Correlação entre a espessura do carcinoma basocelular nodular e a sua remissão após Terapia Fotodinâmica

Abstract

The International Guideline of topical Photodynamic Therapy (TFD) recommends it only for inicial and thin tumors, which means a thickness less than 2mm. However, scant information is available about the impact of tumor thickness and its response to PDT. The aim of this study was to evaluate the relationship between the rate of complete response of nodular basal cell carcinoma (nBCC) to PDT and the pre-treatment thickness of the tumor. It was performed a prospective study with 48 patients treated with 2 PDT sessions, 1 week apart with methyl aminolevulinate 16% cream. Previously to PDT, a total of 72 nBCC were biopsied with a 3mm punch and specimens were submitted to histopathology with measurement of tumor thickness from the granular layer. Complete response was defined as total clinical clearance of the tumor and negative histopathology in post-treatment biopsy. The clinical follow-up for all patients was of at least 2 years. The mean tumor thickness before PDT was 1,51mm, ranging from 0,6 to 3,4mm. The global rate of complete response was of 61% (44/72). The Spearman's rank correlation coefficient, represented by greek letter ρ (rho), was applied to verify the relationship between the tumor thickness and the rate of complete response, resulting in rho = -0,371 (p-value = 0,001) for clinical response and -0,367 (p-value = 0,002) for histological response, i.e. there is a significant inverse relationship between these variables. Also, the chi-squared (2) test was applied in order to obtain a cut-off point and after analysis of several values, it was found that the thickness of 1,25 mm is the best cut-off, with a complete response in 76% (22/29) of tumors ≤ 1,25mm, while tumors > 1,25mm had a complete response in 48% (22/43) of the cases. Based on this result, the statistical of 2 = 4,446 was found, with a theoretical 2 = 3,841, implying that nBCC thinner that 1,25mm in pre treatment biopsy had more chances to remission after PDT. The remission was maintained in 93% (41/44) of the lesions during the follow up that achieved 4 years. So, it was demonstrated that the rate of complete response of nBCC was related to a thinner pre-treatment thickness with an inverse relationship between tumor thickness and rates of complete response. It might suggest that the measurement of tumor thickness pre PDT could be relevant to ensure an adequate selection of lesions suitable for PDT. Also, it should be considered as a predictor of PDT response with potential contribution in order to perform a more rationale indication of PDT, enhancing its efficacy. However, limitations of this study were the number of patients and the possibility that a 3mm punch biopsy could not accurately represent the actual thickness of the entire tumor.