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Biomedical subjects

F Vaida

Publications and source records attributed to F Vaida.

At least 19 recordsLinked to original sources
PubMed2002

Total physical activity in relation to age, body mass, health and other factors in a cohort of Swedish men.

BACKGROUND: Despite a large public health interest in physical activity and its role in obesity and other chronic diseases, only a few reports to date have addressed total levels of physical activity in relation to age, body mass, health and other lifestyle factors. OBJECTIVE: To investigate whether levels of total physical activity among men are associated with age, body mass, self-rated health and other lifestyle factors in a cross-sectional setting. METHODS: In a population-based cohort of 33 466 men aged 45-79 y in central Sweden, we collected information about physical activity through a self-administered questionnaire. Level of total physical activity was assessed quantitatively based on six questions on different activities: work/occupation, housework, walking/bicycling, exercise, inactive leisure time and sleeping. The physical activity levels were measured as metabolic equivalents, MET-h/day. The relation between age, body mass index, smoking, education, marital status and self-rated health, and total physical activity was studied in a cross-sectional analysis, using multivariate regression. RESULTS: Total daily physical activity was decreasing systematically between age 45 and 79 (-4.1%, 95% CI -4.6, -3.6). Obese men reported -2.6% (95% CI -3.0, -2.1) lower physical activity than normal weight men. Those with high education had -7.0% (95%CI -7.3, -6.7) lower total physical activity than those with elementary school. Men with self-rated poor health had -11.3% (95%CI -12.1, -10.6) lower physical activity than those reporting very good health. The cross-sectionally observed decrease with age was greatest among obese men (-8.7%), current smokers (-7.9%), low-educated men (-5.6%) and those with poor health (-9.8%); the subgroups with very good health reported almost the same level of total physical activity (-0.6%) for age 74-79 as for age 45-49. CONCLUSIONS: The observed decreasing levels of total physical activity with age to large degree depend on health status and other factors. The characterization of subjects with low total physical activity levels is of importance for understanding observed worldwide trends in increasing prevalence of obesity. The better understanding of these phenomena might also facilitate a better planning of public health interventions with messages specifically adjusted for subgroups of population with lower physical activity.

Aged↗
PubMed2002

Evolution of toxicity after conformal radiotherapy for prostate cancer.

The limiting factor for radiation (RT) dose-escalation is normal tissue toxicity. In dose-escalation studies, it is important to determine the factors associated with toxicity and the length of follow-up period after which a particular RT dose is considered safe. We analyzed 449 prostate cancer patients treated with RT at our institution and followed for a median of 27 months. Genitourinary (GU) and gastrointerological (GI) complications were graded and analyzed using three different statistical models. Univariate and multivariate analyses were conducted for factors associated with toxicity. There was no RTOG grade 4 or 5 toxicity. Only 23 patients (5%) experienced grade 3 toxicity. After treatment, there was an initial rapid decline in the risk of toxicity following treatment, followed by an increase or stabilization of the toxicity with time of follow-up. The breakpoints between the two periods were 2 y (any toxicity) and 1 y (high toxicity) for GU and 9 months (any toxicity, high toxicity) for GI. Age, dose, fraction size, duration of treatment and hospital of treatment emerge as important factors in the probability of developing toxicity. Our study shows that delivering conventional doses using conformal techniques is associated with minimal high-grade toxicity. However, even within a narrow dose range and fraction size used, differences do emerge which should lead one to be cautious in extending the results of dose escalation study to the community practice without a sufficient follow-up.

Adenocarcinoma↗
PubMed2001

Changing face and different countenances of prostate cancer: racial and geographic differences in prostate-specific antigen (PSA), stage, and grade trends in the PSA era.

The purpose of this investigation was to examine changes in pretreatment prostate-specific antigen (PSA), stage, and grade over the past decade as a function of race and geographic region. A multiinstitutional database representing 6,790 patients (1,417 African-American, 5,373 white) diagnosed with nonmetastatic prostate cancer between 1988 and 1997 was constructed. PSA, stage, and grade data were tabulated by calendar year and region, and time trend analyses based on race and region were performed. There was an overall decline of PSA of 0.8%/year, which was significant (P = 0.0001), with a faster rate of decline in African-Americans (1.9%/year) than for whites (0.6%/year). The odds ratio (OR) for a stage shift was 1.09, which was significant (P < 0.0001), and this shift was greater in whites. The OR for an overall grade shift was 1.15, which was significant (P < 0.0001). Although grade and PSA trends were similar for the different regions, there were significant regional differences in stage trends. The implications are that the face of prostate cancer has changed over the past decade; i.e., the distributions of stage, grade, and PSA (the most important prognosticators) have changed. In addition, the countenances of that face are different for whites and African-Americans. For African-Americans, this is good news: the stage, grade, and PSA distributions are more favorable now than before. For whites, the trends are more complex and more dependent on region. These findings should be used for future clinical and health-policy decisions in the screening and treatment of prostate cancer.

Black People↗
PubMed2000

Proportional hazards model with random effects.

We propose a general proportional hazards model with random effects for handling clustered survival data. This generalizes the usual frailty model by allowing a multivariate random effect with arbitrary design matrix in the log relative risk, in a way similar to the modelling of random effects in linear, generalized linear and non-linear mixed models. The distribution of the random effects is generally assumed to be multivariate normal, but other (preferably symmetrical) distributions are also possible. Maximum likelihood estimates of the regression parameters, the variance components and the baseline hazard function are obtained via the EM algorithm. The E-step of the algorithm involves computation of the conditional expectations of functions of the random effects, for which we use Markov chain Monte Carlo (MCMC) methods. Approximate variances of the estimates are computed by Louis' formula, and posterior expectations and variances of the individual random effects can be obtained as a by-product of the estimation. The inference procedure is exemplified on two data sets.

Algorithms↗
PubMed1999

PSA-based outcome analysis after radiation therapy for prostate cancer: a new definition of biochemical failure after intervention.

OBJECTIVES: To examine pretreatment variables that influence biochemical failure, and to describe and test a new definition of prostate-specific antigen (PSA)-based biochemical failure. METHODS: We introduce and describe a new definition of biochemical failure, which is based on quadratic fitting of the logarithm of the follow-up PSA profile curve. From a data base of 449 patients with prostate cancer treated with definitive radiation therapy, 230 patients who had at least five follow-up PSA observations were chosen for analysis. The new definition of failure was applied to this cohort, as was the conventional definition of two consecutive PSA rises. Univariate and multivariate analyses were performed using established pretreatment prognostic factors as covariates. Also, the association of both definitions of failure with clinical outcome (local recurrence and any recurrence) was examined. RESULTS: Application of the new definition of biochemical failure resulted in smoothing of the "noise" that is inherent in using definitions based on successive PSA rises. This smoothing was verified by smaller P values for the statistically significant covariates in the univariate analysis. Furthermore, the new definition correlated better with clinical outcome, as demonstrated by the statistically significant P values on regression analysis when using the quadratic fitted nadir compared with using the observed nadir. CONCLUSIONS: We devised a new criterion based on quadratic curve fitting for PSA-based biochemical failure. This definition is based on all available PSA information, correlates with both pretreatment factors and post-treatment clinical outcome, is relatively insensitive to noise, and allows for prediction of time of failure.

Humans↗
PubMed1999

Racial differences in prostate-specific antigen levels and prostate-specific antigen densities in patients with prostate cancer.

To compare serum prostate-specific antigen (PSA) levels and PSA density (PSAD) among African American (AA), white, and Hispanic men with prostate cancer (PC) seen in an urban, equal-access urology clinic. Between January 1988 and January 1993, 1,105 men were screened for PC at Cook County Hospital in Chicago, Illinois. A total of 529 men underwent transrectal ultrasound-guided prostate gland biopsies for abnormal digital rectal examination, suspect transrectal ultrasound, elevated PSA, or any combination of these abnormalities. PC was found in 246 patients (204 AAs, 22 whites, and 20 Hispanics). We analyzed the differences in PSA and PSAD among the three racial groups using univariate and multivariate analyses adjusting for race, age, clinical stage, and grade. AAs have a higher mean serum PSA levels (21.56 ng/ml) than whites (mean PSA of 10.96 ng/ml) and Hispanics (mean PSA of 8.25 ng/ml) (p = 0.04). The mean PSAD also was higher in AAs than in the other two groups (0.68 versus 0.34 for whites and 0.31 for Hispanics, p = 0.05). On a multivariate analysis, the PC stage and grade were overwhelmingly significant, whereas the race and age lost their statistical significance. AAs have higher serum PSA and PSAD than whites or Hispanics in an equal-access healthcare environment. Race is a significant factor in determining PSA and PSAD on univariate but not on multivariate analysis. Preliminary studies suggest that these differences are due to sociological, not biologic causes. These findings warrant a large, prospective study to investigate the extent and the causes of the racial differences in PSA and PSAD.

Black or African American↗
PubMed1999

In the radiotherapy of prostate cancer, technique determines the doses to the penile structures.

For 11 consecutive prostate cancer patients undergoing three-dimensional conformal radiotherapy (3DCRT) in our institution, penile structures (PNS) were outlined in CT images obtained for treatment planning purposes. Dose-volume histograms (DVHs) were compared in order to study dose-volume relations for three techniques: 4FLD, an axial coplanar, four-field box technique; 6FLD, a six-field coplanar technique; and 4NAX, a coplanar but non-axial, four-field technique. All three techniques delivered equal doses to the planning target volumes (PTV). Our statistical analyses strongly indicate that the three techniques can be ranked as 6FLD better than 4FLD (and 4FLD better than 4NAX) as far as irradiating PNS volume during treatment of prostate cancer (PC) is concerned. For each technique, there is a "spread" owing to differences in patient anatomy and/or target size, position, and extent, but each technique has a similar "profile" or "shape" distinct from other techniques. Whether irradiating smaller volumes of PNS will influence the sexual potency outcome remains to be demonstrated. However, PNS should be considered as another critical structure in addition to rectum, bladder and femoral heads in the radiotherapy (RT) of PC, especially in 3DCRT dose escalation studies. Sexual potency outcomes can be correlated to dose-volume relations in the future and this will help refine radiotherapy techniques further.

Humans↗
PubMed1998

Comparison of serum prostate-specific antigen levels and PSA density in African-American, white, and Hispanic men without prostate cancer.

OBJECTIVES: To determine the influence of race or ethnicity on serum prostate-specific antigen (PSA) levels and PSA density (PSAD) in a population of healthy men without clinically evident prostate cancer. METHODS: This retrospective study was conducted between January 1988 and January 1993. The serum PSA levels were measured in 859 men (586 African Americans, 142 whites, and 131 Hispanics) who were participants in a prostate cancer screening program or had urinary symptoms suggestive of prostate gland pathology. All men underwent a detailed clinical examination, including digital rectal examination, serum PSA determination, and transrectal ultrasound (TRUS). None of the subjects included had clinical or TRUS evidence of prostate cancer (furthermore, 283 men were pathologically proved to be cancer-free by prostate biopsies). Serum PSA levels and PSA densities as a function of each individual's ethnic background were determined. RESULTS: The mean serum PSA level in African Americans was 2.1 ng/mL, which was significantly higher than that of whites (mean PSA of 1.53 ng/mL) and Hispanics (mean PSA of 1.83 ng/mL) (P = 0.003). Similar differences among the three groups were observed in PSA density (the mean PSAD was 0.078, 0.057, and 0.065 for African Americans, whites, and Hispanics, respectively). A separate analysis for the biopsy-negative men was performed, and the findings were consistent with the observations for the entire study group. After adjustment for age and prostate volume, the differences remained statistically significant. CONCLUSIONS: Among men without evidence of prostate cancer, African Americans have higher serum PSA levels and PSA densities than do whites or Hispanics. Race or ethnicity was an independent factor that affected serum PSA levels even after adjustment for age and prostate volume.

Adult↗
PubMed1998

A new look at an old option in the treatment of early-stage prostate cancer: hormone therapy as an alternative to watchful waiting.

Watchful waiting is an attractive option in the management of early-stage, low-grade prostate cancer because of the high financial costs and complication risks associated with surgery and radiotherapy. Despite the drawbacks of current local therapy, neither treatment can demonstrate a discernible survival benefit over observation alone. Even the slowest progressing disease, however, can potentially develop into a deadly medical problem. As a result, physicians and patients frequently have difficulty accepting untreated cancer. Therefore, we propose that another option be considered in cases of prostate cancer that would otherwise qualify for observation alone: the use of two oral hormonal agents, flutamide and finasteride, to achieve complete androgen blockade. Some evidence exists which suggests that such therapy may improve symptom-free survival, and perhaps overall survival as well. This 'aggressive' form of 'conservative' therapy may satisfy patient concerns that are not adequately addressed by current forms of therapy.

5-alpha Reductase Inhibitors↗
PubMed1996

A comparison of four patient immobilization devices in the treatment of prostate cancer patients with three dimensional conformal radiotherapy.

PURPOSE: To determine the variability of patient positioning during three-dimensional conformal radiotherapy (3D-CRT) for prostate cancer treated with no immobilization or one of four immunobilization devices, and to determine the effects of patient body habitus and pelvic circumference on patient movement with each individual inmobilization technique. METHODS AND MATERIALS: To see whether our immobilization techniques have improved day-to-day patient movement, a retrospective analysis was carried out. A total of 62 patients treated at one facility on a single machine with 3D-CRT via a four-field box technique (anterior-posterior and opposed laterals) in the supine position with either no immobilization or one of four immobilization devices. Five groups of patients were compared: (a) group 1-no immobilization; (b) group 2-alpha cradle from the waist to upper thigh; (c) group 3-alpha cradle from waist to below the knees; (d) group 4-styrofoam leg immobilizer (below knees); and (e) group 5-aquaplast cast encompassing the entire abdomen and pelvis to midthigh with alpha cradle immobilization to their lower legs and feet. Prior to starting radiotherapy, portal films of all four treatment fields were obtained 1 day before treatment. Subsequently, portal films were then obtained at least once a week. Portal films were compared with the simulation films and appropriate changes were made and verified on the next day prior to treatment. A deviation of greater than 0.5 cm or greater was considered to be clincally significant in our analysis. We studied the difference among the types of immobilization and no immobilization by looking at the frequency of movements (overall, and on each of the three axes) that a patient had during the course of his treatment. Using a logistic regression model, the probability of overall and individual directional movement for each group was obtained. In addition, the effects of patient body habitus and pelvic circumference on movement were analyzed. RESULTS: The maximum deviation was 2 cm and the median deviation was 1.2 cm. For each patient, the probability of movement ranged from 0 to 76%, with a mean of 39%. There was no significant difference seen in overall movement with any of the immobilzation devices compared to no immobilization, but there was less vertical (9 vs. 18%; p = 0.03) and AP (6 vs. 15%; p = 0.14) movement with the aquaplast than any other group. However, when examining the lateral direction, the aquaplast had significantly more movement (32 vs. 9%; p < 0.001). When accounting for body habitus and pelvic circumference, no immobilization device was effective in reducing movement in obese patients or in patients with pelvic circumference greater than 105 cm. The aquaplast group had a significantly increased amount of lateral movement with obesity (42 vs. 23%; p < 0.05), and with pelvic circumference >105 cm (33 vs. 29%; p < 0.05). CONCLUSIONS: There was no significant reduction in overall patient movement noted with any of the immobilization devices compared to no immobilization. The aquaplast group had reduced vertical and AP movement of greater than 0.5 cm. There was significantly more lateral movement with aquaplast appreciated in obese patients or patients with pelvic circumferences greater than 105 cm. The aquaplast immobilization appears to be useful in reducing movement in two very clinicaly important dimensions (AP and vertical). Despite our findings, other immobilization may still be useful especially in the treatment of nonobese patients. It is clear that the optimal immobilization technique and patient positioning are yet to be determined.

Body Constitution↗
PubMed1995

The potential for normal tissue dose reduction with neoadjuvant hormonal therapy in conformal treatment planning for stage C prostate cancer.

PURPOSE: Preirradiation hormonal cytoreduction of prostate cancer has been proven to reduce exposure of normal structures by decreasing the size of the target volume. Dose-volume histogram (DVH) analysis, however, does not always appear to demonstrate a strong positive benefit with the use of neoadjuvant hormone therapy. This study analyzes various other factors influencing dose to normal organs, which may determine the success or failure of neoadjuvant hormonal therapy in achieving its goals. METHODS AND MATERIALS: Patients with bulky clinical Stage C adenocarcinoma of the prostate were given 3 months of hormone treatment consisting of oral Flutamide and monthly Zoladex injections prior to irradiation. Computerized tomography (CT) scans of the pelvis were obtained both prior to and following hormonal treatment. Treatment plans were generated by three-dimensional (3D) conformal treatment planning. The change in the volume of the prostate was assessed along with the percentage of prescribed dose delivered to the rectum and bladder. Various factors such as prostate size, bladder/rectum size, and organ shape were studied. Both dose-volume histograms (DVH) and dose-surface area histograms (DSH) were used for analysis. RESULTS: Six of seven patients had reduction in the size of their prostates. The mean volumes of the prostate before and after hormonal manipulation were 129.1 +/- 32.9 standard deviation (SD) cm3 and 73.0 +/- 29.5 SD cm3, respectively (p = 0.0059). The volume of rectum receiving 80% of the prescribed dose was reduced in five of seven patients from a mean of 83.2 to 59.9 cm3 (p = 0.045). The volume of bladder receiving 80% of the prescribed dose was also reduced in five out of seven patients from a mean of 74.5 to 40.2 cm3 (p = 0.098). Correlation between the size of the prostate and volume of rectum and bladder treated was not always consistent: greater reduction in prostate size did not necessarily result in large decreases in dose to bladder or rectum. The total size of the bladder and rectum were found to be important factors in normal tissue radiation exposure; the benefits of hormone therapy may be lost if the bladder and rectum are allowed to decrease in size. Also, the bladder may be prone to sagging into the pelvis of some patients following hormone therapy, resulting in a less optimal therapeutic ratio. CONCLUSION: Reduction in prostate size by neoadjuvant hormonal manipulation does decrease the amount of normal tissue irradiated in most patients. However, the correlation between the reduction in prostate size and amount of rectum or bladder treated is not linear if other variables are not controlled. Factors such as the shape of the organs, as well as the distensible nature of the bladder and rectum, play major roles in dose to normal tissues. These facts may mask the benefits of cytoreduction and could be obstacles in realizing consistent benefits from preirradiation hormonal treatment in the clinical setting if they are ignored.

Adenocarcinoma↗
PubMed1995

Analysis of weekly complete blood counts in patients receiving standard fractionated partial body radiation therapy.

PURPOSE: Hematopoiesis is among the most sensitive systems in the body to radiation. Routine complete blood counts (CBCs) are common in clinical radiotherapy practice. Only a few studies have attempted to characterize the behavior of peripheral blood levels during partial body radiation therapy with field sizes smaller than those used in hemibody or total nodal irradiation. Such information is needed to identify which patients are at risk for cytopenia and require close monitoring. METHODS AND MATERIALS: In 1993, 412 new patients were seen at Michael Reese Hospital for radiotherapy. A total of 972 weekly CBCs were identified for 155 patients receiving a minimum of 5 weeks of treatment for breast, prostate, lung, gynecological, or head and neck malignancies. Linear regression models were fitted to the weekly CBC values for those patients who had pretreatment CBC values recorded. Factors affecting starting levels, rates of decline, and nadirs during treatment were determined for leukocytes, platelets, and hemoglobin. RESULTS: Leukocytes declined most dramatically during the first week of treatment (16% from pretreatment to Week 1 levels) and then at a rate of 3.3% per week from Week 1 to Week 7 (p < 0.001). Total mean leukocyte decrease over 7 weeks of therapy was 30%. Platelets declined 9% on average during the first week of therapy and then at a mean rate of 1.4% per week (p < 0.02). A statistically significant decrease in hemoglobin levels could not be detected. No difference in the rate of decrease could be found for different disease sites, age groups, or amount of marrow irradiated. The effects of chemotherapy were variable, depending on blood element and whether therapy was sequential or concomitant. The odds of a nadir < 2000 counts/mm3 for white blood count (WBC), < 50,000 counts/mm3 for platelets, and < 8.0 g/dl for hemoglobin were all well below 5%. A strong correlation existed between starting CBC values and nadirs; patients with lower Week 1 CBC levels were most likely to have the lowest nadirs. CONCLUSIONS: Low CBC levels during radiation therapy are likely to be the result of other medical problems that cancer patients face. Regional irradiation with small field sizes (< 40% of total body marrow) typically used in clinical radiotherapy is unlikely to be the cause of marrow depression significant enough to warrant medical intervention. Blood levels taken during the first week of treatment (Week 1) can be used to determine risks of developing critical nadirs. Localized breast and prostate cancer patients are unlikely to require routine CBCs if initial levels are normal. Routine CBC levels on all radiation oncology patients without other reasons for hematopoietic depression requires reevaluation, as millions of dollars are spent on unnecessary testing. If weekly CBC blood levels are avoided in localized breast and prostate cancer patients, this alone could potentially result in a savings of as much as $40 million a year nationally.

Adult↗
PubMed1995

Measurement of weekly prostate specific antigen levels in patients receiving pelvic radiotherapy for nonprostatic malignancies.

PURPOSE: To study the response of nonmalignant prostatic tissue to ionizing irradiation in terms of the resultant changes in serum prostate specific antigen (PSA) levels. METHODS AND MATERIALS: Weekly serum PSA values were determined during radiotherapy (RT) in nine patients ("treatment group") without clinical evidence of prostate cancer (PC), and who received pelvic RT for other indications. Slopes for the rate of change in PSA was determined using model: log PSA = beta 0 + beta 1*week + beta 2*week2 + error. These results are compared with 17 normal volunteers ("control group") who were not exposed to ionizing irradiation. An attempt is made to compare any similarities and differences in subsets of 64 T1-T4N0M0 PC patients who received pelvic RT. RESULTS: An elevation in the serum PSA levels were noted in eight of nine patients in the "treatment group" with a median time of 4.2 weeks to reach the maximum serum PSA values. After an initial increase, PSA values declined. In some patients, manifold increase in PSA was noted, for example, from 1.8 to 13.5 ng/ml and 3.3 to 9.8 ng/ml in two patients. The PSA increase ranged from 50-650%. The median slope was 0.601 week-1 (range 0.192-3.045 week-1). No such increases were seen in the "control group" (median slope = 0.03 week-1; range, 0.18-0.13 week-1). When differences between the mean increase/decrease for each week compared to pretreatment values were analyzed, the irradiated group had statistically significant elevations in the PSA for weeks 3 (p = 0.034), 4 (p = 0.035), and 5 (p = 0.024). A similar trend of increasing PSA levels during radiotherapy was noted in prostate cancer patients whose initial PSA values were < or = 20 ng/ml: whereas positive slopes (i.e., increasing PSA levels during radiotherapy course) was seen in 7.1% of those with > 20 ng/ml preradiotherapy PSA values, such trends were seen in 52.7% of those with < or = 20 ng/ml preradiotherapy PSA values. CONCLUSIONS: (a) Incidental exposure of noncancerous prostate to ionizing irradiation appears to lead to an initial elevation followed by a decline in serum PSA. (b) Similar elevations in serum PSA levels are seen in over 50% of prostate cancer patients with < or = 20 ng/ml pretreatment PSA. (c) Acinal cell death and sudden release of PSA into the circulation is the most likely explanation for our observations, although other mechanism cannot be excluded. (d) Our observations have to be considered in modeling PSA kinetics induced by RT and in correlating such kinetics to long-term outcomes. (e) Our findings in the control group indicate that there appears to be no significant variation in serum PSA over many weeks under physiological conditions in normal healthy ambulatory men.

Adult↗
PubMedDate not supplied

[Comparative evolution of the incidence of bronchopulmonary tuberculosis and bronchopulmonary cancer (data of the TB dispensary No. 1 in Galaţi)].

Over a period of 10 years a decrease was noted in the area of the Tuberculosis Dispensary of the Galatzi District, of the incidence through tuberculosis of the adult by approximately 50%, and an increase of the pulmonary cancer incidence three fold. The incidence curves of these two diseases, which were far apart 10 years ago, are much nearer now, and it may be presumed that in a not too remote future they will cross each other. The pneumophysiology network should be prepared further to face the increasing flow of patients with non-tuberculous diseases. With this view physicians should be re-cycled, and various types of specialists should be trained for cytologic diagnosis, and the technical equipment of antituberculous hospitals should be updated.

Adult↗