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Toenail arsenic and bladder cancer PowerPoint Presentation

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  • Slide 1 - Toenail arsenic and bladder cancer: findings from a cohort study of male smokers Dominique S. Michaud Assistant Professor Department of Epidemiology Harvard School of Public Health, Boston
  • Slide 2 - Outline Arsenic and bladder cancer High dose studies Low dose studies Arsenic measurements in toenails Methods: ATBC study Results Discussion Future directions
  • Slide 3 - High arsenic levels and bladder cancer Ecological studies have consistently reported elevated mortality rates of bladder cancer in arsenic endemic areas: Taiwan Argentina northern Chile
  • Slide 4 - High arsenic levels and bladder cancer Elevated bladder cancer incidence and mortality rates have also been observed in cohort studies: in arsenic endemic areas (Taiwan) industrially contamination water (Japan) Fowler’s solution (potassium arsenite)
  • Slide 5 - Risk levels in U.S. EPA 50 g/L in water supplies 10 g/L by January 2006 used extrapolation models to determine risk levels National Research Council Subcommittee “Arsenic in Drinking Water Report”, 1999 and 2001 reviewed the literature, used extrapolation models to assess risk estimated that there are lifetime excess cancer risks in the U.S. for bladder and lung cancers at arsenic drinking water levels between 3-20 g/L
  • Slide 6 - Extrapolation studies--limitations Risk assessment models make assumptions about dose-response curves different models result in different risk estimates Relied heavily on Taiwan data differences in environment, diet and genetic susceptibilities in U.S. and Taiwan Studies used for extrapolations had few bladder cancer cases
  • Slide 7 - Low-level arsenic and bladder cancer Chiou et al. (northeastern Taiwan) arsenic in well-water: <0.15 g/L to >3,000 g/L 8,102 residents were recruited information on hx of well water intake, residential hx, smoking, disease hx, other characteristics collected by interview obtained well water samples from 85% of households incidence data obtained from annual interviews, community hospitals, cancer registry profiles, and national death certifications AJE 2001,153:411-18
  • Slide 8 - Low-level arsenic and bladder cancer Chiou et al. 18 incident urinary tract cancers 11 were transitional cell carcinoma adjusted for age, smoking, gender, duration of well water drinking <10 10-50 50-100 >100 g/L 1.0 1.6 (0.3-8.4) 2.3 (0.4-14) 4.9 (1.2-20) 1.0 1.9 (0.1-32) 8.1 (0.7-98) 15.1 (1.7-139) AJE 2001,153:411-18
  • Slide 9 - Low-level arsenic and bladder cancer Bates et al. (Argentina) arsenic levels: 0 to >200 µg/L, mean 164 µg/L 114 case-control pairs, matched on age, sex, and county water measurements for each residence individual data on smoking, occupation, beverages no association between exposure and bladder cancer risk overall elevated risk among those with exposures 51-70 years prior to diagnosis (smokers only) AJE 2004,159:381-389
  • Slide 10 - Low-level arsenic and bladder cancer Bates et al. (Utah) arsenic levels: 0.5 to 160 µg/L, mean 5 µg/L case-control study arsenic levels in public drinking water available from 88 community supplies in Utah information on residential hx, drinking water source at each residence, hx smoking, occupation cumulative exposure index (water intake/total fluid intake x duration residence x mean arsenic level town) AJE 1995,141:523-30
  • Slide 11 - Low-level arsenic and bladder cancer Bates et al. 71 cases, 160 controls (lived in study town >½ lives) <33 33-52 53-73 >73 mg/L x yrs 1.0 0.69 (0.3-1.5) 0.54 (0.3-1.2) 1.00 (0.5-2.1) 30-39 years prior to 1978: <8 8-9 10-12 >13 mg/L x yrs 1.0 1.27 (0.4-3.6) 1.26 (0.4-3.6) 3.07 (1.1-8.4) AJE 1995,141:523-30
  • Slide 12 - Low-level arsenic and bladder cancer Kurttio et al. (Finland) arsenic levels: <0.05 to 64 µg/L, median 0.14 µg/L case-cohort study design cohort: towns where <10% of water from municipal supplies, born 1900-1930, same address 1967-1980 884 incident bladder cases using Finnish Cancer Registry (1981-1995) 4,590 persons selected in the reference cohort sampled wells for 509 subjects (1996) 275 controls available; 61 cases 183 controls; 42 cases with questionnaire data Environ Health Perspect 1999,107:705-10
  • Slide 13 - Low-level arsenic and bladder cancer Kurttio et al. Relative risks adjusted for age, sex, smoking Latency <0.1 0.1-0.5 >0.5 µg/L Shorter 1.0 1.53 2.44 (1.11-5.37) Longer 1.0 0.81 1.51 (0.67-3.38) Environ Health Perspect 1999,107:705-10
  • Slide 14 - Low-level arsenic and bladder cancer Steinmaus et al. (Nevada and CA) arsenic levels: 0 to >120 µg/L controls frequency matched by age and gender interview by telephone: residential hx, fluid intake hx, tap water from home and work, occupation, smoking hx arsenic measurements obtained from Health Services, included historical measurements linked residence to water arsenic measurement for each residence 181 cases, 328 controls AJE 2003,158:1193-1201
  • Slide 15 - Low-level arsenic and bladder cancer Steinmaus et al. <10 10-80 >80 µg/L Highest 20-year average, 40-year lag 160 10 11 1.0 1.28 1.70 (0.73-3.96) Exposure 51-60 yr prior to diagnosis 166 3 12 1.0 0.73 1.86 (0.80-4.33) AJE 2003,158:1193-1201
  • Slide 16 - Low level arsenic studies: limitations Water arsenic sources only Changes in arsenic levels in water over time (not taken into account) Selection biases: healthier controls restricted to those with available water measurements Arsenic levels outside of study area (negligible) Small numbers of bladder cancers largest study had 181 cases multiple sub-analyses
  • Slide 17 - Use of toenails to measure arsenic Toenails grow slowly (several months to a year)—reflect internal dose 9-18 months prior to collection Reproducibility over 6-year period correlation for arsenic r=0.54 Toenails used in study on arsenic and skin cancer (Karagas et al. AJE 2001)
  • Slide 18 - METHODS
  • Slide 19 - ATBC study Alpha-Tocopherol and Beta-Carotene (ATBC) Prevention Trial 29,133 male smokers 50-69 years old Living in southwestern Finland
  • Slide 20 - ATBC study Alpha-tocopherol (50 mg/day) Beta-carotene (20 mg/day) 2x2 factorial design Double-blind, placebo-controlled Incidence of lung cancer
  • Slide 21 - ATBC study Timeline Recruitment Trial Follow-up 1985 1986 1987 1988 1993 1998
  • Slide 22 - ATBC study Exclusions at baseline: smoked <5 cigarettes per day history of cancer a serious disease (limiting long-term participation) users of vitamins E, A or beta-carotene supplements in excess of predefined doses
  • Slide 23 - Baseline characterisics Health status Smoking history Height and weight Education Occupation Physical activity Dietary questionnaire
  • Slide 24 - Toenail samples Toenails were collected from all participants at the time of recruitment (1985-1988) A number of samples had been pulverized for previous studies; the remaining whole toenails were cleaned for external contamination
  • Slide 25 - Case ascertainment Finnish Cancer Registry (FCR) 95% complete within 0.8-years Hospital Discharge Registry Death Certificates Histologically confirmed incident bladder cancer cases 331 cases with toenail clippings
  • Slide 26 - Nested case-control design 1:1 matching: age (within 2-years interval) date at toenail collection (+/- 1 month) intervention group smoking level (< or >35 years smoked)
  • Slide 27 - Arsenic determination Nuclear Reactor Program, North Carolina State University Neutron Activation Analysis (NAA): Irradiated for 14 hrs each in the PULSTAR reactor at a power of 900 kW (with rotating exposure ports) and were left to decay for 5-6 days Gamma spectroscopy system to analyze for arsenic
  • Slide 28 - Arsenic determination Quality control: Dogfish muscle and liver (certified by the National Research Council Canada) Tuna (certified by the US National Institute for Standards and Technology) Coefficient of variation (CV) % 6.98 overall using reference material 1.13 for three duplicate samples
  • Slide 29 - Detection limit and exclusions 51 cases and 38 controls were excluded because they had non-detectable levels of arsenic (and when the detection limit was greater than 0.09 μg/g) For 59 cases and 69 controls which also had non-detectable values but had detection limits equal or less than 0.09 μg/g, we assigned an arsenic value equal to the detection limit divided by 2. The final sample size was 280 cases and 293 controls.
  • Slide 30 - Statistical analysis Unconditional logistic regression models: matching factors smoking cessation smoking inhalation education level place of residence Tests for trend were conducted by using the median values for each quartile and modeling it as a continuous variable
  • Slide 31 - RESULTS Michaud et al. AJE 2004,160:853-859
  • Slide 32 - Toenail arsenic levels Cases (n=280) Controls (n=293) Median (range) Median (range) Arsenic level, g/g 0.110 (0.014-2.62) 0.105 (0.017-17.5) Karagas et al. 2001 0.089 (0.01 to 0.81) Nichols et al. 1998 0.088 (0.01 to 2.57) Garland et al. 1993 0.083
  • Slide 33 - Baseline characteristics Cases (n=280) Controls (n=293) Mean (SD) Mean (SD) Age, years 59.4 (5.1) 59.5 (5.0) Years smoked regularly 39.8 (7.4) 39.1 (8.0) Cigarettes per day 20.2 (7.8) 19.5 (7.8) Smoking inhalation, % Never/seldom 6.1 5.8 Often/always 93.9 94.2 Smoking cessation, % 15.4 16.0 Urban residence, % 45.4 38.9 Education level, % Primary school 67.5 70.0 High school 7.5 5.5 Vocational 20.4 20.8 University 4.6 3.7 Beverage intake, mL/d 1534 (471) 1569 (523)
  • Slide 34 - Arsenic and bladder cancer risk Median Cases Controls OR 95% CI arsenic level (g/g) Quartile 1 0.033 65 74 1.0 2 0.079 71 73 0.89 0.55-1.42 3 0.130 73 73 0.97 0.60-1.55 4 0.245 71 73 1.00 0.63-1.60 p trend=0.65 *Unconditional logistic regression models adjusted for matching factors, cigarettes/day (continuous) and years smoked (continuous).
  • Slide 35 - Arsenic and bladder cancer risk Median Cases Controls OR* 95% CI arsenic level (g/g) Percentile <50 0.050 136 147 1.0 50.1 – 75 0.130 73 72 1.10 0.73-1.64 75.1 – 90 0.198 37 44 0.93 0.56-1.54 90.1 – 95 0.333 20 16 1.38 0.68-2.80 95.1 –100 0.757 14 14 1.14 0.52-2.51 p trend=0.61 *Unconditional logistic regression models adjusted for matching factors, cigarettes/day (continuous) and years smoked (continuous).
  • Slide 36 - Arsenic and bladder cancer, by smoking duration Tertile of arsenic (g/g) 0.017 – 0.070 0.071 – 0.137 > 0.137 OR* OR 95% CI OR 95% CI Yrs smoked <35 1.0 1.14 0.5-2.9 1.30 0.6-3.1 36-45 1.0 0.90 0.5-1.5 1.16 0.7-1.9 >45 1.0 1.46 0.5-4.1 2.30 0.8-6.9 *Unconditional logistic regression models adjusted for matching factors, cigarettes/day (continuous) and years smoked (continuous).
  • Slide 37 - DISCUSSION
  • Slide 38 - Interpretation of toenail arsenic levels Karagas et al. AJE 2000 Collected data on water arsenic levels and compared them to toenail arsenic N=280 Water level range: 0.002 to 66.6 µg/L Toenail arsenic: <0.01 to 0.81 µg/g Correlations: 0.46 overall, 0.65 for > 1 µg/L A 10-fold increase in water arsenic was associated with a doubling in toenail conc.
  • Slide 39 - Interpretation of toenail arsenic levels Toenail arsenic levels in terms of water concentrations: 50th percentile = ~ 2 µg/L 75th percentile = ~ 10 µg/L 90th percentile = ~ 50 µg/L 95th percentile = ~ 100 µg/L
  • Slide 40 - Potential biological mechanisms Induction of oxidative damage to DNA Inhibition of DNA repair Altered DNA methylation and gene expression Changes in intracellular levels of p53 protein Induction of apoptosis
  • Slide 41 - Strengths Biomarker Reflects internal exposure Long-term marker Prospective study Samples collected prior to disease Data on smoking, other potential confounders Reasonable power
  • Slide 42 - Limitations Measurement error Relevant time period 30-40 years earlier Mobility Range of exposure Generalizability Men Smokers
  • Slide 43 - Previous findings among smokers Bates et al., U.S. No association among never smokers OR = 8.70 (90% CI = 1.7- 44) for high vs. low cumulative arsenic exposure 30-39 yrs prior to diagnosis Kurttio et al., Finland No association among never or ex-smokers RR 6.9 (95% CI = 1.2-93) for >0.5 vs. <0.1 µg/L water arsenic levels Steinmaus et al., U.S. No association among never smokers OR = 4.01 (95 % CI = 1.16-13.9) for >80 vs. <10 µg/day highest 20-year average
  • Slide 44 - Summary No association between toenail arsenic and bladder cancer risk in ATBC study Low level arsenic exposure is unlikely to explain a substantial excess bladder cancer risk
  • Slide 45 - Future directions Studies with toenail arsenic levels in the U.S. Larger case numbers Longer latency periods Data on selenium levels Genetic susceptibility
  • Slide 46 - Acknowledgements National Cancer Institute Demetrius Albanes Ken Cantor Margaret Wright Phil Taylor National Public Health Institute, Finland Jarmo Virtamo Dept. Nuclear Engineering, North Carolina State University Scott Lassell

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