Inguinal nodal region radiotherapy for vulvar cancer: are we missing the target again?
The GROINSS-V II trial, in which NRG is also participating, is an ongoing observational study. As part of definitive therapy, patients with vulvar cancer undergo sentinel lymph node biopsy (SLNB) followed by observation if SLNB is negative or radiotherapy if SLNB is positive. Chemotherapy is at the discretion of the treating institution. Radiation is to be delivered to the bilateral inguinal nodes and the lower half of the external iliac nodes (though can be delivered only ipsilaterally at the discretion of the treating physician if the primary is well lateralized and there is no sign of a sentinel node on the contralateral side). The interim analysis of the ongoing GROINSS-V II trial showed a recurrence in 12.2% (10/82) of patients treated with radiation in the setting of positive sentinel lymph node biopsy [1]. On subset analysis the risk of nodal recurrence was 2.2% for micrometastases (≤2 mm) and 20% for macrometastases. Based on these early results, the study was modified to allow RT only for micrometastases and patients withmacrometastases now go on to receive completion inguinal dissection followed by possible adjuvant RT. When compared to single institution retrospective data for prophylactic groin RT [2,3], this failure rate appears to be on the higher side and raises the question of whether the outcomes seen in GROINSSV II speak more to the biology of disease in this group of patients or to a geographical miss with radiotherapy. When considering this, we were compelled to examine the radiation technique in this trial protocol as compared to historical techniques and current recommendations. In an early attempt to investigate the role of radiation therapy in the setting of vulvar cancer as a potentialmethod to decrease themorbidity associated with inguinal lymph node dissection, GOG 88 randomized patients with stage IB-III, cN0, vulvar cancer status post radical vulvectomy to either bilateral inguinal radiation or bilateral inguinal lymph node dissection followed by radiation to the pelvic and inguinal nodal regions if the dissection was positive [4]. This trial showed a greater number of inguinal recurrences in the radiation arm, however the radiation technique was poor and delivered an inadequate dose to the region at risk. In GOG 88 radiation was delivered without a CT scan for planning. This resulted in twodisadvantages. First, the risk of lymphnode involvement was not assessed and thus patients may indeed have had macroscopic disease for which 50 Gy is not sufficient. Second, the precise