An unusual case of radioactive seed migration to the vertebral venous plexus and renal artery with nerve root compromise.

PURPOSE: We report a case of prostate brachytherapy seed migration to the vertebral venous plexus and subsequently to the renal artery with corresponding dosimetry analysis describing nerve doses.

METHODS AND MATERIALS: A 52-year-old male with low-risk prostate carcinoma (clinical stage T1c; Gleason score=6; prostate-specific antigen level of 5.5) underwent transperineal permanent prostate seed implant. Postimplantation routine imaging had failed to locate the missing seed, but he subsequently presented with back pain and parathesia with radiation down the leg.

RESULTS

CT with bony windows and MRI had located the seed in the left L5 vertebral venous plexus. Neurosurgical intervention failed to locate and remove the migrated seed. Postsurgery, the left lower limb parathesia persisted but had normal nerve conduction studies. Dose to the spinal nerve roots and nearby structures were estimated using a GEANT4 Monte Carlo simulation. Serial X-ray imaging and CT had found that the seed had further migrated to left renal hilum.

CONCLUSIONS

Seed migration to vertebral venous plexus is uncommon and to our knowledge this is the third reported case. Its subsequent migration to the renal hilum is most unusual. CT with bony windows or MRI are required if this is suspected. There is risk of spinal or nerve root damage and dose to these structures has to be estimated using GEANT4, although the tissue tolerance in the setting of low-dose rates are unknown and long-term followup of this patient is required.