A Technical Glitch or Whispers of Changing Epidemiology of HPV Negative Carcinoma Cervix? An Exploratory Study

Purpose/Objective(s)

To study the prevalence of HPV negative Carcinoma Cervix (CC) and its prognostic impact on survival.

Materials/Methods

Data of all CC who were treated with concurrent chemoradiotherapy followed by brachytherapy from 1^st Jan 2014 to 31^st December 2018 was retrieved. A total of 79 patients whose biopsy samples were available for genotyping were included in the study. DNA was extracted from cervical cell suspensions using Qiagen DSP virus kit (Ref-60704). The genotyping was done using 3B Black Bio TRUPCR HPV HR with 16/18 genotyping kit which is based on amplification of E6/E7 region by primers and probes specific for detection of 14 HPV subtypes. All procedures were followed as per instructions on the kit insert. Survival analysis was done using Kaplan Meier survival curves with log rank test used to compare the factors with respect to Overall survival (OS) and recurrence free survival (RFS). Statistical software was used for all statistical analyses.

Results

Seventy one percent (56/79) of the patients were HPV positive whereas 29% (23/76) were HPV negative. Out of the HPV positive patients, P16 positivity was the most predominant genotype with 73.2% (41/56) patients testing positive for it followed by P18 (14.3%). The remaining 12.5% of patients tested positive for HPV 31,35,51,52,56,58,59 and 68 subtypes. The unusual high rates of HPV negativity could be due to cervical cancers evolving independent of high-risk HPV, loss of expression of HPV, misclassification of cancers and inherent false negativity rates of the methods used for testing of HPV. All these factors were kept to a minimum by ensuring that the low and intermediate risk subtypes of HPV responsible were also tested for, the misclassification of uterine endometrioid adenocarcinoma or metastasis as CC was minimized by independent review of two experienced pathologists and testing related errors were kept at bare minimum by following the standard procedures provided by the manufacturers. Based on the extant literature, the combined false negativity rate of all the above factors, combined together, was approximately 7-8%, leaving an unexplained 21-22% of the HPV negative prevalence in the cohort. This could well be due to the rising trend of HPV negative carcinoma cervix which need a nuanced look on a broader basis as it might lead to a readjustment of our tactics in prevention and management of CC. The estimated 5-year OS of the HPV positive and HPV negative population within the study group was 84.5% and 82.6% respectively (P value=0.425). Median overall survival was not reached and needs a longer follow-up.

Conclusion

The HPV negativity rates among patients of CC in our study cohort were unusually high (29%). Detailed and systematic perusal of possible factors contributing to such high rates still left an uncharted void of approximately 21% which might be an early pointer towards rising trend of HPV negative CC.