Clinical relevance of HPV 16/18 testing methods in cervical squamous cell carcinoma

Three different in situ hybridization (ISH) methods were compared for their clinical relevance and suitability in detecting human papillomavirus (HPV) 16/18 in 55 cases of squamous cell carcinoma (SCC) of the uterine cervix. After the initial biopsy, surgery, and/or radiation therapy, patients were followed for 5 to 8 years. A biotinylated cDNA probe for HPV 16/18 was applied to serial sections in combination with conventional streptavidin-biotin-peroxidase ISH (a widely applied routine procedure), streptavidin-Nanogold-silver ISH, and tyramide-signal amplified (TSA) streptavidin-Nanogold-gold ISH. The TSA principle is also known as catalyzed reporter deposition and is, apart from in situ PCR, probably today's most sensitive technique for detecting papillomavirus infection by microscopic means. Nearly 65.5% of the cases showed specific HPV 16/18 detection with TSA ISH, whereas 43.6% were positive with streptavidin-Nanogold-silver-ISH, and only 40.0% with peroxidase-based ISH. Statistical analyses comparing early and advanced stages in both HPV-positive and -negative groups revealed a significantly better outcome for early disease patients; statistical significance was most pronounced with TSA ISH. In a subgroup of patients who had received radiation therapy without prior surgery (n = 35), those with advanced disease were significantly less likely to have HPV 16/18 infection than those with early disease. A significantly better overall survival was observed in those women with HPV 16/18-positive carcinomas who had undergone surgery before radiation therapy (seen with all three methods). We conclude that TSA, in addition to being the most sensitive HPV in situ method applied in this study, gave the most significant and clinically relevant statistical results.