Micronutrient assay for cancer prevention clinical trials: serum retinol, retinyl palmitate, alpha-carotene, and beta-carotene with the use of high-performance liquid chromatography.

Assay of serum levels of retinol, retinyl palmitate, alpha-carotene, and beta-carotene to assess nutritional status, to trials of retinol and/or beta-carotene to assess nutritional status, to monitor compliance with medication schedules, and to conduct toxicity surveillance. The optimal assay method for clinical trial use represents a balance between analytical power and speed/simplicity. Three such methods were evaluated by means of shared samples between two laboratories. Each method required less than 15 minutes per assay and detected all of the analytes of interest. Careful evaluation of calibration materials and procedures permitted different laboratories using different methods to produce results with an interlaboratory variability smaller than the within-laboratory variability for each separate method. Typical precisions for the analytes in serum samples are: retinol, 0.06 relative standard deviation (RSD; standard deviation divided by mean value); retinyl palmitate, 0.08 RSD; alpha-carotene, 0.15 RSD; and beta-carotene, 0.11 RSD. Application of these methods to several hundred samples indicated that retinyl palmitate and beta-carotene levels were indicative of administered retinol and beta-carotene, whereas retinol itself was not. Population variability in pretreatment serum levels of these micronutrients expressed as RSD (retinol, 0.24; alpha-carotene, 1.11; and beta-carotene, 0.98) far exceeded the analytical imprecision in these determinations, confirming that the present assays could meet the needs of current clinical intervention trials.

Risk factors for lung cancer and for intervention effects in CARET, the Beta-Carotene and Retinol Efficacy Trial.

BACKGROUND: Evidence has accumulated from observational studies that people eating more fruits and vegetables, which are rich in beta-carotene (a violet to yellow plant pigment that acts as an antioxidant and can be converted to vitamin A by enzymes in the intestinal wall and liver) and retinol (an alcohol chemical form of vitamin A), and people having higher serum beta-carotene concentrations had lower rates of lung cancer. The Beta-Carotene and Retinol Efficacy Trial (CARET) tested the combination of 30 mg beta-carotene and 25,000 IU retinyl palmitate (vitamin A) taken daily against placebo in 18314 men and women at high risk of developing lung cancer. The CARET intervention was stopped 21 months early because of clear evidence of no benefit and substantial evidence of possible harm; there were 28% more lung cancers and 17% more deaths in the active intervention group (active = the daily combination of 30 mg beta-carotene and 25,000 IU retinyl palmitate). Promptly after the January 18, 1996, announcement that the CARET active intervention had been stopped, we published preliminary findings from CARET regarding cancer, heart disease, and total mortality. PURPOSE: We present for the first time results based on the pre-specified analytic method, details about risk factors for lung cancer, and analyses of subgroups and of factors that possibly influence response to the intervention. METHODS: CARET was a randomized, double-blinded, placebo-controlled chemoprevention trial, initiated with a pilot phase and then expanded 10-fold at six study centers. Cigarette smoking history and status and alcohol intake were assessed through participant self-report. Serum was collected from the participants at base line and periodically after randomization and was analyzed for beta-carotene concentration. An Endpoints Review Committee evaluated endpoint reports, including pathologic review of tissue specimens. The primary analysis is a stratified logrank test for intervention arm differences in lung cancer incidence, with weighting linearly to hypothesized full effect at 24 months after randomization. Relative risks (RRs) were estimated by use of Cox regression models; tests were performed for quantitative and qualitative interactions between the intervention and smoking status or alcohol intake. O'Brien-Fleming boundaries were used for stopping criteria at interim analyses. Statistical significance was set at the .05 alpha value, and all P values were derived from two-sided statistical tests. RESULTS: According to CARET's pre-specified analysis, there was an RR of 1.36 (95% confidence interval [CI] = 1.07-1.73; P = .01) for weighted lung cancer incidence for the active intervention group compared with the placebo group, and RR = 1.59 (95% CI = 1.13-2.23; P = .01) for weighted lung cancer mortality. All subgroups, except former smokers, had a point estimate of RR of 1.10 or greater for lung cancer. There are suggestions of associations of the excess lung cancer incidence with the highest quartile of alcohol intake (RR = 1.99; 95% CI = 1.28-3.09; test for heterogeneity of RR among quartiles of alcohol intake has P = .01, unadjusted for multiple comparisons) and with large-cell histology (RR = 1.89; 95% CI = 1.09-3.26; test for heterogeneity among histologic categories has P = .35), but not with base-line serum beta-carotene concentrations. CONCLUSIONS: CARET participants receiving the combination of beta-carotene and vitamin A had no chemopreventive benefit and had excess lung cancer incidence and mortality. The results are highly consistent with those found for beta-carotene in the Alpha-Tocopherol Beta-Carotene Cancer Prevention Study in 29133 male smokers in Finland.

Randomized phase III intergroup trial of isotretinoin to prevent second primary tumors in stage I non-small-cell lung cancer.

BACKGROUND: Promising data have suggested that retinoid chemoprevention may help to control second primary tumors (SPTs), recurrence, and mortality of stage I non-small-cell lung cancer (NSCLC) patients. METHODS: We carried out a National Cancer Institute (NCI) Intergroup phase III trial (NCI #I91-0001) with 1166 patients with pathologic stage I NSCLC (6 weeks to 3 years from definitive resection and no prior radiotherapy or chemotherapy). Patients were randomly assigned to receive a placebo or the retinoid isotretinoin (30 mg/day) for 3 years in a double-blind fashion. Patients were stratified at randomization by tumor stage, histology, and smoking status. The primary endpoint (time to SPT) and the secondary endpoints (times to recurrence and death) were analyzed by log-rank test and the Cox proportional hazards model. All statistical tests were two-sided. RESULTS: After a median follow-up of 3.5 years, there were no statistically significant differences between the placebo and isotretinoin arms with respect to the time to SPTs, recurrences, or mortality. The unadjusted hazard ratio (HR) of isotretinoin versus placebo was 1.08 (95% confidence interval [CI] = 0.78 to 1.49) for SPTs, 0.99 (95% CI = 0.76 to 1.29) for recurrence, and 1.07 (95% CI = 0.84 to 1.35) for mortality. Multivariate analyses showed that the rate of SPTs was not affected by any stratification factor. Rate of recurrence was affected by tumor stage (HR for T(2) versus T(1) = 1.77 [95% CI = 1.35 to 2.31]) and a treatment-by-smoking interaction (HR for treatment-by-current-versus-never-smoking status = 3.11 [95% CI = 1.00 to 9.71]). Mortality was affected by tumor stage (HR for T(2) versus T(1) = 1.39 [95% CI = 1.10 to 1.77]), histology (HR for squamous versus nonsquamous = 1.31 [95% CI = 1.03 to 1.68]), and a treatment-by-smoking interaction (HR for treatment-by-current-versus-never-smoking = 4.39 [95% CI = 1.11 to 17.29]). Mucocutaneous toxicity (P<.001) and noncompliance (40% versus 25% at 3 years) were higher in the isotretinoin arm than in the placebo arm. CONCLUSIONS: Isotretinoin treatment did not improve the overall rates of SPTs, recurrences, or mortality in stage I NSCLC. Secondary multivariate and subset analyses suggested that isotretinoin was harmful in current smokers and beneficial in never smokers.

The clinical evaluation of cancer chemoprevention agents: defining and contrasting phase I, II, and III objectives.

A number of potential chemoprevention agents are now in clinical trials to evaluate their efficacy. A larger number of compounds await clinical investigation. The design of phase I and phase II trials for cancer chemoprevention agents requires a different approach than for cytotoxic agents. The unique nature of the target populations, the scope of side effect evaluation, and the potential duration of treatment must be considered in the design of these trials. This article will discuss the effect these variables have on the evaluation of a chemoprevention agent and propose models for the phase I and phase II trials of chemoprevention agents.

Effect of verapamil on in vitro cytotoxicity of adriamycin and vinblastine in human tumor cells.

Verapamil has been shown to reverse acquired drug resistance to Adriamycin (ADR) and vinblastine in the P388 leukemia and Ehrlich ascites carcinoma model systems. Because of its potential clinical application, we evaluated the ability of verapamil to modulate the effect of ADR and vinblastine on the in vitro cloning of fresh human tumor cells. Fifty-three tumors were cloned in a soft agar system. Continuous exposure to verapamil at concentrations of 1.0, 5.0, and 10.0 micrograms/ml, did not significantly modulate the overall inhibitory activity of ADR and vinblastine (P greater than 0.05). There was no evidence of an effect when results were analyzed by tumor type or previous treatment except in the subgroup of 13 tumors obtained from patients who previously had a clinical response to ADR but were relapsing at the time the tumor specimen was obtained. In this population, at three concentrations of ADR, there was a significant modulation of drug effect (P = 0.10, 0.03, 0.03, respectively). In each subgroup, some tumors showed marked modulation of drug effect by verapamil. These results suggest that the mechanisms of acquired in vivo resistance to ADR may be similar to those occurring in cell lines. However, the effect on human tumors was minor as compared to the results with cell lines. The in vivo significance of this finding remains to be determined.

Pharmacokinetics of 13-cis-retinoic acid in patients with advanced cancer.

13-cis-Retinoic acid (13-CRA) is a synthetic analog of vitamin A effective reversing preneoplastic lesions in both humans and animals. To study its physiochemical properties and disposition kinetics, we developed a rapid, sensitive, and precise high-performance liquid chromatography assay for 13-CRA in biological samples. This assay system resulted in a clear separation of 13-CRA from all-trans-retinoic acid and retinol and had a detection limit of 20 ng/ml plasma. Recovery was 89 +/- 6% (S.D.) at equivalent physiological concentrations with a precision of 8%. To study the disposition kinetics in humans, 13 patients received a p.o. bolus of 13-CRA and had blood samples collected at timed intervals. For the 10 patients studied on the first day of 13-CRA administration, the mean time to peak plasma concentration was 222 +/- 102 min. Interpatient peak 13-CRA plasma concentrations were found to be variable, suggesting irregular gastrointestinal absorption. Beta-Phase t 1/2 was approximately 25 hr. The prolonged terminal-phase plasma half-life may represent biliary excretion and enterohepatic circulation.

Phase I trial of retinol in cancer patients.

Vitamin A (all-trans-retinol) and its analogues are undergoing evaluation as antineoplastic and chemoprevention agents. Because its toxicity and activity are poorly defined, we have completed a phase I trial of retinol. Retinol was administered to 13 cancer patients in daily doses ranging from 100,000 units/m2 to 350,000 units/m2. Neuropsychiatric changes were the earliest dose-limiting symptomatic toxicities, noted in 3 of 5 patients receiving more than 240,000 U/m2 for 3-4 months. Two patients receiving more than 270,000 U/m2 developed hepatomegaly after 3 and 4 months. Liver biopsies were consistent with vitamin A toxicity. Three patients receiving 200,000 U/m2 developed an increase in serum triglycerides concentration. Mild skin and mucous membrane dryness occurred in most patients receiving more than 150,000 U/m2. A mixed response was seen in one patient with melanoma. Because of neuropsychiatric and hepatic toxicity a retinol dose of 200,000 U/m2/day is recommended for future phase II trials.

Pilot trial of murine monoclonal antibodies in patients with advanced melanoma.

We have performed a pilot trial with two murine monoclonal antibodies (MAbs) directed against two surface membrane antigens, p97 (MAb 96.5) and a proteoglycan antigen (MAb 48.7) primarily expressed in human melanoma. Five patients with disseminated melanoma were studied, all of whom had multiple cutaneous metastases. Four patients received 212 mg each of antibodies 96.5 and 48.7, and one patient received 424 mg of antibody 96.5 alone. MAbs were administered in escalating doses over ten days in four patients and over six days in one patient. There was no clear treatment-related toxicity. Immunohistologic studies on biopsies taken two to 240 hours after treatment showed extensive binding of murine immunoglobulin to melanoma cells, but not to normal cells in the same section. The intensity of antibody binding was uniform across the diameter of the tumor nodules. In two patients, no murine immunoglobulin was detected in biopsies taken ten days after the last treatment. The mean initial elimination half-life (T1/2) of infused MAbs was 40.5 hours in two patients who received a combination of both antibodies and 53.0 hours in a third patient who received only antibody 96.5; none of these patients had previously been exposed to mouse immunoglobulin. The elimination T1/2 was 21 hours in a fourth patient, who three months previously had tumor imaging with 2-mg radiolabeled antigen-binding fragments (Fab) prepared from antibody 48.7. Serum from this patient appeared to contain anti-idiotypic antibodies which specifically bound Fabs of antibody 48.7. Three other patients also developed human anti-mouse antibodies. There were no objective tumor regressions, and no histologic changes were noted on biopsy.

Phase I trial of murine monoclonal antibody L6 in breast, colon, ovarian, and lung cancer.

Murine monoclonal antibody (MAb) L6 binds to an antigen expressed on the surface of breast, colon, ovary, and nonsmall-cell lung cancer. This antibody effects antibody-dependent cellular cytotoxicity (ADCC) with human mononuclear cells and complement-dependent cytotoxicity (CDC) with human complement. Because of these activities, we conducted a phase I trial of MAb L6 in patients with advanced cancer. Nineteen patients whose tumors highly expressed antigen were selected for this trial. Eighteen were evaluable. MAb L6 was administered at dose levels ranging from 5 mg/m2/d to 400 mg/m2/d for 7 days and was well tolerated. The only side effects detected were fever and headaches at the highest dose levels. The serum half-life of L6 was directly related to dose and ranged from a mean of 7.7 hours at 5 mg/m2/d to 29.1 hours at 400 mg/m2/d. Peak serum concentrations ranged from 0.22 micrograms/mL to 362 micrograms/mL. Biopsies at the end of treatment showed L6 to localize well to tumor cells with apparent in vivo saturation occurring at dose levels above 100 mg/m2/d. Thirteen patients formed human antimouse antibodies (HAMA), some as early as day 13. One patient with recurrent breast cancer on the chest wall achieved a complete remission. The response was first noted at 5 weeks and a pathologic complete remission occurred at 14 weeks. Because of its favorable binding properties and the encouraging clinical effect observed, future evaluation of this MAb appears warranted.

Treatment of small cell lung cancer with VP-16, vincristine, doxorubicin (Adriamycin), cyclophosphamide (EVAC), and high-dose chest radiotherapy.

Seventy-one previously untreated patients with small cell lung cancer (SCLC) received a combination of VP-16, vincristine, doxorubicin (Adriamycin), and cyclophosphamide (EVAC) repeated every three weeks. Limited-disease (LD) patients and extensive-disease (ED) patients achieving a complete response (CR) or partial response (PR) after four to six cycles of EVAC received 4,000 rads over four weeks whole-brain radiotherapy (RT) and 5,000 rads over five weeks RT to the original pulmonary primary and mediastinum. ED patients with persisting disease outside the chest after six cycles of EVAC continued chemotherapy and did not receive RT. After RT was completed, EVAC was continued for a total treatment duration of 24 months. Of 65 patients evaluable for response 76% (25 of 33) of LD patients and 34% (11 of 32) of ED patients achieved a CR prior to RT; two additional ED patients achieved a CR after RT. Median survival for all 71 patients was 48 weeks (range, one to 207 weeks); median survival for 33 LD patients was 92 weeks and for 38 ED patients it was 36 weeks. Nine of 25 LD patients and 10 of 13 ED patients have relapsed from CR. The EVAC-RT protocol is promising in view of the high CR rate and long remission duration achieved, especially among patients with LD.

Treatment of limited small-cell lung cancer with concurrent etoposide/cisplatin and radiotherapy followed by intensification with high-dose cyclophosphamide: a Southwest Oncology Group study.

Between March 1986 and May 1988, the Southwest Oncology Group enrolled 58 previously untreated patients with limited small-cell lung cancer on a treatment program that administered high-dose cyclophosphamide (150 mg/kg) as late intensification. Treatment consisted of induction chemo-radiotherapy, (weeks 1 to 11), consolidation chemotherapy (weeks 11 to 18), and intensification (week 18). Median age was 61.5 years. Eighty-nine percent of patients had a Southwest Oncology Group (SWOG) performance status of 0-1. Twenty-one patients completed all prescribed treatments. There were seven treatment-related deaths, four as a result of intensification. Fifty-six patients are available for response analysis. Thirty-two patients achieved a complete remission (CR) (57%) and fifteen achieved a partial remission (PR) (26%). Median survival for all patients is 11.1 months. Among the 21 patients who received intensification, nine remain alive in a CR with a median survival of 27 months. This sequence of treatments was not associated with a survival advantage for the group as a whole, possibly because of the toxicity of induction and consolidation treatment and the delayed administration of high-dose cyclophosphamide.

Treatment of limited small-cell lung cancer with etoposide and cisplatin alternating with vincristine, doxorubicin, and cyclophosphamide versus concurrent etoposide, vincristine, doxorubicin, and cyclophosphamide and chest radiotherapy: a Southwest Oncology Group Study.

The Goldie-Coldman model explaining the kinetics of tumor cell kill and drug resistance has a potential application in designing chemotherapy regimes. In this Southwest Oncology Group (SWOG) trial we tested the alternation of two potentially noncrossresistant drug combinations with a concurrent drug combination in patients with limited small-cell lung cancer. The concurrent drug combination consisted of etoposide (VP-16), 75 mg/m2/intravenously (IV), days 1, 2, and 3; vincristine, 1.0 mg/m2/IV, days 1 and 8; Adriamycin (doxorubicin; Adria Laboratories, Columbus, OH), 40 mg/m2/IV, day 1; and cyclophosphamide, 750 mg/m2/IV, day 1 (EVAC). The alternating combination consisted of VP-16, 100 mg/m2/IV, days 1, 2, and 3; and cisplatin (CDDP), 100 mg/m2/IV, day 1, alternating with vincristine, 1.0 mg/m2/IV, days 1 and 8; Adriamycin, 50 mg/m2/IV, day 1; and cyclophosphamide, 750 mg/m2/IV, day 1 (VP-16/CDDP-VAC). Chemotherapy was administered at 3-week intervals for six cycles both before and after chest (5,000 rads/5 weeks) and whole brain radiotherapy (3,000 rads/2 weeks). One hundred ninety-nine patients received EVAC and 201 received the alternating combination. There was no significant difference in the response rate to the initial six cycles of treatment with EVAC (CR, 40%) versus the alternating combination (CR, 38%). There was no significant difference between the best response, EVAC (CR, 48%) and VP-16/CDDP-VAC (CR, 51%). Median survival for all randomized patients on EVAC is 15.1 months versus 16.5 months on the alternating combination (P = .58). Toxicities consisted primarily of bone marrow suppression, anorexia, nausea and vomiting, peripheral neuropathies, and alopecia. As in previous trials, the chest was the most common site of relapse (33%). There were no differences in the incidence and sites of relapse between the two treatment arms. These treatments appear equally effective at inducing remission and prolonging survival in patients with small-cell lung cancer.

Changes in cholesterol and triglyceride concentrations in the Vanguard population of the Carotene and Retinol Efficacy Trial (CARET).

BACKGROUND: The Beta-Carotene and Retinol Efficacy Trial (CARET) was terminated 21 months ahead of schedule due to an excess of lung cancers. Deaths from cardiovascular disease also increased (relative risk=1.26 (95% confidence interval (CI) 0.99-1.61)) in the group assigned to a combination of 30 mg beta-carotene and 25 000 IU retinyl palmitate (vitamin A) daily. The basis for increased cardiovascular mortality is unexplained. DESIGN: We analyzed data on serum lipids, available for 1474 CARET Vanguard participants who were enrolled in the two CARET pilot studies and transitioned to the Vanguard study. Total cholesterol and triglycerides were measured 2 months prior to, 4 and 12 months following randomization, and annually thereafter for up to 7 y. INTERVENTION: In the asbestos-exposed pilot (N = 816), participants were assigned to beta-carotene and retinol or to placebo; in the smokers pilot (N = 1029), participants were assigned to beta-carotene, retinol, a combination, or placebo. RESULTS: Serum cholesterol showed a decline over time in both arms; serum triglycerides had a continuous decline over time in the placebo arm, but an initial increase that persisted in the active arm. Both serum cholesterol concentrations (P < 0.0003) and serum triglycerides (P < 0.0001) were significantly higher in the participants receiving vitamin A and/or a combination of vitamin A and beta-carotene (n = 863) as compared to the placebo group (n = 611). Those in this active intervention group had an average cholesterol concentration 5.3 mg/dl (0.137 mmol/l) higher than those in the placebo arm. CONCLUSION: The differences in cholesterol and triglyceride concentrations between the groups following randomization may account in part for the unexpected excess in cardiovascular deaths seen in the active intervention arm of CARET.

Prevention of lung cancer.

Lung cancer is the major cause of death in industrialized western societies. Its link to tobacco abuse is well established and efforts should be made to eliminate this potent environmental carcinogen. The concept of chemoprevention, the use of agents to inhibit and reverse lung cancer carcinogenesis, has great appeal. The CARET study, conducted in 18,000 high-risk smokers in the US, found that a combination of beta-carotene and retinyl palmitate resulted in a 28% increase in the incidence of lung cancer. A similar study conducted in Finland, the ATBC trial utilizing alpha tocopherol and beta-carotene, had similar findings for the group taking beta-carotene. These two trials have caused a rethinking of the use of natural compounds as chemoprevention agents. These agents should no longer be regarded as harmless, but as having potential toxicities. A new approach in the chemoprevention of cancer has been the concept of surrogate endpoints, biological changes that are on the pathway to cancer. Trials are underway to determine what are appropriate surrogate endpoints for lung cancer chemoprevention trials.

13-Cis-retinoic acid: pharmacology, toxicology, and clinical applications for the prevention and treatment of human cancer.

Retinoids, particularly 13-cis-retinoic acid, have shown great promise against a number of benign, but serious dermatological conditions. In animal models, 13-cis-retinoic acid functions is a potent antipromoter whether a cancer has been initiated by chemical, physical, or viral agents. Additionally, substantial antiproliferative activity of this compound has been demonstrated in vitro in many culture systems. Clinical activity noted against several types of skin malignancies has led to several investigations to determine the anticancer activity of 13-cis-retinoic acid. Response of a variety of preneoplastic and neoplastic lesions of epithelial histology has been demonstrated. The toxicity of 13-cis-retinoic acid largely reflects its tissue distribution with skin and subcutaneous side-effects limiting dose escalation. The pharmacology and pharmacokinetics of 13-cis-retinoic acid has been explored in a number of patients and a long terminal half-life demonstrated. This review will discuss 13-cis-retinoic acid as a good model for a biological response modifier.

The effect of long-term beta-carotene and vitamin A administration on serum concentrations of alpha-tocopherol.

Many micronutrients are currently being tested for cancer prevention activity. A short-term study recently suggested that two of these nutrients, beta-carotene and alpha-tocopherol, may have an adverse interaction, with beta-carotene supplementation leading to markedly decreased serum concentrations of alpha-tocopherol. We have analyzed the effect of beta-carotene supplementation on serum concentrations of alpha-tocopherol in 2319 participants enrolled in the Carotene and Retinol Efficacy Trial who have taken beta-carotene and vitamin A for up to 6 years. One thousand thirty-five participants enrolled in two pilot trials to the Carotene and Retinol Efficacy Trial had serum collected at yearly intervals; an additional 1284 recently recruited participants had serum collected at biennial intervals. Using standard high pressure liquid chromatography techniques, with attention to quality control, these samples were analyzed for beta-carotene and alpha-tocopherol. After up to 6 years of supplementation with beta-carotene (30 mg/day) and vitamin A (25,000 international units/day) we found a small but statistically significant increase in the serum concentration of alpha-tocopherol in participants taking the active agents. No evidence of a decrease was found in any of the subpopulations examined. We conclude that long-term supplementation with the combination of beta-carotene and vitamin A does not decrease serum concentrations of alpha-tocopherol. Our long-term trial validates results from several shorter trials conducted by others. The concept of adverse interactions between supplemental micronutrients is important. All cancer prevention trials should closely monitor serum concentrations of micronutrients, as well as the incidence of other significant disease.

Long-term vitamin A does not produce clinically significant hypertriglyceridemia: results from CARET, the beta-carotene and retinol efficacy trial.

Retinol and retinyl palmitate in the moderate doses tested in chemoprevention trials produce only a negligible increase in serum triglyceride levels. The effect is nonprogressive and is not associated with the kind of exaggerated response reported for interacting factors such as presence of diabetes mellitus and/or high baseline values for serum triglyceride concentration. These findings seem to represent an advantage for safety of retinol in relation to isotretinoin (13-cis-retinoic acid).

The association between participant characteristics and serum concentrations of beta-carotene, retinol, retinyl palmitate, and alpha-tocopherol among participants in the Carotene and Retinol Efficacy Trial (CARET) for prevention of lung cancer.

As part of the multicenter Carotene and Retinol Efficacy Trial (CARET) lung cancer prevention study, we investigated the associations of baseline demographic, health history, and nutritional intake information and the prerandomization serum concentrations of beta-carotene, retinol, retinyl palmitate, and alpha-tocopherol in a random subset of 1182 smokers and asbestos-exposed workers. Dietary intake was estimated via a self-administered food frequency questionnaire using the recently updated United States Department of Agriculture/National Cancer Institute database. In multiple regression analyses, supplemental vitamin use was the strongest predictor of each of the four analytes. There was a statistically significant inverse relationship between smoking and beta-carotene concentrations. Lower serum beta-carotene was associated with current smoking, higher daily cigarettes smoked, and more pack-years. Serum beta-carotene concentrations were higher with increasing years since stopping cigarette use, which suggests a biological mechanism for the lower serum concentration of beta-carotene in smokers. We found weak inverse associations between alcohol intake and the serum concentrations of both beta-carotene and retinol. As in previous reports, dietary intakes as measured by a food frequency questionnaire can only moderately predict serum concentrations of beta-carotene, retinol, retinyl palmitate, and alpha-tocopherol.

The Carotene and Retinol Efficacy Trial (CARET) to prevent lung cancer in high-risk populations: pilot study with cigarette smokers.

In preparation for a phase IV lung cancer chemoprevention trial, we conducted a pilot trial of beta-carotene and retinol in high-risk smokers. Eligibility criteria were ages of 50-69 years, a smoking history of at least 20 pack-years, and either being a current smoker or having quit within the past 6 years. Participants were recruited by mailing an interest survey to 29,928 age-selected members of King County Medical Blue Shield. We randomized 1,029 women and men to one of four intervention arms: placebo, retinol, 25,000 international units/day; beta-carotene, 30 mg/day; or retinol plus beta-carotene. Participants were followed for side effects and adherence every 2 months either by a telephone call or a clinic visit. Blood was sampled for retinoid, carotenoid, and liver function analyses annually. beta-carotene and retinol were well tolerated during the follow-up period, which had a median of 1.5 years and a maximum of 3.3 years. Yellowing of the skin was seen in both beta-carotene arms. No differences were seen among arms or over time in incidence or severity of the other 15 monitored symptoms and signs or in serum liver function tests. Adherence was good: 83% of participants remained active on study at 1 year and 75% at 2 years. Serum beta-carotene increased from a prerandomization median concentration of 170 to 2100 ng/ml after 4 months of supplementation, and retinyl palmitate median levels more than tripled.(ABSTRACT TRUNCATED AT 250 WORDS)

Predictors of serum selenium in cigarette smokers and the lack of association with lung and prostate cancer risk.

Epidemiological studies have suggested that low levels of selenium are associated with a higher incidence of both lung and prostate cancer. We analyzed the selenium serum concentration in 356 Carotene and Retinol Efficacy Trial (CARET) participants who later developed lung cancer and 356 matched controls and in 235 prostate cancer cases and 456 matched controls. Serum samples were obtained a mean of 4.7 years before diagnosis for both tumor types. Controls were matched to cases by year of randomization, age, smoking status, treatment arm, exposure population (asbestos workers or cigarette smokers), and year of blood draw. In the control population (n = 820), significant predictors of low serum selenium concentration were current smoking status and East Coast locations of the study center. Overall, there was no significant difference in mean serum selenium in lung cancer cases versus controls (11.91 microg/dl versus 11.77 microg/dl) or prostate cancer cases versus controls (11.48 microg/dl versus 11.43 microg/dl). No statistically significant trend in odds ratio was seen across quartiles of serum selenium for lung cancer (P = 0.49) or prostate cancer (P = 0.69). In a subpopulation of 174 prostate cancer patients who had clinical and pathological staging material reviewed, there was no association between serum selenium and Gleason score or clinical or pathological stage. In the CARET population of current and former smokers consuming an ad libitum diet, the serum concentration of selenium was not a risk factor for either lung cancer or prostate cancer.