Möglichkeiten und Grenzen der Fluoreszenzdiagnostik und photodynamischen Therapie: Teil 2: Photodynamische Therapie

Plattenepithelkarzinome im Kopf-Hals-Bereich

INTRODUCTION

Photodynamic therapy (PDT) is a relatively new method of treating superficial tumours of the skin or mucous membranes. After the injection of a photosensitiser, the tumour area is exposed to non-thermal laser light. This causes a phototoxic reaction, producing oxygen radicals that destroy the tumour cells.

PATIENTS AND METHODS

From November 2004 to February 2006, a total of 24 patients with recurrent or secondary tumours after squamous cell carcinoma of the head and neck were treated with PDT at the German Armed Forces Hospital in Ulm after other treatment options had failed. Meta-tetrahydroxyphenyl chlorin (mTHPC), known under the trade name of Foscan, was used as the photosensitising agent.

RESULTS

Complete remission was observed in 12 patients (50%) and partial remission was seen in nine (37.5%). Three patients did not respond to treatment. The mean duration of overall survival was 305.7 days (+/-199.4) after completion of treatment. The mean duration of recurrence-free survival was 302.7 days (+/-144.9) for patients with complete remission. There were no serious complications.

CONCLUSIONS

Photodynamic therapy is an important treatment option for patients who develop recurrent or secondary tumours after squamous cell carcinoma of the upper aerodigestive tract and fail to respond to other treatments. In addition, PDT may play a role in the primary treatment of superficial tumours of the oral cavity, pharynx and larynx in the future.

Chemoprevention of squamous cell carcinoma of the oral cavity

Squamous cell carcinoma of the oral cavity has long been seen as an attractive candidate for chemoprevention strategies. Because of the poor out-comes associated with the disease, the presence of identifiable premalignant lesions, and the failure of local preventive therapies, such as surgery, many investigators have hoped to find an effective chemopreventive compound. Initial enthusiasm surrounding high-dose retinoids gave way to concerns regarding toxicity and short duration of response. Although many of the other agents discussed above have shown promise, as yet none have been proven safe and effective in large-scale randomized trials. Much has been learned,however, about the molecular process of oral carcinogenesis from studies of these agents. Ongoing and future studies of chemopreventive agents in oral cancer hopefully will be able to exploit our expanding knowledge of these molecular pathways.

Oral cancer prevention and the evolution of molecular-targeted drug development

The multifaceted rationale for molecular-targeted prevention of oral cancer is strong. Oral cancer is a major global threat to public health, causing great morbidity and mortality rates that have not improved in decades. Oral cancer development is a tobacco-related multistep and multifocal process involving field carcinogenesis and intraepithelial clonal spread. Biomarkers of genomic instability, such as aneuploidy and allelic imbalance, can accurately measure the cancer risk of oral premalignant lesions, or intraepithelial neoplasia (IEN). Retinoid-oral IEN studies (eg, of retinoic acid receptor-beta, p53, genetic instability, loss of heterozygosity, and cyclin D1) have advanced the overall understanding of the biology of intraepithelial carcinogenesis and of preventive agent molecular mechanisms and targets-important advances for monitoring preventive interventions and assessing cancer risk and pharmacogenomics. Clinical management of oral IEN varies from watchful waiting to complete resection, although complete resection does not prevent oral cancer in high-risk patients. New approaches, such as interventions with molecular-targeted agents and agent combinations in molecularly defined high-risk oral IEN patients, are urgently needed to reduce the devastating worldwide consequences of oral cancer.