Schneeberg Study Criticisms

[precura.martin@T-ONLINE.DE (Dr. Karl Martin)]

Dear Jim,



your three problems with the study became obviously some more when you listed 

them. They are worth, together with your proposals, to be discussed.



1. Number of cases

You are right, the number of cases is very small. Therefore we are working to 

include in the study more female cases and additionally non-smoking male cases. 

This will help to increase the confidence and narrow the CI. We do not expect a 

fundamental change in the risk estimate.



The risk analysis was made with two extreme approaches: table 17 with raw data 

(14 smokers and all types of histology and cases without confirmed histology 

included) and table 18 with stratified data including only cases fullfilling the 

strictest demands in data quality (validated non-smokers only and lung cancer 

histologic confirmed). Only for table 18 your criticism regarding number of 

cases "6 or less" applies.



Both curves (raw and stratified data) are quite similar, confirming that the 

lung cancer risk for non-smokers from radon is higher than that from smokers and 

that the results from the most demanding data quality is in accordance with the 

raw data (only 14 cases smokers, 22%).



We did not pretend to have found a threshold - it was not our intention. In 7.3 

"Results from the research", part "Contribution to the discussion of LNT", it 

was stated: "The Schneeberg Study is considered by its authors as a contribution 

to the growing body of scientific evidence that the LNT model might not be valid 

in the low dose range, and that further research is needed". When a "safe 

threshold" is mentioned, than only in the sense, that in the low exposure 

categories no health risk could be established. We avoided therefore the 

expression "certain threshold". Maybe this was not an excact enough wording to 

express what was really meant. Sorry. 



Despite its small size the overall power of the Schneeberg study is very high. A 

comparison of the power of all recent population studies you can take from our 

website: Publikationen, "Lembcke, J: Zur Power der Deutschen Radonstudie (Ost), 

vollständiger Text, 2000". This paper is in German but you can read easily table 

4, adjusted OR, smokers among controls known, mobility considered.



2. Retrospective cases

Response after Easter.



3. Death certificates

The data collection for cases and controls is mainly based on data from the 

cancer registry (1952 to 1989). During this period it was mandatory for each 

doctor to notify the local cancer registry by standardised forms. From 1990 on 

to 1995 due to reunification of Germany, mandatory notification of cancer cases 

stopped. Nowadays the cancer registry continues on the Federal State level for 

Saxony, including the study area Schneeberg, and mandatory notification of 

cancer cases is introduced again. Only cases from 1990 on are collected from 

death certificates. Primary cancers only were eligible for inclusion in the 

study.



4. Exposure categories

It looks as if the exposure categories were chosen arbitrarily. The reason for 

this is, that other population studies, prior to the Schneeberg Study, have 

chosen this categorisation (mostly up to >140 Bq/m³). We intend to do a 

reanalysis of our data. We have already tried less and other categorisations 

with improved results for confidence. 



Your summarising remark, that a positive trend for indoor radon exposure and 

lung cancer was found is correct, when applied to high exposure levels. What is 

questioned is whether low radon levels such as found in most houses may increase 

the lung cancer risk. An other conclusion from the Schneeberg study is that the 

confounder smoking cannot be controlled invalidating risk estimates for lung 

cancer from indoor radon with case-control studies with mainly smokers among 

cases and controls. Consequently, we should focus future studies on non-smokers 

in highly exposed populations only with a wide range of exposure for instance 

from 50 Bq/m³ to > 3.000 Bq/m³.                 



5. Publication

A first attempt with HP has failed. It will be repeated after some recommended 

changes.



Regards, Karl



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