PhD defence S. (Sarocha) Chootipongchaivat

Below is a brief summary of the dissertation:

Breast cancer is the most common cause of cancer death among women worldwide. Since the introduction of breast cancer screening, the number of diagnosed ductal carcinoma in situ (DCIS; DCIS refers to abnormal cells in the milk ducts) has increased rapidly. This PhD thesis focused on 1) the natural progression of DCIS and 2) the effectiveness of screening among different female populations. The microsimulation model MISCAN-Fadia was used  to understand the natural progression of DCIS, but also to estimate the benefits and harms of screening. The findings in this thesis lead to the following conclusions:
-    The majority of the screen-detectable but unbiopsied preclinical DCIS lesions progress to invasive breast cancer and the mean sojourn time is relatively short (Chapter 2)
-    Low-grade DCIS have longer sojourn times than high-grade DCIS. Furthermore, overdiagnosis is also estimated to be substantially higher in low-grade DCIS than among intermediate and high-grade DCIS, regardless of ER (estrogen receptor) status. (Chapter 3)
-    Due to a lower breast cancer risk and shorter life expectancy, breast cancer screening in women with Down syndrome has far less favourable harms/benefits ratios than screening in average-risk women (Chapter 4)
-    For Singapore, most cost-effective screening strategies include scenarios with screening starting at age 40 years. (Chapter 5)
-    Screening with clinical breast examination could lead to a breast-cancer mortality reduction up to 16% when screening all women in India aged 30-69 biennially (Chapter 6).