How would you approach an HPV+ retroperitoneal mass s/p resection involving the psoas/ureter, with uterus/cervix negative for any cancer?

When the PET and EUA are negative, I have treated HPV positive unknown primary with post-op or definitive chemo RT based on location. There is limited published data on HPV positive groin or pelvic nodes with occult primary. The last one I treated for unresectable RP mass had good response locally b...