Microscopic size does matter
Microscopic size does matter.
Mittra et al argue that the detection of invasive cancers less than 1
cm and ductal carcinoma in situ by mammography is unlikely to be
clinically important (1). This is not underpinned by robust clinical
evidence or biological plausibility.
First, their assumption that breast cancer growth is exponential is
wrong. It is a well-known fact that the growth of the cancer cells follow
the Gompertzian model (2).
Secondly, clinical tumour size has prognostic significance. There is
no biological basis to suggest that a microscopic doubling of tumour does
not affect the prognosis. In fact evidence suggests that the microscopic
increase in size of a tumour indicates selection of cancer cells with
aggressive phenotype and genotype (3) (4) due to nutritional deprivation
Finally, no solid tumour can grow beyond 1mm without
neovascularistion (3) and angiogenesis is an adverse prognostic factor
(5). These factors favour the early detection of small breast tumours by
mammography and other techniques.
As regards the cost effectiveness of mammography, it is very much a
political question. This is exemplified very well by the recent demand for
advanced train protection systems in all the trains, where the cost per
life saved would indeed be very high.
(1) Mittra I, Baum M, Thornton H, Houghton J. Is clinical breast
examination an acceptable alternative to mammographic screening? BMJ 2000;
(2) Norton, L. A Gompertzian model of human breast cancer growth. Cancer
Res. 1988; 48: 7067-71.
(3) Folkman, J. How is blood vessel growth regulated in normal and
neoplastic tissue? G.H.A. Clowes memorial Award lecture. Cancer Res.1986;
(4) Graeber, T. G., C. Osmanian, et al. Hypoxia-mediated selection of
cells with diminished apoptotic potential in solid tumours. Nature.1996;
(5) Hansen, S., D. A. Grabau, et al. Vascular grading of angiogenesis:
prognostic significance in breast cancer. Br J Cancer.2000; 82(2): 339-47.
Competing interests: No competing interests