For early-stage vulvar cancer that is clinically/radiographically node negative with no surgical lymph node evaluation (e.g., patient or surgeon refusal), would elective nodal irradiation be reasonable in the absence of risk factors warranting treatment to the primary site?

It is tempting to skip elective nodal irradiation in this setting, especially if the radiographic evaluation includes a PET-CT, where the negative predictive value is probably close to 90%. However, if the risk of groin LN involvement is at least 15%, based on primary tumor characteristics such as s...

Yes, studies done with adequate volume, including depth and dose, have shown good efficacy.

Even in our series with locally advanced cancer with imaging N0 disease treated with modern volume-based RT, no patient had isolated inguinal nodal recurrence.

Richman et al., PMID 32981696

With a negative (reviewed by RadOnc) nodal CT and PET, I would be comfortable avoiding RT to the nodes. However, the dose for microscopic disease without sensitizing chemotherapy would be of low toxicity and fully reasonable.

With “absence of risk factors” then inherent to that meaning, you probably shouldn’t do something prophylactically that can cause harm (side effects, etc.).

It depends on the a priori risk of nodal involvement based on tumor size, depth of invasion, LVSI, etc.

If the risk is high enough, we can consider vs close observation with ultrasound or PET/CT.