Introduction to Mathematical Oncology by Yang Kuang & John D. Nagy & Steffen E. Eikenberry

Author:Yang Kuang & John D. Nagy & Steffen E. Eikenberry
Language: eng
Format: epub
Publisher: Taylor & Francis Group, LLC
Published: 2016-02-18T05:00:00+00:00

7.7.1 Pre-clinical breast cancer and DCIS

Optimizing the value of screening is hindered by the fact that little is known about the natural history of pre-clinical breast cancer. Since the advent of mass mammography screening the incidence of ductal carcinoma in situ (DCIS) has increased dramatically. It now accounts for about 20% of new breast cancers, compared to less than 2% in the past, and this increase is largely attributable to mammography. DCIS is a neoplasm of ductal epithelial cells that has not penetrated the basement membrane to invade the surrounding stroma, although it may have spread widely within the duct lumen.

DCIS is generally believed to represent an early stage in the evolution of invasive carcinomas, and it shares many of the genetic and morphological characteristics of invasive disease. However, recent research has shown that not all cases of DCIS will progress to invasive cancer, and the proportion that do is unknown. Moreover, some more aggressive cancers may lack a recognizable in situ phase. Several studies have examined the rates of invasive carcinoma in women who received only a biopsy for DCIS and were initially misdiagnosed as having benign disease. These studies suggest that 14–53% of DCIS gives rise to invasive disease, but they had small sample sizes and considered only low-grade DCIS [25].

Welch and Black [79] reviewed seven autopsy series of women who died without evidence of breast cancer during life, and found the median prevalence of undetected DCIS to be 8.9%, although the prevalence was higher in studies that sampled more breast tissue (up to 14.7%). Furthermore, the prevalence was much higher in younger women. At the upper limit, 39% of women aged 40–49 had in situ disease, and another 12% had atypical ductal hyperplasia. This result suggests that a large pool of DCIS in younger women becomes depleted with increasing age. Depletion could occur either by spontaneous regression or progression to invasive cancer.

In accordance with Welch and Black’s results, other evidence points to markedly decreasing DCIS incidence detected by screening after age 70 [24]. In addition, invasive cancers in older women tend to be lower grade with more favorable prognostic factors [24, 25]. The cause of this shift in incidence and grade remains unclear at the time of this writing.

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