Toenail arsenic and bladder cancer: findings from a cohort study of male smokers Dominique S....

Toenail arsenic and bladder cancer: Toenail arsenic and bladder cancer: findings from a cohort study of male findings from a cohort study of male smokerssmokers

Dominique S. MichaudAssistant Professor

Department of EpidemiologyHarvard School of Public Health, Boston

OutlineOutline

Arsenic and bladder cancer– High dose studies– Low dose studies

Arsenic measurements in toenails Methods: ATBC study Results Discussion Future directions

High arsenic levels and bladder cancerHigh arsenic levels and bladder cancer

Ecological studies have consistently reported elevated mortality rates of bladder cancer in arsenic endemic areas: – Taiwan– Argentina– northern Chile

High arsenic levels and bladder cancerHigh 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)

Risk levels in U.S.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

Extrapolation studies--limitationsExtrapolation 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

Low-level arsenic and bladder cancerLow-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


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


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


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


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


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


Kurttio et al.

Relative risks adjusted for age, sex, smoking

Latency <0.1 0.1-0.5 >0.5 µg/L

Shorter1.0 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


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


Steinmaus et al.

<10 10-80 >80 µg/L

Highest 20-year average, 40-year lag160 10 111.0 1.28 1.70 (0.73-3.96)

Exposure 51-60 yr prior to diagnosis166 3 12

1.0 0.73 1.86 (0.80-4.33)

AJE 2003,158:1193-1201

Low level arsenic studies: limitationsLow 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

Use of toenails to measure arsenicUse 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)

METHODSMETHODS

ATBC studyATBC study

Alpha-Tocopherol and Beta-Carotene (ATBC) Prevention Trial

29,133 male smokers

50-69 years old

Living in southwestern Finland


Alpha-tocopherol (50 mg/day)

Beta-carotene (20 mg/day)

2x2 factorial design

Double-blind, placebo-controlled

Incidence of lung cancer


Timeline

Recruitment

Trial

Follow-up

1985 1986 1987 1988 1993 1998


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

Baseline characterisicsBaseline characterisics

Health statusSmoking historyHeight and weight EducationOccupationPhysical activityDietary questionnaire

Toenail samplesToenail 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

Case ascertainmentCase ascertainment

Finnish Cancer Registry (FCR)– 95% complete within 0.8-years

Hospital Discharge RegistryDeath CertificatesHistologically confirmed incident bladder

cancer cases – 331 cases with toenail clippings

Nested case-control designNested 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)

Arsenic determinationArsenic 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

Arsenic determinationArsenic 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

Detection limit and exclusionsDetection 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.

Statistical analysisStatistical 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

RESULTSRESULTS

Michaud et al.AJE 2004,160:853-859

Toenail arsenic levelsToenail 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

Baseline characteristicsBaseline 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 16.0Urban residence, % 45.4 38.9Education 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)

Arsenic and bladder cancer riskArsenic and bladder cancer risk

Median Cases Controls OR 95% CI arsenic level (g/g)

Quartile1 0.033 65 74 1.02 0.079 71 73 0.89 0.55-1.423 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).

Arsenic and bladder cancer riskArsenic and bladder cancer risk

Median Cases Controls OR* 95% CI arsenic level (g/g)

Percentile<50 0.050 136 147 1.050.1 – 75 0.130 73 72 1.10 0.73-1.6475.1 – 90 0.198 37 44 0.93 0.56-1.5490.1 – 95 0.333 20 16 1.38 0.68-2.8095.1 –100 0.757 14 14 1.14 0.52-2.51

p trend=0.61


Arsenic and bladder cancer, by smoking Arsenic and bladder cancer, by smoking durationduration

Tertile of arsenic (g/g) 0.017 – 0.070 0.071 – 0.137 > 0.137

OR* OR 95% CI OR 95% CIYrs smoked <35 1.0 1.14 0.5-2.9 1.30 0.6-3.136-45 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


DISCUSSIONDISCUSSION

Interpretation of toenail arsenic levelsInterpretation 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.

Interpretation of toenail arsenic levelsInterpretation of toenail arsenic levels

Toenail arsenic levels in terms of water concentrations:

50th percentile = ~ 2 µg/L




Potential biological mechanismsPotential biological mechanisms

Induction of oxidative damage to DNAInhibition of DNA repairAltered DNA methylation and gene

expressionChanges in intracellular levels of p53

proteinInduction of apoptosis

StrengthsStrengths

Biomarker– Reflects internal exposure– Long-term marker

Prospective study– Samples collected prior to disease– Data on smoking, other potential

confoundersReasonable power

LimitationsLimitations

Measurement error– Relevant time period 30-40 years earlier– Mobility

Range of exposure

Generalizability– Men– Smokers

Previous findings among smokersPrevious 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

SummarySummary

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

Future directionsFuture directions

Studies with toenail arsenic levels in the U.S.

Larger case numbersLonger latency periodsData on selenium levelsGenetic susceptibility

AcknowledgementsAcknowledgements

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

Toenail arsenic and bladder cancer: findings from a cohort study of male smokers Dominique S....

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