Normal variants and frequent marrow alterations that simulate bone marrow lesions at MR imaging

Multiparametric Whole-Body MRI: A Game Changer in Metastatic Prostate Cancer

Prostate cancer ranks among the most prevalent tumours globally. While early detection reduces the likelihood of metastasis, managing advanced cases poses challenges in diagnosis and treatment. Current international guidelines support the concurrent use of 99Tc-Bone Scintigraphy and Contrast-Enhanced Chest and Abdomen CT for the staging of metastatic disease and response assessment. However, emerging evidence underscores the superiority of next-generation imaging techniques including PSMA-PET/CT and whole-body MRI (WB-MRI). This review explores the relevant scientific literature on the role of WB-MRI in metastatic prostate cancer. This multiparametric imaging technique, combining the high anatomical resolution of standard MRI sequences with functional sequences such as diffusion-weighted imaging (DWI) and bone marrow relative fat fraction (rFF%) has proved effective in comprehensive patient assessment, evaluating local disease, most of the nodal involvement, bone metastases and their complications, and detecting the increasing visceral metastases in prostate cancer. It does have the advantage of avoiding the injection of contrast medium/radionuclide administration, spares the patient the exposure to ionizing radiation, and lacks the confounder of FLARE described with nuclear medicine techniques. Up-to-date literature regarding the diagnostic capabilities of WB-MRI, though still limited compared to PSMA-PET/CT, strongly supports its widespread incorporation into standard clinical practice, alongside the latest nuclear medicine techniques.

Differentiation of bone metastases from benign red marrow depositions: utilizing qualitative and quantitative analysis of conventional T1-weighted imaging and fat-suppressed T2-weighted imaging

OBJECTIVES

To distinguish bone metastases (BMs) from benign red marrow depositions (BRMs) by qualitative and quantitative analyses of T1-weighted imaging and fat-suppressed T2-weighted imaging (T2 FS).

METHODS

For 75 lesions including 38 BMs and 37 BRMs, two radiologists independently evaluated magnetic resonance images by qualitative (signal intensity [SI] of lesions compared to that of normal muscle [NM] or normal bone marrow [NBM]) and quantitative (parameters of the region of interests in the lesions, including T1 ratio [T1 SI ratio of lesion and NM], T2FMu ratio [T2 FS SI ratio of lesion and NM], and T2FMa ratio [T2 FS SI ratio of lesion and NBM]) analyses.

RESULTS

Hyperintensity relative to NM or NBM on T2 FS was more frequent in BMs than in BRMs (100% vs 59.5%-78.4%, respectively; P ≤ 0.001) but also was present in more than half of BRMs. All quantitative parameters showed a significant difference between BMs and BRMs (T1 ratio, 1.075 vs 1.227 [P = 0.002]; T2FMu ratio, 2.094 vs 1.282 [P < 0.001]; T2FMa ratio, 3.232 vs 1.810 [P < 0.001]). The receiver operating characteristics areas under the curves of T2FMu and T2FMa ratios were clinically useful (0.781 and 0.841, respectively) and did not demonstrate statistically significant differences.

CONCLUSIONS

The quantitative analysis of T2 FS facilitates distinguishing between BMs and BRMs, regardless of whether the reference was NM or NBM.

ADVANCES IN KNOWLEDGE

Quantitative parameters derived from T2 FS facilitate differentiation of BMs BRMs without additional scans. The role of NBM as an internal standard for T2 FS to differentiate between BMs and BRMs is similar to that of NM.

The T1 Ratio of Marrow (TROM) as a Novel Tool to Identify Metastatic from Nonmalignant Marrow Lesions of the Spine: A Pilot Study

Objective  The purpose of this study was to analyze quantitative values of normal and abnormal marrow on T1-weighted images of spine, to propose a ratio for T1 values of abnormal to normal vertebrae, and to assess whether this ratio could be helpful in predicting presence of neoplastic lesions in the spine. Materials and Methods  One-hundred randomly selected magnetic resonance imagings of lumbar spine without infection, fracture, and tumor were selected to form normal cohort. A second cohort of 100 metastasis of lumbar spine was identified. Ratio of T1 value of vertebral body to the T1 value of the inferior vertebral body was performed for normal cohort from D11 to L5. Ratio of T1 value of metastasis to adjacent normal vertebral body was done for metastatic cohort. Data was analyzed using standard t -test and kappa was performed for intra- and inter-observer reliability. Results  A decline in T1 value of abnormal to normal marrow was seen in patients with metastasis that was statistically significant. We call this the T1 ratio of marrow (TROM). The sensitivity and accuracy with the cutoff value of TROM at 0.7 (92% sensitivity, 97.1% accuracy) are better than at 0.6 (75% sensitivity, 96.2% accuracy) or 0.5 (47% sensitivity, 93.2% accuracy). A subset analysis of the other T1 hypointense benign lesions including atypical hemangiomas and focal marrow hyperplasia, however, revealed overlapping TROM values with the metastatic cohort. Conclusion  Using the TROM on T1-weighted images could not confidently differentiate malignant from benign T1 hypointense lesions of the spine.

Normal Bone Marrow and Non-neoplastic Systemic Hematopoietic Disorders in the Adult

This article provides an overview of the imaging appearances of normal adult bone marrow with an emphasis on magnetic resonance imaging. We also review the cellular processes and imaging features of normal developmental yellow-to-red marrow conversion and compensatory physiologic or pathologic red marrow reconversion. Key imaging features that differentiate between normal adult marrow, normal variants, non-neoplastic hematopoietic disorders, and malignant marrow disease are discussed, as well as posttreatment changes.

Advances in Bone Marrow Imaging: Strengths and Limitations from a Clinical Perspective

Conventional magnetic resonance imaging (MRI) remains the modality of choice to image bone marrow. However, the last few decades have witnessed the emergence and development of novel MRI techniques, such as chemical shift imaging, diffusion-weighted imaging, dynamic contrast-enhanced MRI, and whole-body MRI, as well as spectral computed tomography and nuclear medicine techniques. We summarize the technical bases behind these methods, in relation to the common physiologic and pathologic processes involving the bone marrow. We present the strengths and limitations of these imaging methods and consider their added value compared with conventional imaging in assessing non-neoplastic disorders like septic, rheumatologic, traumatic, and metabolic conditions. The potential usefulness of these methods to differentiate between benign and malignant bone marrow lesions is discussed. Finally, we consider the limitations hampering a more widespread use of these techniques in clinical practice.

Imaging of metastatic epidural spinal cord compression

Metastatic epidural spinal cord compression develops in 5-10% of patients with cancer and is becoming more common as advancement in cancer treatment prolongs survival in patients with cancer (1-3). It represents an oncological emergency as metastatic epidural compression in adjacent neural structures, including the spinal cord and cauda equina, and exiting nerve roots may result in irreversible neurological deficits, pain, and spinal instability. Although management of metastatic epidural spinal cord compression remains palliative, early diagnosis and intervention may improve outcomes by preserving neurological function, stabilizing the vertebral column, and achieving localized tumor and pain control. Imaging serves an essential role in early diagnosis of metastatic epidural spinal cord compression, evaluation of the degree of spinal cord compression and extent of tumor burden, and preoperative planning. This review focuses on imaging features and techniques for diagnosing metastatic epidural spinal cord compression, differential diagnosis, and management guidelines.

Spinal collision lesions

Collision lesions are rare neoplasms often described in the hepatobiliary system, genitourinary system and adrenal glands. Vertebral haemangiomas (VH) are the most common lesions involving the vertebral bodies. VHs are usually asymptomatic and considered as "Do not touch" lesions. Rarely they can be symptomatic. Imaging findings of typical and atypical haemangiomas, variant forms of haemangioma such as aggressive haemangiomas are well known. Collision lesions involving VHs are extremely rare. This article presents a series of cases with collision lesions of the vertebral body involving VHs.

ADVANCES IN KNOWLEDGE

This Case series demonstrates the various collision lesions in spinal haemangioma.

Differentiation of Vertebral Metastases From Focal Hematopoietic Marrow Depositions on MRI: Added Value of Proton Density Fat Fraction

OBJECTIVE. The purpose of this study was to evaluate the added value of proton density fat fraction (PDFF) in differentiating vertebral metastases from focal hematopoietic marrow depositions. MATERIALS AND METHODS. The study included 44 patients with 30 vertebral metastases and 14 focal hematopoietic marrow depositions who underwent spinal MRI. The final diagnoses were based on histologic confirmation, follow-up MRI, or PET/CT. Two musculoskeletal radiologists with 1 and 15 years of experience independently interpreted both image sets (i.e., images from conventional MRI alone versus images from conventional MRI and PDFF combined). Using a 5-point scale, the readers scored their confidence in the malignancy of the vertebral lesions. The diagnostic performance (AUC) of the two image sets was assessed via ROC curve analyses. Sensitivities, specificities, and accuracies (for both image sets) were compared using the McNemar test. Kappa coefficients were calculated to assess interobserver agreement. RESULTS. Both readers showed improved diagnostic performance after PDFF was added (AUC, 0.840-0.912 and 0.805-0.895 for readers 1 and 2, respectively). However, adding PDFF did not significantly improve the sensitivity and specificity of either reader (p > .05). Interobserver agreement significantly improved from moderate (κ = 0.563) to excellent (κ = 0.947) after PDFF was added. CONCLUSION. The addition of PDFF to a conventional MRI protocol improved the diagnostic performance for differentiating vertebral metastases from focal hematopoietic marrow depositions but without resulting in significant improvement in sensitivity and specificity.

Focal nodular marrow hyperplasia: Imaging features of 53 cases

OBJECTIVE

To describe the characteristic imaging features of focal nodular marrow hyperplasia (FNMH).

METHODS AND MATERIALS

Retrospective review of all patients with a diagnosis of FNMH between January 2007 and September 2019.

RESULTS

The study included 53 patients, 7 males and 46 females with a mean age of 58 years (range 12-95 years). All had MRI with conventional spin echo sequences showing a poorly defined round/oval lesion with mild T₁W iso/hyperintensity compared to skeletal muscle, low T₂W turbo spin echo (TSE) signal intensity (SI) compared to marrow fat and variable SI on STIR, but never associated with reactive marrow oedema. All 53 patients had follow-up MRI, with all lesions remaining stable or partially resolving. In-phase (IP) and out-of-phase (OP) chemical shift imaging (CSI) was obtained in 31 of these, with 28 (90.3%) showing >20% SI drop on the OP sequence, while 3 (9.7%) demonstrated <20% SI drop. CT was available in 26 cases, 17 (65.4%) showing mild medullary sclerosis. Single-photon emission computed tomography CT (SPECT-CT) was available in four cases and Flourodeoxyglucose positron emission tomography CT (FDG PET-CT) in 2, all showing increased uptake. Focal uptake was also seen in three of eight patients who had undergone whole body bone scintigraphy. Only one lesion was biopsied, confirming FNMH.

CONCLUSION

The imaging appearances of FNMH have been described on various modalities, particularly MRI with emphasis on the role of IP and OP CSI typically demonstrating >20% SI reduction. FNMH should be recognised and treated as a 'do not touch' lesion which does not require biopsy or prolonged follow-up.

ADVANCES IN KNOWLEDGE

We describe and clarify the imaging characteristics of FNMH on MRI, including CSI, CT and various nuclear medicine modalities. An imaging algorithm is suggested for allowing a non-invasive diagnosis.

Whole-body MRI, dynamic contrast-enhanced MRI, and diffusion-weighted imaging for the staging of multiple myeloma

Magnetic resonance imaging (MRI) is the most sensitive imaging technique for the detection of bone marrow infiltration, and has therefore recently been included in the new diagnostic myeloma criteria, as proposed by the International Myeloma Working Group. Nevertheless, conventional MRI only provides anatomical information and is therefore only of limited use in the response assessment of patients with multiple myeloma. The additional information from functional MRI techniques, such as diffusion-weighted imaging and dynamic contrast-enhanced MRI, can improve the detection rate of bone marrow infiltration and the assessment of response. This can further enhance the sensitivity and specificity of MRI in the staging of multiple myeloma patients. This article provides an overview of the technical aspects of conventional and functional MRI techniques with practical recommendations. It reviews the diagnostic performance, prognostic value, and role in therapy assessment in multiple myeloma and its precursor stages.

Differentiation of focal indeterminate marrow abnormalities with multiparametric MRI

PURPOSE

To explore magnetic resonance imaging (MRI) parameters from intravoxel incoherent motion diffusion-weighted imaging (IVIM-DWI), multiecho Dixon imaging (ME-Dixon), and dynamic contrast-enhanced imaging (DCE) for differentiating focal indeterminate marrow abnormalities MATERIALS AND METHODS: Forty-two patients with 14 benign and 28 malignant focal marrow abnormalities were included. The following were independently analyzed by two readers: signal intensity (SI), contour, and margin on conventional MR images; SI on b-800 images (SI_b-800 ), apparent diffusion coefficient (ADC), IVIM parameters (D_slow, D_fast , and f), fat fraction (Ff), and DCE parameters (time-to-signal intensity curve pattern, iAUC, K^trans , k_ep , and v_e ). The MR characteristics and parameters from benign and malignant lesions were compared with a chi-squared test and the Mann-Whitney U-test, respectively. The area under receiver operating characteristic (ROC) curves (AUC) of each sequence were also compared. Interobserver agreements were assessed with Cohen's κ, and intraclass correlation coefficient (ICC).

RESULTS

ADC, D_slow , and Ff demonstrated a significant difference between benign and malignant marrow abnormalities for both readers (P < 0.001). SI_b-800 and perfusion-related parameters from IVIM-DWI and DCE were not significantly different between the two groups (P = 0.145, 0.439, and 0.337 for reader 1, P = 0.378, 0.368, and 0.343 for reader 2, respectively). The AUCs of ADC, D_slow , and Ff were significantly higher for differentiating indeterminate marrow abnormalities in both readers (P < 0.001). Interobserver agreements were substantial in SI_b-800 , and ICCs were almost perfect for ADC, D_slow , f, and Ff, and substantial for iAUC, k_ep , K^trans , v_e , and D_fast .

CONCLUSION

ADC, D_slow , and Ff may provide information for differentiating focal indeterminate abnormalities.

LEVEL OF EVIDENCE

3 Technical Efficacy: Stage 2 J. MAGN. RESON. IMAGING 2017;46:49-60.

Esophageal Cancer with Bone Marrow Hyperplasia Mimicking Bone Metastasis: Report of a Case

A 63-year-old man visited the clinic with numbness in the right hand. Magnetic resonance imaging demonstrated multiple low-intensity lesions in the cervical vertebrae and sacrum, which was suspicious of cervical bone metastasis. Fluorodeoxyglucose positron emission tomography/computed tomography revealed areas of increased fluorodeoxyglucose uptake in the thoracic esophagus, sternum and sacrum. A flat, elevated esophageal cancer was identified by upper gastrointestinal endoscopy, and the macroscopic appearance indicated early-stage disease. From the cervical, thoracic and abdominal computed tomography images, there were no metastatic lesions except for the bone lesions. To confirm whether the bone lesions were metastatic, we performed bone biopsy. The histopathological diagnosis was bone marrow hyperplasia. It was crucial for treatment planning to establish whether the lesions were distant metastases. Here, we report a case of esophageal cancer with bone marrow hyperplasia mimicking bone metastasis.

Magnetic resonance imaging of the spinal marrow: Basic understanding of the normal marrow pattern and its variant

For now, magnetic resonance (MR) is the best noninvasive imaging modality to evaluate vertebral bone marrow thanks to its inherent soft-tissue contrast and non-ionizing nature. A daily challenging scenario for every radiologist interpreting MR of the vertebral column is discerning the diseased from normal marrow. This requires the radiologist to be acquainted with the used MR techniques to judge the spinal marrow as well as its normal MR variants. Conventional sequences used basically to image marrow include T1W, fat-suppressed T2W and short tau inversion recovery (STIR) imaging provides gross morphological data. Interestingly, using non-routine MR sequences; such as opposed phase, diffusion weighted, MR spectroscopy and contrasted-enhanced imaging; may elucidate the nature of bone marrow heterogeneities; by inferring cellular and chemical composition; and adding new functional prospects. Recalling the normal composition of bone marrow elements and the physiologic processes of spinal marrow conversion and reconversion eases basic understanding of spinal marrow imaging. Additionally, orientation with some common variants seen during spinal marrow MR imaging as hemangiomas and bone islands is a must. Moreover, awareness of the age-associated bone marrow changes as well as changes accompanying different variations of the subject’s health state is essential for radiologists to avoid overrating normal MR marrow patterns as pathologic states and metigate unnecessary further work-up.

Distinguishing imaging features between spinal hyperplastic hematopoietic bone marrow and bone metastasis

BACKGROUND AND PURPOSE

Systematic investigations of the distinguishing imaging features between spinal hyperplastic hematopoietic bone marrow and bone metastasis have not been reported, to our knowledge. The purpose of this study was to determine the distinguishing imaging features of the 2 entities.

MATERIALS AND METHODS

We retrospectively reviewed the radiologic images of 8 consecutive male patients (age range, 52-78 years; mean, 64 years) with suspected spinal metastasis on MR imaging and FDG-PET, which was later confirmed as hyperplastic hematopoietic bone marrow. MR imaging, FDG-PET, CT, and bone scintigraphy images were qualitatively and/or quantitatively evaluated. Imaging findings in 24 patients with spinal metastasis were compared, and differences were statistically analyzed.

RESULTS

All 8 vertebral hyperplastic hematopoietic bone marrow lesions were hypointense on T1- and T2-weighted images; lesions contiguous with the adjacent vertebra were significantly more often seen in hyperplastic hematopoietic bone marrow than in metastasis (P = .035). T2 signal intensity of the lesion was significantly different between the 2 entities (P = .033). FDG-PET showed slightly higher uptake in all hyperplastic hematopoietic bone marrow lesions; their maximum standard uptake value was significantly lower than that of metastatic lesions (P = .037). CT attenuation of hyperplastic hematopoietic bone marrow was equal to or slightly higher than that of adjacent normal-appearing vertebra; the CT appearances of hyperplastic hematopoietic bone marrow and metastasis were significantly different (P < .01). Bone scintigraphy showed normal uptake for all vertebrae with hyperplastic hematopoietic bone marrow; the uptake was significantly different from that of metastasis (P < .01).

CONCLUSIONS

If a lesion was isointense to hyperintense to normal-appearing marrow on MR imaging or had a maximum standard uptake value of >3.6, the lesion was considered metastatic. A normal appearance on CT or bone scintigraphy excluded metastasis.

MRI for response assessment in metastatic bone disease

BACKGROUND

Beyond lesion detection and characterisation, and disease staging, the quantification of the tumour load and assessment of response to treatment are daily expectations in oncology.

METHODS

Bone lesions have been considered "non-measurable" for years as opposed to lesions involving soft tissues and "solid" organs like the lungs or liver, for which response evaluation criteria are used in every day practice. This is due to the lack of sensitivity, specificity and measurement capabilities of imaging techniques available for bone assessment, i.e. skeletal scintigraphy (SS), radiographs and computed tomography (CT).

RESULTS

This paper reviews the possibilities and limitations of these techniques and highlights the possibilities of positron emission tomography (PET), but mainly concentrates on magnetic resonance imaging (MRI).

CONCLUSION

Practical morphological and quantitative approaches are proposed to evaluate the treatment response of bone marrow lesions using "anatomical" MRI. Recent developments of MRI, i.e. dynamic contrast-enhanced (DCE) imaging and diffusion-weighted imaging (DWI), are also covered.

KEY POINTS

• MRI offers improved evaluation of skeletal metastases and their response to treatment. • This new indication for MRI has wide potential impact on radiological practice. • MRI helps meet the expectations of the oncological community. • We emphasise the practical aspects, with didactic cases and illustrations.

Early radiation-induced bone marrow injury: serial MR imaging during initial 4 weeks after irradiation

RATIONALE AND OBJECTIVES

Magnetic resonance (MR) imaging has been widely used to detect bone marrow (BM) changes after radiotherapy. However, little information about the dynamic MR appearance of early radiation-induced BM injury is available. This experimental study was designed to determine the MR appearance of irradiated BM during the initial 4 weeks after irradiation.

MATERIALS AND METHODS

After focal BM irradiation (20 Gy, single dose, x-ray), 12 of 20 rabbits underwent serial MR studies weekly from days 7 to 28; eight rabbits were used for histologic investigation on days 7, 14, 21, and 28 after irradiation.

RESULTS

Under microscopy, early BM changes after irradiation consisted of sinusoid dilatation and congestion, followed by a progressive decrease in cellularity and later fat degeneration. All irradiated BM showed relative hyperintensity on short-inversion time inversion recovery (STIR) imaging from days 7 to 21 after irradiation and increased enhancement with gadolinium diethylenetriamine pentaacetic acid (DTPA) administration from days 7 to 28 after irradiation. However, on STIR imaging and gadolinium DTPA enhancement, the relative signal intensity of irradiated BM appeared to decline in a time-dependent way. On fast spin-echo (FSE) T1-weighted imaging, relative hyperintensity was detected in irradiated BM from day 21 after irradiation. On fat-suppressed FSE T1-weighted imaging, a slight increase in signal intensity was shown in some irradiated BM (in five of 12 rabbits) on day 7 after irradiation.

CONCLUSION

STIR imaging was sensitive to early BM congestion and sinusoidal dilatation, spin-echo T1-weighted imaging was effective in detecting later fatty degeneration in irradiated BM, and gadolinium DTPA enhancement may contribute to the evaluation of BM vascular injury in response to irradiation.

Magnetic resonance imaging of bone marrow in oncology, Part 1

Magnetic resonance imaging plays an integral role in the detection and characterization of marrow lesions, planning for biopsy or surgery, and post-treatment follow-up. To evaluate findings in bone marrow on MR imaging, it is essential to understand the normal composition and distribution of bone marrow and the changes in marrow that occur with age, as well as the basis for the MR signals from marrow and the factors that affect those signals. The normal distribution of red and yellow marrow in the skeleton changes with age in a predictable sequence. Important factors that affect MR signals and allow detection of marrow lesions include alterations in fat-water distribution, destruction of bony trabeculae, and contrast enhancement. This two-part article reviews and illustrates these issues, with an emphasis on the practical application of MR imaging to facilitate differentiation of normal marrow, tumor, and treatment-related marrow changes in oncology patients.

MR Imaging Evaluation of the Bone Marrow and Marrow Infiltrative Disorders of the Lumbar Spine

The use of MR imaging in assessing lumbar bone marrow first requires an understanding of the bone marrow's normal composition and the various imaging sequences available for use. One of the most useful sequences is the T1-weighted spin-echo sequence. This sequence may be combined with other sequences such as T2-weighted or diffusion-weighted sequences; techniques such as fat suppression, chemical shift imaging, and contrast-enhanced imaging are discussed. The varying features of normal lumbar marrow related to the normal physiologic changes that occur with aging and with changes in hematopoietic demand are important to understand and are described. The appearances of infiltrative marrow disease are explained on the basis of marrow composition and whether disease causes proliferation, replacement, or depletion of normal marrow components.

MR imaging of therapy-induced changes of bone marrow

MR imaging of bone marrow infiltration by hematologic malignancies provides non-invasive assays of bone marrow cellularity and vascularity to supplement the information provided by bone marrow biopsies. This article will review the MR imaging findings of bone marrow infiltration by hematologic malignancies with special focus on treatment effects. MR imaging findings of the bone marrow after radiation therapy and chemotherapy will be described. In addition, changes in bone marrow microcirculation and metabolism after anti-angiogenesis treatment will be reviewed. Finally, new specific imaging techniques for the depiction of regulatory events that control blood vessel growth and cell proliferation will be discussed. Future developments are directed to yield comprehensive information about bone marrow structure, function and microenvironment.

[18F]fluorodeoxyglucose positron emission tomography is more sensitive than skeletal scintigraphy for detecting bone metastasis in endemic nasopharyngeal carcinoma at initial staging

PURPOSE

Bone metastasis occurs frequently in patients with endemic nasopharyngeal carcinoma (NPC). The main objective of this study is to evaluate positron emission tomography (PET) using fluorine-18-labeled fluorodeoxyglucose ([18F]FDG) and conventional skeletal scintigraphy (SS) for detecting bone metastasis at initial staging. Auxiliary objectives are to identify risk factors for bone metastasis and features associated with poor survival in patients with bone metastasis.

PATIENTS AND METHODS

Patients with endemic NPC before initiation of treatment were enrolled. PET and SS were performed at initial staging and compared using McNemar's paired-sample test. Bone metastasis was considered to be present if there was any reliable evidence identified within 1 year after primary diagnosis. Multiple logistic regression and Cox's proportional hazards models were used for auxiliary objectives.

RESULTS

Thirty (15%) of 202 eligible patients were found to have bone metastasis. [18F]FDG PET was found to be more sensitive than SS in the patient-based analysis (P = .006) and in the region-based analysis at the spine (P = .001). Advanced N stage was the only significant risk factor (P < .0001), and the coexistence of hepatic metastasis was a prognosticator of poor survival (P = .017). The survival was not significantly better for patients with bone metastasis undetected at primary staging than for those with initially detectable bone metastasis (P = .620).

CONCLUSION

[18F]FDG PET is more sensitive than SS for detecting bone metastasis in endemic NPC at initial staging, whereas SS can be considered as supplementary in this setting.