Molecular detection of human papillomavirus and viral DNA load after radiotherapy for cervical carcinomas

Infection with high-risk types of human papillomavirus (HPV) is a necessary cause for cervical carcinoma. Radiation therapy together with surgery is the most effective treatment. The purpose of this study was to investigate the molecular basis of the response to radiotherapy in cervical cancer cells.

Tumor cells were obtained from biopsies of 44 cervical cancers, collected before and after radiotherapy. The presence of HPV was analyzed by polymerase chain reaction (PCR) using primers specific for the L1 region.

The prevalence of HPV was 70.4%, with HPV16 being the most common (54.5%) and HPV18 the second (15.9%). Our analyses show that ionizing radiation does not influence HPV detection, as the percentage of HPV-positive biopsies was similar in patients before and after radiotherapy (HPV16 60% vs. 51.7% and HPV18 20% vs. 13.7%, respectively). However, the detection of HPV did vary by tumor stage, with the highest proportion observed in late-stage tumors (HPV16 and HPV18 in 80% and 60% of stage III tumors, respectively). We also found that HPV viral load is influenced by radiotherapy and tumor stage, with the highest viral loads in late-stage tumors (stage III) after 1 day since radiotherapy (p<0.05). According to Kaplan-Meier curves, higher HPV viral load was associated with significantly shortened progression-free survival (p = 0.04).

Our data provide prospective evidence that ionizing radiation can affect the HPV viral load and this might offer the best strategies for assessment of therapeutic efficacy.