ASCO reading room | Maaike Oonk, MD, on radiation therapy for vulvar cancer with sentinel node micrometastasis

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Inguinofemoral radiation therapy could save vulvar cancer patients with sentinel node (SN) micrometastases the morbidity of lymphadenectomy, researchers reported.

The introduction of the SN procedure was a great advance in the treatment of vulvar cancer. The earlier Groningen International Study on Sentinel Nodes in Vulvar Cancer (GROINSS-V) -I showed that inguinofemoral lymphadenectomy can safely be omitted in SN-negative patients, which leads to a significant reduction in morbidity. However, patients with metastatic SN will continue to undergo lymphadenectomy and have treatment-related morbidity.

The new GROINSS V II study, published in Journal of Clinical Oncology, investigated the safety of radiation therapy instead of lymphadenectomy in patients with vulvar cancer with metastatic SN. The Phase II prospective, multicenter, single-arm treatment study included 1,535 patients with early-stage vulvar cancer (4 cm diameter) with no evidence of lymph node involvement on imaging who underwent primary surgical treatment (local excision with SN biopsy). If the SN was involved in metastases of any size, inguinofemoral radiation therapy at 50 Gy was given.

In the following interview, Maaike HM Oonk, PhD, from the University Medical Center Groningen in the Netherlands explains the team’s results.

What does the study contribute to the literature on radiation therapy versus inguinofemoral lymphadenectomy for vulvar cancer with sentinel node micrometastasis?

Oonk: There are no prospective data on this topic in the literature. This is the first study to investigate this in what is by far the largest prospective study population for the treatment of vulvar cancer.

The most important finding is the fact that radiotherapy of the groin is a safe alternative to inguinofemoral lymphadenectomy in patients with SN micrometastases. We have also observed that this treatment is insufficient in patients with SN macrometastases. In patients with micrometastases, no treatment at all is a good option because the rate of inguinal recurrence is much higher without treatment.

When choosing between therapies, how does a doctor balance recurrence with acceptable treatment-related morbidity?

Oonk: Since groin recurrences are difficult to treat and often fatal, only a minimal increase in the rate of groin recurrence is acceptable given the decline in treatment-related morbidity.

Radiation therapy is contraindicated in patients planning to become pregnant or who have had prior pelvic radiation therapy. Premenopausal women must weigh the decrease in treatment-related morbidity against the fact that groin radiation makes them postmenopausal, so hormone replacement therapy is indicated.

What’s the next step in this research?

Oonk: We have introduced GROINSS / V III for patients with SN macrometastases. In this study, these patients will be treated with chemoradiotherapy. The radiation therapy dose is increased to 56 Gy and chemotherapy is added to make the treatment more effective.

What is the bottom line for practicing oncologists?

Oonk: Patients with vulvar cancer and SN micrometastases should be advised of the option of radiotherapy instead of inguinofemoral lymphadenectomy. If you have patients with vulvar cancer and SN macrometastasis, consider adding them to the GROINSS / V III study.

Read the study here and the expert commentary on the clinical implications here

Oonk stated that he had no potential conflicts of interest.

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