e14646 Background: Non-melanoma skin cancer (NMSC) is the most common form of human cancer. Aminolevulinic acid photodynamic therapy (ALA PDT) is a safe and effective treatment for NMSC precursors. It is unknown if ALA PDT treatment will affect incidence of NMSC in high risk patients (pts). Methods: A retrospective study was undertaken using a Veteran Affairs Boston Health Care System Medical Record Database. Study population included immunocompetent pts with history of NMSC, multiple actinic keratosis (AKs), and moderate to severe dermatoheliosis (DH). Study pts received a single application of 20 % ALA to the face or scalp following by exposure to blue light at 10 J/cm2. Differences in incidence of NMSC two years prior and two years after ALA PDT were tested using the Wilcoxon rank sum test. Data were analyzed by the median and interquartile range (IQR). Results: 43 Caucasian males (range 59- 87 yrs), 37 (87%) had history of NMSC on the face or scalp, 32 (78%) had basal cell carcinoma (BCC), 11 (22%) squamous cell carcinoma (SCC), 100% of patients had multiple (>4) AKs prior to treatment and 23 (75% ) had moderate to severe DH determined by Griffiths scale. Prior to ALA-PDT 74 NMSC's were documented: 40 (54%) BCC and 34 (46%) SCC. 46 NMSC's were documented following ALA-PDT: 22 (48%) BCC and 24 (52%) SCC. Prior to ALA-PDT, the frequency of BCC averaged 2 [IQR 1 to 3, max=4], and the frequency of SCC averaged 1 [IQR 1 to 1, max=3]. Following ALA-PDT, the occurrence of BCC averaged 1 [IQR 0 to 1, max=5], and that of SCC averaged 1 [IQR 0 to 2, max= 4]. The difference between BCC frequency before and after ALA-PDT treatment shown a significant reduction in BCC incidence (P = 0.0018). No such differences were observed between the frequency of SCC before and after ALA-PDT (P=0.6230) Conclusions: A single ALA-PDT treatment to the face or scalp in high risk patients significantly reduces the incidence of BCC, the incidence of SCC was not reduced. The potential role of ALA PDT as a NMSC chemopreventive modality warrants further investigation in larger samples with an alternative treatment protocols. No significant financial relationships to disclose.
Quantitative intracellular oxygen availability before and after 5-aminolevulinic acid skin photodynamic therapy
