Associations of Obesity with Prostate Cancer Risk Differ Between U.S. African-American and Non-Hispanic White Men: Results from the Selenium and Vitamin E Cancer Prevention Trial

African-American (AA) men have the highest rates of prostate cancer incidence and mortality in the US. Understanding underlying reasons for this disparity could identify preventive interventions important to AA men. PURPOSE: To determine whether the association of obesity with prostate cancer risk differs between AA and non-Hispanic white (NHW) men and whether obesity modifies the excess risk associated with AA race. METHODS: This is a prospective study among 3398 AA and 22673 NHW men who participated in the Selenium and Vitamin E Cancer Prevention Trial (2001–2011). Using Cox regression, we estimated hazard ratios (HRs) and corresponding 95% confidence intervals (CIs) associated with AA and NHW race and body mass index (BMI) [kg/m2] on total, low- (Gleason score <7), and high-grade (Gleason score ≥7) prostate cancer incidence while adjusting for relevant covariates. RESULTS: There were 270, 148, and 88 cases of total, low-, and high-grade prostate cancers among AA men and a corresponding 1453, 898, and 441 cases in NHW men (median follow-up of 5.6 years). BMI was not associated with risk of total cancer among NHW men, but was positively associated with risk among AA men (BMI < 25 kg/m2 vs. ≥35 kg/m2, HR = 1.49; 95% CI, 0.95–2.34; Ptrend = 0.03). Consequently, the risk associated with AA race increased from 28% (HR = 1.28; 95% CI, 0.91–1.80) among men with BMI < 25 kg/m2 to 103% (HR = 2.03; 95% CI, 1.38–2.98) among AA men with BMI≥35 kg/m2 (Ptrend = 0.03). BMI was inversely associated with low-grade prostate cancer risk among NHW men (BMI < 25 kg/m2 vs. ≥35 kg/m2, HR = 0.80; 95% CI, 0.58–1.09; Ptrend = 0.02), but positively associated with risk among AA men (BMI < 25 kg/m2 vs. ≥35 kg/m2, HR = 1.77; 95% CI, 1.14–2.76; Ptrend = 0.05). BMI was positively associated with risk of high-grade prostate cancer in both NHW (BMI < 25 kg/m2 vs. ≥35 kg/m2, HR = 1.33; 95% CI, 0.90–1.97; Ptrend = 0.01) and AA men (BMI < 25 kg/m2 vs. ≥35 kg/m2, HR = 1.81; 95% CI, 0.79–4.11; Ptrend = 0.02), but associations were not significantly different. CONCLUSION: Obesity is more strongly associated with increased prostate cancer risk among AA than NHW men and reducing obesity among AA men could reduce the racial disparity in cancer incidence. Research is needed to test mechanisms underpinning these associations.

Deriving benefit of early detection from biomarker-based prognostic models

Many prognostic models for cancer use biomarkers that have utility in early detection. For example, in prostate cancer, models predicting disease-specific survival use serum prostate-specific antigen levels. These models typically show that higher marker levels are associated with poorer prognosis. Consequently, they are often interpreted as indicating that detecting disease at a lower threshold of the biomarker is likely to generate a survival benefit. However, lowering the threshold of the biomarker is tantamount to early detection. For survival benefit to not be simply an artifact of starting the survival clock earlier, we must account for the lead time of early detection. It is not known whether the existing prognostic models imply a survival benefit under early detection once lead time has been accounted for. In this article, we investigate survival benefit implied by prognostic models where the predictor(s) of disease-specific survival are age and/or biomarker level at disease detection. We show that the benefit depends on the rate of biomarker change, the lead time, and the biomarker level at the original date of diagnosis as well as on the parameters of the prognostic model. Even if the prognostic model indicates that lowering the threshold of the biomarker is associated with longer disease-specific survival, this does not necessarily imply that early detection will confer an extension of life expectancy.

Cost-effectiveness of microsatellite instability screening as a method for detecting hereditary nonpolyposis colorectal cancer

BACKGROUND

The National Cancer Institute has published consensus guidelines for universal screening for hereditary nonpolyposis colorectal cancer (HNPCC) in patients with newly diagnosed colorectal cancer.

OBJECTIVE

To determine the cost-effectiveness of screening compared with standard care in eligible patients with colorectal cancer and their siblings and children.

DESIGN

Cost-effectiveness analysis.

DATA SOURCES

National colorectal cancer registry data, the Creighton International Hereditary Colorectal Cancer Registry, Medicare claims records, and published literature.

TARGET POPULATION

Patients with newly diagnosed colorectal cancer and their siblings and children.

TIME HORIZON

Lifetime (varies depending on age at screening).

PERSPECTIVE

Societal.

INTERVENTIONS

Initial office-based screening to determine eligibility (based on personal and family cancer history), followed by tumor testing for microsatellite instability. Those with microsatellite instability were offered genetic testing for HNPCC. Siblings and children of patients with cancer and the HNPCC mutation were offered genetic testing, and those who were found to carry the mutation received lifelong colorectal cancer screening.

MEASUREMENTS

Life-years gained.

RESULTS OF BASE-CASE ANALYSIS

When only the patients with cancer were considered, cost-effectiveness of screening was $42 210 per life-year gained. When patients with cancer and their siblings and children were considered together, cost-effectiveness increased to $7556 per life-year gained.

RESULTS OF SENSITIVITY ANALYSIS

The model was most sensitive to the estimated survival gain from screening siblings and children, to the prevalence of HNPCC mutations among patients with newly diagnosed cancer, and to the discount rate. In probabilistic analysis, the 90% CI for the cost-effectiveness of screening patients with cancer plus their relatives was $4874 to $21 576 per life-year gained.

CONCLUSION

Screening patients with newly diagnosed colorectal cancer for HNPCC is cost-effective, especially if the benefits to their immediate relatives are considered.

Serial prostate specific antigen, free-to-total prostate specific antigen ratio and complexed prostate specific antigen for the diagnosis of prostate cancer

PURPOSE

The free-to-total prostate specific antigen (PSA) ratio and complexed PSA have been introduced as adjuncts to total PSA for prostate cancer screening. Little data exist on the use of these tests for serial PSA screening. We compared serial total PSA, the free-to-total PSA ratio and calculated complexed PSA in men diagnosed with prostate cancer and matched controls in a population based study.

MATERIALS AND METHODS

We identified 90 men diagnosed with prostate cancer between 1988 and 1996 with at least 3 serial serum samples obtained at 2-year intervals who were participants in the beta-Carotene and Retinol Efficacy Trial for the prevention of lung cancer. Samples were available up to 10 years before diagnosis. A total of 90 age matched men from the same cohort without prostate carcinoma were identified as controls. Free and total PSA was measured by the Abbott AxSYM system.

RESULTS

Baseline demographics of cases and controls were similar. At baseline and diagnosis the men with prostate cancer had higher total and complexed PSA, and a lower free-to-total PSA ratio than controls. Mean followup was 5.2 years in cases and 5.5 in controls. The yearly change in PSA parameters in cases versus controls was 20.7% versus 3.5% for total, -3.4% versus 0.2% for free-to-total and 21.5% versus 3.4% for complexed PSA (p <0.0001). At diagnosis PSA alone was estimated to perform with more than 90% specificity in our model.

CONCLUSIONS

In this population based study total PSA was superior to the free-to-total PSA ratio for predicting the development of prostate cancer. While serial changes in free-to-total PSA ratios with time were statistically significantly different in men diagnosed with prostate cancer and controls, the magnitude of these serial changes were slight enough to render them clinically insignificant.

The impact of including future medical care costs when estimating the costs attributable to a disease: a colorectal cancer case study

A source of controversy in the economic literature concerns whether to include or exclude future medical care costs when computing attributable costs for lifesaving interventions. Although it is hypothesized that including future medical care costs will offset the cost savings achieved through prevention, the magnitude of the effect is not known. The objectives of the present study are to develop a methodology for estimating the excess costs of care among colorectal cancer patients, including and excluding future costs of care, and comparing these results with previous studies that do not include costs in added years of life. Subjects in the study included those identified with colorectal cancer drawn from the Surveillance, Epidemiology and End Results (SEER)-Medicare database and an age- and gender-matched control group drawn from the general Medicare population. Using the Kaplan-Meier Sample Average estimator, we directly estimate expected 11-year costs, and then, with the addition of some simple extrapolating assumptions, determine expected 25-year costs. The latter time horizon captures lifetime costs for over 90% of the cohort. Males results for discounted, stage-specific 11- versus 25-year excess costs: in situ, 22411 dollars versus 23494 dollars; Stage 1, 29365 dollars versus 32510 dollars; Stage 2, 28114 dollars versus 25263 dollars; Stage 3, 27397 dollars versus 19647 dollars; Stage 4, 3006 dollars versus 7837 dollars. Trends were similar for females. It can be concluded that adding costs of care in future years for those whose colorectal cancer is prevented owing to screening greatly alters the estimate of lifetime excess costs for colorectal cancer patients, and can produce negative results for advanced stage disease. The results emphasize the need to adopt a standard approach for dealing with future costs when evaluating lifesaving interventions for cost-effectiveness analyses.

Simulation modeling of outcomes and cost effectiveness

Modeling will continue to be used to address important issues in clinical practice and health policy issues that have not been adequately studied with high-quality clinical trials. The apparent ad hoc nature of models belies the methodologic rigor that is applied to create the best models in cancer prevention and care. Models have progressed from simple decision trees to extremely complex microsimulation analyses, yet all are built using a logical process based on objective evaluation of the path between intervention and outcome. The best modelers take great care to justify both the structure and content of the model and then test their assumptions using a comprehensive process of sensitivity analysis and model validation. Like clinical trials, models sometimes produce results that are later found to be invalid as other data become available. When weighing the value of models in health care decision making, it is reasonable to consider the alternatives. In the absence of data, clinical policy decisions are often based on the recommendations of expert opinion panels or on poorly defined notions of the standard of care or medical necessity. Because such decision making rarely entails the rigorous process of data collection, synthesis, and testing that is the core of well-conducted modeling, it is usually not possible for external audiences to examine the assumptions and data that were used to derive the decisions. One of the modeler's most challenging tasks is to make the structure and content of the model transparent to the intended audience. The purpose of this article is to clarify the process of modeling, so that readers of models are more knowledgeable about their uses, strengths, and limitations.

Quality of life in survivors of colorectal carcinoma

BACKGROUND

Colon carcinoma is a common malignancy that accounts for a substantial share of all cancer-related morbidity and mortality. However, little is known with regard to general and disease specific quality of life in survivors of colorectal carcinoma, particularly from community-based samples of cases across stage and survival times from diagnosis.

METHODS

Subjects with colorectal carcinoma were recruited from the National Cancer Institute's Surveillance, Epidemiology, and End Results cancer registry. Subjects completed two self-administered surveys: the Functional Assessment of Cancer Therapy Scales for Colorectal Cancer (FACT-C) and the Health Utilities Index (HUI) Mark III.

RESULTS

One hundred seventy-three respondents (average age: 70.4 years, 71.4% female) completed the survey. In the first 3 years after diagnosis, quality of life was lower and varied substantially among respondents. After 3 years, respondents in all TNM stages of disease except Stage IV reported a relatively uniform and high quality of life. Pain, functional well-being, and social well-being were affected most substantially across all stages and times from diagnosis. Low income status was associated with worse outcomes for pain, ambulation, and social and emotional well-being. Only emotional well-being scores improved significantly over time in both surveys.

CONCLUSIONS

Those individuals who achieve a long term remission from colorectal carcinoma may experience a relatively high quality of life, although deficits remain for several areas, particularly in those of low socioeconomic status. Sampling design may have excluded the most severely ill patients.

The effectiveness of mammography promotion by volunteers in rural communities

INTRODUCTION

The Community Trial of Mammography Promotion assessed the effectiveness of mammography promotion by community volunteer groups in rural areas. Three interventions were tested. One used an individual counseling strategy, one used a community activities strategy, and a third combined the two strategies.

METHODS

The effects of the interventions were tested by randomizing 40 communities either to the study interventions or to a control group. A cohort of 352 women from each community was randomly selected and used to evaluate the interventions' effectiveness. Of these, 6592 women were eligible for screening mammography at baseline and follow-up and were successfully interviewed prior to and after study intervention activities.

RESULTS

Although the interventions did not significantly increase women's overall use of mammography, the community activities intervention increased use at follow-up by regular users over baseline by 2.9% (p = 0.01). Intervention appears to have increased the use of mammography among certain groups of women who were not regular users at baseline, including those in communities without female physicians (10% to 16%; p < 0.05), and among women with no health insurance (10% to 23%; p </= 0.05).

CONCLUSION

Volunteers can effectively promote mammography in rural communities.

Reduced dose intravenous immunoglobulin does not decrease transplant-related complications in adults given related donor marrow allografts

Graft-vs.-host disease (GVHD) and infection are major complications of allogeneic bone marrow transplantation. Intravenous immunoglobulin (IVIg) given at a dose of 500 mg/kg/wk has been shown to decrease the risk of acute GVHD, interstitial pneumonia, and infection in adults early after allogeneic transplantation. The current study is a controlled trial to determine whether a lower total dose of IVIg given with pretransplant loading reduces the incidence of transplant-related complications. In a randomized trial of 241 patients > or =20 years of age who were given related donor marrow allografts, 121 individuals receiving Ig prophylaxis (500 mg/kg/d loading from day -6 to -1 and then 100 mg/kg every 3 days from day 3 to 90) were compared with 120 control patients who did not receive IVIg. Randomization was stratified by human leucocyte antigen-matching, remission status of malignancy, GVHD prophylaxis, and cytomegalovirus (CMV) serology. The study was powered to detect a reduction in acute GVHD by 18% and a decrease in transplant-related mortality by 17%. Pretransplant IVIg loading and posttransplant maintenance achieved median serum IgG levels >1350 mg/dL, which were approximately twofold greater than the untreated controls (p<0.01). White blood cell and platelet recoveries were similar for the two groups, although control patients required fewer units of platelets per day (2.5 vs. 3.3, p = 0.008). No significant differences in the incidence of CMV infection, interstitial pneumonia, or bacteremia were observed. The incidence of acute GVHD did not differ between the two groups; however, acute GVHD was less frequent among IVIg recipients achieving maximum serum IgG levels >3000 mg/dL (60 vs. 79%). Neither transplant-related mortality nor disease-free survival was significantly altered by Ig prophylaxis. However, the cumulative incidence of relapse of malignancy was higher in IVIg recipients than in controls (31 vs. 18%, p = 0.03). Multivariable regression analysis demonstrated a 1.89 increased relative risk of relapse for individuals given IVIg (p = 0.021). We conclude that pretransplant loading and a shorter course and lower total dose of IVIg prophylaxis did not appear to decrease the risk of acute GVHD or mortality among adults receiving related donor marrow transplants. Note, IVIg administration may be associated with an increased risk of recurrent malignancy, a finding that warrants further investigation.

Serial prostate specific antigen screening for prostate cancer: a computer model evaluates competing strategies

PURPOSE

We compare prostate specific antigen (PSA) screening strategies in terms of expected years of life saved with screening, number of screens, number of false-positive screens and rates of over diagnosis, defined as detection by PSA screening of patients who would never have been diagnosed without screening.

MATERIALS AND METHODS

A computer model of disease progression, clinical diagnosis, PSA growth and PSA screening was used. Under baseline conditions, when screening is not considered, the model replicates clinical diagnosis and disease mortality rates recorded by the Surveillance, Epidemiology and End Results Program of the National Cancer Institute in the mid 1980s.

RESULTS

Biannual screening with PSA greater than 4.0 ng./ml. was projected to reduce the number of screens and false-positive tests by almost 50% relative to annual screening while retaining 93% of years of life saved. With annual screening use of an age specific bound for PSA to consider a test positive instead of the standard 4.0 ng./ml. was projected to reduce false-positive screens by 27% and over diagnosis by a third while retaining almost 95% of years of life saved. Sensitivity analyses did not change the relative efficacy of biannual screening.

CONCLUSIONS

Under the model assumptions biannual PSA screening is a cost-effective alternative to annual PSA screening for prostate cancer. With annual screening use of an age specific bound for PSA positivity appears to reduce false-positive results and over diagnosis rates sharply relative to a bound of 4 ng./ml. while retaining most of the survival benefits.

Community attitudes and mammography use: does it really matter what other people think?

This study examined whether community characteristics, particularly community attitudes regarding mammography use, are associated with women's use of mammography in rural communities. Forty communities in predominantly rural areas of Washington State were selected for inclusion in this study based on their size and distance from an urban center. Characteristics of the communities were assessed as were characteristics of women living in the communities. From each community, random samples of 352 women between 50 and 80 years old participated by completing a telephone survey that included questions on a variety of topics, including their use of mammography. Logistic regression analyses revealed community of residence to be a significant predictor of individual women's mammography use after adjusting for individual level predictors of mammography use including age, education, employment, marital status, financial situation, and ease of access to medical services. An examination of the influence of community characteristics revealed women living in communities with supportive community attitudes towards mammography use report higher levels of mammography use than do women living in communities with less supportive attitudes. The presence or absence of male or female physicians or of mammography facilities in a local community was not associated with statistically significant effects on women's mammography use. Community attitudes are associated with mammography use in rural communities. Public health interventions that change community attitudes may have effects that extend beyond the people directly contacted by these interventions.

Incorporating the time dimension in receiver operating characteristic curves: a case study of prostate cancer

Early diagnosis of disease has potential to reduce morbidity and mortality. Biomarkers may be useful for detecting disease at early stages before it becomes clinically apparent. Prostate-specific antigen (PSA) is one such marker for prostate cancer. This article is concerned with modeling receiver operating characteristic (ROC) curves associated with biomarkers at various times prior to the time at which the disease is detected clinically, by two methods. The first models the biomarkers statistically using mixed-effects regression models, and uses parameter estimates from these models to estimate the time-specific ROC curves. The second directly models the ROC curves as a function of time prior to diagnosis and may be implemented using software packages with binary regression or generalized linear model routines. The approaches are applied to data from 71 prostate cancer cases and 71 controls who participated in a lung cancer prevention trial. Two biomarkers for prostate cancer were considered: total serum PSA and the ratio of free to total PSA. Not surprisingly, both markers performed better as the interval between PSA measurement and clinical diagnosis decreased. Although the two markers performed similarly eight years prior to diagnosis, it appears that total PSA performed better than the ratio measure at times closer to diagnosis. The area under the ROC curve was consistently greater for total PSA than for the ratio four and two years prior to diagnosis and at the time of diagnosis.

Cancer surveillance series: interpreting trends in prostate cancer--part III: Quantifying the link between population prostate-specific antigen testing and recent declines in prostate cancer mortality

BACKGROUND

The objective of this study was to investigate the circumstances under which dissemination of prostate-specific antigen (PSA) testing, beginning in 1988, could plausibly explain the declines in prostate cancer mortality observed from 1992 through 1994.

METHODS

We developed a computer simulation model by use of information on population-based PSA testing patterns, cancer detection rates, average lead time (the time by which diagnosis is advanced by screening), and projected decreased risk of death associated with early diagnosis of prostate cancer through PSA testing. The model provides estimates of the number of deaths prevented by PSA testing for the 7-year period from 1988 through 1994 and projects what prostate cancer mortality for these years would have been in the absence of PSA testing.

RESULTS

Results were generated by assuming a level of screening efficacy similar to that hypothesized for the Prostate, Lung, Colorectal, and Ovarian (PLCO) Cancer Screening Trial. Under this assumption, the projected mortality in the absence of PSA testing continued the increasing trend observed before 1991 only when it was assumed that the mean lead time was 3 years or less. Projected mortality trends in the absence of PSA screening were not consistent with pre-1991 increasing trends for lead times of 5 years and 7 years.

CONCLUSIONS

When screening is assumed to be at least as efficacious as hypothesized in the PLCO trial, it is unlikely that the entire decline in prostate cancer mortality can be explained by PSA testing based on current beliefs concerning lead time. Only very short lead times would produce a decline in mortality of the magnitude that has been observed.

Asymptomatic incidence and duration of prostate cancer

Prostate cancer is known as a disease with an extremely high prevalence relative to its clinical incidence in the population. The combination of preclinical incidence and duration that could yield this phenomenon is of tremendous interest to researchers trying to understand the natural history of the disease and to develop efficient screening strategies. In this article, the authors present estimates of the age-specific asymptomatic incidence and average preclinical duration of prostate cancer. The methodological approach is to first estimate the age-specific incidence of new (stage AI) prostate cancers using preclinical prevalence data from autopsy studies performed between 1941 and 1964 and clinical incidence data for the years 1960-1986 from the Surveillance, Epidemiology, and End Results (SEER) program of the National Cancer Institute. Then, the preclinical prevalence estimates are divided by the derived preclinical incidence estimates to yield estimates of the average duration of asymptomatic disease. The estimated mean duration among white men is between 11 and 12 years and appears to be approximately 1 year shorter for blacks than for whites. Comparison of the lifetime risks of preclinical and clinical disease suggests that approximately 75% of prostate cancers will never become diagnosed if clinical incidence remains at levels observed in 1984-1986, prior to the introduction of prostate-specific antigen (PSA) screening in the population.

Optimizing sampling strategies for estimating quality-adjusted life years

Accurate estimation of quality of life is critical to cost-effectiveness analysis. Nevertheless, development of sampling algorithms to maximize the accuracy and efficiency of estimated quality of life has received little consideration to date. This paper presents a method to optimize sampling strategies for estimating quality-adjusted life years. In particular, the authors address the questions of when to sample and how many observations to sample at each sampling time, assuming realistically that the sample variance of quality of life is not constant over time. The method is particularly useful for the design problems researchers face when time or research budget constraints limit the number of individuals that can be surveyed to estimate quality of life. The article focuses on cross-sectional sampling. The method proposed requires some knowledge of survival in the population of interest, the approximate variances in utilities at various points along the curve, and the general shape of the quality-adjusted survival curve. Such data are frequently available from disease registries, the literature, or previous studies.

Use of a stochastic simulation model to identify an efficient protocol for ovarian cancer screening

The intervention protocol for an ovarian cancer screening trial should be efficient as well as effective, because it may become the standard of care if the trial demonstrates mortality reduction. To identify an efficient ovarian cancer screening protocol, the effectiveness and cost-effectiveness of selected single modality and multimodal screening strategies were estimated using a stochastic simulation model. Screening was simulated over a 30-year period in a hypothetical cohort of 1 million women aged 50 at the beginning of the period. The net present value of the cost per year of life saved was estimated for six protocols involving transvaginal sonography (TVS) and/or the tumor antigen CA 125. Internal and external validation was performed, and sensitivity analyses were conducted to assess the robustness of the ranking of the strategies. A multimodal strategy involving CA 125 with a threshold for positivity of either elevation above 35 U/ml or doubling since the previous screen, followed by TVS only if CA 125 is positive, was found to be efficient in the sense that no other strategies saved as many years of life at lower cost per year of life saved. Used annually, this strategy cost under $100,000 per year of life saved over a range of assumptions. The model's predictions are consistent with results reported in the literature regarding the performance of TVS and CA 125. The multimodal strategy used annually or every six months was efficient compared to either ultrasound or CA 125 used alone, over a range of assumptions. Simulation of screening may be useful in selecting a screening protocol to be tested in a randomized controlled trial.

Estimating medical costs from incomplete follow-up data

Estimation of the average total cost for treating patients with a particular disease is often complicated by the fact that the survival times are censored on some study subjects and their subsequent costs are unknown. The naive sample average of the observed costs from all study subjects or from the uncensored cases only can be severely biased, and the standard survival analysis techniques are not applicable. To minimize the bias induced by censoring, we partition the entire time period of interest into a number of small intervals and estimate the average total cost either by the sum of the Kaplan-Meier estimator for the probability of dying in each interval multiplied by the sample mean of the total costs from the observed deaths in that interval or by the sum of the Kaplan-Meier estimator for the probability of being alive at the start of each interval multiplied by an appropriate estimator for the average cost over the interval conditional on surviving to the start of the interval. The resultant estimators are consistent if censoring occurs solely at the boundaries of the intervals. In addition, the estimators are asymptotically normal with easily estimated variances. Extensive numerical studies show that the asymptotic approximations are adequate for practical use and the biases of the proposed estimators are small even when censoring may occur in the interiors of the intervals. An ovarian cancer study is provided.

Estimating asymptomatic duration in cancer: the AIDS connection

Many chronic diseases, including AIDS and cancer, do not manifest themselves clinically until some time after their inception. In studies of disease natural history, the duration of the asymptomatic period is of interest-in AIDS, to predict the epidemic's course, and in cancer, to develop efficient screening strategies. This article provides a bridge between the two fields with respect to estimation of the asymptomatic period. By adapting AIDS methodology to cancer, the article identifies a non-parametric method for estimating the duration of the asymptomatic period in cancer. The method is similar to one developed by Louis et al. (Mathematical Biosciences, 40, 111-144 (1978)), and is designed to apply to data from a cohort of individuals, screened periodically. After reviewing the similarities and differences between the AIDS and cancer contexts, we develop an EM algorithm that, at convergence, yields a maximum or saddle point of the likelihood. We investigate the performance of the algorithm by means of a simulation study, explore the effect of adding a smoothing step to the estimation procedure, and adapt the method for use with a data set in which disease prevalence is low. We apply the method to data from the HIP breast cancer screening trial.

Serum prostate-specific antigen and digital rectal examination for early detection of prostate cancer in a national community-based program. The Prostate Cancer Education Council

OBJECTIVES

This study analyzed methods of prostate cancer early detection in community settings throughout the United States against standards and findings of earlier studies conducted at academic medical centers.

METHODS

The study was conducted at 148 clinical centers during Prostate Cancer Awareness Week in September 1993 and continued through June 1994. A total of 31,953 eligible subjects were tested by both digital rectal examination (DRE) and prostate-specific antigen (PSA). PSA was tested with the Abbott IMx PSA assay and reported by Roche Biomedical, Inc.

RESULTS

The study confirmed that elevated PSA levels (greater than 4.0 ng/mL) aid in the detection of organ-confined prostate cancer when used in conjunction with the DRE. Reflecting more conservative biopsy decision-making practices, study results nonetheless are comparable to earlier reports. Among 1307 subjects who underwent biopsy, 322 cancers were detected. The cancer detection rate was 3.6% for PSA, 3.0% for DRE, and 4.7% if either test result was positive. The positive predictive value (PPV) for elevated PSA levels (greater than 4.0 ng/mL) was 3l.6%, significantly better (P < 0.0001) than the PPV for abnormal DRE results (25.5%). Nearly 90% (88.9%) of staged cancers were diagnosed as localized. Elevated PSA levels detected more localized cancers (76 of 105 [72.4%]) than the DRE (72 of 105 [68.6%]). Of localized tumors, 33 (31.4%) were missed by DRE and detected solely by PSA, and 29 (27.6%) were missed by PSA and detected solely by DRE. The combined use of the two methods detected 33 additional localized tumors.

CONCLUSIONS

Community practice throughout the United States demonstrates that PSA and DRE are consistently effective and efficient in the early detection of prostate cancer.

Estimating the costs attributable to a disease with application to ovarian cancer

This article is concerned with the methodological issues that arise when estimating the expected costs attributable to a disease. In particular, the article considers methods appropriate for handling incomplete or censored cost and survival data, incorporating discounting, and computing attributable costs. After motivating the need for an estimate of the average, present value of the attributable costs, we present the Kaplan-Meier sample-average (KMSA) estimator, which takes into account the censored nature of the data that are typically available. We investigate the statistical properties of the estimator and compare it to others employed in the literature, showing how certain methods for incorporating discounting can introduce bias. We demonstrate the utility of the estimator by applying it to estimation of the costs attributable to ovarian cancer, using data from a database linking Medicare claims with the Surveillance, Epidemiology, and End Results cancer registry. Our analysis suggests that the average, present value of the 15-year costs attributable to ovarian cancer is $21,285 for local-stage cases and $32,126 for distant-state cases in 1990 dollars.

Age-specific prostate-specific antigen: a reassessment

BACKGROUND

Our objective was to compare expected survival benefits when screening for prostate cancer with PSA, using an age-specific bound relative to a cutoff of 4.0 ng/ml.

METHODS

We used a decision analysis modeling the cancer yield in a cohort screened by both screening tests, and the survival of cancer cases given screen detection and in the absence of screening. Expected cancer yields and positive predictive values were from an ultrasound-guided biopsy series. Stage distributions of screen-detected cases were obtained from the literature. For localized causes, survival given screen detection was assumed to be equal to normal life expectancy for the population. For these cases, survival in the absence of screening was modeled as time from clinical diagnosis to death added to time remaining after time of screen and before clinical diagnosis was made (lead time). For nonlocalized cases at screen detection, survival given screen detection was assumed to be equal to survival in the absence of screening. The average difference between expected survival with and without screening as calculated for age-specific PSA and for PSA > 4.0 ng/ml and compared.

RESULTS

Average years of life saved per subject screened using PSA > 4.0 ng/ml were comparable to those using the age-specific bound. Average years of life saved per cancer case, however, appeared to be potentially greater for PSA > 4.0 ng/ml than for age-specific. PSA. PSA > 4.0 ng/ml detected markedly more prostate cancer cases than age-specific PSA.

CONCLUSIONS

Using a bound of 4.0 ng/ml for all ages appears to be more efficient in identifying men with cancer in a screening cohort, which translates into a greater expected survival benefit per cancer case.

Community organization to promote breast cancer screening among women ages 50-75

BACKGROUND

To reduce breast cancer mortality, ways to promote the use of mammography screening among women age 50 and above are needed. Community organization may be a useful approach.

METHODS

The Washington State Community Breast Cancer Screening Project involved implementation of promotional activities initiated by physician and lay community boards in two communities. Two comparable communities served as controls for evaluation purposes. Random-digit-dial telephone interviews were used to assess recent use of mammography at baseline and follow-up in independent samples of women ages 50 to 75 from the four communities. The extent of exposure to intervention activities and the relationship between exposure to intervention activities and mammography use were estimated from data collected at follow-up.

RESULTS

Exposure to patient reminders from physicians, wallet reminder cards, and newspaper advertisements were consistently related to mammography use. Physician office staff encouragement and a display board were significantly related to mammography use only in Intervention Communities A and B, respectively. Neither exposure to promotional activities nor the change in prevalence of mammography use was significantly higher in the intervention communities than in the comparison communities at follow-up.

CONCLUSIONS

Although several activities were useful in promoting mammography use, organization of the community did not enhance efforts undertaken spontaneously by comparable communities.

Tacrolimus (FK506) alone or in combination with methotrexate or methylprednisolone for the prevention of acute graft-versus-host disease after marrow transplantation from HLA-matched siblings: a single-center study

The pharmacokinetics, safety, and efficacy in marrow transplantation of FK506-based immunosuppression for graft-versus-host disease (GVHD) prophylaxis was evaluated in an open label pilot study of 18 patients. Patients more than 12 years of age (median, 35 years; range, 15 to 50 years) with advanced hematologic malignancies receiving HLA-matched sibling marrow grafts were randomized to receive FK506 alone, FK506 and methotrexate (MTX), or FK506 and methyl-prednisolone. Of 17 evaluable patients, all had evidence of sustained marrow engraftment. The median time to an absolute neutrophil count of greater than 500/microL was 15 days for patients receiving FK506 alone or FK506 plus methylprednisolone and 23 days for FK506 plus short MTX. Pharmacokinetic studies did not show any significant difference in clearance of FK506 when administered alone or in combination with methylprednisolone or MTX. The mean bioavailability after oral administration in these same three groups was 0.49 +/- 0.1, 0.27 +/- 0.12, and 0.16 +/- 0.08, respectively (P = .003). The decrease in bioavailability may have resulted from an exacerbation of radiation-induced gastroenteritis by MTX. The most significant adverse effect associated with the administration of FK506 was nephrotoxicity, which occurred in 14 of 18 patients (78%). The mean glomerular filtration rate, determined by clearance of (99MTc)DTPA, decreased to 56% (+/- 18%) of the pretransplant baseline level by week 8 (P = .002). Eight of 18 patients (44%) developed grades II-IV acute GVHD, predominantly of the skin and gastrointestinal tract. The actuarial probability of transplant-related mortality during the first 100 days was 24%. The actuarial probability of 1-year disease-free survival was 39%. In conclusion, although bioavailability of FK506 may be affected in patients receiving MTX, this study suggests that FK506 may have a role in the management of patients after allogeneic marrow transplantation.

On the catch-up time method for analyzing cancer screening trials

In randomized cancer screening trials, the ratio of the mortality rate for the screened group to that for the control group is typically not constant as a function of years from randomization. This is due to an initial lag effect, but also to a dilution effect that results from the accrual of comparable cases in both groups after the end of the screening period. In order to combat the potential loss of power when applying conventional analysis tools, specifically the logrank test, Aron and Prorok (International Journal of Epidemiology 15, 36-43), have advocated analyzing the mortality experience using only the subcohort of cases ascertained within a given time period. However, it is not clear how to select an appropriate case ascertainment point, since this will depend on aspects of the natural history of the disease process which are poorly identified. Aron and Prorok suggest choosing the case ascertainment point to be the point at which the cumulative number of cases in the control group first becomes equal to that in the intervention group, that is, the "catch-up time." In this paper, we undertake a thorough evaluation of the bias and power properties of the catch-up time method. We base our study on simulated data resembling the Health Insurance Plan of Greater New York study cohort. We consider several models for postdiagnosis survival under the null hypothesis of no screening effect on mortality, and under the alternative hypothesis of an effect of screening. We show that the catch-up method can yield tests with sizeable bias. In the absence of detailed knowledge about the underlying disease process, we suggest some adaptive tests that maintain nominal size but have more attractive power properties than the standard logrank test.

A likelihood ratio test for cancer screening trials

In randomized cancer screening trials, mortality rates for the screened group relative to those of the control group are not likely to be constant as a function of years from randomization due to the inherent lag between initiation of screening and any putative effects of screening on mortality. In this situation, a log rank test for differences in mortality between the randomization groups will not be optimal. Although optimality could potentially be recovered by use of a weighted log rank statistic, the optimal weights are difficult to specify a priori and the potential loss of power by use of poorly specified weights is great. We describe a likelihood ratio test with two degrees of freedom for use in this situation which is based on a fit of a weakly structured full model. Computation of an approximate significance level for this test is described and a large sample justification for this approximation is given. Size and power properties of the proposed statistic are compared to that of several other statistics in a small simulation study and the statistic is applied to data from the HIP Breast Cancer Screening Trial.

Marrow transplantation from unrelated volunteer donors

Marrow transplants from human leukocyte antigen (HLA)-compatible unrelated volunteer donors have become feasible for more than 30% of patients without a family match and have allowed long-term, disease-free survival in 15-65% of patients with a variety of hematological disorders. However, unrelated donor transplants have a higher incidence of graft failure and graft versus host disease (GVHD) than do HLA-matched sibling transplants. This increase may be due to disparities between donor and recipient for undetected HLA determinants or for non-HLA histocompatibility genes. Because of the large number of HLA loci and their high degree of polymorphism, fully compatible donors will not be found for most patients. Fortunately, a limited degree of HLA mismatch does not necessarily impair long-term survival in patients with hematologic malignancy. Current studies are defining the risk associated with mismatching for each histocompatibility locus and are developing methods for marrow transplantation that can decrease morbidity and improve survival despite genetic disparity between donor and recipient.

Monitoring of a pilot toxicity study with two adverse outcomes

We consider monitoring a pilot toxicity study in which the adverse outcome is bivariate and the goal is to terminate the trial if evidence of excessive toxicity is encountered. We develop a Bayesian monitoring rule, based on the posterior probability that the frequency of either adverse outcome exceeds that observed under standard therapy. This rule is intuitive and ethical, and extends in a straightforward fashion from the univariate to the multivariate case. Since p-values and confidence intervals are standard methods for reporting the results of clinical trials, we also suggest how frequentist inferences may be drawn at the conclusion of a study monitored in this fashion. This work thus represents an integration of Bayesian and frequentist methodology for sequential clinical trials.

Role of the mixed lymphocyte culture (MLC) reaction in marrow donor selection: matching for transplants from related haploidentical donors

The utility of the MLC assay as a test of HLA-D region matching and predictor of acute graft-versus-host disease (GvHD) was evaluated in 157 patients receiving marrow grafts from HLA-A, B identical related haploidentical donors. All donors and recipients were tested by HLA-DR serology, by Dw phenotyping with homozygous typing cells (HTC) and by standard MLC. Ninety-nine of the donor-recipient pairs were mismatched for a serologically defined HLA-DR antigen while 109 pairs were mismatched for the HLA-DR region by HTC typing. Donor antirecipient relative responses (RR) in MLC, corresponding to the GvHD vector in marrow transplantation, ranged from -4% to 100%, with a median of 25%. A comparison of reactivity in MLC with presence or absence of matching by Dw phenotyping, however, showed a significant overlap in the distribution of RRs from HLA-Dw matched versus Dw mismatched pairs, suggesting that the MLC was not a reliable predictor of HLA-Dw matching. Using an optimally-defined cutoff of 3% RR, the MLC was correlated with risk of developing clinically significant grades II-IV acute GvHD (p = 0.03) but not with risk of developing severe grades III-IV GvHD (p = 0.18). In contrast, matching by Dw phenotype was a significant predictor of GvHD, with Dw-compatible transplant recipients less likely to develop either grades II-IV (p = 0.004) or III-IV (p = 0.036) GvHD than Dw-incompatible transplant recipients. Overall, these results underscore the difficulty in using the MLC to measure HLA-D region compatibility and predict the risk of severe graft-versus-host disease among patients receiving related haploidentical marrow grafts. HLA-D (HTC) typing results correlate primarily with DRB compatibility, and with the advent of DRB1 allele matching by sequence-specific oligonucleotide probes (SSOP) or by direct sequencing, the precision in donor matching achievable with these methods is far greater than with either HLA-D typing or direct MLC testing.

Cyclophosphamide combined with antithymocyte globulin in preparation for allogeneic marrow transplants in patients with aplastic anemia

Graft rejection has been a problem after marrow grafts for patients with aplastic anemia who were conditioned with cyclophosphamide (CY). Rejection lessened when patients were given the marrow donor's peripheral blood buffy-coat cells in addition to the marrow, but this result was achieved at the price of more chronic graft-versus-host disease (GVHD). Results with second transplants suggested that CY alternating with antithymocyte globulin (ATG) was more immunosuppressive than CY alone. Therefore, the current study explored CY and ATG without buffy-coat cell transfusions in 39 patients with aplastic anemia given marrow transplants from HLA-identical family members (siblings in 38 cases, father in 1 case). We hoped both to minimize the risks of graft rejection and of chronic GVHD and to improve survival. Patients were 2 to 52 years of age (median, 24.5); 87% had received previous transfusions, and 41% had therapy with immunosuppressive agents before transplant. They were administered four daily doses of CY (total, 200 mg/kg) alternating with three doses of ATG (total, 90 mg/kg) followed by an HLA-identical marrow graft. Methotrexate and cyclosporine were administered to prevent GVHD. Two patients rejected their grafts (5%), and both were successfully retransplanted. Acute (grade 2 or 3) GVHD occurred in 15% and chronic GVHD in 34% of patients. The actuarial survival rate at 3 years was 92%, which compares favorably to the 72% survival rate in 39 historical patients who were matched with current patients for age and risk factors for rejection and GVHD. CY/ATG is a well-tolerated and effective conditioning program for marrow grafting in aplastic anemia that, when combined with GVHD prevention by methotrexate/cyclosporine, results in excellent survival.

Small bowel obstruction after nephrectomy for Wilms' tumor. A report of the National Wilms' Tumor Study-3

OBJECTIVE

This study was undertaken to define the incidence and etiology of small bowel obstruction (SBO) after nephrectomy for Wilms' tumor.

SUMMARY BACKGROUND DATA

Intestinal obstruction is one of the most common postoperative complications after nephrectomy for nephroblastoma. However, few reports have evaluated risk factors for SBO. Radiation therapy has been associated with increased intestinal complications in some adult cancer patients, but this has not been reported in children undergoing cancer surgery.

METHODS

Postoperative SBO occurred in 131 of 1,910 children (6.9%) enrolled in the Third National Wilms' Tumor Study (NWTS). The etiology of the SBO was bowel adhesions in 104 cases, intussusception in 17, internal hernia in 2, and uncertain in the remaining 8 children.

RESULTS

The factors found to be of potential importance in explaining the incidence of SBO were higher local tumor stage, extrarenal intravascular involvement, and en bloc resection of other organs at the time of nephrectomy. The incidence of postoperative SBO was not increased in children who received postoperative radiation therapy.

CONCLUSIONS

Although the overall incidence of SBO after nephrectomy for Wilms' tumor is comparable to that after other major abdominal operations in children, it can be responsible for significant morbidity. There were 4 children among the 1,910 patients with infectious complications of SBO, which contributed to their death.

Surgical complications after nephrectomy for Wilms' tumor

We reviewed the charts of 1,910 children enrolled in the Third National Wilms' Tumor Study who underwent primary nephrectomy. Four hundred and ninety-five surgical complications occurred in 379 children (19.8 percent). Patients with inoperable tumors, bilateral renal tumors, peroperative therapy and those who refused treatment were excluded from this review. The most common complication was intestinal obstruction, which occurred in 132 patients (6.9 percent). This was followed by extensive intraoperative hemorrhage (112 patients), defined as blood loss exceeding 50 milliliters per kilogram of body weight. Intraoperative injuries to other visceral organs (including intestine, liver and spleen) occurred in 21 children and extensive vascular injuries were reported in 27 patients. There were nine deaths attributed to surgical complications (0.5 percent), only one of which was intraoperative. Survival of patients with complications was similar to patients without complications when stratified by histologic study and stage. Factors associated with the development of surgical complications included advanced local tumor stage at diagnosis, intravascular tumor extension and resection of other visceral organs at the time of nephrectomy. Complete removal of the tumor is important, but not at the expense of radical removal of adjacent structures, because of gross appearances at operation. They are often not invaded by the tumor, but rather are compressed, distorted or adherent without tumor infiltration. Identification of these groups will aid the surgeon in choosing the appropriate management for these patients at high risk. When initial exploration and precise surgical staging indicate that only a formidable operation will achieve total excision, shrinkage of the tumor with selective use of chemotherapy or radiotherapy, or both, may facilitate removal and decrease surgical morbidity. Preoperative therapy may also be the preferred approach for children with extensive intravascular tumor.