Topical imiquimod versus surgery for vulvar intraepithelial neoplasia: a multicentre, randomised, phase 3, non-inferiority trial.

Background: The optimal management of vulvar high-grade squamous intraepithelial lesions (vHSILs) is challenging. Surgery is the standard treatment, but recurrences are observed in half of patients. Medical treatment with imiquimod is an effective alternative, but the two modalities have not been compared in a randomised trial. The aim of this study was to compare the clinical effectiveness, histological response, human papillomavirus (HPV) clearance, acceptance, and psychosexual morbidity of primary imiquimod treatment versus surgical treatment in women with vHSIL.

Methods: This study was a multicentre, randomised, phase 3, non-inferiority clinical trial done by the Austrian Gynaecological Oncology group at six hospitals in Austria. We recruited female patients aged 18-90 years with histologically confirmed vHSIL with visible unifocal or multifocal lesions. Main exclusion criteria were clinical suspicion of invasion, a history of vulvar cancer or severe inflammatory dermatosis of the vulva, and any active treatment for vHSIL within the previous 3 months. Women with known immunodeficiency, who were pregnant, or who were lactating were excluded. Patients were randomly assigned (1:1) by block randomisation to imiquimod or surgery, and stratified by unifocal or multifocal disease. Treatment with imiquimod was self-administered in a slowly escalating dosage scheme up to three times per week for a period of 4-6 months. Surgery consisted of excision or ablation. Patients were assessed with vulvoscopy, vulvar biopsy, HPV tests, and patient-reported outcomes at baseline and after 6 months and 12 months. The primary endpoint was complete clinical response (CCR) at 6 months after local imiquimod treatment or one surgical intervention. Primary analysis was per protocol with a non-inferiority margin of 20%. This trial is registered at ClinicalTrials.gov, NCT01861535.

Findings: 110 patients with vHSIL (78% with unifocal vHSIL and 22% with multifocal vHSIL) were randomly assigned between June 7, 2013, and Jan 8, 2020. Clinical response to treatment could be assessed in 107 patients (54 in the imiquimod group and 53 in the surgery group), and 98 patients (46 in the imiquimod group and 52 in the surgery group) completed the study per protocol. 37 (80%) of 46 patients using imiquimod had CCR, compared with 41 (79%) of 52 patients after one surgical intervention, showing non-inferiority of the new treatment (difference in proportion -0·016, 95% CI -0·15 to -0·18; p=0·0056). Invasive disease was found in five patients at primary or secondary surgery, but not in patients with per-protocol imiquimod treatment. There was no significant difference in HPV clearance, adverse events, and treatment satisfaction between study groups.

Interpretation: Imiquimod is a safe, effective, and well accepted alternative to surgery for women with vHSIL and can be considered as first-line treatment.

Funding: Austrian Science Fund and Austrian Gynaecological Oncology group.