Abstract

It is a known fact that skin cancer is due mainly to exposure to UV radiation. It is also currently assumed that subtypes of skin cancer can likewise be caused by ionising radiation. However, many of the models and risk assessments for skin cancer due to ionising radiation date back to the 1990s or even before. In an advisory mandate of June 2020, the Federal Ministry for the Environment, Nature Conservation, Nuclear Safety and Consumer Protection (BMUV) asked the German Commission on Radiological Protection (SSK) to comment on the following questions:

• What is the current scientific data on radiation-induced skin cancer?
• Do the current international recommendations for protection against ionising radiation take adequate account of these data, particularly with regard to the assessment of the risk and detriment of skin cancer?
• What is the possible impact of these insights on the tissue weighting factors of the skin and the dose limit for the equivalent dose to the skin?

The SSK reviewed the literature published between 1990 and 2021. Of 106 publications, 28 publications were identified as relevant and sufficiently reliable to provide answers to the above questions. The previous assessment that neither malignant melanoma nor squamous cell carcinoma can be caused by ionising radiation continues to be confirmed by more up-to-date studies. Therefore, statements on the risk of radiation-induced skin cancer relate exclusively to basal cell carcinoma. Unlike the previous assumptions and models, risk assessments on skin cancer, and for most other types of cancer, can be made on the basis of more recent evaluations of the studies among Japanese atomic bomb survivors (Life Span Study, LSS). Depending on the choice of fitting model (e.g. assumption of a threshold dose or assumption of a linear dose-response relationship with no threshold), the risk contributions differ significantly for basal cell carcinoma. The choice and the combination of the models and parameters used to calculate the amount of damage (detriment) used in radiation protection have a profound impact on the assessment of whether and to what extent skin cancer contributes to the radiation risk. There is evidence suggesting that there is no increase in the risk of skin cancer in the dose range below 0.5 Gy. This would mean that skin cancer could potentially be dropped from the list of cancers that are inducible by radiation. However, a final assessment on this question cannot be made at present.

This statement was adopted at the 329th meeting of the SSK on 7/8 December 2023.