f wr.
ite
wae,
ne
‘on aol
we
voces?
at
decreased with iitotic cesipetence, then estinates, of carcincgcnesis based
on a fictitious averaging. of a local inhomogeneous dose over a much lerger
-
.
volume ould be necessa ily conservative.
Since radiation careinggensis
can, and infact, does increase to anomalously large values while the mitotic
competence becomes venishlingly small, the fictiti 5 averaging Ct dose
over larger volumes is not neces sarily ‘c
ervative.
Instead it would
appear that an inten 2 local dose of ionizing radiation can be a more:
efficient carcinogen than a diffuse tissue exposure »ith the sane type of
ts
jonizing radiation and the sane totel energy.
a
The above then imojies that
averaging of dose over larger volumes may be far from conservative.
It is obyious that as a local exposure becomes more intense, a
stage must finally be reached where the carcinogenic efficiency of the
exposure (cn a
per unit energy basis) is reduced.
to previous argurents.
This is not pertinent
It would, however, be important to knew the
characteristics of the most carcinogenicly efficient exposures.
Thefollowing excerpt taken frou the BEIR report (p. 95) summarizes
the state of knowledge concerning the causation of cancer (emphasis added):
"Although the mechanisns of carcinogenesis, or _of
a
i
radiétion carcinc™enasismm particular, are not fully
known, evealleble wnioreacicon implies inac OSU, WV nee
all,”types of cancer dovelop as a result of the combined
effects of multiple factors. These causative factors
may include: prezyqotic (inherited) mutations of
chromosamal aberrations, which cen spread during development to many kinds of colls; somatic cell mutations cr
chromosomal aberrations, which can be acquired at any
time afier conception: changes resulting from the action
of Viruses 3 and chanyes tn systemic arowth factors {e.g.»
depressed immune compotance, hacmonal imbalance) and
inlocal tissue Vequlation(disoraani zation, damage),
such es may Fesult Tren discases other Lian cancer or
Troma aavencing age (1).
"Although point mutations, chroaosanat abborations,
and other chanaes at the cellular and meteculer level
tay require Gily seald cases, tissue cisercaanizalion ind