Causes of non-melanoma skin cancer

Henrik F. Lorentzen | Apr 2020 | Dermatologi | Onkologi / Hematologi |

Henrik F. Lorentzen
Senior Clinical Lecturer,
Aarhus University Hospital

X-ray radiation increases the risk of cancer including non-melanoma skin cancer (NMSC). The previous indiscriminate use of Bucky’s rays for the treatment of skin conditions, including acne and psoriasis in children and adolescents is associated with the development of basal cell carcinoma (BCC) with a latent period of more than 20 years. Deeper reaching radiotherapy is associated with various types of cancer including BCC and squamous cell carcinoma (SCC) – also with a latent period of more than 20 years. This is the reason why it is preferable to treat skin cancer in younger people surgically, whereas it is safe to treat older people with radiation due to the shorter remaining life expectancy. X-ray therapy causes direct DNA damage and thereby mutations, but also causes indirect damages due to the formation of free oxygen radicals. UVB light causes cell damage and increases the risk of NMSC via three mechanisms: • direct DNA damage; • formation of reactive oxygen radicals; • immunosuppression. Reactive oxygen radicals (ROS) are high affinity molecules capable of binding to, for example, cell membranes, DNA or mitochondrial DNA which can lead to changes in these. Normal cells contain low amounts of ROS that can affect the normal proliferation. With higher amounts of ROS, the DNA damage will be sufficient to cause disrupted cell division and cancer but it will not be sufficient to cause cell death. With radiotherapy and certain types of chemotherapy and photo dynamic therapy (PDT), massive amounts of ROS are created, which leads to cell death via necrosis, apoptosis or ferroptosis. UVA light is »not» absorbed by DNA and the carcinogenic effect occurs via ROS and immunosuppression. Visible light may lead to the formation of ROS and can contribute to photoaging of the skin, and a carcinogenic effect cannot be ruled out. UV radiation and temperature At the surface of the earth, UV stress and temperature do not follow each other (Figure 1). This is comparable to a pot of water you place on a stove. The energy from the cooking plate is constant and will result in the...