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[cdn-nucl-l] American, French and Japanese scientists visit
The article below appeared today in the February edition of AECL's
I thought you might like to read it.
American, French and Japanese scientists visit
By Jerry Cuttler
Following the Canadian participation in the June conference of the World
Council of Nuclear Workers (see Contact, August issue, page 7) a group of
renowned medical scientists visited the International Centre for Low Dose
Radiation Research, at the University of Ottawa, to participate in a meeting
of the Scientific Advisory Committee. A program of research involving
Canadian and foreign laboratories was drafted and a meeting of international
scientists studying health effects of low radiation doses was planned. The
visitors gave lectures at the Faculty of Medicine and suggested areas of
cooperation, including therapeutic applications.
In Toronto, they visited the Princess Margaret Hospital (PMH) and the
Canadian Nuclear Society's (CNS) Sheridan Park and Toronto branches. The
lectures at the PMH were followed by a two-hour meeting to discuss
replicating Japanese research on the effects of low-dose radiation on
animals and the therapeutic applications of low-dose, total-body irradiation
(TBI) for cancer patients. A tour was provided of the new PMH facilities
for conformal (high-dose) radiation therapy to destroy local tumors.
The lectures at the CNS Sheridan Park Branch featured Professors Maurice
Tubiana, member, French Academy of Sciences, and Kiyohiko Sakamoto,
director, Tohoku Radiological Science Center. Professor Tubiana spoke about
the risk of cancer from low doses of radiation. He said that the linear
no-threshold (LNT) model is a very conservative hypothesis and a cautious
approach for radiation protection purposes, but should not be confused with
statements of scientific fact.
The LNT model assumes that the incidence of cancer is proportional to the
radiation dose, implying that the body's ability to repair damaged cells is
fixed. However, studies have shown that repair efficiency is stimulated
after low doses and overwhelmed after high doses.
The risk of cancer attributed to the effects of 100 rad (or 1 Gy) radiation
on Hiroshima-Nagasaki (H-N) survivors is much greater than the risk
determined for this dose in other studies. What is the cause of this
discrepancy? One difference is the dose rate; the bomb blast lasted only a
few milliseconds. Another difference is the underestimation of the dose,
The original 1965 estimate of the H-N dose included the effect of neutrons.
In 1985, the dose was reestimated and the effect of neutrons was neglected,
which made the dose four times smaller and the risk four times greater.
The neutron field, now being recalculated, could be as large as the neutron
field estimate that was made in 1965, which would reduce the risk by a
factor of four. Also, the risk appears to decrease as the survivors become
older; they are living longer than the (unirradiated) people in neighbouring
cities. The efficacy of DNA repair is not constant, and the actual
proliferation of cancer cells is not compatible with the LNT model.
Professor Tubiana discussed the non-linear results of the studies on the
radium dial painters and the patients given Thorotrast to increase the
contrast of X-ray images. These studies indicate definite thresholds.
Below the thresholds, up to half the cell population was damaged by alpha
particles, yet no cancer was observed. He identified many communities where
environmental radiation (gamma radiation, radon) is quite high compared to
regulatory limits, yet no increases in cancer incidence or birth defects
have been observed.
The key factor in the much lower risk, he pointed out, is DNA repair. Life
would be impossible without DNA repair and the killing of mis-repaired
cells. For this reason, the LNT model breaks down at low doses and dose
rates. Neither the LNT model nor the collective dose, which is the addition
of individual tiny doses, should be used to estimate the number of cancers
caused by an irradiation. The ALARA (as low as reasonably achievable)
principle may be good for workers, but it's bad for the public, causing
Professor Sakamoto has been using TBI and half-body irradiation (HBI)
therapies for the past 20 years. He has studied its effects on mice, and
observed the stimulation of many biological processes that cause beneficial
effects, resulting in cancer cures, when the dose is in the range from 1 to
30 rad (10 to 300 mGy).
Professor Sakamoto was asked to treat a 60-year-old patient with an advanced
ovarian tumor who was not expected to live beyond six months following
surgery. Palliative radiotherapy was requested for the residual tumors and
the metastases in regional lymph nodes. Professor Sakamoto applied a
combined treatment of TBI plus repeated local irradiation to the abdominal
region. The TBI (6 MV X-rays) consisted of a one-minute dose of 10 rad,
given three times a week for five weeks, for a total of 150 rad. The result
was so successful, the patient lived for two and a half years. Her death
was caused by a colon blockage, likely caused by scarring from the high-dose
local irradiation; no cancer was detected by an extensive pathological
Since then, Professor Sakamoto has treated about 150 cancer patients (many
with non-Hodgkin's lymphoma) with TBI and HBI, using local irradiation as
required. The 10-year, 84 per cent survival data indicate the significantly
positive effects of the TBI/HBI therapy. Comparisons with chemotherapy data
suggest superior results for TBI, without symptomatic adverse side-effects.
He gave other examples of remarkable cancer cures.
Professor Sakamoto is a survivor of colon cancer. Following surgery to
remove tumors in three places, he applied his TBI protocol to himself in
July 1997 and repeated it in February 1998 as a booster and is now in
As to whether TBI is being applied in North America, Professor Myron
Pollycove, U.S. Nuclear Regulatory Commission, stated that it is not an
accepted therapy due to concerns about the health effects of low doses and
the widespread acceptance of chemotherapy. He then described the TBI
therapy provided this summer by the Johns Hopkins Medical Center to a
retired captain in Admiral Hyman Rickover's nuclear Navy*. This 80-year-old
veteran had undergone chemotherapy, but his cancer later returned. He then
decided not to repeat this therapy. Ted Rockwell, retired technical
director of Rickover's Naval Reactors office, suggested trying Sakamoto's
TBI therapy. With the advice and information of Professor Pollycove, this
therapy was given by James S. Welsh, associate professor of Radiation
Oncology. The captain made a remarkable, but incomplete recovery. He has
indicated that he intends to repeat this therapy, as needed, to keep the
malignancy under control.
* Admiral Hyman Rickover was the proponent of nuclear-powered submarines who
exploited the scientific breakthrough of the atomic bomb project. He
created the U.S. nuclear Navy and the world's first commercial nuclear power
plant built solely for electric power generation.