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Second primary breast and thyroid cancers (Israel).
Siegal Sadetzki1, Ronit Calderon-Margalit, Chava Peretz
1Cancer Epidemiology Unit, Gertner Institute, Chaim Sheba Medical Center, Tel Hashomer, Israel. siegals@gertner.health.gov.il
Cancer Causes & Control : CCC
|July 9, 2003
Summary
This study found a slightly increased risk of developing a second primary thyroid cancer after breast cancer, and vice versa, in Jewish women in Israel. The findings suggest shared risk factors or genetic susceptibility rather than cancer treatment causing the second primary cancer.
Area of Science:
- Oncology
- Epidemiology
- Cancer Research
Background:
- Understanding the risk of subsequent primary cancers is crucial for cancer patient management.
- Previous studies have explored the relationship between breast cancer and thyroid cancer, but nationwide data is limited.
Purpose of the Study:
- To evaluate the nationwide risk of developing second primary thyroid cancer (TC) after breast cancer (BC).
- To assess the risk of second primary BC after TC.
Main Methods:
- Utilized data from the Israel Cancer Registry for Jewish females diagnosed with BC or TC between 1960-1998.
- Calculated standardized incidence ratios (SIRs) using Poisson regression, stratifying by age, birth country, and diagnosis period.
Main Results:
- Identified 49,207 BC and 4911 TC cases.
- Found SIRs of 1.34 for second primary TC after BC and 1.07 for second primary BC after TC, excluding concomitant diagnoses.
- Younger age, earlier diagnosis year, and shorter follow-up were linked to higher second primary cancer risk.
Conclusions:
- The observed excess risk of second primary cancers shortly after the first challenges the hypothesis that cancer treatments initiate secondary malignancies.
- Plausible explanations include detection bias in closely monitored patients, shared early-life exposures to common risk factors, or genetic predispositions in specific subpopulations.