  Tomasetti and Vogelstein (2015) collected data on 31 different tissue types
and found a correlation of 0.8 between the logarithms of the incidence of
cancer (LCI), and the estimated number of stem cell divisions in those tissues
(LSCD). Some of their conclusions however are statistically erroneous. Their
excess risk score, "ERS" (log10 LCI x log10 LSCD), is non-monotonic under a
change of time units for the rates, which renders meaningless the results
derived from it, including a cluster of 22 "R-tumor" types for which they
conclude, "primary prevention measures are not likely to be very effective".
Further, r = 0.8 is consistent with the three orders of magnitude variation in
other unmeasured factors, leaving room for the possibility of primary
prevention if such factors can be intervened upon. Further exploration of the
data reveals additional findings: (1) that LCI grows at approximately the
square root of LSCD, which may provide a clue to the biology; (2) among
different possible combinations of the primary data, the one maximizing the
correlations with LCI is almost precisely the formula used by Tomasetti and
Vogelstein to estimate LSCD, giving support to stem cell divisions as an
independent factor in carcinogenesis, while not excluding other such factors.
