Trial Design
HPV FOCAL is a three-armed, RCT over a four year period (Figure 1).
Control arm: LBC at entry and again at two years; ASCUS cases are triaged with hr-HPV testing; combined LBC and hr-HPV at four years (exit screen) among those with initial negative results.
Two Year Safety Check arm: hr-HPV at entry; LBC at two years (exit screen) in those with initial negative hr-HPV results with LBC triage of hr-HPV positives at either round.
Four Year Intervention Arm: hr-HPV at entry with LBC triage of hr-HPV positives; combined hr-HPV and LBC at four years (exit screen) among those with initial hr-HPV negative results.
British Columbia Population Based Cervical Cancer Screening Program
Since the 1960s, cervical cancer screening in British Columbia has been organized as a centrally administered program[22]. A single provincial laboratory (Provincial Health Services Laboratories) processes and interprets Pap test samples from all clinicians in the province. A unified set of recommendations for the management of women with abnormal Pap tests is produced by the British Columbia Cancer Agency (BCCA), and is communicated to the healthcare providers with the Pap test results. BCCA also manages a coordinated follow-up system involving regional colposcopy clinics across the province for women with abnormal Pap tests. BCCA's Cervical Cancer Screening Program maintains a single data structure linking all Pap test results and disease outcomes, and provides overall program administration and coordination of promotion, recruitment, follow-up reminder system, follow-up tracking, quality management, program evaluation and research support.
Study Population and Recruitment
Women aged 25 to 65, registered with Medical Services Plan in British Columbia, who receive care from a participating family physician (FP) for routine cervical screening are eligible. Exclusion criteria are: a history of histologically proven CIN2 or worse requiring treatment in the last five years; a history of histologically proven invasive cervical cancer; a Pap smear within the preceding twelve months; no cervix; pregnant at time of enrolment; HIV positive or on immunosuppressive treatments; or unwilling or unable to provide informed consent.
Women are invited to participate in the study when they present for cervical cancer screening and are deemed eligible to participate by their FP or when pre-identified as being due for screening from the BCCA centralized provincial cytology database. For the pre-identified, the FP office sends the woman a study package that includes an invitation letter, a study information pamphlet and the informed consent form. The invitation letter requests women to phone their FP to make an appointment for their cervical screening test and also provides them with the opportunity to contact, or be contacted by study staff to learn more about the trial and decide on participation. All participants are consented by their FP and are asked to complete an epidemiologic questionnaire. A financial implications questionnaire is also completed by a random sample of participants. Full cervical cancer screening history is available through data linkage to the cervical cancer screening program, and HPV vaccination status is self reported.
Study Protocol (Figure 1)
In addition to the control arm and the intervention arm, a 'two year safety-check' arm is included in this trial. At the time of the trial design, there were ethical concerns identified in changing the screening interval at the same time as changing the primary screening tool in a clinical trial. To that end, we included a safety check arm, to examine the safety of hr-HPV testing within the usual screening interval. This information will be used by the data safety monitoring board to verify the safety of hr-HPV testing at the two year interval and infer the suitability of the intervention arm as the trial proceeds.
Two samples are collected during the initial screening appointment. Specimen1 (LBC) is collected first with the ThinPrep® Broom-like collection device and is placed in a ThinPrep® PreservCyt vial (Hologic Inc, Bedford MA) and is used for all the HPV FOCAL trial testing. Specimen 2 is collected in Digene STM® (Qiagen, Mississauga ON) and is frozen for future use. Both specimens are sent to the central laboratory in Vancouver, for trial testing (specimen 1) and for storage (specimen 2). Upon sample receipt, the woman is randomized to one of the three study arms and specimen 1 is aliquoted (Figure 1). For those allocated to hr-HPV testing arms, an aliquot is removed and processed using the Qiagen sample conversion kit, and tested using the Digene Hybrid Capture 2 (HC2) assay (Qiagen, Mississauga ON), which tests simultaneously for the presence of DNA from 13 hr-HPV types. Results are classified as hr-HPV negative, hr-HPV positive or unsatisfactory. LBC testing is conducted on specimen 1 using the ThinPrep® collected device, according to the manufacturer's recommendations. Cytological evaluation and reporting follow the Bethesda classification system [23].
Colposcopy
If the woman's test results indicate that a colposcopy referral is recommended (Figure 1), this will be conveyed to the FP with the study sample results. All colposcopy examinations are performed at study-designated colposcopy clinics in Vancouver and Victoria to ensure consistency in diagnostic performance. Colposcopic examinations performed in British Columbia are highly standardized, and clinicians providing colposcopy adhere to a study-agreed protocol.
Women referred for colposcopy fall into the following major groupings:
a) Cytology: AGC (hr-HPV positive or not done);
b) Cytology: ASC-H or ≥ LSIL (hr-HPV positive or not done);
c) Cytology: ASC-US; (hr-HPV positive or persistent ASC-US which was initially hr-HPV negative).
Women are managed according to the standard provincial guidelines in the province of British Columbia[24]. Colposcopy is used to assess the highest grade lesion seen on the cervix and directed biopsy(s) is performed as well as an endocervical curettage when appropriate. The standard treatment for CIN2+ in British Columbia is an excisional treatment, most commonly loop electrosurgical excision procedure (LEEP) and occasionally cone biopsy
Histology
Pathological interpretation of biopsies is conducted at two centres which provide services to the participating colposcopy clinics. Pathologists are blinded to cytology and hr-HPV result when interpreting the slides. Histology results are stored in the same Laboratory Information System (LIS) as the cytology results.
Following standard practice, if there is significant discordance between the cytologic and histologic evaluation which would potentially influence patient management, the colposcopist contacts the laboratory to request review and correlation of the histology and cytology in order to resolve the discrepancy (e.g. a case where HSIL cytology is noted, but negative histology,) and determine an appropriate disease management strategy.
A review of exit screen histology is an essential component of the trial. Approximately 50% of exit screen histology results will undergo second review by senior study pathologists. If the primary and review histology results agree, this will be the final study diagnosis, but in the case of disagreement between primary and review histology, the slide will be referred to another senior pathologist. If this result agrees with either the primary result or first review the agreed results will be the final study diagnosis. If all 3 results are different, the final study diagnosis will be established by consensus between all three pathologists.
Randomization and Blinding
A database has been developed specifically for the HPV FOCAL trial. Randomization occurs through this database when samples are received at the laboratory. At the time of randomization a Study Identification Number (SIN) is allocated to the participant. Samples are stratified by age and simple equal (1/3 probability) random allocation occurs at the laboratory. Upon randomization, study staff label and batch the specimens for initial processing (hr-HPV or LBC).
FPs and participants are blinded to study arm allocation. Participant results are communicated from the BCCA to the FP office as soon as they are known. If the participant's initial screening results (hr-HPV or cytology) are "negative" the report states "within normal limits". The report also states that the recommended follow-up for that participant will be communicated to the FP in two years' time. This ensures blinding is maintained for as long as possible and prevents any bias that may potentially occur from knowledge of negative results. If the screening results are hr-HPV and/or cytology positive, the results are communicated from the BCCA to the FP along with the recommended follow-up.
Statistical Considerations
Sample Size
The planned intake sample size is 11,000 women per arm (33,000 total). Power calculations were performed using the nQuery Advisor, version 2, software package. Rates of hr-HPV infection and associated histologically proven disease were based on results from the HART study[9], prevalence rates from the CCCaST trial conducted in Quebec and Newfoundland[8, 25]. Sample sizes were based on requiring at least an 80% power to detect relative differences (alternative hypothesis) of 20% in the outcome comparisons for intervention versus control at four years and control versus safety check arms at two years.
Analysis
Primary Outcome Measures
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Control and intervention arms: Cumulative incident ≥ CIN3 detected up to and including four years in both the control arm and the intervention arm
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Control and safety check arms: Incident ≥ CIN2 detected at two years. If the number of ≥ CIN2 in the safety-check group exceeds 0.8 times that in the control arm at the 2 year screen, then the trial will conclude and women in the four year intervention arm will be recalled at two years for their exit screen.
Secondary Outcome Measures
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Rates of ≥ CIN2 and hr-HPV respectively at initial screen in control and safety/intervention arms;
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Rates of incident ≥ CIN2 at two years in control arm and at four years in intervention arm;
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The total estimated cost per woman screened and the total estimated cost per quality-adjusted life-year gained for each technology;
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Clearance of hr-HPV infection in women who are hr-HPV-positive and cytology negative at initial screen.
The primary outcome analysis will be a comparison of histologically confirmed ≥ CIN3 between the intervention and control arms. Rates of lesion occurrence will be calculated using person-time denominators for the different study intervals and compared via Kaplan-Meier plots[26]. Rates will be calculated for specific age groups within the study. Significance testing will be based on Poisson statistics and performed at the 5% level (2-sided). Analysis will also be performed using logistic regression to permit control of potential confounding factors since for some comparisons balance may not be assured by randomization. The primary comparison of disease rates between test negative groups (at entry screen) will not control for potential confounding factors since they are not balanced by randomization and the tests may select for different characteristics. Covariate-adjusted analyses will be performed to determine the extent to which any difference is explicable by potential confounders (e.g., age and sexual behaviour).
Ethical Issues
This study is being conducted in accordance with the Ethical Conduct for Research Involving Humans Tri-Council Policy Statement http://www.nserc-crsng.gc.ca/NSERC-CRSNG/governance-gouvernance/ethics-ethiques_eng.asp. Ethics approval has been obtained from appropriate local research ethics boards. The trial registration number is International Standard Randomised Controlled Trial Number Register: ISRCTN79347302. All information about this trial is kept behind locked doors or in secure computer files. On interim and final reports, all data will be de-identified.
