Phase II activity trial of high-dose radiation and chemosensitization in patients with macrometastatic lymph node spread after sentinel node biopsy in vulvar cancer: GROningen INternational Study on Sentinel nodes in Vulvar cancer III (GROINSS-V III/NRG-GY024)

Background: Standard treatment of early-stage vulvar cancer is a radical, wide, local excision of the primary tumor and a sentinel lymph node (SLN) procedure for the groins. An inguinofemoral lymphadenectomy is no longer necessary for patients who have a negative SLN or micrometastasis (≤2 mm). When there is macrometastasis (>2 mm) in the SLN, an inguinofemoral lymphadenectomy is indicated; however, this procedure is associated with major morbidity, such as wound healing, lymphoceles, and lymphedema.

Primary objective: To investigate the safety of replacing inguinofemoral lymphadenectomy by chemoradiation in patients with early-stage vulvar cancer with a macrometastasis (>2 mm) and/or extracapsular extension in the sentinel node.

Study hypothesis: Combination of 56 Gy of radiation to the inguinal site and concurrent cisplatin chemotherapy without completion inguinofemoral lymphadenectomy will be feasible and safe, with low groin recurrence rates.

Trial design: This is a single-arm, prospective phase II treatment trial with stopping rules for unacceptable groin recurrences. Eligible patients will receive 56 Gy of radiation to the involved inguinal site and chemotherapy with concurrent cisplatin.

Major inclusion/exclusion criteria: Eligible patients undergoing sentinel node procedure will have stage I, unifocal, invasive (>1 mm depth of invasion) squamous cell carcinoma of the vulva with tumor size <4 cm, and no suspicious nodes on imaging. Those eligible for the trial are those with a metastasis >2 mm in the sentinel node and/or extracapsular extension, or more than one sentinel node with micrometastasis ≤2 mm.

Primary endpoint: Groin recurrence rate in the first 2 years after primary treatment.

Sample size: 157 patients with macrometastases in their SLN.

Estimated dates for completing accrual and presenting results: January 1, 2029.

Trial registration number: NCT05076942.