Purpose: There are limited data on the success of conservative treatment of high-grade cervical squamous intraepithelial lesions (HSIL) with imiquimod directly compared to standard of treatment with LLETZ. LLETZ as standard treatment is possibly associated with premature labour, higher subfertility rate and a higher rate of spontaneous abortion. Since premature delivery is one of the most important causes of perinatal morbidity and mortality, alternative conservative methods for SIL treatment are constantly being evaluated. The immunomodulator imiquimod is one of the main target compounds for treating HSIL.

Primary objective: to establish the efficacy of treatment with imiquimod (experimental arm) and compare it to the standard treatment with LLETZ (control arm).

Secondary objective:

• incidence and severity of the side effects in both groups;
• need for treatment with LLETZ two years after primary treatment with imiquimod in the experimental arm or re-treatment with LLETZ two years after primary treatment with LLETZ in the control arm;
• modulatory effect of imiquimod on immunoregulatory molecules.

Study design: Single-centre randomized controlled intervention trial.

Study population: 104 women with HSIL (52 in each arm).

Intervention:

- randomization in two arms:

1. Experimental arm (imiquimod): treatment for 16 weeks with 5% imiquimod.
2. Control arm (LLETZ).

Successful treatment in the experimental arm is defined as absence of histological HSIL in diagnostic biopsies at 20-week follow-up (4 weeks after treatment completion) and in the control arm successful treatment is defined as absence of cytological HSIL in cytology 6 months after LLETZ (same as in our national guidelines).

Imiquimod is one of the target topical drugs for treating HSIL. It is a Toll-like receptor 7 agonist that acts locally so that it induces cellular response, which can aid in the regression of HPV-associated lesions. Imiquimod is currently used for treating genital warts. In vitro studies have shown promising effects in the treatment of several diseases, such as endometrial, cervical and prostate cancer, endometriosis, melanoma, and cervical and vulvar intraepithelial lesions. Clinical studies are however lacking. With this in mind, the aim of our study was to evaluate whether topical treatment of HSIL with imiquimod is comparable to standard treatment with LLETZ. As mentioned in the Brief summary, we have set different outcome measures in the experimental and control arm. The different outcome measures were based on moderate accuracy of PAP smear, therefore in order to minimize potential progression of cervical disease to cancer and to avoid LLETZ and possible overtreatment and to assess as accurately as possible the potential residual disease, colposcopy with biopsies will be performed 4 weeks after treatment with imiquimod is completed (20th week after treatment initiation). Follow up after LLETZ will performed using cytology (PAP smear), which is in concordance with our national guidelines. Biopsies will be performed in case of clinically visible lesions. Secondary outcomes of the study are the incidence and severity of the side effects in both groups, which will be evaluated during and after treatment using the 5th version of the Common Terminology Criteria for Adverse Events (CTCAE) guidelines. Other secondary outcomes, namely the need for treatment with LLETZ two years after primary treatment with imiquimod in the experimental arm or re-treatment with LLETZ two years after primary treatment with LLETZ in the control arm, respectively, and the modulatory effect of imiquimod on immunoregulatory molecules are expected to be available in three years' time after treatment is completed in all patients in both arms.

Inclusion Criteria:

• newly diagnosed and previously untreated HSIL in women aged 18 to 35 years or up to 40 years in case of nulliparity;
• satisfactory colposcopy (i.e., fully visible lesion and transformation zone);
• negative pregnancy test;
• safe contraception;
• signed, informed consent.

Exclusion Criteria:

• previously diagnosed HSIL or AIS;
• previous LLETZ or classical conisation;
• concomitant vulvar or vaginal lesion or neoplasia;
• other malignancies;
• insufficient colposcopy;
• pregnancy or lactation;
• known hypersensitivity to imiquimod;
• any known contraindications to immunotherapy;
• known HIV or acute or chronic hepatitis;
• immune deficiency;
• participation in any other ongoing clinical trial.