Use of photodynamic therapy for the management of pleural malignancies

Pleural malignancies

Pleural malignancies, primary or metastatic, portend a grim prognosis. In addition to the serious oncologic implications of a pleural malignancy, these tumors can be highly symptomatic. A malignant pleural effusion can cause dyspnea, secondary to lung compression, or even tension physiology from a hydrothorax under pressure. The need to palliate these effusions is a seemingly straightforward clinical scenario, but with nuances that can result in disastrous complications for the patient if not attended to appropriately. Solid pleural malignancies can cause great pain from chest wall invasion or can cause a myriad of morbid symptoms because of the invasion of thoracic structures, such as the heart, lungs, or esophagus. This article reviews pleural malignancies, the purely palliative treatments, and the treatments that are performed with definitive (curative) intent.

Broadband reflectance measurements of light penetration, blood oxygenation, hemoglobin concentration, and drug concentration in human intraperitoneal tissues before and after photodynamic therapy

We evaluate Photofrin-mediated photodynamic therapy (PDT) in a phase 2 clinical trial as an adjuvant to surgery to treat peritoneal carcinomatosis. We extract tissue optical [reduced scattering (mu(s)'), absorption (mu(a)), and attenuation coefficients (mu(eff))] and physiological [blood oxygen saturation (%S(t)O2), total hemoglobin concentration (THC), and photosensitizer concentration (c(Photofrin))] properties in 12 patients using a diffuse reflectance instrument and algorithms based on the diffusion equation. Before PDT, in normal intraperitoneal tissues %S(t)O2 and THC ranged between 32 to 100% and 19 to 263 microM, respectively; corresponding data from tumor tissues ranged between 11 to 44% and 61 to 224 microM. Tumor %S(t)O2 is significantly lower than oxygenation of normal intraperitoneal tissues in the same patients. The mean (+/-standard error of mean) penetration depth (delta) in millimeters at 630 nm is 4.8(+/-0.6) for small bowel, 5.2 (+/-0.67) for large bowel, 3.39(+/-0.29) for peritoneum, 5.19(+/-1.4) for skin, 1.0(+/-0.1) for liver, and 3.02(+/-0.66) for tumor. c(Photofrin) in micromolars is 4.9(+/-2.3) for small bowel, 4.8(+/-2.3) for large bowel, 3.0 (+/-1.0) for peritoneum, 2.5(+/-0.9) for skin, and 7.4(+/-2.8) for tumor. In all tissues examined, mean c(Photofrin) tends to decrease after PDT, perhaps due to photobleaching. These results provide benchmark in-vivo tissue optical property data, and demonstrate the feasibility of in-situ measurements during clinical PDT treatments.

Malignant pleural mesothelioma: surgical roles and novel therapies

Malignant pleural mesothelioma (MPM) is a uniformly fatal disease that has been recalcitrant to curative therapies. Median survivals of 8-18 months have, for the most part, led to a sense of frustration and nihilism in the medical and surgical community with regard to management of the disease, and the relatively small numbers of patients with mesothelioma have made it an orphan among other cancers with regard to research efforts and funding. This review will comment on the clinical presentation of the disease and therapeutic options that are available at this time. The role, timing, degree, and availability of cytoreductive surgery in the context of a multimodality approach for MPM will be highlighted, and various strategies that incorporate adjunctive therapies before, during, or after the operation will be discussed. Newer cytotoxic chemotherapies, either alone or in combination, are reviewed, with an emphasis on the increasing number of options with increased response rates that are becoming available for MPM patients. The results of protocols at selected centers that offer gene therapy, photodynamic therapy, hyperthermic chemotherapeutic perfusion, and intrapleural chemokines will be discussed, as well as newer preclinical approaches that base targeted therapies on novel molecular findings. In considering the newest approaches to the disease, one is encouraged to seek specialty consultation at centers that concentrate programmatic efforts on mesothelioma in order to design translational-based approaches on preclinical findings. By using such an approach, the patient and physician will find that there are considerably more options in the new century for mesothelioma.

Wedge-shaped applicator for additional light delivery and dosimetry in the diaphragmal sinus during photodynamic therapy for malignant pleural mesothelioma

In situ light dosimetry during photodynamic therapy (PDT) of malignant pleural mesothelioma (MPM) after tumour resection facilitates the delivery of a controlled light distribution to the inner thoracic surface. Illumination of the diaphragm-induced sinus, however, remains difficult. Our aim was to develop a wedge-shaped light applicator with incorporated light dosimetry to deliver an additional fluence limited to the sinus. The wedge-shaped applicator contains a cylindrical diffuser for light delivery and two isotropic detectors for simultaneous light dosimetry. These detectors were placed at strategic positions where the fluence rate is maximal or minimal (middle and edge). Prior to its clinical use, the performance of the sinus light applicator was tested in several optical tissue phantoms with different optical properties. The fluence rate distribution over the surface of the applicator showed little change when the wedge was submerged in four different optical phantoms. During clinical PDT of MPM the applicator had to be re-located manually four times in order to give an additional fluence of approximately 2 J cm(-2) to the entire sinus. The light applicator enables dosimetry-controlled light delivery for additional illumination of the sinus region that is often under-illuminated during thoracic integral illumination of MPM.

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.

Advances in the treatment of malignant pleural mesothelioma

Malignant pleural mesothelioma is a neoplasm that is commonly fatal and for which there are no widely accepted curative approaches. Mesothelioma is unresponsive to most chemotherapy and radiotherapy regimens, and it typically recurs even after the most aggressive attempts at surgical resection. Multimodality approaches have been of some benefit in prolonging survival of very highly selected subgroups of patients, but they have had a relatively small impact on the majority of the patients diagnosed with this disease. As the incidence of pleural mesothelioma peaks in the United States and Europe over the next 10 to 20 years, new therapeutic measures will be necessary. This review will discuss the roles of chemotherapy, radiotherapy, surgery, and combined modality approaches in the treatment of pleural mesothelioma, as well as scientific advances made in the past decade that have led to the development of experimental techniques, such as photodynamic therapy, immunotherapy, and gene therapy, that are currently undergoing human clinical trials. These promising new avenues may modify the therapeutic nihilism that is rampant among clinicians dealing with mesothelioma.

Operation and photodynamic therapy for pleural mesothelioma: 6-year follow-up

BACKGROUND

Conventional therapy for pleural mesothelioma has met with disappointing results.

METHODS

From 1991 to 1996, 40 patients with malignant pleural mesothelioma were treated with surgical resection followed by immediate intracavitary photodynamic therapy.

RESULTS

The series included 9 women and 31 men with a mean age of 60 years. Morbidity and treatment-related mortality rates for the entire series, pleurectomy, and extrapleural pneumonectomy were 45% and 7.5%, 39% and 3.6%, and 71% and 28.6%, respectively. Median survival and the estimated 2-year survival rate for the entire series, stages I and II patients (n = 13), and stages III and IV patients (n = 24) were 15 months and 23%, 36 months and 61%, and 10 months and 0%, respectively. Multivariate analysis identified stage, length of hospital stay, photodynamic therapy dose, and nodal status as independent prognostic indicators for survival.

CONCLUSIONS

Surgical intervention and photodynamic therapy offer good survival results in patients with stage I or II pleural mesothelioma. For patients in stage III or IV, better treatment modalities need to be developed. Improvements in early detection and preoperative staging are necessary for proper patient selection for treatment.

Photodynamic therapy

Photodynamic therapy involves administration of a tumor-localizing photosensitizing agent, which may require metabolic synthesis (i.e., a prodrug), followed by activation of the agent by light of a specific wavelength. This therapy results in a sequence of photochemical and photobiologic processes that cause irreversible photodamage to tumor tissues. Results from preclinical and clinical studies conducted worldwide over a 25-year period have established photodynamic therapy as a useful treatment approach for some cancers. Since 1993, regulatory approval for photodynamic therapy involving use of a partially purified, commercially available hematoporphyrin derivative compound (Photofrin) in patients with early and advanced stage cancer of the lung, digestive tract, and genitourinary tract has been obtained in Canada, The Netherlands, France, Germany, Japan, and the United States. We have attempted to conduct and present a comprehensive review of this rapidly expanding field. Mechanisms of subcellular and tumor localization of photosensitizing agents, as well as of molecular, cellular, and tumor responses associated with photodynamic therapy, are discussed. Technical issues regarding light dosimetry are also considered.

ESR studies of a series of phthalocyanines. Mechanism of phototoxicity. Comparative quantitation of O2-. using ESR spin-trapping and cytochrome c reduction techniques

ESR experiments with 2,2,6,6-tetramethyl-4-piperidone (4-oxo-TEMP) and the spin-trap 5,5-dimethyl pyrroline-N-oxide (DMPO) have been performed on a series of new phthalocyanines: the bis(tri-n-hexylsiloxy) silicon phthalocyanine ([(nhex)3SiO]2SiPc), the hexadecachloro zinc phthalocyanine (ZnPcCl16), the hexadecachloro aluminum phthalocyanine (AlPcCl16), the hexadecachloro aluminum phthalocyanine sulfate (HSO4AlPcCl16), whose photocytotoxicity has been studied against various leukemic and melanotic cell lines. Type I and Type II pathways occur simultaneously in DMF although the Type II seems to be prevalent. These results are not changed when the bis(tri-n-hexylsiloxy) silicon phthalocyanine is entrapped into liposomes. By contrast, the Type I process is favored in membrane models for all the perchlorinated phthalocyanines. This modified behavior may be accounted on a possible stacking of phthalocyanines in membranes and a preventing effect of axial ligands against aggregation in the case of the bis(tri-n-hexylsiloxy) silicon phthalocyanine. The photodynamic action of zinc perchlorinated phthalocyanine is not dependent on singlet oxygen, phototoxicity of this molecule being essentially mediated by oxygen free radicals. Quantitation of the superoxide radical was accomplished, with good agreement, by two techniques: the cytochrome c reduction and the ESR quantitation based on the double integration of the first derivative of the ESR signal. The disproportionation of the superoxide radical or degradation of the spin-trap seem to be avoided in aprotic solvents such as DMF.

A review of chemotherapy trials for malignant mesothelioma

Treatment of malignant pleural mesothelioma continues to be frustrating regardless of the modality employed. Numerous trials of chemotherapeutic agents have been performed, but until recently, these studies were small and subject to inaccuracies of disease measurement. To our knowledge, no chemotherapeutic regimen has emerged as a standard of care. A review of the literature reveals that small activity against this disease has been shown by the anthracyclines, platinum compounds, and alkylating agents, whereas higher activity has been reported with the antimetabolites. The plant alkaloids have not demonstrated any activity against mesothelioma. Dose-escalated chemotherapeutic regimens may offer an advantage, whereas combination chemotherapy has not shown any benefit over single-agent therapy. Favorable responses have been reported with the administration of intrapleural biological response modifiers. Further trials and the investigation of new agents in the treatment of this disease are necessary.

Phototoxicity of some novel porphyrin hybrids against the human leukemic cell line TF-1

Photodynamic induced cytotoxicity by porphyrin-DNA cross linker/intercalator hybrid diads and triads has been studied on the human leukemic cell line TF-1. Cells were incubated for 1 to 4 h with these new photosensitizers and irradiated with white light. Cell survival was assessed by the propidium iodide staining, using flow cytometry analysis. A comparison of the dark and light cell survival factor values suggests that irradiation has a significant effect on the toxicity at low concentrations for the porphyrin-chlorambucil diad and to a lesser extent at high concentrations for the porphyrin-acridone diad, the porphyrin-acridine diad and the porphyrin-cholic acid-chlorambucil triad. While the intrinsic antileukemic (via DNA cross-linking) activity of the chlorambucil moiety and the structural details may be responsible for the photoenhancement of the toxicity, the presence of acridine or acridone which are avid intercalators of DNA, is responsible for a similar effect seen for diads.