Mesothelioma of the Pleura - Photodynamic Therapy
Photodynamic therapy of malignant mesothelioma of pleura
4. DISCUSSION
Single modality therapeutic management has yielded few long-term survivors in malignant pleural mesothelioma. The role of surgery is generally considered to be limited. Pleurectomy/decortication is an incomplete tumour-debulking procedure and therefore ineffective as a single treatment with curative aim.
Extensive surgery by EPP has been advocated as a theoretically more attractive operation because it may allow a radical excision, but only a minority of patients with mesothelioma qualify for this operation and it carries a higher risk. Studies have shown that patients undergoing EPP have a greater tendency towards development of distant diseasel6. The therapeutic challenge is two-fold, effective treatment regimens for malignant mesothelioma must address the problem of systemic disease as well in order to obtain local and systemic control of the malignancy. Combined treatment modality appears to offer some promise in this otherwise rapidly fatal diseasel7.
The impact of the presented method in a small and heterogeneous patient group is difficult to evaluate. However, patients no. 2 and 6 reoperated a year after initial treatment were completely free from tumour within the thoracic cavity. During the follow-up, in 3 patienes distant metastases.were seen prior to recurrency within the treated hemithorax. Such results of relatively long-lasting local control were obtained in patients undergoing various surgical procedures with low mortality/morbidity. The tumours of these patienes presented photosensitizer Suorescence of even distribution and of high intensity. Patients with tumours of inhomogenious (related to the differentiation grade) and low fluorescence intensities showed rapid recurrency and metastases.
Patient no. 6, presenting a relatively high nuorescence intensity of the initial tumour and a significantly lower intensity in the metastatic tumour, showed generalized malignancy only 3 months after retreatment.
An approach by thoracoscopic PDT13 was considered not useful in these patients all of whom presented tumour masses of large size located in the costophrenic sulcus. CT scans did not offer sufficent accuracy to evaluate tumour thickness, especially in the costophrenic sulcus. We experienced improved surgical radicality as well as improved access for light exposure in this area by doing complete diaphragmatic resection.
As a conclusion we present the hypothesis that associated PDT-treatment has a clinical effect and that predictability of PDT-efficiency seem to be related to the distribution and intensity of the fluorescence induced by the photosensitiser in tumour (Table 1). The PDT-effect may enhance the potential to complete local tumour eradication even in the case of less aggressive surgical debulking procedure. However, as clearly visualized in this study a multimodal therapeutic approach addressing to the systemic disease seems necessary to further improve survival.
5. ACKNOWLEDGMENT
This study was finacially supported by The Norwegian Cancer Society. Photosensitiser and some of the technical equipment was a gift from Lederle, American Cyanamid.
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