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Biomedical subjects

A Rijnders

Publications and source records attributed to A Rijnders.

10 recordsLinked to original sources
PubMed1996

The time course of development of late side effects after irradiation of the prostate with multiple fractions per day.

BACKGROUND AND PURPOSE: A group of patients with prostate cancer was irradiated in the early 1980s with a TID schedule, resulting in a very high frequency of side effects. The time course of development of severe late complications was evaluated. MATERIALS AND METHODS: We retrospectively reviewed the records of 91 patients with prostate cancer, irradiated on a linear accelerator or a cobalt unit between 1980 and 1983. They received a split-course irradiation with multiple fractions per day (MFD) up to a nominal dose of 60 Gy. The rate of development of severe late urological and gastrointestinal complications, grade 3 or more according to the RTOG scoring system, was analysed. RESULTS: The 5-year actuarial incidence of urological complications was 51%. After a lag time of a few months, patients develop "first events' at a nearly constant rate of 10% for 5 years after treatment. Subsequent events ("all events') seem to continue to appear even after 5 years. The actuarial incidence at 5 years of gastrointestinal complications was 14%, with no new events developing later than 3 years after treatment. CONCLUSIONS: The irradiation schedule used resulted in an unacceptable high incidence of late side effects, probably due to incomplete repair between fractions. MFD fractions to the pelvis should be avoided, unless sufficient time in between fractions can be allowed. Moreover, the fact that after this treatment schedule with very pronounced biological effects, new severe complications continued to develop up to 5 years after therapy, indicates that sufficiently long follow-up time has to be respected when investigating new radiation techniques for pelvic tumours.

Aged↗
PubMed1995

Does tumor control decrease by prolonging overall treatment time or interrupting treatment in laryngeal cancer?

PURPOSE: To evaluate treatment results of radiotherapy in laryngeal cancer and to retrospectively investigate the influence of treatment interruptions on local control rates. A multivariate analysis was performed to investigate the role of overall treatment time on local control rates. MATERIAL AND METHODS: From 1962 to end 1986, 864 patients with cancer of the larynx were treated with primary radiotherapy, with a variation of doses and treatment times. In 352 patients a systematic interruption of 2 weeks was done after 50 Gy (split-course). Local control rates were calculated by the actuarial method. A multivariate analysis was subsequently performed in order to identify independent variables influencing local control rates. RESULTS: The univariate analysis showed that in patients treated with a split-course schedule, local control rates were significantly lower in glottic cancer (p < 0.001), with differences of 7% in T1 (p = 0.05) and 11% in T2 (p = 0.11). In node-negative supraglottic cancer a difference of 10% (p = 0.16) was observed. The multivariate analysis showed the following factors to significantly influence local control: site, total dose, total treatment time, T and N stage. Split-course treatment was not an independently significant factor, probably caused by time being a stronger factor. In subgroup analysis, the effect of total treatment time remained statistically significant in T2 glottic cancer. CONCLUSION: A significant negative influence of treatment interruption was seen in glottic cancer, and a trend toward significance in node-negative supraglottic cancer in univariate analysis. A multivariate analysis showed a negative influence of prolonging treatment time in the total patient group. The effect remained significant in T2 glottic cancer in subsequent subgroup analysis, possibly due to the fact that there is little variation in tumour volume in this group. In larger tumours, where there is substantial variation in tumour volume and a higher probability of heterogeneity in radiosensitivity, the effect of dose-time variations could be more difficult to discern.

Female↗
PubMed1990

Breast conserving treatment of Paget's disease.

Between 1971 and 1984, 13 patients with histologically proven Paget's disease were treated conservatively with radiotherapy only. The disease was clinically confined to the nipple or surrounding skin, without signs of an underlying tumor. With a mean follow-up of 58.6 months (ranging between 15 and 118 months), and a median follow up of 52 months, no recurrences locally or at distance were seen. Therefore in these selected cases a mastectomy could be avoided. The results with this breast conserving management suggest a place for radiotherapy in the treatment of Paget's disease limited to the nipple.

Aged↗
PubMed1989

Cosmetic evaluation of breast conserving treatment for mammary cancer. 2. A quantitative analysis of the influence of radiation dose, fractionation schedules and surgical treatment techniques on cosmetic results.

The effects of surgical treatment techniques, radiation doses and fraction sizes on cosmetic outcome were analysed in a population of 161 patients with stage I and II breast cancer treated with breast conserving surgery and a wide range of radiotherapy doses. In 142 patients also quantitative measurements of nipple position asymmetries and breast contour retraction were carried out. The scoring and measurement results were analysed using a multivariate model to assess the relative importance of the various factors involved. In this material radiation dose to the breast was the most significant parameter correlated with cosmetic outcome (p = 0.0001). Radiation doses higher than 75 Gy in 37 fractions led to very poor results in more than 30% of patients. For the quantitative measurements of radiation fibrosis, a dose-response curve could be demonstrated over a dose range of 40 to 86 Gy in fraction sizes of 2 Gy. Above 50 Gy, increases in dose of 1 Gy correlated with an average displacement of nipple and breast contour of 1 mm, in upward direction and of 0.75 mm to the median. An increased amount of fibrosis was observed when part of the treatment was given in larger fraction sizes (4-6 Gy). Plotting the data against dose equivalent TE values, an alpha/beta value of 2.5 Gy could be estimated for the development of late fibrosis. Other treatment factors whose influence on cosmetic outcome could be identified and quantified were the differences in surgical techniques for the removal of the primary tumor (tumorectomy vs. segmentectomy, p = 0.05) and for the axillary clearance ("en bloc" dissection vs. separate incisions, p = 0.018). Also technical aspects of the radiotherapy on the regional lymph nodes, sometimes leading to matchline fibrosis, proved to be important (p = 0.0075). Finally, a number of tumor-related factors were assessed in order to take their relative importance into account, if necessary, when studying therapy factors. While tumor stage had only a limited impact in the range of tumors included in this study, the localisation of the tumor significantly influenced cosmetic outcome with worse results for inferior and medial localisations. While quantitative measurements were not correlated with all the factors identified for poor cosmesis, their great value is to quantify the radiation-induced fibrosis as well as the effects of different surgical techniques on nipple retraction.

Breast↗
PubMed1988

Practical implications of backscatter from outside the patient on the dose distribution during total body irradiation.

Total body irradiation (TBI) sometimes requires the set-up of the patient very close to the wall of the treatment room in order to obtain sufficiently large irradiation fields. Under these conditions, backscattered electrons can become clinically important. In the present study, an attempt was made to quantify the dose contribution to the patient from these electrons. Measurements were performed both in experimental conditions and on patients during their TBI treatment. It is concluded that, with the patient close to the wall, backscattered electrons constitute a significant (up to 20% of the dose obtained under electronic equilibrium at the exit port of the beam) radiation dose which can (under certain conditions) influence measurements of exist dose leading to an overestimation of the midline dose and contribute a superficial irradiation of the patient without therapeutic benefit. This problem can be solved by interposing a 2 cm thick low-Z absorber between wall and patient.

Construction Materials↗
PubMed1987

Tumor excision and radiotherapy as primary treatment of breast cancer. Analysis of patient and treatment parameters and local control.

From 1966 to 1979, 235 patients with operable breast cancer were treated by tumor excision and radiotherapy. The actuarial survival at 10 years was 94.8% for stage I and 58% for stage II tumors. Local recurrent cancer was seen in 23/235 patients and was related to T stage, N stage, width of surgical excision, radiation dose to the tumor bed and anatomopathological differentiation. Recurrences were seen in 1/7 of T0, 3/57 (5.2%) of T1, 11/102 (10.8%) of T2 and 2/6 of T3 tumors. Local control in the breast decreased significantly in N1b cases (p = 0.005) or when 3 or more axillary lymph nodes were positive (p = 0.0074). Local control after segmentectomy or tumorectomy was identical. However, a poorer local control was found in 20 cases treated with subtotal resection (p less than 0.05). A clear dose-local control relationship was found in this material, with a 100% local control in all T0, T1 tumors which received more than 1800 ret and all T2 tumors which received more than 2000 ret. As 19 of 23 breast recurrences were seen at the primary site in the breast we believe that booster doses should be given in order to maximise local control.

Adult↗
PubMed1985

Determination of ionisation chamber collection efficiency in a swept electron beam by means of thermoluminescent detectors and the "two-voltage" method.

Two methods for determining the collection efficiency of a 0.6 cm3 thimble ionisation chamber exposed to the swept electron beam of a linear accelerator Therac 20 Saturne (CGR MeV) have been compared. In one method the chamber signal has been compared to that of simultaneously exposed thermoluminescent LiF dosemeters (TLD), in the other the "two-voltage" method of Boag, adapted for swept beams, has been used. By variation of the electron energy between 20 and 13 MeV, of the focus-skin-distance (FSD) between 200 and 100 cm and of the monitor rate between 400 monitor units (m.u.) and 100 m.u. per minute, different values could be produced for the peak charge density M. The collection efficiency of the chamber, operating at a standard voltage of 250 V, decreases from 0.99 to 0.84 for a charge density increasing from 0.3 X 10(-4) C/m3 to 7.5 X 10(-4) C/m3, respectively. The maximum deviation observed between the TLD and the "two-voltage" method adopted for similar M is never more than 2% and mostly smaller than 1%. It can be concluded that, under the present experimental conditions, the calculated ionisation chamber collection efficiency is confirmed by the experimental method using TL dosimetry.

Animals↗
PubMed1984

A modified radiotherapy technique in the treatment of medulloblastoma.

Craniospinal irradiation is a standard treatment technique in patients who receive surgery for medulloblastoma. In most centers megavoltage photon irradiation is used, resulting in significant irradiation exposure to critical organs. In order to overcome this difficulty, we recently modified the technique applied in our center, by using high energy electrons (20 MeV) for irradiation of the spinal cord. The reliability of this technique was checked by performing dosimetry in a specially constructed wax phantom. Attention was focused upon dose variations at the junction of fields. Furthermore, the influence of vertebrae on the absorbed dose distribution of high energy electrons is presented. This technique seems to be safe and reliable in selected patients (children and teenagers).

Adolescent↗
PubMed1984

Differences in repopulation kinetics in mouse skin during split course multiple fractions per day (MFD) or daily fractionated irradiations.

The influence of protraction and distribution of irradiation as a function of time on the repopulation kinetics of mouse skin have been evaluated. Twenty fractions have been given either daily for 5 days per week during 4 weeks, or thrice a day to 10 irradiations in 3 days, repeated after a rest period of 19 days, resulting also in an overall time of 4 weeks. The acute skin reaction was scored. It was found that the split course multiple fractions per day (MFD) schedule induced less skin reaction than continuous daily fractionation, which was mainly attributable to recovery of skin damage during the rest period. Therefore, it can be postulated that the repopulation of the surviving clonogenic epidermal cells is less efficient during continuous daily irradiation than during split course MFD schedule given in the same overall treatment time.

Animals↗