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• Authors' reply to Auvinen
  Martin Tondel
  Published on: 27 April 2016
• Too much, too soon?
  Anssi Auvinen
  Published on: 27 April 2016

• Published on: 27 April 2016

  Authors' reply to Auvinen

  • Martin Tondel, MD
  • Other Contributors:
    • Peter Hjalmarsson, Lennart Hardell, Göran Carlsson

  Dear Editor

  Auvinen has criticised our conclusion that a dose related increase in cancer incidence in Northern Sweden could be related to the Chernobyl nuclear power plant accident.[1] The justification for the critique is the short latency period. We are certainly aware of the short latency time in our study and therefore the cohort should be followed as there could come a second increase in the cancer incidence...

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  Dear Editor

  Auvinen has criticised our conclusion that a dose related increase in cancer incidence in Northern Sweden could be related to the Chernobyl nuclear power plant accident.[1] The justification for the critique is the short latency period. We are certainly aware of the short latency time in our study and therefore the cohort should be followed as there could come a second increase in the cancer incidence later on. Of course we have looked into the short latency seen in our study and tried to explain it. In the literature much emphasis has been put into the medical effects after the atomic bombs over Hiroshima and Nagasaki. These studies have to a large extent influenced the risk estimates in regard to cancer. This is natural because the high dose exposure gives a high statistical power to detect an increased risk and because the cohort is the largest with such a long follow-up. However, there are limitations when interpreting these data into the low dose range of ionising radiation, but also in the study of short latency to cancer as the cohort was created five years after the explosions.[2]

  In our study we have clearly discussed short latency in human studies after exposure to ionising radiation (page 1014, right column), but had to leave out some details.[3] Evaluations of radon progeny exposure and lung cancer is of interest in this context as it indicates that relatively recent exposure might hold a stronger effect according to the analytical models applied in a comprehensive report on this issue.[4] A short latency period has also been seen in a mortality study on 14 111 patients with ankylosing spondylitis where a significant increase in total cancer mortality was noted already 0-2 years after the x-ray treatment.[5] In a cohort of radon exposed uranium miners, different lag times to lung cancer were tested. A lag of six years for cumulative exposures fitted the data best.[6] In yet another study on uranium miners there was a continuous increased relative risk for lung cancer 2.0-8.5 years since first exposure followed by a subsequent decline in risk.[7] In a follow-up of the Three Mile Island accident in 1979 for the period 1979-1998, deaths in total malignancies were non-significantly increased for both men and women in 1979-1984 and followed by a decline. Then, there was an increased standardised mortality ratio again for men in 1990-1998.[8]

  Our findings of an increase in total cancer incidence in Sweden soon after the Chernobyl accident are therefore not a unique finding. In this context it is interesting that the increased number of thyroid cancers in children of Belarus in 1990, four years after the Chernobyl accident, now have been linked to a specific genetic rearrangements caused by radiation resulting in increased growth rate and a subsequent shorter latency period. This rapid form of thyroid cancer was followed by a slow growing form of thyroid cancer with yet another chromosomal rearrangement, hence it took longer time to diagnose.[9, 10] One interpretation of our results could therefore be that the ionising radiation might have acted as a late stage general promotor for cancer, or subtypes with shorter latency, resulting in early detection. It is unlikely that our short latency could be explained by different reporting of cancer to the national Swedish cancer registry as the exposure categories consists of parishes from different parts of the Country, except the highest category, and therefore it is unlikely that there would be a systematic parish biased registration. Registration of new cancer cases is also compulsory for both clinicians and pathologists in Sweden, hence only a few cases could have escaped from being reported to the National Cancer Registry, which seems to be complete to about 96 percent.[11]

  We therefore conclude that short latency period for cancer should be addressed in future similar epidemiological studies.

  References

  1. Auvinen A. Too much, too soon? [electronic response to Tondel et al. Increase of regional total cancer incidence in north Sweden due to the Chernobyl accident?] jech.com 2004 URL direct link to eLetter

  2. Stewart AM, Kneale GW. A-bomb survivors: factors that may lead to a re-assessment of the radiation hazard. Int J Epidemiol 2000;29:708-14.

  3. Tondel M, Hjalmarsson H, Hardell L, et al. Increase of regional total cancer incidence in north Sweden due to the Chernobyl accident? J Epidemiol Community Health 2004;58:1011-6.

  4. Committee on Health Risks of Exposure to Radon (BEIRVI), Board on Radiation Effects Research, Commission on Life Sciences, National Research Council. Health effects of exposure to radon. Washington: National Academy Press, 1999.

  5. Smith PG, Doll R. Mortality among patients with ankylosing spondylitis after a single treatment course with x rays. BMJ 1982;284:449-60.

  6. Hornung RW, Meinhardt TJ. Quantitative risk assessment of lung cancer in U.S. uranium miners. Health Physics 1987;52:417-30.

  7. Langholz B, Thomas D, Xiang A, et al. Latency analysis in epidemiological studies of occupational exposures: application to the Colorado Plateau uranium miners cohort. Am J Ind Med 1999;35:246-56.

  8. Talbott EO, Youk AO, McHugh-Pemu KP, et al. Long-term follow-up of the residents of the Three Mile Island accident area 1979-1998. Environ Health Perspect 2003;111:341-8.

  9. Williams D. Cancer after nuclear fallout: lessons from the Chernobyl accident. Nat Rev Cancer 2002;2:543-9.

  10. Williams ED, Abrosimov A, Bogdanova T et al. Thyroid carcinoma after Chernobyl latent period, morphology and aggressiveness. Br J Cancer 2004;90:2219-24.

  11. Mattsson, B. Cancer registration in Sweden - studies on completeness and validity of incidence and mortality registers [PhD Thesis]. Stockholm: Karolinska Institute, 1984.

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  Conflict of Interest:
  None declared.

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• Published on: 27 April 2016

  Too much, too soon?

  • Anssi Auvinen, Professor

  Dear Editor

  Tondel and co-workers followed up >1 million people in northern Sweden exposed to low doses of radiation as a result of fallout from the Chernobyl nuclear accident.[1] They show a small increase (10-20%) in overall cancer incidence and suggest it might be attributable to radiation exposure from the Chernobyl fallout. Yet, based on the substantial knowledge obtained from previous studies ranging fro...

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  Dear Editor

  Tondel and co-workers followed up >1 million people in northern Sweden exposed to low doses of radiation as a result of fallout from the Chernobyl nuclear accident.[1] They show a small increase (10-20%) in overall cancer incidence and suggest it might be attributable to radiation exposure from the Chernobyl fallout. Yet, based on the substantial knowledge obtained from previous studies ranging from atomic bomb survivors, medically irradiated persons and those exposed to natural radiation, the minimum latency for radiation-induced cancer (other than leukaemia and thyroid cancer) has been established as approximately 10 years. As the entire follow-up period falls within 10 years from the exposure, it seems that the findings contribute very little towards assessment of the health effects of Chernobyl fallout.

  Reference

  1. Tondel M, Hjalmarsson P, Hardell L, Carlsson G, and Axelson O. Increase of regional total cancer incidence in north Sweden due to the Chernobyl accident? J Epidemiol Community Health 2004;58:1011-1016.

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  Conflict of Interest:
  None declared.

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