PDT in squamous cell carcinoma of the skin

Topical photodynamic therapy (PDT) has been demonstrated to be an effective and safe treatment option for pre-malignancies such as actinic keratoses (AK) and Bowen's disease (BD), with an increasing amount of evidence indicating good long term outcomes. Studies comparing PDT to other options such as cryotherapy and 5-fluorouracil generally demonstrate that PDT is equal to or better than these therapies with respect to patient satisfaction, cosmesis, and efficacy for AK and BD. While there are studies using squamous cell carcinoma (SCC) cells to elucidate the cellular and molecular mechanisms of PDT, this therapy is currently not indicated for treating SCC and surgery is still the first line of therapy. There has been special interest in using PDT to prevent warts, basal cell carcinoma, AK, and BD in solid organ transplant recipients, as these skin lesions are more common in immunosuppressed patients, and trials have been somewhat successful and very promising. Pain remains an obstacle for some patients and techniques such as nerve blocks, cooling packs, and hydration have been attempted to mitigate pain with an overall reduction in pain scores. Optimizing PDT is still a priority and the delivery of pro-drug as well as induction of cellular differentiation are being explored as ways to improve the efficacy of PDT. Perhaps the most interesting use of PDT in treating SCC is the potential for a tumor-specific vaccine, which is currently being developed.