Evaluation of the Effect of Photodynamic Therapy on CAM-Grown Sarcomas

Resection margin adequacy plays a critical role in the local control of sarcomas. Fluorescence-guided surgery has increased complete resection rates and local recurrence-free survival in several oncological disciplines. The purpose of this study was to determine whether sarcomas exhibit sufficient tumor fluorescence (photodynamic diagnosis (PDD)) after administration of 5-aminolevulinic acid (5-ALA) and whether photodynamic therapy (PDT) has an impact on tumor vitality in vivo. Sixteen primary cell cultures were derived from patient samples of 12 different sarcoma subtypes and transplanted onto the chorio-allantoic membrane (CAM) of chick embryos to generate 3-dimensional cell-derived xenografts (CDXs). After treatment with 5-ALA, the CDXs were incubated for another 4 h. Subsequently accumulated protoporphyrin IX (PPIX) was excited by blue light and the intensity of tumor fluorescence was analyzed. A subset of CDXs was exposed to red light and morphological changes of both CAMs and tumors were documented. Twenty-four hours after PDT, the tumors were excised and examined histologically. High rates of cell-derived engraftments on the CAM were achieved in all sarcoma subtypes and an intense PPIX fluorescence was observed. PDT of CDXs resulted in a disruption of tumor-feeding vessels and 52.4% of CDXs presented as regressive after PDT treatment, whereas control CDXs remained vital in all cases. Therefore, 5-ALA mediated PDD and PDT appear to be promising tools in defining sarcoma resection margins (PDD) and adjuvant treatment of the tumor bed (PDT).

Photosensitivity Reaction From Operating Room Lights After Oral Administration of 5-Aminolevulinic Acid for Fluorescence-Guided Resection of a Malignant Glioma

Orally administered 5-aminolevulinic acid (5-ALA), which was approved in the United States in 2017, is preferentially metabolized by malignant glioma cells into protoporphyrin IX and enhances tumor visualization when using a blue light filter on an operating microscope. Photosensitivity after 5-ALA administration is a known side effect, but a photosensitivity reaction from operating room lights has not yet been documented. We report the case of a 56-year-old man with a history of previous resection of a grade II astrocytoma who presented with imaging concerning for tumor recurrence and possible malignant transformation. Repeat surgical resection utilized 5-ALA. Soon after the surgery, he developed reddening of his skin, particularly over the right side of his head and neck, with blistering and peeling in a distribution that was particularly exposed to operating room lights during surgery. No other areas of his skin experienced the same redness, blistering, or peeling. Topical lotions were applied and the skin changes resolved spontaneously over weeks. Significant photosensitivity after administration of oral 5-ALA is a rare complication, but neurosurgeons who perform fluorescence-guided tumor resection should remain cognizant of its potential association with exposure to intense light, including in the operating room. Phototoxicity typically is self-limited, but awareness is important to minimize its occurrence.