Abstract P3-07-03: The impact of Carcinoma in situ of the breast and family history on risk of subsequent breast cancer events and mortality - a population based study from Sweden

Abstract

Abstract Purpose: To evaluate the long-term risk of subsequent breast cancer and mortality among women diagnosed with carcinoma in situ of the breast. Patients and Methods: Using the population-based Swedish Multi-Generation and Cancer Registers we selected 8,111 women diagnosed with in situ breast cancer between 1980 and 2004. We estimated the relative risks of subsequent ipsi- and contralateral invasive breast cancer or a contalateral in situ expressed as standardized incidence ratios (SIRs), in relation to age, year, time since diagnosis and family history (1st degree relative) for breast cancer. The relative risk of death was expressed as standardized mortality ratio, (SMR). Results: Of 8,111 women identified with first in situ, 859 had a family history for breast cancer. The overall risk of a subsequent invasive breast cancer is over four fold and the risk for contralateral in situ breasts cancer was almost seven fold, compared with the risk in healthy women. Women with a family history had almost a 50% increased risk for a contralateral invasive breast cancer, IRR 1.49 (95% CI 1.06–2.09) compared to women without, but had no increased risk for a contralateral in situ cancer or ipsilateral invasive breast cancer. The risk for subsequent breast cancer decreased over time after diagnosis, but still 15 years after first in situ diagnosis the risk was over three times higher compared to the general population. Women below 40 years at diagnosis had the highest risk for a subsequent breast event, SIR 8.54 (95% CI 6.07–11.67). The overall mortality for women with no second invasive event was the same as for women in the general population, SIR 1.01 (95% CI 0.95–1.08). Women below 50 years at first in situ diagnosis, with a second invasive cancer, had a higher mortality compare to women above 50 years, SIR 8.3 (95% CI 5.38–11.54) and SIR 1.70 (95% CI 1.39–2.06) respectively. Conclusion: The risk for a subsequent invasive breast cancer, as well as mortality was substantially higher in younger women, which should be taken into account when planning their treatment and follow-up. Family history did not increase the risk for a subsequent ipsilateral invasive cancer. Citation Information: Cancer Res 2012;72(24 Suppl):Abstract nr P3-07-03.