I’ve just had a small comment on breast cancer
published on Science’s website. The comment is in reply to an interesting article discussing over-treatment in ductal carcinoma in situ (DCIS: a
type of cancer that is contained in the milk duct). My comment is reprinted
below. Unfortunately Science’s website submission system mucked up some of the
letter (formatting etc.) but no matter as it can be read here:
Finding
biomarkers in DCIS and the effects of breast cancer screening
Marshall’s article [1] raised the important issue of
overtreatment in breast cancer. It is challenging to assess which ductal
carcinomas in situ (DCIS) are overtreated without risking a patient’s life. The
studies being conducted by Esserman and colleagues are an important step in addressing
this problem. Such studies could assist in the identification of biomarkers
(blood tests, MRI, etc.) that can separate those types of DCIS that will
proceed to a life threatening stage from those that are indolent. MRI has
assisted in breast cancer detection and characterization with a high level of
sensitivity and the additional tumours detected have generally not been
accompanied by a change in the way such tumours are treated. Multifocal cancer
is often treated with mastectomy which is likely to be an excessive treatment
option in some cases where small multifocal DCIS lesions are detected by MRI.
The article also comments on the lack of a drop in advanced
stage tumours at a population level after an increase in mammographic use [1]. Randomized
controlled trials do report reductions in the rate of advanced stage tumours in
those who receive mammography [2]. At the population level we are not monitoring
who receives mammography and who does not. Brody et al. [3] have raised a potentially
relevant point that environmental carcinogens are likely to be contributing to
an increase in breast cancer rates. Older subjects will have been exposed to
environmental carcinogens for a longer period of time and as such should
exhibit higher rates of cancer. Since it is well known that breast cancer rates
increase with age, we should consider the possibility that environmental
carcinogens are a contributing factor to this effect. If true, then a stable
rate of late stage cancers in an environment where the rate should be
increasing would be an indication that mammography has indeed lowered the rate
from what it would otherwise be. The rate of advanced stage cancer [1] would
thus consist of lower rates for those receiving mammography and higher rates
for those who are not.
Jacob Levman,
PhD
University of Oxford
[1] Marshall, Dare to Do Less, Science, (2014)343(6178):1454-1456
[2] Marmot, et
al., The benefits and harms of breast cancer screening: an independent
review, British Journal of Cancer, (2013)108:2205-2240
[3] Brody, et
al., Breast Cancer and Environmental Research, Science, (2014)344(6184):577