Photodynamic therapy for thoracic malignancies

Management of Malignant Mesothelioma by Decortication and Adjunct Phototherapy

Malignant mesothelioma is a relatively rare tumor that originates in the pleural space and almost invariably results from exposure to asbestos. Between September 1989 and December 1999, 100 patients were managed with curative intent using a combination of full decortication, adjunct phototherapy after administration of hematoporphyrin derivative, and strip radiotherapy to any areas where adequate clearance was not obtained. The survival curve was compared to that of 17 matched patients treated by decortication alone. Median survival increased from 250 to 440 days in the combined treatment group.

Photodynamic therapy as an innovative treatment for malignant pleural mesothelioma

Photodynamic therapy (PDT) of the pleura is an experimental treatment aimed at eradicating residual microscopic disease after macroscopic complete resection of malignant pleural mesothelioma (MPM) by means of intracavitary administration. A light-based treatment, PDT consists of 3 components: a nontoxic photosensitizing compound, oxygen, and visible light. The treatment is FDA-approved for several oncological targets, but remains experimental for MPM. PDT can be combined with lung-sparing pleurectomy and decortication and does not preclude other treatments such as adjuvant chemotherapy and/or radiation therapy. Additionally, PDT appears to bolster an immunologic effect by rendering the cancer cells that have been destroyed by the light-activated photosensitizer more presentable to the immune system. Local control and survival rates have been sufficiently rewarding to merit ongoing development of this combination of surgical technique and PDT.

Malignant pleural mesothelioma--an update

Exposure to asbestos is the most frequent, but not exclusive, cause of malignant mesothelioma. Clinical features include dyspnea, cough, nonspecific chest pain, weight loss and night sweats. Diagnosis may be complicated by histologic difficulties. Thoracoscopic techniques are proving beneficial, but no one method of imaging has proven superior, and disease staging is inconsistent. Conventional treatments such as chemotherapy, surgery, and radiotherapy have had variable impacts, although chemotherapy is useful in palliation and can improve both survival and quality of life. There is hope for new antimetabolite agents. The role of radical surgery is yet to be evaluated in a large trial. New radiotherapeutic techniques to improve local control are promising. Multimodality treatments appear to be the most successful for management of potentially resectable disease. It is likely that biological markers will improve accuracy in staging and prognosis. With new treatments based on better understanding of the biology of the disease, there is cautious optimism for the future for patients with malignant pleural mesothelioma.

Malignant pleural mesothelioma

Malignant pleural mesothelioma remains a difficult tumor to treat, much less cure. Currently, the best chance for long-term survival lies with early diagnosis and aggressive surgical extirpation, but given the typically long delay between the onset of symptoms and diagnosis, this is only possible with a high index of suspicion and an aggressive diagnosis workup. Early referral to a tertiary center experienced in the treatment of MPM may be important for several reasons: (1) decreased risk of tumor spread along multiple thoracenesis/biopsy tracts, (2) the availability of specialized pathologic assays for definitive diagnosis, (3) the availability of critical staging modalities (aggressive mediastinoscopy +/- thoracoscopy, MRI scans performed according to specific mesothelioma protocols, and perhaps PET scans), (4) surgical experience with pleurectomy/decortication and/or extrapleural pneumonectomy, that may decrease morbidity and mortality, and (5) the availability of novel adjuvant protocols. Single-modality therapy is unlikely to result in long-term survival. Aggressive surgery is required for optimal debulking, and extrapleural pneumonectomy may offer better local control compared with pleurectomy/ecortication. Delivery of optimal radiation schedules, which may involve large fractions as well as large total doses, is limited by the presence of nearby dose-limiting structures. Current chemotherapy is severely lacking in producing objective responses and improved survival although gemcitabine and IL-2 may be active agents to be combined with radiation and/or other agents. Hyperthermia, photodynamic therapy, intracavitary therapy, and gene therapy are all relatively new techniques under active investigation that should be supported by enrollment in on-going protocols. Predictably, many of these techniques provide greater benefit when used in the setting of adjuvant protocols or minimal residual disease, emphasizing the importance of multimodality therapy.

Photodynamic therapy for the hypercalcemic type of the small cell carcinoma of the ovary in a mouse xenograft model

OBJECTIVE

The hypercalcemic type of the small cell carcinoma of the ovary (HTSCCO) is a rapidly fatal ovarian tumor in young women. Photodynamic therapy (PDT) induces selective necrosis to malignant tissues. The aim of this study was to determine the sensitivity of the HTSCCO to PDT in a mouse xenograft model.

METHODS

Tumors were obtained from a patient with a HTSCCO and were transplanted into nude mice. Following photosensitization with m-THPC, either superficial or interstitial laser light was administered to the tumors. Necroses were measured by morphometry. Serum calcium levels were determined prior to and after PDT.

RESULTS

Superficial irradiation of m-THPC sensitized tumors showed over three times more necrosis than control tumors (P = 0.037). Interstitially irradiated tumors showed over seven times more necrosis than control tumors (P = 0.0012). All animals showed a highly significant hypercalcemia prior to PDT (P < 0.0001). PDT induced a significant decrease in serum calcium levels (P = 0.0297).

CONCLUSION

This study suggests that PDT may be of therapeutic value for the HTSCCO.

Photodynamic therapy in lung cancer. A review

Photodynamic therapy (PDT) in lung cancer was introduced in 1980 to treat tumours located in the major airways. After systemic injection of photosensitizers, tumour illumination is performed using a laser fibre to transmit light of a specific wavelength. PDT can be performed under local anaesthesia using the flexible fibreoptic bronchoscope. Skin photosensitivity is the most important treatment morbidity caused by the prolonged cutaneous retention of photosensitizer molecules. Ample data have shown that PDT is effective in obtaining tumour necrosis, but the skin photosensitivity issue limits its palliative potential. Moreover, competing bronchoscopic techniques, such as electrosurgery, Nd-YAG laser and brachytherapy, are available and seem to be equally palliative for the debulking of intraluminal obstructive lung tumours. The curative potential of PDT in patients with roentgenologically occult lung cancer is the most interesting aspect of this treatment modality. A significant number of patients with lung cancer have limited pulmonary function. A normal tissue sparing treatment such as PDT may provide an alternative, as patients may also have subsequent multiple lung cancer primaries. Since early lung cancer detection is now becoming feasible, PDT may be applied to treat roentgenologically occult tumours with curative intent. This may optimize treatment efficacy in the near future.

Bronchoesophagopleural fistula after photodynamic therapy for malignant mesothelioma

A 66-year-old woman presented with a bronchoesophagopleural fistula 10 weeks after thoracic photodynamic therapy for malignant mesothelioma. This is the third reported case of an esophagopleural fistula developing subsequent to photodynamic therapy for mesothelioma. We review the literature on this topic and report our successful management of this complication.

Cytologic effects of photodynamic therapy in body fluids

Photodynamic therapy (PDT) has been used in phase I clinical trials at the National Institutes of Health for the treatment of malignancies disseminated within the peritoneal and pleural cavities. Review of records revealed 18 patients who were treated with PDT between April 1988-June 1993. Sixty-five pleural and peritoneal fluids, 22 pre- and 43 post-PDT, were available for evaluation. Mesothelial cell changes seen post-PDT included: increased nuclear-to-cytoplasmic ratios in 7/18 (39%), cytomegaly in 9/18 (50%), and multinucleation in 12/18 (67%), with Touton-like giant cells in 3/18 (17%). Additional changes noted post-PDT comprised histiocytic aggregates in 9/18 patients (50%), with granuloma-like clusters in 3/18 (17%), acute and chronic inflammation in 13/18 (72%), and eosinophilia in 8/18 (44%). Residual tumor was present in 7/18 (39%) patients post-PDT. In 2 patients with malignant mesothelioma, benign mesothelial cells with cytologic changes post-PDT were difficult to distinguish from malignant cells. Mesothelial cell changes following PDT, specifically increased nuclear-to-cytoplasmic ratios and cytomegaly, should be recognized to avert false-positive diagnoses of tumor. In patients with malignant mesothelioma, and less commonly with adenocarcinoma, benign mesothelial cells with changes secondary to PDT may be difficult to distinguish from tumor cells.