Cryotherapy for Human Papillomavirus Clearance in Biopsy-confirmed Cervical Low-grade Squamous Intraepithelial Lesions: a Randomized Controlled Trial
This will be a hospital-based, parallel, assessor-blinded, randomized controlled trial.
Study subjects refer to LSIL patients, more than 30 years-old, with positive HPV testing who
do not have any contraindication of performing cryotherapy. Therefore, after recruitment
LSIL patients whose age more than 30 years-old, we will exclude only those who have negative
HPV testing or any contraindications of performing cryotherapy. The primary outcome is HPV
clearance (negative HPV testing for the baseline HPV type) at 12 months after the treatment.
Subjects will be randomly allocated to be treated by cryotherapy or observation only by
using block randomization with varied block size of 2, 4, and 6. The sample size of at least
25 for each arm was planned to have the power of 80% to detect 20% difference rates of HPV
clearance after 12 months of treatment between the two arms, with significance level of
0.05, two-sided test.
Biopsy-confirmed LSIL patients, age more than 30 years-old, referred to either Srinagarind
Hospital's, Khon Kaen Hospital's, or Roi Et Hospital's colposcopic clinics.
- Baseline HPV testing is positive.
- Be able to give their informed consent to this study.
- Having active cervical infection
- Having lesion of 2 mm-larger than probe
- Having lesion inside cervical os
- Having suspected cervical cancer lesion
Sample and sample size:
From previous studies, HPV clearance rate after cryotherapy at 12 months is 83.9%. (Elfgren,
2002) Spontaneous HPV clearance rate in young women at 24 months is 70%. (Moscicki, 1998)
However, this HPV clearance rate in women older than 34 years-old at 12 months is only
53.6%. (Clavel, 2005) Using these numbers respectively as PE and PC putting in the formula
below, we can calculate our sample size in each group. The sample size will be calculated to
detect the 20-40% difference between the HPV clearance rates after 12 months, at significant
level of 95% and power of 80% (two-sided test), using the approach of Lachin that was
reviewed in the paper of Donner.(Donner, 1984)
Required sample size at different rate of clearance
P-control P-experimental Alpha level Power N Difference 95%CI 0.50 0.70 5% 80% 103 20
6.9-33.1 0.50 0.75 5% 80% 66 25 9-41 0.50 0.80 5% 80% 45 30 11.3-48.7 0.50 0.85 5% 80% 33 35
14-56 0.50 0.90 5% 80% 25 40 17.1-62.9
The sample size of at least 25 patients in each group will be chosen because of its
precision and feasibility. Such sample size can detect 40% difference of HPV clearance rate
between the two groups, at 95% significant level, with the power of 80%, 95%CI of 17.1-62.9,
After signing on the consent form, all eligible patients will be examined by the baseline
standard procedures and PCR-HPV testing for 37 HPV types. Only positive HPV testing ones
will be enrolled in the trial and then randomized to receive the cryotherapy or observation.
The method of block randomization, with block size varies from 2 to 6, will be used to
The allocation ratio is 1:1. The allocation sequence will be generated by computer, using
STATA software version 10.0.
Based on the obtained schedule, the number of sealed envelopes, which are equal to the
required blocks, will be prepared and labeled. Each envelope contains the corresponding
sealed allocation cards that will allocate treatments to patients.
Colposcopy and cryotherapy instruments are available in our colposcopic clinic. However, we
will reimburse for all CO2-gases tanks and materials used for Pap smears and HPV testing.
The people, who prepare the randomized scheme, will not involve in the trial. The allocation
schedule will be concealed to the assessor (who measure the HPV testing) until the end of
Data collection and measurement:
Because of the difference between two treatments, only the assessor (who measure the HPV
testing) will be blinded from the treatments.
The specimens will be sent to the assessor without patient's name or HN that can be linked
to the treatment received. They will be provided only the study ID number in which only the
principle investigator can link it to the treatment received.
The main outcome is HPV clearance. It is measured by the gold-standard HPV testing. This
will be performed at baseline and 12 months later.
There were two main parts of analysis - describing selected characteristics of the study
patients and analysis for answering the research questions. The first part, selected
baseline characteristics of the patients in each treatment were compared i.e. age, sex,
sexual experiences, underlying diseases, etc. Comparability of the distribution of those
selected characteristics based on judgment rather than statistical significant tests. In
this part, proportion was use for summarizing categorical data. For continuous data, the
statistics include mean, standard deviation, minimum, maximum, and median.
For the second part, the analysis was based on the group in which the study patients were
randomized (intention-to-treat basis). The different rate of clearance between the two arms
of the trial and its 95% confidence interval will be calculated. This will be done at 12
months after the treatment. Z-test will be used for testing if such differences are
different from zero. Multiple logistic regression will be used to control effects of any
important confounding factors. Absolute risk reduction (ARR), relative risk reduction (RRR)
and number needed to treat (NNT) will also be calculated.
The statistical analysis of this clinical trial will be performed based on
intention-to-treat principle. All hypothesis tests are two-tailed at significant level of
0.05. Statistical package for all analysis is STATA version 10.0.
Allocation: Randomized, Endpoint Classification: Efficacy Study, Intervention Model: Parallel Assignment, Masking: Single Blind (Outcomes Assessor), Primary Purpose: Treatment
Number of Patients With Human Papillomavirus Clearance
At 12 months after treatment, a patient with negative results for HPV testing of previous types was considered as a clearance.
Bandit Chumworathayi, MD
Gynecologic Oncology Division, OBGYN Department, Faculty of Medicine, Khon Kaen University
Thailand: Khon Kaen University Ethics Committee for Human Research