The emergence of photodynamic therapy as a major modality in cancer treatment

Cancer therapies are either locoregional, i.e., directed at the primary sit e and regional lymph nodes (radiotherapy or surgery), or systemic, i.e., di rected at disseminated disease (chemotherapy or immunotherapy). Photodynami c therapy (PDT), in its present form, is a locoregional cancer treatment. P DT is a superficial treatment modality and may also offer some specificity for tumour tissue versus normal tissues. The strengths and limitations of t his approach must be recognized in order to evaluate its overall role in on cology. The appropriate choice of treatment for any cancer depends upon the natural history of the cancer and on the stage of the cancer. PDT will bec ome integrated into oncology only if certain conditions are met: it must, f or example, be used in clinical situations where its unique properties offe r substantial therapeutic gain over standard treatments; and its efficacy m ust be evaluated in properly designed clinical trials which take into accou nt the special difficulties relating to photosensitizer and light dosimetry . PDT possesses few, if any, advantages over surgery or radiotherapy in the treatment of large, locally advanced, tumours, but it may have a role as a djuvant therapy for these tumours after surgical resection. At the present time, PDT is likely to be of most use in the treatment of premalignant cond itions, carcinoma in situ, and in surface malignancies. The future of PDT l ies in selected clinical situations, which permit the unique qualities of t his treatment modality to be employed to the greatest effect.