Poor Uptake of Fluorodeoxyglucose in Positron Emission Tomography-Computed Tomography Scan for Intraocular Choroidal Melanoma in Asian Indian Eyes

PET-CT in Clinical Adult Oncology-VI. Primary Cutaneous Cancer, Sarcomas and Neuroendocrine Tumors

PET-CT is an advanced imaging modality with many oncologic applications, including staging, therapeutic assessment, restaging and surveillance for recurrence. The goal of this series of six review articles is to provide practical information to providers and imaging professionals regarding the best use of PET-CT for specific oncologic indications, the potential pitfalls and nuances that characterize these applications, and guidelines for image interpretation. Tumor-specific clinical information and representative PET-CT images are provided. The current, sixth article in this series addresses PET-CT in an evaluation of aggressive cutaneous malignancies, sarcomas and neuroendocrine tumors. A discussion of the role of FDG PET for all types of tumors in these categories is beyond the scope of this review. Rather, this article focuses on the most common malignancies in adult patients encountered in clinical practice. It also focuses on Food and Drug Agency (FDA)-approved and clinically available radiopharmaceuticals rather than research tracers or those requiring a local cyclotron. This information will serve as a guide to primary providers for the appropriate role of PET-CT in managing patients with cutaneous malignancies, sarcomas and neuroendocrine tumors. The nuances of PET-CT interpretation as a practical guide for imaging providers, including radiologists, nuclear medicine physicians and their trainees, are also addressed.

Non-Cutaneous Melanoma, Findings and Prognostic Value of FDG PET/CT: A Case Series of 23 patients and review of the literature

Objectives

Non-cutaneous malignant melanomas (NCM) are rare malignancies. Due to their nonspecific symptoms, they present later in life. The value of FDG PET/CT in this group of patients is not clear. The aim of this study is to assess the role of FDG PET/CT in the management of NCM and its prognostic implication.

Methods

We retrospectively selected twenty-three patients with a diagnosis of NCM evaluated with FDG PET/CT in Shariati hospital between 2019 and 2021. The PET/CT data were reviewed and compared with available conventional imaging findings. Five patients died within five months. The surviving patients were followed within a time interval of 7 to 27.5 months after their PET/CT study, regarding their disease status.

Results

Among 23 patients (8 ocular, 5 sinonasal, 3 pharyngeal, 2 anorectal, 2 vulvovaginal, and 3 unknown primaries), PET/CT was able to detect residual primary disease, assess treatment response, and reveal or exclude metastases. Additional lesions compared to conventional imaging were found in five, while in one with brain metastases PET/CT was unable to detect lesions on MRI. Thirteen patients had negative PET/CT finding of which 11 (85%) did not have remarkable finding on follow-up. Metastatic disease was recognized in eight. Patients with extensive metastases on FDG PET/CT had a poorer outcome.

Conclusion

Similar to cutaneous melanoma, PET/CT is valuable in the management of NCM patients and is superior to conventional imaging modalities, with the exception of brain metastases. Patients with negative PET/CT findings have a better outcome as opposed to patients with significant positive PET/CT findings.

99mTc-3PRGD2 single-photon emission computed tomography/computed tomography for the diagnosis of choroidal melanoma: A preliminary STROBE-compliant observational study

Recent successes in monitoring and diagnosing a variety of tumors using Tc-PEG4-E[PEG4-c(RGDfK)]2 (Tc-3PRGD2) single-photon emission computed tomography (SPECT) imaging encouraged us to expand the use of this tracer. This case-control study aimed to evaluate the feasibility of Tc-3PRGD2 imaging for detecting choroidal melanoma (CM) and for monitoring tumor response to plaque brachytherapy (PB). Ten consecutive patients with CM who underwent Tc-3PRGD2 imaging before and 3 months after PB were reviewed. The tumor-to-occipital bone (T/O) and mirrored contralateral normal tissue-to-occipital bone (N/O) ratios were calculated by region of interest analysis at baseline and 3 months post-PB. T/O values were compared between patients with CM with comorbid secondary retinal detachment (RD) and those without RD. The relationship between T/O value and tumor volume was also investigated. Tc-3PRGD2 SPECT/CT showed focal uptake in CM. The mean T/O ratio before PB was 1.90 ± 1.26 and the mean N/O ratio was 0.80 ± 0.21 (P = .02). The Tc-3PRGD2 concentrations in 5 patients with CM with RD were higher (T/O = 2.69 ± 1.39) than in those without secondary RD (T/O = 1.10 ± 0.18) (P = .008). T/O ratios at 3 months post-PB were significantly lower than that at baseline (1.23 ± 0.59, P = .03). There was a linear relationship between T/O and tumor volume (y-hat = 0.028 + 0.003x, R = 0.768, P = .001). The 95% confidence interval for the (T/O)/volume ratio was 0.002 to 0.005. Tc-3PRGD2 imaging is a feasible modality for the diagnosis of CM. Furthermore, follow-up for at least 20 months after PB indicated that coanalysis of Tc-3PRGD2 imaging and tumor volume may provide a promising prognostic predictor in patients with CM.

Imaging Techniques in the Diagnosis and Management of Ocular Tumors: Prospects and Challenges

Different types of imaging modalities are used in the diagnosis of ocular cancer. Selection of an imaging modality is based on the features of a tumor as well as the inherent characteristics of the imaging technique. It is vital to select an appropriate imaging modality in diagnosis of ocular tumor with confidence. This review focuses on five most commonly used imaging modalities, i.e., positron emission tomography-computed tomography (PET/CT), single photon emission computed tomography (SPECT), optical coherence tomography (OCT), ultrasound (US), and magnetic resonance imaging (MRI). The principal of imaging modalities is briefly explained, along with their role in the diagnosis and management of the most common ocular tumors such as retinoblastoma and uveal melanoma. Further, the diagnostic features of ocular tumors corresponding to each imaging modality and possibilities of utilizing imaging techniques in the process of ocular drug development are included in this review.