Dr Chandanos and colleagues from Swedern undertook a population-based cohort study of all women aged over 50 years with breast cancer in the Swedish Cancer Register in 1961 to 2003.
Those diagnosed before 1987 were regarded as unexposed to tamoxifen.
The research team considered those diagnosed after that date as potentially exposed.
Crosslinkages within the Cancer Register and the Registers of Death and Emigration enabled follow-up.
The research team evaluated standardized incidence ratios of esophageal and gastric cancer represented relative risks.
The team assessed 138,885 cohort members contributing with 1,075,724 person-years of follow-up.
The researchers found a nonsignificantly increased risk of esophageal adenocarcinoma during the potential tamoxifen exposure period.
However, the risk estimates decreased with increasing latency interval.
|The risk of non-cardia gastric cancer almost doubled in the period of longest latency |
|British Journal of Cancer|
The researchers found no association during the unexposed period.
No increased risk of cardia adenocarcinoma was identified in either period.
The team noted that the risk of non-cardia gastric adenocarcinoma was increased in the potential tamoxifen period.
The risk of non-cardia gastric adenocarcinoma almost doubled in the period of longest latency.
The corresponding overall standardized incidence ratios was increased in the unexposed group.
The team also observed that the standardized incidence ratios did not increase with longer latency intervals.
An increased risk of tobacco-related tumors, that is, esophageal squamous-cell carcinoma and lung cancer, was limited to the unexposed cohort.
The team reported that confounding by smoking might explain the increased standardized incidence ratios during the unexposed period.
Dr Chandanos' team concludes, “There might be a link between tamoxifen and risk of non-cardia gastric adenocarcinoma.”