Background
GROINSS-V II. Prospective multicenter phase II cohort. N=322, early-stage (T1–T2, ≤4 cm) vulvar squamous cell carcinoma with ≥1 positive sentinel node (SN+, any metastatic volume). Replaced full inguinofemoral lymphadenectomy (IFL) with bilateral inguinofemoral radiotherapy (IF-RT) as definitive groin treatment.
Interventions and follow up
Arm: Bilateral inguinofemoral RT (IF-RT) 56 Gy in 28 fractions to bilateral groins
Primary endpoint: 2-year isolated groin recurrence rate (safety; pre-specified boundary <8%)
mFollow up: Median 24 month
Primary endpoint: 2-year isolated groin recurrence rate (safety; pre-specified boundary <8%)
mFollow up: Median 24 month
Results
2-year isolated groin recurrence: 1.6% (5/322) — within safety boundary
Historical IFL benchmark (GROINSS-V I SN+): ~2.9% 2-year groin recurrence
2-year OS: 85% (SN+ treated with IF-RT)
Lymphedema: 25.2% IF-RT vs ~40% historical IFL
Historical IFL benchmark (GROINSS-V I SN+): ~2.9% 2-year groin recurrence
2-year OS: 85% (SN+ treated with IF-RT)
Lymphedema: 25.2% IF-RT vs ~40% historical IFL
Adverse events
Skin: Grade 3 acute (RT) 24%
Lymphedema: Grade ≥2 (long-term) 25.2% IF-RT vs ~40% IFL
GI: Late grade 3+ rare (<3%)
Death: No treatment-related deaths
Lymphedema: Grade ≥2 (long-term) 25.2% IF-RT vs ~40% IFL
GI: Late grade 3+ rare (<3%)
Death: No treatment-related deaths
Conclusions
Inguinofemoral RT alone achieves excellent groin control (2-year recurrence 1.6%) in SN-positive vulvar cancer with lower lymphedema than full IFL. IF-RT is a safe, effective alternative to IFL lymphadenectomy in SN-positive patients.
Key Limitations
Single-arm phase II; no randomized comparison vs IFL. Macrometastatic SN disease (>2 mm) trended toward higher failure, prompting protocol amendment excluding >2 mm SN deposits. Lymphedema remains substantial (25%). Short median follow-up (24 month). Generalizability limited to SN-expert centers.
Clinical Context
Supports inguinofemoral RT as an alternative to full IFL for SN-positive vulvar cancer, reducing (not eliminating) groin morbidity. With GROINSS-V I, drove a paradigm shift to SN biopsy + IF-RT for early-stage management. Given the macrometastasis signal and limited follow-up, many centers still reserve IFL for ≥2 mm nodal metastases or multiple positive SNs. Full publication Lancet Oncol 2021.