[ RadSafe ] AW: Diagnostic X rays and breast cancer risk

Fri Apr 4 07:52:58 CDT 2008

Bobby:

Thank you very much for your enlightening analysis of the paper by C.M. Ronckers and colleagues entitled "Multiple diagnostic X-rays for spine deformities and risk of breast cancer" that was published in Cancer Epidemiol. Biomarkers Prev. 17(3):605-613, 2008.

You expose the same old and most common trap employed by true LNT believers (as e.g. exercised in Ronckers' reference No. 1, the 'famous' paper:  Preston DL, Mattson AM, Holmberg E, Shore R, Hildreth N, Boice JD, Jr. Radiation effects on breast cancer risk: a pooled analysis of eight cohorts. Radiat Res 2002;158:220 - 35. Erratum in: Radiat Res 2002;158:666.). 

That is: 

#1) Extend the exposure range to doses high enough to yield a significant excess risk, if only for the highest dose point(s).

#2) Postulate a LNT model and report the results of a curve fitting algorithm.

#3) If alternative postulates (models) other than LNT are mentioned at all, e. g., 

(i) no effect, 
(ii) constant effect, 
(iii) linear with some off-set, 
(iv) pure quadratic, 
(v) linear quadratic, etc., 

NEVER report the results of F-tests which assess the significance of reduced residual variances for the different fits, in this case between postulate (model) (i) and the LNT fit.

In more recent papers you sometimes do find a discussion like here (p. 607):

"Modeling ERR as a linear function of breast dose yielded a borderline statistically significant ERR/Gy of 2.86 [95% confidence interval (95% CI), -0.07 to 8.62; P = 0.058; one-tailed P = 0.029; Table 3; Fig. 1]. There was no deviation from linearity at higher doses (as evaluated by comparison with pure quadratic, linear quadratic, or linear-exponential models)."

Given the error bars of the data, such an exercise is patently futile. Moreover, such a 'pretended' openness to other models cannot cover-up the most important BUT NOT REPORTED finding, i. e., that the residual variance for the LNT fit is also not significantly reduced compared to the no-effect model and hence the parsimony principle of science, Occam's razor, would REQUIRE to select the no effect model as representative for these data.

Thank you once more and kind regards, Rainer

________________________________

Von: Scott, Bobby [mailto:BScott at lrri.org]
Gesendet: Do 20.03.2008 19:37
An: stoneh at mail.nih.gov; Metting, Noelle; edouple at nas.edu; Kozumbo, Walter J Civ AFRL/AFOSR; Hirsch, Roland; Coons, Teresa Dr.; Jane Orient; Jerry Cuttler; Facius, Rainer; Kaminski, Joseph (NIH/NIAID) [E]; Kazuo SAKAI; Dr Kaushala Prasad Mishra; tubiana; Carmel Mothersill; Mary H Barcellos-Hoff; Eleanor A Blakely; hsducoff at uiuc.edu; Ulsh, Brant A. (CDC/NIOSH/OD); Brynn Voy; Cyndi Jones; Doug Boreham; Mitchel, Ron; clsanders; floyd.frost at aurora.org; fcucinot at ems.jsc.nasa.gov; Galina V. Zhuntova; hoel at musc.edu; Redpath, Leslie; jb at jbutley.net; Muckerheide, Jim (CDA); m.kadhim at har.mrc.ac.uk; Oleg.Belyakov at stuk.fi; Philippe J. Duport; philip.hanfeldt at tufts.edu; Vigneulle, Roy M Dr GENERAL DYNAMICS; Pam.Sykes at flinders.edu.au; seymouc at mcmaster.ca
Cc: Marx, Pat; Henry, Roberta; Lyndy Volker; info at norwalkradiology.com; info at hemetradiology.com; info at chi-rad-soc.org; info at phs.org; Edward J. Calabrese, Ph.D.
Betreff: Diagnostic X rays and breast cancer risk

Dear Colleagues:

Attached is a new paper by C.M. Ronckers and colleagues entitled "Multiple diagnostic X-rays for spine deformities and risk of breast cancer" that was published in Cancer Epidemiol. Biomarkers Prev. 17(3):605-613, 2008.  The authors report results of a retrospective cohort study of diagnostic X-ray induced breast cancer among a cohort of 3,010 women diagnosed with spinal curvature. A key unjustifiable conclusion of the paper based on forced employment of the LNT risk model was "our data argue against existence of a low-dose threshold on the order of 1 to 3 cGy for radiation exposure contributing to breast carcinogenesis." Implied is that there is no threshold or that it is at lower doses.  In my brief analysis of data from their paper (attached PowerPoint file) for doses in the range 0 to 20 cGy (0 to 200 mGy), I found no evidence for a significant  increase in breast cancer risk over the indicated dose range.  Rather, the data are found to be consistent with the possibility of a threshold in excess of 200 mGy (20 cGy).  Interestingly, RR = 1 was set for the 30 mGy dose group rather than the zero dose group (RR = 1.35) for the key data in Table 2 of the paper. The zero dose group I refer to corresponds to what the authors called the minimally-exposed group (245 women who had no recorded X rays at the pediatric center where spinal deformity was diagnosed). I thought you may find the attached figure (in PowerPoint file) to be of interest. The figure can be compared to the forced employment of the LNT model by the authors in their Figure 1 (which includes doses > 200 mGy or 20 cGy). 

Best wishes,

Bobby R. Scott, Ph.D.

Senior Scientist

Lovelace Respiratory Research Institute

2425 Ridgecrest Drive SE

Albuquerque, NM 87108

Phone: 505-348-9470