A combination therapy might hold promise for extending the lives and preserving more lung function of patients with malignant pleural mesothelioma, a cancer of the lining inside the chest.
Patients in mesothelioma treatment often undergo an extensive surgery known as a modified extrapleural pneumonectomy, which involves removal of the lung and surrounding tissue and is usually accompanied by radiation of the whole chest area. But the new combination approach for mesothelioma patients adds a treatment called photodynamic therapy to a more conservative, lung-sparing surgery called a pleurectomy.
Photodynamic therapy is a light-based treatment that is designed to eliminate any microscopic bits of residual cancer that surgeons are unable to remove. The therapy, which penetrates just a few millimeters into tissue, has three components that are administered: a nontoxic compound that sensitizes cancer cells to light; then oxygen; then specially tailored light. While the therapy is federally approved for treatment of several cancers, it remains experimental for malignant pleural mesothelioma.
Researchers at the University of Pennsylvania in Philadelphia set out to determine whether the lung-sparing surgery could be used instead of an extrapleural pneumonectomy, and whether the use of photodynamic therapy would extend patients’ survival time, compared with typical survival times in mesothelioma patients.
Nine women and 19 men with malignant pleural mesothelioma, ranging in age from 27 to 81, participated in the Phase II study from 2004 to 2008. Half received the more extensive surgery along with photodynamic therapy, while the other half had the lung-sparing surgery along with the light-based therapy.
Twelve patients in each group had stage III/IV mesothelioma—and researchers noted that many of the research subjects, due to the advanced stage of their mesothelioma or to their advanced age, would not be candidates for surgical treatment. In all, 22 patients also had chemotherapy. The two groups were comprised of mesothelioma patients with similar demographic traits such as age, sex and disease characteristics.
Among the patients who had the more extensive surgery and photodynamic therapy, the median overall survival—the point in time after treatment was completed at which half the patients were still alive—was 8.4 months. For the patients receiving the lung-sparing surgery plus the light therapy, that median point had not been reached yet, after more than two years of follow-up.
The surgeon who performed the procedures in the study, Dr. Joseph Friedberg of the Penn Mesothelioma and Pleural Program, said researchers had hoped that preservation of patients’ lungs would improve their quality of life, and that the extended survival time of those patients was a complete surprise. The scientists are continuing to investigate exactly how the photodynamic therapy might be helping to fight mesothelioma—possibly by creating a “vaccine” effect with residual disease that sparks the immune system to fight any remaining cancer. Or, the photodynamic therapy might have made any residual cancer more vulnerable to other follow-up treatments.