British Society for Dermatological Surgery: Summaries of Papers

DS-1 Nonmelanoma skin cancer: the cutaneous surgeon’s guide to radiotherapy S. Orpin, A. Loffeld, A.H.M. Heagerty and J. Hamilton* Heart of England NHS Foundation Trust, Birmingham, West Midlands, U.K. and *University Hospitals Coventry and Warwickshire NHS Trust, Coventry, West Midlands, U.K. The majority of dermatologists perform some excisional surgery for nonmelanoma skin cancers (NMSC). The main alternative to surgical treatment is radiotherapy. The rate of recurrence of NMSC after radiotherapy is 5–10% which compares well with 4–6% for simple excisional surgery. The therapeutic effects of radiation result from damage to DNA. This can be from direct interaction with the cell nucleus or via the production of free radicals secondary to interactions with other molecules within the cell that can subsequently damage chemical bonds. It is only when cell division takes place that the biological effects are expressed. Clearly the clinical response of a given nonmelanoma tumour relies on the biological properties of the tissue treated; the so-called ‘5 Rs’ of radiobiology. Radiosensitivity is an intrinsic property of the cell population in question. The ability of given cells to repair themselves after radiation exposure is usually more pronounced in nonproliferating tissues while repopulation of malignant cells becomes more marked once treatment has begun. Reoxygenation of tissues improves as radiation exposure proceeds, hypoxic cells are relatively radioresistant, so longer treatment times allow for an improved response. Similarly the redistribution of cells to more radiosensitive parts of the cell cycle occurs as treatment progresses. The practicalities of radiotherapy mean it is given daily, each fraction taking around 10 min. There are no systemic side-effects but the unwanted local features are erythema, soreness and slow healing which takes approximately 6–8 weeks after cessation of treatment. The two main modalities of radiotherapy used to treat skin cancers are orthovoltage, sometimes called superficial radiotherapy (SXR), and electron beam. As implied by the name the former cannot treat deep lesions but it is relatively easy to plan and is useful for small tumours particularly close to the eyes because it needs a smaller margin than electron beam. It can, however, cause significant damage to any underlying cartilaginous structures. Electron based treatments are more complex to arrange and plan but because the energy involved can be tightly controlled it is possible to be much more precise with the depth of tissue treated and the distribution of the radiation dose within such tissues. The possibility of a further NMSC developing within a radiation field is perhaps overstated and occurs in at most 5% of cases with a latent period from 10 to 40 years. If we are to have a meaningful dialogue with our patients with NMSC about their treatment options it is important that we have a good basic understanding of the different modes of treatment our oncology colleagues have available to offer as well as the biological effects both wanted and unwanted that can be expected.