Risk of second primary cancer among women with breast cancer: A population-based study in Granada (Spain)

^a Andalusian School of Public Health, Granada Cancer Registry, Campus Universitario de Cartuja, Cuesta del Observatorio 4, E-18080 Granada, Spain
^b CIBER de Epidemiología y Salud Pública, CIBERESP, Spain
^c Centro Nacional de Epidemiología, Instituto de Salud Carlos III, C/Monforte de Lemos, 5 Madrid, Spain
^d Instituto de Salud Carlos III, Contrato Río Hortega, CM 10/00143, Spain
^e Hospital Universitario San Cecilio (HUSC), Avenida de Madrid, Granada, Spain

Highlights

•: We examined risk of second primary cancers in women diagnosed with a first primary breast cancer in Granada (Spain).
•: This is the first Spanish population-based study on this issue, comprising a total of 5897 breast cancer cases.
•: Women diagnosed with breast cancer have higher second cancer incidence, although risk differs by age and second cancer site.

Abstract

Objective

The higher risk of developing new cancers in breast cancer survivors is a public health concern. Our aim was to examine risk of second primary cancers among women diagnosed with breast cancer.

Methods

We studied two cohorts of female cancer patients identified in a population-based cancer registry in Granada (Spain): women first diagnosed with a primary breast cancer (n = 5897) and those with a primary cancer in another site (n = 22,814), followed during 1985–2007 for second cancers and breast cancer occurrence, respectively. We used Standardized Incidence Ratios (SIRs) to estimate second cancer risk by age (< 50 y, ≥ 50 y), time since diagnosis (≤ 5 y, > 5 y) and calendar periods (≤ 1995, > 1996). SIR for breast cancer was calculated in the second cohort.

Results

The risk of developing second cancers (n = 314) was 39% higher (95% CI = 1.23–1.54) among breast cancer patients, and particularly high among women under 50 (SIR = 1.96, 95% CI = 1.48–2.44). Excess risk for endometrial cancer (SIR = 3.04, 95% CI = 2.14–3.94) was statistically significant and remained so in women over 50. Younger women were at higher risk of second ovarian cancer (SIR = 4.90, 95% CI = 1.27–8.53). Increased SIRs were observed during the first five years after breast cancer diagnosis, whereas SIRs decreased thereafter. Breast cancer incidence (n = 171) was not higher among women previously diagnosed with other cancer types (SIR = 0.86, 95% CI = 0.74–1.00).

Conclusion

Women diagnosed with breast cancer have a higher incidence of second primary cancers, particularly of endometrial cancer in women over 50 at diagnosis, and ovarian cancer in younger women. These findings may be explained by treatment-related effects or shared risk factors.

Keywords

Female breast cancer;
Second primary cancer;
Population-based cancer registries

Figures and tables from this article:

: Fig. 1. Standardized incidence ratios (SIRs) and 95% CI for second primary cancers after a first primary breast cancer, by year after diagnosis (dots and vertical bars). The line and shaded region represent the cumulative standardized incidence ratio and its 95% CI.