A Novel Immobilization Method Using 3D Printing for the Treatment of Head and Neck Cancer

Abstract

<h3>Purpose/Objective(s)</h3> Radiation therapy requires immobilization hardware that may produce significant anxiety for a patient under treatment, particularly when covering the face. In cases where such anxiety is treatment limiting, 3D printing can provide for a better tolerated custom immobilization. The technical hurdles, fidelity of positioning, and clinical outcomes are reviewed for the treatment of oropharyngeal cancer in a patient who was unable to tolerate traditional mask-based immobilization. <h3>Materials/Methods</h3> A 3D printer was used to create a custom immobilization cradle for the treatment of squamous cell carcinoma of the oropharynx. This was used in the treatment of a patient who was unable to be simulated despite nine separate attempts, using a variety of open-faced immobilization techniques, anxiolytics, and coaching. Operative management was not feasible due to the patient's habitus and comorbidities. Despite acknowledging the severity of the situation, the patient could not complete simulation. Thus, after he was confirmed to still have locoregionally limited disease, we proposed creation of a 3D-printed cradle for the back of his head and neck, based on CT imaging without immobilization. Three separate attempts were made to complete the printing of the cradle. Major issues stemmed from the need to find a set of support structures that would allow for the proper printing of the area supporting the ears, as well as the back of the head. Ultimately, a dense array of column supports was successful, but still required buttressing of the columns with tape at several points during the print. In total, 664g of polylactic acid filament was used, as well as 525g of polyvinyl alcohol, a water soluble support material. Total print time was just under 78 hours for the final successful print. <h3>Results</h3> The patient was able to tolerate simulation and the full course of fractionated chemoradiotherapy. The cradle provided for a setup requiring mean absolute shift of 0.35 mm in the anterior-posterior direction, 0.17 cm in the cranio-caudal direction, and 0.36 cm in the lateral direction, and a couch kick of 1.28 degrees to bring the patient into alignment on final imaging. The patient is currently in stable condition and following up with both medical oncology and radiation oncology at regular intervals. Imaging and laryngoscopy, conducted at multiple time points following completion, shows him to have no evidence of disease, now at 10 months. <h3>Conclusion</h3> The full uses of 3D printing are still developing, as evidenced by the difficulty of creating a workable print, both in terms of prototyping and the time needed to create a print. The impact of 3D printing within the context of radiation oncology, as well as in other specialties, will undoubtedly continue to increase the variety of viable treatment options available to patients as the technology improves.