Second Primary Cancers of the Breast: Incidence and Risk Factors
Author Information
Author(s): T.G. Hislop, J.M. Elwood, A.J. Coldman, J.J. Spinelli, A.J. Worth, L.G. Ellison
Primary Institution: Cancer Control Agency of British Columbia
Hypothesis
What factors influence the incidence of second primary tumors of the contralateral breast?
Conclusion
Women with a personal history of breast cancer have a greater risk of developing a second breast malignancy, especially if they have certain risk factors.
Supporting Evidence
- The average annual incidence rates for a second primary in the contralateral breast were 5.0, 4.1, and 3.0 per 1,000 women for different age groups.
- Two risk factors for bilateral cancer within 1 year of the first primary were lobular carcinoma and absence of pathologic involvement of axillary nodes.
- A family history of breast cancer was found to be a significant risk factor for bilateral breast cancer after one year.
Takeaway
If a woman has had breast cancer, she might get cancer in the other breast too, especially if she has certain family or health history.
Methodology
The study reviewed medical records of over 9,000 women diagnosed with primary breast cancer and identified risk factors for bilateral breast cancer using a case-control study design.
Potential Biases
Referral bias may affect the incidence rates as the study population was selected from a tertiary care treatment center.
Limitations
The study may overestimate the incidence of bilateral breast cancer due to referral bias and the potential underdiagnosis of second primaries in patients with metastatic disease.
Participant Demographics
Women diagnosed with primary breast cancer between 1946 and 1976, with a focus on those who later developed a second primary in the contralateral breast.
Statistical Information
P-Value
0.001
Confidence Interval
0.6-4.1
Statistical Significance
p<0.05
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