THE GROWTH LAW OF PRIMARY BREAST-CANCER AS INFERRED FROM MAMMOGRAPHY SCREENING TRIALS DATA

Despite considerable progress in understanding tumour development, the law of growth for human tumours is still a matter of some dispute. In this study, we used large-scale mammography screening trial data to d educe the growth law of primary breast cancer. We compared the empiric al tumour population size distributions of primary breast cancer infer red from these data to the distributions that correspond to various po ssible theoretical growth functions. From this, we showed that the dat a are inconsistent with the exponential, logistic and Gompertz laws, b ut support power law growth (exponent approximate to 0.5). This law in dicates unbounded growth but with slowing mass-specific growth rate an d doubling time. In the clinical size ranges, it implies a greater dec line in the mass-specific growth rate than would be predicted by the G ompertz law using the accepted parameters. This suggests that large tu mours would be less sensitive to cycle-specific therapies, and be bett er treated first by non-cell cycle-specific agents. We discussed the u se of our study to estimate the sensitivity of mammography for the det ection of small tumours. For example, we estimated that mammography is about 30% less sensitive in the detection of tumours in the 1 to 1.5- cm range than it is in detecting larger tumours.