Differentiating osteoradionecrosis from nasopharyngeal carcinoma tumour recurrence using⁹⁹Tc^m-sestamibi SPECT/CT

Abstract

ABSTRACT. Osteoradionecrosis (ORN) of the base of skull is a known complication of external beam radiotherapy in the treatment of nasopharyngeal carcinoma, and is widely believed to be sequelae of radiation-induced endarteritis, leading to cellular death and fibrosis. Differentiating ORN from tumour recurrence is challenging and has direct clinical implications. We present a case where 99 Tc m -sestamibi SPECT/CT was used to differentiate ORN from tumour recurrence and in which prior imaging using bone scintigraphy and fluorodeoxyglucose PET/CT were equivocal. Nasopharyngeal carcinomas are tumours that arise from or near the fossa of Rossenmuller, and occur in endemic numbers among people of southern Chinese descent, with reported incidence rates of 11.8 per 100 000 among males and 5.2 per 100 000 in females [1]. The mainstay of therapy is external beam radiation therapy to the nasopharyngeal bed and primary draining lymph node echelons and cisplatin-based chemotherapy [2].Accurate assessment of treatment response and early detection of tumour recurrence is essential to initiate early salvage therapies, but radiation-induced necrosis of the bone or osteoradionecrosis (ORN) can confound post-treatment evaluations.We present a case in which 99 Tc m -sestamibi single photon emission (SPECT)/CT was used to differentiate ORN from nasopharyngeal carcinoma tumour recurrence. Case reportThe patient was a 70-year-old Chinese male who was diagnosed with locally advanced nasopharyngeal carcinoma in 2009 and was treated with combination chemoradiation therapy.Follow-up imaging using SPECT acquisition was based on a dual head camera system rotating 180 degrees, in 3 degree, 30 s angular steps. A low-energy high-resolution collimator was used, with imaging captured on a 128 6 128 matrix. Unenhanced spiral CT acquisition was performed at the same sitting (10.6 mm rotation 21 , 0.6 s rotation time, 130-140 kV, 100 mA) with 2 mm reconstructed axial slices at 2 mm intervals. SPECT images were iteratively reconstructed with ordered subset expectation maximisation algorithm implemented on a clinical workstation, with a final pixel size of 3.2 mm. CT data were used for attenuation correction, anatomical correlation and morphological assessment.The fused images were reviewed using the Philips Jetstream workstation after processing, which allowed for coronal and sagittal reconstruction and fusion. (Figure 3 and 4).A biopsy of the posterior nasopharynx was subsequently performed, and histopathology demonstrated only scattered acute and chronic inflammatory infiltrates admixed with giant cell reaction. No granulomas or malignancy was detected.Additionally, the bony changes demonstrate long term interval stability (15 months), further collaborating with our imaging findings and histopathology results ( Figure 5). The final diagnosis for the patient was radiation-induced necrosis of the base of skull.

Role of surgery in the treatment of osteoradionecrosis and its complications after radiotherapy for nasopharyngeal carcinoma

“…Diagnosis can be difficult in some patients and can be confused, or coexist, with local recurrence of the tumor. 15,16 Bony destruction is the usual finding, 17 but the degree of involvement can be highly variable. In some patients, soft tissue reaction with abnormal thickening can coexist with the bony destruction.…”

Application of Machine Learning for Differentiating Bone Malignancy on Imaging: A Systematic Review

“…This is a crucial diagnostic challenge as the treatment for the two entities are vastly different, and accurate diagnosis is also important to prevent unnecessary invasive biopsy and/or chemoradiotherapy. However, radiological evaluation of bone tumours after treatment can be quite difficult [ 191 , 192 ]. Zhong et al [ 73 ] created an MRI-derived radiomics nomogram that was found to be clinically useful in discriminating between cervical spine osteoradionecrosis following radiotherapy and metastases with an AUC of 0.72 in the validation set.…”

Osteoradionecrosis versus Cancer Recurrence: An Unresolved Clinical Dilemma

“…The discrepancy in observations may be due to small numbers and differences in patient population, and timing of imaging study. 99Tcm-sestamibi SPECT/CT has been shown to differentiate ORN from viable tumor in nasopharyngeal carcinoma [34], but this technique was not explored in our sample. The utility of PET/CT in differentiating RPSCC from ORN warrants further evaluation in larger groups.…”