The Swedish National Cervical Screening Registry collects and evaluates nationwide, comprehensive data as a basis for optimization of organized cervical cancer prevention. Most data are imported via exports from administrative databases at the healthcare providers, but the comprehensive biobanking system of all cases of cancer in the nation is also a carrier of population-based data that could be read and imported to the registry. As a proof-of-principle, we identified all cervical cancers diagnosed in Sweden during a 10 year period (2002-2011; 4254 confirmed cases), requested the archival blocks and subjected them to HPV genotyping.
The Swedish Cancer Registry was used to identify the cases and the diagnosing pathology lab. The diagnostic blocks were requested and sectioned at an accredited sectioning company. In between each case block, a blank block containing only paraffin was sectioned, as a control for contamination. The blank-block had to be negative in all tests and the case-block positive for beta-globin. Following DNA extraction, HPV genotype data were retrieved using beta-globin real-time PCR and HPV genotyping using modified general primer (MGP)-PCR (primer target L1) and Luminex. Confirmed invasive cancers that were “HPV-negative” by Luminex were also analysed by real-time PCR for HPV16 and HPV18 (primer target E7 and E6), and will be sequenced using Illumina technology.
Although all pathology biobanks were - in principle - open access, not all agreed to participate. 2954/4254 (69%) cases were actually included and valid genotyping data could be obtained for 2852 cases (97% of included). The most common type was HPV16 (60% of HPV-positive, 50% of all valid cases), followed by HPV18 (19%/15%), HPV45 (8%/6%), HPV31 (3%/2%), HPV33 (2%), HPV52 (2%), HPV39 (1%), HPV70 (1%), HPV56 (1%), HPV35 (1%), HPV58 (1%) and HPV59 (1%). 96% of all HPV-positive tumours contained only one HPV type. Real-time PCR for E6/E7 performed only for “HPV negative” cases found that 12% of these were HPV16 positive and 7% were HPV18 positive.
Nationwide, comprehensive HPV genotyping of consecutive series of invasive cervical cancers is readily doable as part of the data importing tasks of a cervical screening registry, improving the possibilities to monitor the effectiveness of cervical cancer prevention and continued monitoring of the HPV-type specific disease burden.