Association of post-treatment positron emission tomography with locoregional control and survival after radiation therapy for squamous cell carcinoma of the vulva.

Background/purpose: The aim of this study was to investigate the use of post-treatment F-18 fluorodeoxyglucose (FDG) positron emission tomography/computed tomography (PET/CT) for vulvar cancer and compare metabolic response to clinical outcomes.
Materials/methods: This retrospective study included 21 patients with vulvar squamous cell carcinoma treated with curative-intent radiation between 2007 and 2015. All patients received intensity-modulated radiation treatment (IMRT), a pre-treatment FDG/PET-CT, and a post-treatment FDG-PET/CT performed at a median time of 3months post-IMRT.
Results: Median follow-up time was 28months. Post-treatment FDG-PET/CT demonstrated no evidence of disease (NED) in 12 patients and residual or progressive disease (PD) in 9. FDG-PET/CT response significantly correlated with biopsy-proven locoregional failure (p=0.02) and was the only significant factor associated with overall survival (OS) (p=0.049). Patients with NED on FDG-PET had a 2-year locoregional control (LRC) of 89% versus 25% for those with PD (p<0.01). Patients with NED on FDG-PET/CT had a 2-year OS of 100% versus 42% for those with PD (p=0.02). FDG-PET/CT evaluation had a sensitivity of 100% and a specificity of 71% for detecting pathologically proven residual disease in patients receiving neoadjuvant or definitive radiation.
Conclusion: In this single-institution study of women with vulvar cancer, post-treatment response on FDG-PET/CT was associated with LRC and OS.
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