Comparison of efficiency of photodynamic diagnostics with topical use of the 3% and 15% aminolevulinic acid in the detection of vulvar lesions.

UNLABELLED

The essence of the photodynamic diagnostic method is interaction between light and chemical compounds that form in reaction to light. In order to obtain fluorescence, tissue has to be exposed to energy in the form of light with the wavelength corresponding to the bandwidth of the photosensitizer absorption. The photodynamic method allows for the detection of even small lesions. This method facilitates the process of detecting vulvar cancer, especially in its early stages when it can develop on the foundation of overgrown epithelium. At that point the vulvoscopic image is difficult to interpret, in particular when multifocal growth occurs.

OBJECTIVES

The objective of the study was evaluating the efficiency of the photodynamic method PDD (photodynamic diagnosis) in the detection of vulvar lesions when two concentrations of the photosensitizer were used (3%- and 15%-aminolevulinic acid), as well as evaluating the efficiency of this method when compared to the efficiency of vulvoscopy, against the result of histological examination.

METHODS

Two concentrations of the 5-ALA cream (aminolevulinic acid) - 3% and 15% - were used in the PDD testing. The study group was divided into two subgroups A and B. In subgroup A the 15% eucerine-based cream was used. In subgroup B the 3% ALA gel with and addition of 2% DSMO was used. The photosensitizer was applied to the vulva 4-6h before the examination. In order to obtain fluorescence, energy in the form of light whose wavelength was approximately 405 nm, and whose source was a SLED diode, was transmitted to vulvar tissue. The positive result of the exam was obtaining tissue fluorescence. All patients underwent vulvoscopy and a histological examination of tissue samples was performed in all cases. The efficiency of the photodynamic testing in subgroups A and B was compared with the efficiency of vulvoscopy, against the result of histological examination. Sensitivity, specificity, as well as positive and negative predictive values of the PDD examination and vulvoscopy in both subgroups, were evaluated.

RESULTS

When the 15% ALA was used in detecting vulvar lesions, the photodynamic diagnostics was characterized by sensitivity of 100%, specificity of 92%, positive predictive value of 80%, negative predictive value of 100%, and correlation with the histopathological examination of 93.9%. When the 3% ALA was used, we observed: sensitivity of 100%, specificity of 91.4%, positive predictive value of 78.5%, negative predictive value of 100%, and correlation with the histopathological examination of 93.4%. Differences in the two subgroups were not statistically significant.

CONCLUSIONS

High correlation was observed between the accuracy of the photodynamic method of examining vulvar lesions and the accuracy of the histological examination, especially in cases of precancerous lesions and vulvar cancer. The photodynamic examination, when the 3%-ALA/2%DSMO is used, is characterized by a greater sensitivity, comparable specificity, as well as, comparable positive and negative prognostic values, in comparison to the vulvoscopic examination. The photodynamic method, when used with other diagnostic methods, facilitates performing the needle aspiration biopsy and allows for a greater precision of histological diagnoses. The pathological fluorescence obtained during the PDD examination gives information about the spread and multifocality of vulvar lesions, which can facilitate making presurgical decisions concerning the extensiveness of surgery. The photodynamic method, when the 3% ALA/2% DSMO is applied topically, is of comparable efficiency as the 15% ALA, in the detection of vulvar lesions. High safety of the photodynamic method was shown, both in terms of the topical application of the aminolevulinic acid and the subsequent use of light.