A revision of the number of radon-related lung cancers in Ireland: preliminary results

Size: px

Start display at page:

Download "A revision of the number of radon-related lung cancers in Ireland: preliminary results"

Elfrieda Garrett
5 years ago
Views:

1 A revision of the number of radon-related lung cancers in Ireland: preliminary results Paul M Walsh National Cancer Registry (NCRI) (in collaboration with EPA & others)

2 Background / Rationale Radon is the second most important cause of lung cancer, after tobacco smoking. In 2005, RPII & NCRI estimated that 195 lung cancer deaths per year in Ireland were attributable to radon exposure (91.5% in smokers & 8.5% in non-smokers). Updated, now population-weighted national estimates of average radon exposure for Ireland have become available, and populations have grown or redistributed. Numbers of lung cancer cases & deaths numbers have changed - population growth & ageing, and trends in rate/risk of lung cancer ( in men but in women). Updated methodology to estimates radon-related cancers among smoker and non-smoker subgroups.

3 Lung cancer: annual numbers of cases and deaths ( averages) Both sexes Male Female Cases (NCRI) Current smokers (imputed) Ex-smokers (imputed) Never-smokers (imputed) 1022 (1267) 646 (812) Unknown 467 (0) 44% (54%) 28% (35%) 8% (11%) 20% (0%) Deaths (CSO) Imputed = unknown assigned to known smoking status proportionally based on age, sex and cell-type

4 All-Ireland cancer atlas : lung cancer relative risk by ED (smoothed)

5 Lung cancer incidence and mortality trends in Ireland,

6 Sources of data: risk estimates, exposure estimates, baseline data Pooled analysis of 13 European case control studies (Darby et al. 2005) excess risk of lung cancer associated with radon exposure. Lung cancer mortality risk in lifelong non-smokers (Thun et al. 2006) for smoker v non-smoker breakdown. New, population-weighted 2017 estimate of average radon exposure of Irish population (EPA / Dr Patrick Murphy, UCD) annual average lung cancer cases (NCRI) annual average lung cancer deaths (CSO) population data (CSO). Methodology for estimating proportions of lung cancer attributable to radon (Gray et al. 2009, Darby et al. 2005).

7 Methods: briefly 1.16 (+16%) = increased risk of lung cancer diagnosis associated with 100 Bq/m 3 increase in household radon exposure. Population-weighted average exposure 98 Bq/m 3 implies 15.7% excess risk for Ireland. Risk appears to applies equally across range of radon exposure, regardless of smoking status (Darby et al. 2005). Back-calculate from total lung cancer cases and deaths annually to derive radon-attributable cases and deaths. Apply US data on age-specific rates of lung cancer in lifelong non-smokers to Irish populations to estimate total lung cancer deaths (and radon-attributable deaths) occurring in neversmokers and, by subtraction, ever-smokers.

% increase in lung cancer risk per 100 Bq/m 3 increase in radon concentration Effect modification: No good evidence that the proportionate increase in lung cancer risk differed by

8 % increase in lung cancer risk per 100 Bq/m 3 increase in radon concentration Effect modification: No good evidence that the proportionate increase in lung cancer risk differed by study Source: Darby et al Radon in homes and risk of lung cancer: collaborative analysis of individual data from 13 European case-control studies. BMJ :223. Epub 2004.

9 % increase in lung cancer risk per 100 Bq/m 3 increase in radon concentration Effect modification: No good evidence that the proportionate increase in lung cancer risk differed by age sex or smoking status, and evidence not quite significant for cell type except higher risk for small cell carcinoma Source: Darby et al Radon in homes and risk of lung cancer: collaborative analysis of individual data from 13 European case-control studies. BMJ :223. Epub 2004.

Relative risk of lung cancer increases linearly with radon exposure RR per 100 Bq/m 3 increase = 1.16 i.e. +16% Source: Darby et al. 2004.

10 Relative risk of lung cancer increases linearly with radon exposure RR per 100 Bq/m 3 increase = 1.16 i.e. +16% Source: Darby et al Radon in homes and risk of lung cancer: collaborative analysis of individual data from 13 European case-control studies. BMJ :223. Epub 2004.

1.08 to 1.16, i.e. from +8% +16% Source: Darby et al. 2004.

11 Correction for usual vs measured radon increases slope of relative risk Because random measurement errors associated with high measurements are not symmetric Correction increases RR per 100 Bq/m 3 increase from 1.08 to 1.16, i.e. from +8% +16% Source: Darby et al Radon in homes and risk of lung cancer: collaborative analysis of individual data from 13 European case-control studies. BMJ :223. Epub 2004.

12 Basic calculations (Gray/Darby methodology) Estimated population-weighted average radon exposure Ireland 2017 = 98 Bq/m 3 (95% CI ) Excess risk of lung cancer per 100 Bq/m 3 increase in radon exposure = 16% Estimated excess risk for Irish population = (98/100)*16% = 15.7% Average annual no of lung cancer cases (deaths) diagnosed in Ireland ( ) = 2332 cases (1821 deaths) Estimated annual no of cases attributable to radon = (15.7%/115.7%)*2332 = 316 (*95% CI ) = 13.6% ( %) Estimated annual no of deaths attributable to radon = (15.7%/115.7%)*1821 = 246 (*95% CI ) = 13.6% ( %) *95% confidence intervals based on only 95% CI for average radon exposure estimate, not taking other sources of error into account.

13 Further summary / comparison with UK Estimated proportion of all lung cancer cases (or deaths) attributable to radon in Ireland ( ) : 13.6% (@ 98 Bq/m 3 ) Equivalent proportion for UK (2006): 3.3% (@ 21 Bq/m 3 ) Annual lung cancer deaths attributable to radon in Ireland ( ): 248 (population 4.58 million) Annual lung cancer deaths attributable to radon in UK (2006): 1110 (population million) Annual lung cancer deaths attributable to radon in Ireland if crude UK rate applied to Irish population and radon exposure was equal: 4.58*(1110/60.85) = 84; or taking radon differences into account : 1110*((4.58*(98/21))/60.85) = 390; but lower (248) because younger population or higher survival Ireland?

14 Numbers of radon-attributable lung cancers by smoking status (Gray / Thun methodology) Radon attributable ( ) total Smokers (ever smokers) Non-smokers (never smokers) Lung cancer cases 316 *( ) 271 ( ) 45 (43-28) 86% 14% Lung cancer deaths 248 ( ) 211 ( ) 35 (33-37) 86% 14% *95% confidence intervals based on only 95% CI for average radon exposure estimate, not taking other sources of error into account.

15 Assumptions / limitations (among others ) Calculations using an overall estimate of radon exposure (even population-weighted) assume distribution of smokingrelated lung cancers mirrors the general population distribution unlikely given higher urban lung cancer rates. If smoking rates differed substantially in lower-radon areas, estimates of radon-attributable cancers would be incorrect. Even if distribution of lung cancer cases is accounted for, different estimates may result from use of different geographic scales e.g. prediction of exposures at electoral division (ED) level or in relation to underlying geology or alternative methods of calculating radon-attributable risk. Estimation of radon-attributable cancers by smoking status also has potential limitations use of US never-smoker data, ex-smoker definition/risk, passive smoking

16 Comparisons of (some) available estimates for Ireland Radon attributable / Lung cancer cases 316 ( ) 250 source NCRI/EPA HSE Lung cancer deaths 248 ( ) 195 source NCRI/EPA NCRI/RPII Some other estimates exist (published or in prep.) based on varying methodologies

17 Thank you!

Residential Radon, Smoking and Lung Cancer. Sarah C Darby University of Oxford

Residential Radon, Smoking and Lung Cancer Sarah C Darby University of Oxford Plan of talk Most radon exposure occurs indoors in ordinary homes Lung cancer risk increases with indoor radon concentration