Review for 10.1186/1471-230X-6-41 (2006)

Reviewer's report 
 Time trends in socioeconomic differences in inciedence rates of cancers of gastro-intestinal tract in Title: 
Finland 
 1  19 July 2006 Version: Date: 
 Farin Kamangar Reviewer: 
Reviewer's report: 
General 
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Major Compulsory Revisions (that the author must respond to before a decision on publication can be 
reached) 
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Minor Essential Revisions (such as missing labels on figures, or the wrong use of a term, which the author 
can be trusted to correct) 
In this interesting report, Weiderpass and Pukkala discuss gastrointestinal tract incidence rates in Finland 
by sex, birth cohort, time period, and socioeconomic status. The authors take advantage of a 
comprehensive cancer registry and a census for this purpose. 
The majority of the findings are consistent with finding of other reports. For example, esophageal and 
gastric cancer rates were higher in lower SES groups, whereas colon cancer rates were higher in higher 
SES groups. A rapid decline in gastric non-cardia cancer was observed for both men and women, but colon 
cancer incidence increased during the study period. There are, however, some differences compared to other Western studies. For example, several other reports have shown increased rates of gastric cardia cancer in the past three decades, whereas this study found no marked changes over time. 
I suggest that the authors consider revising this manuscript to make several parts clearer and more 
symmetric. In various parts of the text, only some cancers have been discussed. For example: 
1. In Introduction section, paragraph 1, the authors present references for changes in incidence and 
mortality of colon cancer over time, but they donâ €™t present similar references for other cancers. In this 
same paragraph, the authors have discussed the associations between SES and cancers of colon, rectum, small intestine, liver, gallbladder, and biliary tract, but they have not discussed the associations between 
SES and esophageal, gastric (cardia and non-cardia), and pancreatic cancers. 
1. Figures 1 and 2 show changes in incidence rates for six gastrointestinal cancers, but they do not show 
changes for cancers of the cardia and small intestine. The authors do not explain why these figures are 
shown for only some cancers. 
1. Table 2 shows sex/period/SES-specific SIRs for colon cancer. However, similar tables have not been 
made for other cancers. It is not clear why the authors chose to show these data for colon cancer, but not 
for other cancers. Colon cancer rates changed through time, but so did gastric cancer rates. Is this Table for 
demonstration purposes only? If so, the authors need to mention. Otherwise, I suggest that they delete this 
table. 
Other questions or suggestions: 
1. Esophageal squamous cell cancer rates have decreased in most Western countries in the past 30 years. 
In contrast, during this same period, esophageal adenocarcinoma rates have sharply increased. Why have 
the authors not presented the results for esophageal squamous cell carcinomas and esophageal 
adenocarcinomas separately? I assume this is perhaps because they had few cases of esophageal adenocarcinoma. If so, they need to explain. 
2. In the last line of the Abstract, the authors make the conclusion that â €œSocioeconomic differences point 
to life styles or life conditions such as diet, physical activity, smoking, alcohol consumption, or combinations 
of these factorsâ €. This is a general statement and it is not the conclusion of this manuscript. I suggest 
that the author make their conclusion based on the data from their own study. 
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Discretionary Revisions (which the author can choose to ignore) 
 Accept after minor essential revisions What next?: 
 An article whose findings are important to those with closely related research interests Level of interest: 
 Needs some language corrections before being published Quality of written English: 
 No Statistical review: 
Declaration of competing interests: 
I declare that I have no competing interests.