3248 - Management of a Head and Neck Cancer Patient with a Deep Brain Stimulator Undergoing Radiation Therapy

Purpose/Objective(s):

Deep brain stimulation (DBS) is an effective treatment option for patients with Parkinson’s disease (PD), epilepsy, essential tremor, and dystonia. Statistics show that the number of new coincidences of DBS patients undergoing radiation therapy (RT) was calculated to be about 7 in the US in 2024. To date, only eight case reports have been published on such coincident cases. Here, we report an uncommon coincident case of a head and neck cancer patient with an implanted DBS for the treatment of his PD undergoing RT.

Materials/Methods: Among the eight published DBS case reports, only one was on a head and neck RT patient. The treatment dose, 66 Gy in 33 fractions, was lower than our treatment dose, 70 Gy in 35 fractions delivered in a combination of simultaneous integrated boost (SIB) and sequential boost. In addition, the RT plan in the published case report used 4 MV photon beams and was delivered in Intensity-Modulated RT (IMRT) modality while our RT plan was optimized with 6 MV photon beams delivered in Volumetric-Modulated Arc Therapy (VMAT) modality. VMAT is a more advanced RT modality and is known for reducing total treatment time, radiation leakage, and scattered radiation dose.

Results: A new clinical procedure was developed specifically for this DBS patient. Based on the calculated DBS dose and the device location with respect to the field edges, a neurology consult was requested by the treating radiation oncologist. The DBS device was interrogated before the initiation of RT. The RT plan was designed with three full arcs to produce an optimal planning target volume (PTV) dose distribution while sparing the DBS. The DBS and leads were contoured and a planning organ at risk volume (PRV) structure was created with a 0.5-cm margin for minimizing the DBS dose. Directional blocking was utilized in VMAT optimization, achieving a total DBS dose of 285.4 cGy for the entire course. In vivo dosimetry was performed on the DBS with a calibrated small field dosimetry (SFD) diode on the first day of treatment. The measured dose agreed within 1.2% of the calculated dose. The patient completed RT treatment course with no reported damage to the DBS device five months post RT.

Conclusion: AAPM and ASTRO have not established any clinical guidelines on the management of DBS patients receiving RT. The case presented here shows that a patient with an implanted DBS device was safely treated with RT with a maximum dose of 285.4 cGy to the DBS device using 6MV photon beams. Thus, VMAT may be more suitable to cancer patients with a DBS device. It is very important for all institutions to report such special coincident cases and share their clinical experience with other neurosurgeons, radiation oncologists, and medical physicists so that necessary precautions can be taken if they encounter similar cases in the future.