Duration of Ameluz Application in Acral Actinic Keratoses Response

A phase IV study of a single topical application of ALA for 3 hours or 4 hours to AK on acral sites (hands, feet, arms and legs), and subsequent measurement of clinical efficacy with corresponding PpIX fluorescence imaging.

Photodynamic therapy (PDT) is a relatively new treatment for skin cancer and sun-damaged skin, which may turn cancerous or pre-cancerous. PDT treatment consists of applying a gel containing aminolevulinic acid hydrochloride (licensed for clinical use as Ameluz®) to the abnormal area. Inside the diseased cells this gel is changed over a few hours into a light-sensitive chemical (photosensitiser) that reacts with light. The photosensitiser is inactive by itself. A red light is then shone on to the lesion; this reacts with the photosensitiser and destroys the abnormal cells. Only the treated area will be affected and inflamed. The area will be cured in most cases after the inflammation clears. Actinic keratosis (AK) is a type of pre-cancerous lesion caused by sun damage. If left, they can progress to become skin cancer. These can be treated in different ways, with different topical creams, liquid nitrogen or PDT. Some lesions may have reoccurred after topical creams, patients also have unacceptable amount of inflammation or the lesion involve too large an area. Liquid nitrogen is as good as PDT in treating AKs, however have been reported to leave a less good cosmetic result. PDT is a licensed treatment for AK. However, PDT has been shown to be less effective for AKs on certain areas such as hands and feet. Further understanding of the build-up of the photosensitiser may enable better cure rates at these body parts, enabling more patients to benefit from PDT. The proposed theory is that a longer application of the Ameluz gel will increase the amount of photosensitiser, which accumulates in the treated areas, and thus increase the amount of damage to cells, and mean that more patients have a successful treatment. The aim of this study is to investigate whether applying the Ameluz gel for 4 hours (trial group) rather than 3 hours (control group) will improve treatment success rates in AK lesions on hands, feet, arms and legs. The information gained from this study may result in better treatment design of PDT for AK. To do this the investigators plan to apply Ameluz® gel to AK lesions for either the standard 3 hours or the currently unlicensed 4 hours. The investigators will then measure the amount of that has changed into the photosensitiser, using a special digital camera. This camera device is not invasive and does not have any side effects. Some patients may have multiple AK lesions on multiple sites; the investigator aim to treat all these in the same manner due to practicality, and will record data for these lesions as well. The investigator will record if patients report any associated pain during light delivery, as well as the temperature of the lesion during treatment. Some patients opt to have an external cooling system or water spray during the light treatment, but in order to standardise treatment during the trial this will not be used. The investigator will however give patients the option of taking paracetamol themselves prior to the treatment. A dermatology doctor will then review the patients at three months following treatment to see if their AK has been cured, and receive further treatment if needed. The pathway is the same as standard PDT treatment and does not involve an extra visit.