mTHPC mediated, systemic photodynamic therapy (PDT) for nonmelanoma skin cancers: Case and literature review.

BACKGROUND AND

OBJECTIVE

Patients with multiple nonmelanoma skin cancers (NMSCs), like immunosuppressed or nevoid basal cell carcinomas, offer a therapeutic challenge. Photodynamic therapy (PDT) using the systemic photosensitizer meta-tetrahydroxyphenylchlorin (mTHPC) has the ability to treat multiple NMSCs up to a depth of 10 mm in a single session. These unique properties offer an attractive alternative to regular therapies (e.g., surgery or radiation) to these patients.

STUDY

DESIGN

A systemic search was carried out that focused on the main clinical studies using mTHPC-PDT on NMSCs in humans. This review describes some of the basic principles of the treatment, the most effective treatment parameters as well as its possible adverse outcomes, which is illustrated with a short description of our own experiences using this treatment modality on four patients with multiple NMSCs.

RESULTS

To date, only four clinical studies have been published. It was demonstrated that mTHPC-PDT could be highly effective. On illuminating 1-2 days after drug administration, plasma drug levels were high and the tumor clearance rates were high (up to 100%), with relative few side effects and excellent cosmetic and functional outcomes. These results were obtained with a relatively low, patient friendly photosensitizer dose (0.04-0.05 mg/kg) as skin photosensitivity was shorter after the procedure. Although the patients personally experienced consistently good cure rates, the healing times varied greatly between anatomical areas. The head and neck areas heal well with good cosmesis, while the lower leg and foot areas show delayed, at times compromised, healing with scarring.

CONCLUSIONS

Although mTHPC-PDT is described in the literature as an interesting and promising therapeutic option, especially for multiple NMSCs, a randomized clinical trial is lacking and personal experiences warrant too much skepticism. With the recent introduction of the hedgehog pathway inhibitor vismodegib, mTHPC-PDT seems to be less suitable as a first line of treatment; it should be considered as a last resort therapy.