RESUMO
Tyrosinase-based reverse transcriptase-polymerase chain reaction (RT-PCR) is a method for the detection of circulating melanoma cells in peripheral blood. To our knowledge, no long-term studies on the prognostic impact of tyrosinase PCR in uveal melanoma have yet been reported. In this prospective, non-randomized, observational cohort study, we included 41 patients with uveal malignant melanoma. RT-PCR for tyrosinase was performed in each patient before and after treatment. A clinical follow-up was performed for each patient for at least 5 years, including chest X-ray, serum liver enzyme determination, ultrasound of the liver and bone scintigraphy. The PCR results, age of the patients, tumour size, tumour location, tumour therapy, internal reflectivity, histology, development of distant metastasis and survival rate during follow-up were analysed. At the time of diagnosis, tyrosinase messenger RNA (mRNA) in peripheral blood, suggesting the presence of circulating melanoma cells, was detected in 16 of the 41 patients. Sixty-nine percent of the PCR samples with a positive result prior to therapy revealed a negative result after therapy. The internal reflectivity of the tumour (P=0.021) and the 5-year survival (P=0.023) showed a statistically significant association with positive PCR. It can be concluded that tyrosinase RT-PCR is a sensitive method for the detection of melanoma cells in peripheral blood. This study indicates that the presence of tumour cells in peripheral blood correlates with 5-year survival. Our results suggest a prognostic value of this method. Nevertheless, prospective analysis of a larger cohort is needed to determine the ultimate value of RT-PCR for tyrosinase in blood testing.
