RERF Report No. 7-16

Paper published in Radiation Research§“Lung, Laryngeal, and Other Respiratory Cancer Incidence among Japanese Atomic
Bomb Survivors: An Updated Analysis from 1958 through 2009”
Elizabeth K. Cahoon, Dale L. Preston, Donald A. Pierce, Eric Grant, Alina V. Brenner, Kiyohiko
Mabuchi, Mai Utada, Kotaro Ozasa
Radiat Res 2017(May); 187(5):538-48(doi: 10.1667/RR14583.1)
Study Findings
This study showed the relationship between radiation dose and incidence of respiratory cancers.
The risk of lung cancer was found to have increased with increasing radiation dose. Strong smoking
risks were seen for lung cancer, laryngeal, and other respiratory cancers. When the joint effects ofradiation and smoking were analyzed, radiation risks for lung cancer were higher among low-tomoderate smokers when compared with heavy smokers.
Due to its size and long-term follow-up, the Life Span Study (LSS) of atomic bomb survivors
offers a good opportunity to study the relationship between radiation and the incidence of respiratory
cancers.
Explanation
We conducted a study on the relationship between lung, laryngeal, and other respiratory cancer
incidence and radiation dose among the Life Span Study (LSS) of atomic bomb survivors. Data oncancer occurrence were collected from the Hiroshima and Nagasaki cancer registries, and the followup period was 1958–2009. The effects of smoking and radiation were investigated both separately andin combination. Smoking data were collected from periodic mail surveys and surveys conductedduring clinical visits.
1. Study purpose
An important task of the long-term follow-up of the atomic bomb survivors is to document theoccurrence and risks of cancer. Recently, a manuscript was published on the risks of all solid cancers
in aggregate; this paper is the first in a series that will document the radiation risks in a specific organsystem. More manuscripts are in preparation regarding other organ systems with consideration paid tothe effect of lifestyle-related risk factors on individual organ cancers.
2. Study methods
LSS cohort members in this study numbered 105,444 and included those alive with no history ofcancer as of January 1, 1958, and had a known radiation dose. Incident cancers of the lung, larynx, andother respiratory organs were identified through linkage with the Hiroshima and Nagasaki cancer
registries. Follow up was conducted through December 31, 2009. The study used smoking history
information based on mail and clinical surveys. Individual radiation doses to the lung were estimatedfor each cohort member using the revised DS02 dosimetry system (DS02R1). Risks of respiratory
cancers as a function of radiation dose, sex, pack-years of smoking*, age at exposure, and attained age
were estimated using statistical models. Estimates of risk were expressed as an excess relative risk(ERR) per unit dose of radiation.
*When evaluating health impact of smoking, this index is used to indicate “tobacco consumption per
day x number of years of smoking.” In Japan, tobacco consumption per day is calculated as
number of cigarettes; in the case of Western countries, consumption is typically indicated bynumber of packs (1 pack = 20 cigarettes).

3. Study results
A total of 2,446 lung cancers, 180 laryngeal cancers, and 115 other respiratory cancers (of thetrachea, mediastinum, and other ill-defined sites) were observed over the follow-up period. For nonsmokers, an ERR of 0.81/Gy was observed for lung cancer. A linear ERR model fit best, and there was1

RERF Report No. 7-16

no evidence of curvature for either men or women. The ERR of smoking was estimated to be about 6
per 50 pack-years in both men and women. Of the total number of lung cancers, 113 (5%) could be
attributed to radiation. Of the 1,165 lung cancers that occurred among smokers, 886 (76%) could beattributed to smoking. When considering these numbers, one must remember that many in thepopulation smoked (86% of men and 18% of women), but the number of people with very highradiation doses was relatively small.
Study SignificanceThis study showed that respiratory cancer risks, particularly lung cancer, were increased withradiation exposure from the atomic bombs even more than 60 years after the exposures. We found thatsmoking increased the risks of all respiratory cancers. Confirming results from a previous study, we
found that radiation and smoking acted jointly to increase the risks of lung cancer among lightsmokers. We found that the excess relative risk due to radiation exposure had a linear response. Thispaper is the first in a series of organ-specific manuscripts based on already-published data in which theanalysis aggregated all solid cancers. Additional manuscripts on other major organ systems are beingprepared.

The Radiation Effects Research Foundation has studied A-bomb survivors and their offspring in Hiroshima
and Nagasaki for around 70 years. RERF’s research achievements are considered the principal scientific basisfor radiation risk assessment by the United Nations Scientific Committee on the Effects of Atomic Radiation(UNSCEAR) and for recommendations regarding radiation protection standards by the InternationalCommission on Radiological Protection (ICRP). RERF expresses its profound gratitude to the A-bomb survivors
and survivors’ offspring for their cooperation in our studies.

§Radiation Research, which is an official monthly journal of the Radiation Research Society, publishes
original peer-reviewed papers and review articles on radiation effects and related issues in the fields ofphysics, chemistry, biology, and medicine. (Impact factor in 2015: 3.022)

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