1. Women with non-screen detected ductal carcinoma in situ had worse outcomes for the 25 years following their diagnosis.

2. When compared with surgery, mastectomies had better results at lowering the risks of invasive breast cancer.

Evidence Rating Level: 2 (Good)

A breast screening program developed by the National Health Service has contributed to the increased incidence of ductal carcinoma in situ. However, not all women with this type of cancer have been diagnosed through the screening program. A study examining outcomes of a population of 27543 women in England who had been diagnosed with non-screen detected ductal carcinoma in situ as their first cancer diagnosis. By the end of 2018, 3651 women in this study developed invasive breast cancer with a rate of 13.28 (95% CI 12.85 to 13.71) per 1000 women, years overall. Based on breast cancer rates in the general population, the rate of invasive breast cancer was four times more than expected. The observed to expected rate ratio was 4.21 (95% CI interval 4.07 to 4.35) with the rate also varying with age. During the study, the death rate for breast cancer was 3.05 per 1000 woman years average, and 908 participants died from non-screen detected ductal carcinoma in situ. Cumulatively, the risk of breast cancer was followed for the next 25 years and was found to be 7.6% for <45 years, 5.8% for 45-49 years, 5.9% for 50-59 years, and 6.2% for 60-70 years of age. English women who were diagnosed with ductal carcinoma through mechanisms other than screening had a four times higher risk of invasive breast cancer along with death from breast cancer than women in the general population. Between the eligible screening ages of 50-64, there were 9679 women diagnosed with non-screen detected ductal carcinoma in situ. In contrast, 31141 women in the same age range were diagnosed via screening.  When comparing ductal carcinoma in situ between women who were diagnosed through non-screening compared to those via screening, the ratio was 1.26 (95% CI, 1.17 to 1.35). While the ratio for breast cancer mortality was 1.37 (1.17 to 1.60), for the 22753 patients surveyed with unilateral ductal carcinoma who elected for full mastectomy, they had a lower overall rate of invasive breast cancer in the 25 years (mastectomy 8.2% (95% CI 7.0% to 9.4%), breast-conserving surgery along with radiotherapy 19.8% (16.2% to 23.4%) and breast-conserving surgery alone 20.6% (18.7% to 22.4%)). It was also found that women diagnosed with breast cancer more recently have lower rates of death, possibly due to better treatment methods. Regarding the women who were not diagnosed with screening, there was no information on the route of diagnosis they experienced. Overall, after receiving a diagnosis of ductal carcinoma, there is an increased risk of invasive disease and death lasting for at least 25 years, regardless of the detection method. The study results suggest that women who undergo a mastectomy have lower long-term risks compared to women who receive breast-conserving therapy.

Click to read the study in BMJ

Image: PD

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