Treating sun damage to reduce the risk of skin cancer
Low level sun damage over many years causes mutations in the skin’s surface cells (keratinocytes). Over time these mutated cells expand over the skin. This is called field cancerisation. This increases the risk of common skin cancers - squamous cell carcinoma (SCC) and basal cell carcinoma (BCC).
Clinically, field cancerisation can present as actinic keratoses (AKs), which are precancerous scaly lesions. Patients with large numbers of AKs have a signficantly increased (approximately 5-10x) risk of SCC and an increased (approximately 2-4x) increased risk of BCC. Additionally patients may not like the appearance of AKs or find them symptomatic or annoying.
Sun protection is the foundation of prevention because it reduces new UV-induced mutations and helps reduce the formation of new AKs and some skin cancers over time. However for patients with multiple AKS, even perfect sun protection starting today cannot undo UV damage already present in the skin. Mutated cell clones will persist which is why patients with previous heavy sun exposure, multiple AKs, or prior BCC or SCC remain at increased risk even when they are now very careful. This is where field treatments are valuable.
Topical field treatment with Efudix (5-fluorouracil)
Efudix (5-fluorouracil, 5-FU) is a long-established field therapy for AKs and sun-damaged “at-risk” skin. It is a topical chemotherapy cream that is applied for a 4 week period and preferentially targets rapidly dividing abnormal keratinocytes and causes an inflammatory reaction in areas where abnormal cells are present (including “invisible” or subclinical AKs).
Patients should expect the gradual onset of severe inflammation, crusting, weeping and blistering over a couple of weeks. This will then gradually resolve over a few more weeks after the treatment is completed. 5-FU reduces the risk of SCC development by approximately 75% for at least a year after a course of treatment. However, for many patients the prolonged treatment course and severe inflammation is difficult to manage.
More details: Efudix
Topical field treatment with Efudix and Dovonex
Combining 5-FU with calcipotriol (Dovonex) is a newer approach that has been proposed. Calcipotriol appears to amplify local immune signalling in sun-damaged skin, which allows a shorter treatment course of 4 days, however we do not yet know whether it is as effective as the standard course of treatment.
More details: Efudix + Dovonex
Topical field treatment with Klisyri (tirbanibulin)
Klisyri (tirbanibulin) is a newer field treatment for AKs. It works by disrupting processes abnormal cells need to grow (including microtubules and signalling pathways). A key advantage is the short treatment course, which is easier for patients to complete. Local skin reactions (redness, scaling, tenderness) are common, but the overall “downtime” can be more manageable for selected patients.
More details: Klisyri
Photodynamic therapy (PDT)
Photodynamic therapy (PDT) treats a field of sun damage using a light-sensitising agent followed by activation with a medical light source. This generates reactive oxygen species that selectively damage abnormal cells. PDT is widely used for AKs, especially on the face and scalp, and is often chosen when cosmetic outcome is a priorityand when prolonged courses of topical treatment are not suitable. It is usually much better tolerated than 5-FU and reduces the number of AKs and is believed to reduce the risk of skin cancer, however the evidence is not as strong as for 5-FU.
The treatment is performed in clinic - a cream is left on for 1-2 hours and then the area is exposed to a light. Patients should expect significant inflammation, weeping, crusting and inflammation after the treatment.
More details:
- Photodynamic therapy
- PDT aftercare
Non-ablative fractional laser resurfacing
Non-ablative fractional lasers create microscopic columns of heat in the skin while leaving the surface largely intact. They are commonly used for photodamage and texture change. Some smaller studies indicate that they can reduce the risk of skin cancer, however this evidence is not as robust as for 5-FU or photodynamic therapy. An advantage is that they are generally safe with only a few days of downtime and low risk of complications.
More details: Fractional non-ablative laser
Ablative fractional laser resurfacing
Ablative fractional resurfacing removes microscopic columns of skin and triggers regeneration and remodelling. It is usually reserved for patients with severe sun damage because while it can be very effective it is associated with a prolonged healing period and significant risks.
More details: Fractional ablative laser
Nicotinamide (vitamin B3)
Oral nicotinamide is a vitamin. Clinical trials have shown a reduction in AKs and skin cancer in higher-risk patients. It is generally well tolerated. Studies in this area are still ongoing and we do not yet know for sure how effective it is.
More details: Nicotinamide
Acitretin
Acitretin is an oral retinoid (tablet) sometimes used as chemoprevention in very high-risk patients, particularly those who are immunosuppressed (for example, some organ transplant recipients) and develop frequent SCCs. It requires careful monitoring and has important side effects, including dryness, lipid changes, liver effects, and strong teratogenicity. For most patients, it is not a routine prevention option, but it is relevant for selected high-risk cases.
Diclofenac 3% gel (Solaraze)
Solaraze is a milder topical option that may reduce the presence of AKs but is not always effective. It is generally well tolerated but requires a longer course and there is not robust evidence that it reduces skin cancer risk.
More information: Solaraze
Cryotherapy
Cryotherapy (freezing) is not a field treatment but it can be used to treat multiple AKs in a single session and is often combined with a combined with a field therapy plan.
More details: Cryotherapy
Topical retinoids
Topical retinoids can improve some aspects of photoaging and sun-damaged skin. They are not a standalone proven method to prevent NMSC, but can be useful when there are other concerns.
More details: Topical retinoids
