Detection of squamous cell carcinoma of the oral cavity by imaging 5-aminolevulinic acid-induced protoporphyrin IX fluorescence

Abstract

Objectives: Early cancer detection is the best way to improve the prognosis of patients with oral cancer. Therefore this study presents quantitative fluorescence measurements and results in the visualization of cancerous oral mucosa with 5-aminolevulinic acid (5-ALA)-induced protoporphyrin IX (PPIX).

Methods: Time progression and type of porphyrin accumulation were analyzed in neoplastic and surrounding healthy tissue of 58 patients with a suspected cancer of the oral cavity by measuring emission spectra of 5-ALA-induced PPIX fluorescence. Fluorescence images in the red and green spectral range from the tumor tissue were recorded with a charge-coupled device camera.

Results: After topical application of 0.4% 5-ALA and incubation for 1 to 2.5 hours, all patients revealed higher intensities of red fluorescence in neoplastic tissue compared with the surrounding normal tissue. Maximum contrast was reached after 1.5 hours of incubation. In 13.8% (n = 8) of the patients, additional findings like dysplasia, carcinoma in situ, primary tumor, secondary carcinomas, and tumor branches were found by means of fluorescence marking in contrast to white light examination. An evaluation of the biopsy specimens resulted in a specificity of 60% and a sensitivity of 99%.

Conclusions: As a fluorescent marker, PPIX could represent a possible new diagnostic tool to detect early malignant and secondary lesions in the oral cavity. In addition, 5-ALA-induced PPIX fluorescence is promising as a useful intraoperative tool for determining adequate surgical margins of resection. Further investigations aim to assess this diagnostic procedure as a sensitive and clinically reliable method for patients with oral cancer.