Long-Term Tumor Control despite Late Pseudoprogression on 18F-FDG-PET following Extremely Hypofractionated Stereotactic Radiotherapy for Retropharyngeal Lymph Node Metastasis from Esthesioneuroblastoma

Abstract

¹⁸F-FDG-PET is a valuable adjunct to conventional imaging for evaluating treatment response following stereotactic body radiotherapy (SBRT) for head and neck malignancies (HNM). The effect of treatment-related inflammation is generally deemed negligible after 12 weeks following conventionally fractionated radiotherapy. Herein, we describe an unusual case showing pseudoprogression on ¹⁸F-FDG-PET 2 years after SBRT for retropharyngeal lymph node metastasis (RPLNm) from esthesioneuroblastoma. A 36-year-old man presented with right RPLNm 32 months after the diagnosis of esthesioneuroblastoma associated with ectopic adrenocorticotropic hormone production. The RPLNm was treated with SBRT in 2 fractions over 8 days using dynamic conformal arcs with concomitant chemotherapy with cisplatin and etoposide. Although follow-up MRI showed sustained lesion regression, the early/delayed maximum standardized uptake (SUVmax) values on dual-time-point ¹⁸F-FDG-PET obtained 1 and 2 years after SBRT were 7.7/8.3 and 8.5/10.1, respectively, suggesting local progression. Despite no subsequent focal or systemic treatment, the SUVmax values gradually decreased thereafter over a period of 4 years (3.3/3.4 at 76 months). MRI obtained 7 years after SBRT revealed sustained tumor regression. No obvious relevant toxicities have occurred. Thus, caution should be exercised in the interpretation of the SUVmax change following ablative irradiation for HNM.

68Ga-DOTATOC PET/CT and MR in the Evaluation of Meningeal Metastasis From Esthesioneuroblastoma

“…1 Esthesioneuroblastoma is locally aggressive and frequently recurrent, with cervical nodal metastasis (10%-44% of the cases) being an important prognostic factor in association with grade. [2][3][4][5] In the workup for diagnosis, follow-up, and restaging, imaging techniques such as MR and CT are usually applied. 2 PET/CT is demonstrating a growing role for the evaluation of ENB, being able to change the clinical management of disease in a significant part of the cases.…”

“…Symptoms often include nasal obstruction, epistaxis, paranasal sinus pain, and anosmia 1. Esthesioneuroblastoma is locally aggressive and frequently recurrent, with cervical nodal metastasis (10%-44% of the cases) being an important prognostic factor in association with grade [2][3][4][5]. In the workup for diagnosis, follow-up, and restaging, imaging techniques such as MR and CT are usually applied 2.…”