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Biomedical subjects

Val Gebski

Publications and source records attributed to Val Gebski.

14 recordsLinked to original sources
PubMed2003

A randomized trial evaluating rigid immobilization for pelvic irradiation.

BACKGROUND: Accuracy and reproducibility of the patient's position is fundamental to the successful delivery of radiation therapy. In recent years, a number of pelvic immobilization techniques have been developed. Few have been evaluated in randomized trials, and many of these studies have produced contradictory and inconclusive results. PURPOSE: To assess whether the use of rigid immobilization devices improve the accuracy and reproducibility of prostate irradiation to a clinically useful degree. METHODS AND MATERIALS: A total of 100 patients receiving radical irradiation for either prostate or bladder cancer were randomized to be treated with or without the use of rigid immobilization (RI) devices. Of these, 96 patients were suitable for analysis. The control group consisted of the patients being simulated and treated in the prone position with no immobilization devices. Patients randomized to the immobilized arm were simulated and treated prone using a customized Uvex cast of the pelvis as well as ankle- and shoulder-stabilizing devices. Weekly orthogonal port films (PFs) were obtained for each patient. Using previously specified bone landmarks, we measured variations in the isocenter position on each PF compared with the simulation film. The assessors were unaware of the treatment assignment. Patient comfort, skin toxicity, and treatment times were recorded. RESULTS: The average simulation-to-treatment deviation of the isocenter position was 8.5 mm in the control group and 6.2 mm in the immobilization group (p < 0.001). In the control arm, 30.9% of port films had isocenter deviations >10 mm compared with 10.6% in the immobilized arm (p = 0.001). For the control group, average deviations in the anteroposterior, right-left, and superior-inferior directions were 5.2 mm, 3.2 mm, and 4.3 mm, respectively, compared with 2.9 mm, 2.1 mm, and 3.9 mm for the immobilized group (p = <0.001, p < 0.001, p = 0.55). The RTOG skin reaction was greater with in patients with a cast (28% having Grade 2 toxicity vs. 10% in the control arm), although this was not statistically significant (p = 0.68). Patients in both groups found the treatment position comfortable: 90% in the immobilized group and 87% in the control group scored the treatment position either reasonably or very comfortable. Treatment times were very similar between the two groups: the average treatment time was 15.5 min in the control group vs. 16.1 min in the immobilized group (p = 0.82). CONCLUSIONS: The use of rigid immobilization improves the accuracy of treatment delivery for the prone position, especially in the anteroposterior direction. Of clinical importance, the number of major deviations >10 mm (that is, that would result in a geographic miss) was reduced from 31% to 11%.

Aged↗
PubMed2003

Patterns of metastases in familial and non-familial melanoma.

Family history is a strong risk factor for the development of primary melanoma and is associated in a subset with inherited mutations in melanoma susceptibility genes. This study sought to determine whether differences in metastatic pattern exist between patients with a positive family history (FH+) and those with a negative family history (FH-). Such differences could have importance for clinical management and in the determination of the function of both known and putative melanoma susceptibility genes. A retrospective, nested case-controlled study was performed. Of the FH+ cohort (n = 38), 26 were from kindreds with two histologically verified affected first-degree relatives and 12 were from kindreds with three or more affected members, at least two of whom were first-degree relatives. Three FH- controls from the Sydney Melanoma Unit database were matched to each case for age, sex, stage at diagnosis, number of primary melanomas and year of diagnosis (n = 114). There were no statistically significant differences between the two groups with regard to overall survival from initial diagnosis (FH+, 57.4 months; FH-, 50.0 months; P = 0.99), median survival from time of first metastasis (FH+, 15.4 months; FH-, 15.9 months; P = 0.94), or median disease-free interval (FH+, 26.4 months; FH-, 29.7 months; P = 0.73). On multivariate conditional logistic regression analysis, there was no statistically significant difference between the two groups in the probability of developing initial metastases or of ever developing metastases at specific sites. Survival, disease-free interval and distribution of metastatic sites are similar in both familial and non-familial melanoma. Genetic susceptibility for melanoma may lower the threshold for entering an otherwise common molecular pathway for tumour development and evolution.

Adolescent↗
PubMed2002

Estimating risks of radiotherapy complications as part of informed consent: the high degree of variability between radiation oncologists may be related to experience.

PURPOSE: Estimating the risks of radiotherapy (RT) toxicity is important for informed consent; however, the consistency in estimates has not been studied. This study aimed to explore the variability and factors affecting risk estimates (REs). METHODS AND MATERIALS: A survey was mailed to Australian radiation oncologists, who were asked to estimate risks of RT complications given 49 clinical scenarios. The REs were assessed for association with oncologist experience, subspecialization, and private practice. RESULTS: The REs were extremely variable, with a 50-fold median variability. The least variability (sevenfold) was for estimates of late, small intestinal perforation/obstruction after a one-third volume received 50 Gy with concurrent 5-fluorouracil (RE range 5-35%). The variation between the smallest and largest REs in 17 scenarios was >or=100-fold. The years of experience was significantly associated with REs of soft/connective-tissue toxicity (p = 0.01) but inversely associated with estimates of neurologic/central nervous system toxicity (p = 0.08). Ninety-six percent of respondents believed REs were important to RT practice; only 24% rated evidence to support their estimates as good. Sixty-seven percent believed national/international groups should pursue the issue further. CONCLUSION: Enormous variability exists in REs for normal tissue complications due to RT that is influenced by the years of experience. Risk estimation is perceived as an important issue without a good evidence base. Additional studies are strongly recommended.

Antimetabolites, Antineoplastic↗
PubMed2002

On the issue of 'multiple' first failures in competing risks analysis.

In the classical competing risks framework, a subject may only fail from one of several distinct causes. However, in the context of cancer clinical trials where information on first relapse is usually of interest, there could be occasions when 'multiple' first recurrences are identified at a particular follow-up. In this instance, the competing risks methodology cannot be implemented without first tackling the issue of 'tied' first failure. When the tied events were substantial, Arriagada et al. regarded each competing failure separately, and combined the 'simultaneous' failures into a single category for analysis. This paper describes two other methods of accounting for 'multiple' failures. First, the ties were dealt with by applying a weighting factor which was equal to the reciprocal of the number of ties. We also considered 'jittering' which randomly adds or subtracts a small number to each 'tied' event time to randomly break the tie. As illustrated using the data obtained from a randomized trial of patients with operable osteosarcoma, the estimates based on Arriagada's approach have larger standard errors. Estimates from the other alternative methods were similar. Multiple jittering has the advantage of wide applicability in any situation of tied survival times. However, it takes a longer computer running time, especially when the number of replicates is large. The weighted Cox approach is the method of choice where statistical software allows its implementation without extra programming effort.

Antineoplastic Agents↗
PubMed2002

Secondary cytoreductive surgery for recurrent epithelial ovarian cancer.

OBJECTIVE: To review our experience with secondary cytoreductive surgery for recurrent epithelial ovarian cancer with regard to its feasibility, morbidity, mortality, patient selection, and survival. METHODS: Forty-six patients who underwent secondary cytoreductive surgery at the Royal Hospital for Women, Sydney, between July 1988 and October 1996 were retrospectively reviewed. The mean age at surgery was 50.3 years, and the median disease-free interval was 26 months. Eighty-nine percent of patients had a disease-free interval of at least 12 months. Twenty-five patients (54%) had localized disease at the time of surgery. Univariate survival outcomes were analyzed using the log rank test, and survival curves were calculated using the method of Kaplan-Meier. RESULTS: Two patients (4%) were inoperable and 19 patients (41%) were cytoreduced to no macroscopic disease. There was one postoperative death (2%), and four patients (8.7%) had significant postoperative morbidity. With a median follow-up of 88 months, the overall median survival was 22.5 months. Patients with a disease-free interval of less than 12 months after their initial treatment had a median survival of 6 months, compared with 11 months if the disease-free interval was 12-24 months and 39 months for those with a disease-free interval of 24 months or more (P =.001, log rank). Patients who had any residual disease had a median survival of 11 months, whereas those with no residual disease had a median survival of 38 months (P =.002, log rank). CONCLUSION: For carefully selected patients with recurrent epithelial ovarian cancer: 1) complete surgical resection is feasible more commonly than with primary cytoreduction, 2) serious morbidity and mortality are acceptable, and 3) significant survival benefit accrues when a) all macroscopic disease can be resected, or b) the disease-free interval is 24 months or more.

Adult↗
PubMed2002

The Chinese herbal formulation biminne in management of perennial allergic rhinitis: a randomized, double-blind, placebo-controlled, 12-week clinical trial.

BACKGROUND: Herbal therapies have been widely used in allergic rhinitis (AR), but none have been shown to be effective in controlled scientific clinical trials. OBJECTIVE: The aim of this study was to test the effects of the Chinese herbal formulation Biminne in patients with moderate to severe perennial AR. METHODS: In a randomized, double-blind, placebo-controlled clinical trial, 58 patients were randomized to receive either Biminne capsules (n = 26) or placebo (n = 32) in doses of five capsules twice a day for 12 weeks. Main outcomes were measured by changes in symptom diaries, quality of life scores, patients' evaluations of improvement on visual analog scores, and physicians' overall evaluation. Total serum immunoglobulin E was measured in all patients without knowledge of which group they were in. After 1 year we performed a randomized, double-blind, dose-response study in 22 patients who had previously received placebo. RESULTS: The trial outcomes evaluated by four instruments showed a statistically significant improvement in some of the symptoms of AR, whereas others exhibited a positive trend that did not reach statistical significance. Followup 1 year after completion of the trial suggested that benefit of the treatment persisted. A pilot dose-response study showed both half and full strengths were effective. Total serum immunoglobulin E was reduced after the herbal treatment. CONCLUSIONS: Our results suggest the Biminne formulation is effective in treatment of perennial AR. Its mode of action is unknown.

Administration, Oral↗
PubMed2002

Statistical power in stuttering research: a tutorial.

The capacity to make reliable inductive statements about populations is critical for the advancement of scientific knowledge. An important contribution to that advancement of knowledge is determining that effects are either present or not present in populations. Statistical power is an important methodological qualification for any research that presents statistical results, and particularly so for research that presents null results. In this paper we describe the statistical concept of power, outline parameters of research that influence it, and demonstrate how it is calculated. With reference to selected published research, attention is drawn to the problems associated with a body of underpowered research, one being that population effects may go undetected. One way to prevent this problem is to calculate power a priori in planning research and include confidence intervals when presenting the results of research. However, it is difficult, if not impossible in many cases, to obtain high participant numbers for communication disorders of low prevalence such as stuttering. With this in mind, the paper concludes with an attempt to open discussion about ways to redress the problems associated with statistical power.

Humans↗
PubMed2002

Parotid lymph-node metastases from cutaneous squamous-cell carcinomas: treatment outcome and prognostic factors following surgery and adjuvant radiotherapy.

Australia has the highest incidence of cutaneous squamous cell carcinoma (SCC) in the world. The majority of lesions occur in the head and neck, and regional lymph-node metastases from cutaneous SCCs, though uncommon, reflect an aggressive manifestation. Surgery and adjuvant radiotherapy are currently considered best practice. Fifty-two eligible patients during 1980-1997 were identified in a retrospective review of patients treated within the department of Radiation Oncology, Westmead Hospital, Sydney. Relevant data were extracted from the files, referring clinicians and the New South Wales Cancer Council. The median age at diagnosis was 63 years and the majority were men (87%). Unfavourable pathological features were present in many of the patients. Only extranodal spread (P = 0.02) was identified as an independent predictor for locoregional recurrence on multivariate analysis. The cumulative locoregional recurrence rates were 28 and 45% at 2 and 5 years, respectively. The 5-year cause-specific survival rate in this study was 65%. We conclude that parotid lymph-node metastases from cutaneous SCCs of the head and neck are associated with a high rate of locoregional recurrence and cause-specific mortality despite surgery and adjuvant radiotherapy. The role of altered fractionation after surgery as a means to further enhance locoregional control warrants further investigation.

Adult↗
PubMed2002

Effect of long-term mobile communication microwave exposure on vascular permeability in mouse brain.

AIMS: To study the effect of long-term exposure to global system for mobile communication (GSM) radiofrequency fields on vascular permeability in murine brains. METHODS: Using a purpose-designed exposure system at 900 MHz, mice were given a 60-minute far-field, whole body exposure on each of 5 days per week for 104 weeks at specific absorption rates (SAR) of 0.25, 1.0,2.0 and 4.0 W/kg. Control mice were sham-exposed or permitted free movement in a cage to evaluate any stress-related effects. Albumin immunohistochemistry was used to detect increased vascular permeability and the efficacy of the vascular tracer was confirmed with a positive control group exposed to a clostridial toxin known to increase vascular permeability in the brain. RESULTS: In all exposed and control groups, albumin extravasation was minimal, often leptomeningeal, and was deemed insignificant as a maximum of three capillaries or venules in a given brain showed leakage from the very many blood vessels present in the three coronal brain sections. CONCLUSIONS: These results suggest that prolonged exposure to mobile telephone-type radiation produces negligible disruption to blood-brain barrier integrity at the light microscope level using endogenous albumin as a vascular tracer.

Animals↗
PubMed2002

Long-term exposure of E-mu-Pim1 transgenic mice to 898.4 MHz microwaves does not increase lymphoma incidence.

A total of 120 E mu-Pim1 heterozygous mice and 120 wild-type mice were exposed for 1 h/day 5 days/week at each of the four exposure levels in "Ferris-wheel" exposure systems for up to 104 weeks to GSM-modulated 898.4 MHz radiation at SARs of 0.25, 1.0, 2.0 and 4.0 W/kg. In addition, 120 heterozygous and 120 wild-type mice were sham-exposed; there was also an unrestrained negative control group. Four exposure levels were used to investigate whether a dose-response effect could be detected. Independent verification confirmed that the exposures in the current study were nonthermal. There was no significant difference in the incidence of lymphomas between exposed and sham-exposed groups at any of the exposure levels. A dose-response effect was not detected. The findings showed that long-term exposures of lymphoma-prone mice to 898.4 MHz GSM radiofrequency (RF) radiation at SARs of 0.25, 1.0, 2.0 and 4.0 W/kg had no significant effects when compared to sham-irradiated animals. A previous study (Repacholi et al., Radiat. Res. 147, 631-640, 1997) reported that long-term exposure of lymphoma-prone mice to one exposure level of 900 MHz RF radiation significantly increased the incidence of non-lymphoblastic lymphomas when compared to sham-irradiated animals.

Adenoma↗