of a therapeutic cycle of combined radiotherapy. The results reached are compared with the results of tumour oxygenation in the course of a conventional therapeutic procedure. It has become apparent that even after the irradiation of a tumour of uterus cervix by a small dose of gamma-neutron radiation with 252Cf there is, beginning with 2nd week of therapy, a significant reoxygenation of the tumour population. The changes of oxygenation after a conventional irradiation have been less marked and reached, in the 4th week of therapy, only marginally significant increase. Differences in reoxygenation of tumours of uterus cervix were confirmed by analysis of the oxygen test. The importance of tumour reoxygenation after the application of 252Cf source of radiation for facilitation of its regression in a combined treatment with Californium-252 and gamma irradiation is discussed.

Brachytherapy↗
PubMed1989

[Manual afterloading applicators for intracavitary brachytherapy].

A technical description of uterovaginal and rectal applicator system of manual afterloading is described. A simple solution while using domestic materials covering the requirements of present-day brachytherapy. The applicators proved to be suitable for gamma radiation sources as well as for gamma-neutron radiation of 252Cf sources.

Brachytherapy↗