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

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
Outline

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 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 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.

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--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 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
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
10-50
1.0
1.0
1.6 (0.3-8.4) 2.3 (0.4-14) 4.9 (1.2-20)
1.9 (0.1-32) 8.1 (0.7-98) 15.1 (1.7-139)
AJE 2001,153:411-18
50-100
>100 g/L
<10
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
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
Low-level arsenic and bladder cancer
Bates et al.
– 71 cases, 160 controls (lived in study town >½ lives)
<33
33-52
53-73
1.0
0.69 (0.3-1.5) 0.54 (0.3-1.2)
>73 mg/L x yrs
1.00 (0.5-2.1)
30-39 years prior to 1978:
<8
8-9
10-12
>13 mg/L x yrs
1.0
3.07 (1.1-8.4)
1.27 (0.4-3.6) 1.26 (0.4-3.6)
AJE 1995,141:523-30
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
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
Longer 1.0
1.53
0.81
2.44 (1.11-5.37)
1.51 (0.67-3.38)
Environ Health Perspect 1999,107:705-10
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
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
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
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)
METHODS
ATBC study

Alpha-Tocopherol and Beta-Carotene
(ATBC) Prevention Trial

29,133 male smokers

50-69 years old

Living in southwestern Finland
ATBC study

Alpha-tocopherol (50 mg/day)

Beta-carotene (20 mg/day)

2x2 factorial design

Double-blind, placebo-controlled

Incidence of lung cancer
ATBC study

Timeline
Recruitment
Trial
Follow-up
1985 1986 1987 1988
1993
1998
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
Baseline characterisics
Health status
 Smoking history
 Height and weight
 Education
 Occupation
 Physical activity
 Dietary questionnaire

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
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
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)
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
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
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)
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For 59 cases and 69 controls which also had nondetectable 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 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
RESULTS
Michaud et al.
AJE 2004,160:853-859
Toenail arsenic levels
Cases (n=280)
Median (range)
Arsenic level,
g/g
0.110 (0.014-2.62)
Karagas et al. 2001
Nichols et al. 1998
Garland et al. 1993
Controls (n=293)
Median (range)
0.105 (0.017-17.5)
0.089 (0.01 to 0.81)
0.088 (0.01 to 2.57)
0.083
Baseline characteristics
Age, years
Years smoked regularly
Cigarettes per day
Smoking inhalation, %
Never/seldom
Often/always
Smoking cessation, %
Urban residence, %
Education level, %
Primary school
High school
Vocational
University
Beverage intake, mL/d
Cases (n=280)
Mean (SD)
59.4 (5.1)
39.8 (7.4)
20.2 (7.8)
6.1
93.9
15.4
45.4
67.5
7.5
20.4
4.6
1534 (471)
Controls (n=293)
Mean (SD)
59.5 (5.0)
39.1 (8.0)
19.5 (7.8)
5.8
94.2
16.0
38.9
70.0
5.5
20.8
3.7
1569 (523)
Arsenic and bladder cancer risk
Median
Cases
arsenic
level (g/g)
Quartile
1
0.033
65
2
0.079
71
3
0.130
73
4
0.245
71
Controls
74
73
73
73
OR
95% CI
1.0
0.89
0.55-1.42
0.97
0.60-1.55
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 risk
Median Cases Controls
arsenic
level (g/g)
Percentile
<50
50.1 – 75
75.1 – 90
90.1 – 95
95.1 –100
0.050
0.130
0.198
0.333
0.757
136
73
37
20
14
147
72
44
16
14
OR*
1.0
1.10
0.93
1.38
1.14
95% CI
0.73-1.64
0.56-1.54
0.68-2.80
0.52-2.51
p trend=0.61
*Unconditional logistic regression models adjusted for matching factors,
cigarettes/day (continuous) and years smoked (continuous).
Arsenic and bladder cancer, by smoking
duration
Tertile of arsenic (g/g)
0.017 – 0.070
0.071 – 0.137
OR*
Yrs
smoked
<35
1.0
36-45
1.0
>45
1.0
> 0.137
OR
95% CI
OR
95% CI
1.14
0.90
1.46
0.5-2.9
0.5-1.5
0.5-4.1
1.30
1.16
2.30
0.6-3.1
0.7-1.9
0.8-6.9
*Unconditional logistic regression models adjusted for matching factors,
cigarettes/day (continuous) and years smoked (continuous).
DISCUSSION
Interpretation of toenail arsenic levels
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
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 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
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

Strengths

Biomarker
– Reflects internal exposure
– Long-term marker

Prospective study
– Samples collected prior to disease
– Data on smoking, other potential
confounders

Reasonable power
Limitations

Measurement error
– Relevant time period 30-40 years earlier
– Mobility

Range of exposure

Generalizability
– Men
– Smokers
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
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
Future directions
Studies with toenail arsenic levels in the
U.S.
 Larger case numbers
 Longer latency periods
 Data on selenium levels
 Genetic susceptibility

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