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OCR for page 36
APPENDIX A
Specific Comments on the Working Group's Draft Report
p. 13, line 2: Clarify whether the excess risk, excess relative risk, or some other measure was
assumed to be lognormally distributed over time since exposure.
p. 13, section 5, line 5: The reference to section TT.C.l appears to be incorrect.
p. 14, line 3: Why would risk 5-14 years after exposure have been overestimated?
p. 16, section B. last sentence: Is there any reason to be concerned about possible differential
ascertainment by calendar time or dose?
p. 20, section 2 ff: Although the discussion of whether radiation accelerates the appearance of
cancer or increases the risk is relevant to some of the points made by Robins and
Greenland, a more fundamental issue is the bias in AS as an estimator of the mean of
individual PCs produced by heterogeneity in baseline rates. This point is discussed
elsewhere in the National Research Council Oversight Committee's report, but merits
some discussion in the working group's report.
p. 29, lines 2-3 after the formula: The g following ~ should be omitted because it is not the
parameter, but the observed covariate value (sex).
p. 32, in analyzing the Japanese atomic-bomb survivor data, very little uncertainty in neutron
RBE is allowed. That seems incongruous with the current debate over neutron RBEs in
that study and with the wide range of findings in the experimental literature regarding
neutron RBEs.
pp. 32-33, no indication is given of what the "systematic biases" in the atomic-bomb dose-
estimation procedure consist of.
p. 34, no justification is given as to why 5 hours is the critical value to distinguish acute from
fractionated exposures in the assigned-shares model.
p. 37, figure {V.F.3 might be easier to interpret if presented in terms of the dose-response curves
themselves, that is, ~ + ,8 D X DDREFaCU~e (D).
p. 37 and elsewhere, the mode of presentation (especially graphic) of the DDREF is
counterintuitive and might confuse many people who are not conversant with the lingo of
radiobiology. One normally thinks of a ``factor'' as multiplicative or additive, but in the
case of DDREF it is a division factor. It would be better to plot I/DDREF (to show that a
higher DDREF yields less effect, not more, as the graph seems to imply). Text should be
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OCR for page 37
added on p. 33 to clearly indicate that, for example, a DDREF of 2 implies half as large a
slope.
p. 41, arguably, one should attach some uncertainty to the low-LET doses, because gamma
exposures are believed to have a slightly lower RBE than 250-kVp x rays, and low-
energy x rays are thought to have a higher RBE than 250-kVp x rays.
o. 46. section 2: Did Land and others tI994] restrict their analyses to age at first full-term
pregnancy, or were the other standard breast-cancer risk factors also examined? How
was this variable coded for nulliparous women? Even though these authors adopted the
parameterization given here, elsewhere in this report ~ = ~ corresponds to the
multiplicative model and ~ = 0 to the additive model. Perhaps internal consistency would
be less confusing.
p. 47, last paragraph: The three references to tables {V.G should be to tables IV.~. Some
discussion of the literature on alternative forms of mixture models (such as
multiplicative, Guerro-Johnson, and Box-Cox models) might be worth while.
I,
p. 49, section J: The possibility of an interaction of the ATM gene with ionizing radiation
should be mentioned here. Although experts differ about the ATM-radiation interaction,
it would be right to raise the concerns that there is some controversy about it (Won" et
al., 1997; Nichols et al., 1999; Shaman et al., 2000~.
p. 49, it is doubtful that xeroderma pigmentosa patients have increased susceptibility to
carcinogenesis induced by ionizing radiation, even though they are exquisitely sensitive
to ultraviolet radiation. Did the authors instead mean nevoid basal-cell carcinoma
syndrome patients who have a well-documented radiosensitivity?
p. 5 I, section 2: Why were these two situations excluded?
section 5b: It seems inconsistent with the treatment of other uncertainties to fix the
coefficient of D2 at I.0 as though it is known with certainty.
p. 54, section 7: The reference to section IV.G appears incorrect; was IV.D intended?
p. 70-76, it would be useful if these tables gave the 99th percentile estimate from the ~ 985
calculations for comparison with the new calculations.
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Representative terms from entire chapter:
ionizing radiation
