[ RadSafe ] Is this the beginning of the end of the debate on low-dose radiation effects?

[Doss, Mohan]

Dear Otto,
    There are examples of clinical trials where acute radiation dose of 10 cGy to the whole body given 15 times during 5 weeks resulted in systemic reduction of cancers, as seen in this publication http://www.ncbi.nlm.nih.gov/pubmed/823140 , with the outcomes being as good as chemotherapy.  Higher doses, if given instead of 10 cGy per fraction, would undoubtedly raise the cancer risk. Similarly, second cancers (per kg of tissue) were lower for the regions of body having 20-50 cGy radiation dose in radiation therapy patients, whereas much higher doses resulted in increased second cancers as seen in Tubiana's paper http://www.ncbi.nlm.nih.gov/pubmed/21595074 .  The different parts of the body had radiation exposures with the same time characteristics, with low-dose resulting in cancer reduction (compared to zero dose) whereas high doses resulted in increased cancers.  Your model, since it does not have the opposite effects at low doses and high doses, would have a difficult time explaining these data.
   With best regards,
                                            Mohan


-----Original Message-----
From: radsafe-bounces at agni.phys.iit.edu [mailto:radsafe-bounces at agni.phys.iit.edu] On Behalf Of Otto G. Raabe
Sent: Wednesday, July 09, 2014 12:59 PM
To: The International Radiation Protection (Health Physics) Mailing List
Subject: [ RadSafe ] Is this the beginning of the end of the debate on low-dose radiation effects?

9 July 2014

The important contrast is between a single instantaneous radiation exposure and protracted exposure over time.

A very small instantaneous exposure will have a meaninglessly small promotion effect on ongoing cancer advancement even if it is not zero.

In sharp contrast, a protracted exposure at low dose rates can interfere with ongoing "natural" cancer processes,

See my Figure 16 in Health Phys. 98:515-536; 2010 where I show a statistically significant reduction (zero cases) in bone sarcoma from Sr+Y-90 protracted radiation exposures for cumulative doses smaller than 10 Sv. This I call a life-span virtual threshold for radiation induced cancer.

If you do not have this paper I will send it to you

Otto

**********************************************
Prof. Otto G. Raabe, Ph.D., CHP
Center for Health & the Environment
University of California
One Shields Avenue
Davis, CA 95616
E-Mail: ograabe at ucdavis.edu
Phone: (530) 752-7754   FAX: (530) 758-6140
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