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Sella turcica and petrous bone metastasis from differentiated thyroid carcinoma are rare clinical entities, with only a few limited cases reported to date. Two cases, one of sella turcica metastasis and the other of petrous bone metastasis from carcinoma of the thyroid gland, are presented. The cases diagnosed to have arisen from poorly differentiated thyroid carcinoma and follicular carcinoma of thyroid, respectively, subsequently underwent total thyroidectomy, radioiodine (RAI) scans and RAI therapies with iodine-131, external radiotherapy, and levothyroxine suppression with follow-up. Their clinical symptoms gradually subsided, with reduction in serum thyroglobulin, and finally resulted in disease stabilization. With the multimodality therapeutic approach, both patients are alive to date, with 48- and 60-month survival post diagnosis, respectively.

A 50-year-old female patient of heavily pre-treated (chemotherapy and multiple treatment-resistant) and progressive intermediate-grade metastatic neuroendocrine neoplasm is presented, wherein the lesions showed mixed response following topotecan treatment and multiple hepatic metastasis showed increase in the SSTR expression and decrease in FDG concentration on dual-tracer PET/CT (68Ga-DOTATATE and 18F-FDG PET/CT). Such observation allowed 177Lu-DOTATATE PRRT to be considered for an advanced, symptomatic, and multiple treatment-resistant patient with limited palliative treatment options left.

Pulmonary metastases in thyroid carcinoma demonstrates varying imaging characteristics and disease biology and the outcome. The valuable complimentary role of high-resolution CT (HRCT) in conjunction with functional imaging such as radioiodine scan has been discussed and illustrated in this review along with the varied clinical and imaging presentations of lung metastases from differentiated thyroid cancer (DTC). A multi-modality patient-specific diagnostic approach and awareness about the atypical presentations helps in early identification as well as effective management of these patients, and especially in certain situations that could need multi-disciplinary management. While HRCT of the lungs as an added tool provides detailed visualization of the lung parenchyma, in the era of hybrid imaging, the routine adoption of SPECT-CT in patients with pulmonary metastases (in diagnostic or post-treatment settings) could provide equivalent or even incremental information from further management viewpoint.

Most of the established guidelines mention and recommend the use of FDG-PET/CT (fluorodeoxyglucose positron emission tomography/computed tomography) in carcinoma of unknown primary (CUP) especially in head–neck squamous cell carcinoma; as described in this article, this forms a powerful one-stop shop in diagnosing and staging modality and has multiple applications in difficult situations of CUPs. Although not used as a screening modality, FDG-PET/CT is recommended as the primary imaging modality in the evaluation of primary, staging, and response evaluation for CUP with histology known to demonstrate FDG avidity, especially patients presenting with lymph nodal disease. It should be remembered that many histological types do not concentrate on FDG and FDG also shows false-positive results in many other conditions like infection-inflammation; however, at the same time, it delivers high negative predictive values, an important consideration when employing FDG-PET/CT in the CUP scenario. SSTR-based PET/CT plays a pivotal role in primary diagnosis, staging, therapy planning, and response assessment in CUPs with neuroendocrine tumor or neuroendocrine neoplasm histology. The last two decades has witnessed great advancement in PET instrumentation and radiopharmaceuticals: particularly techniques like PET/magnetic resonance imaging and radiopharmaceuticals like FAPI (fibroblast-activation protein inhibitor)-based PET tracers. Hence, the role of PET/CT is expected to expand its reach in the coming years in line with accruing literature evidence, thereby upgrading its role and reliability in oncological practice strategies.

We in this article have presented a review of the guideline recommendations on theranostic positron emission tomography-computed tomography (PET-CT) imaging which will be helpful to assist practitioners in providing appropriate patient care. Multiple guidelines by different societies and medical associations provide standards for diagnosis, imaging, and treatment of cancer patients. They have generated a number of recommendations related to 68Ga-DOTATATE and 68Ga-PSMA-11 PET-CT, which are the classical examples of theranostic PET-CT imaging in current practice.

This communication gives a short review of clinical utilities of PET/computed-tomography (CT) imaging in bone and joint infections. PET/CT imaging provides additional information over conventional modalities by providing information regarding disease extent in the bone as well as whole body, giving an idea of active pathology at the molecular level, and response evaluation. The roles of fluorodeoxyglucose have been examined in multiple indications, particularly in osteomyelitis, prosthetic joint infections, diabetic foot, and systemic diseases with skeletal involvement. The role of PET/CT imaging using other tracers like 18F-sodium fluoride, gallium-68 citrate, 18F-fluorodeoxyglucose-labeled WBCs, and futuristic PET/MR have been also discussed shortly.

Hurthle cell thyroid carcinoma (HCTC) demonstrates inferior prognosis compared with other types of differentiated thyroid cancer (DTC), along with radioiodine refractoriness and relatively poor 131I concentrating ability. We herein report a case of a middle-aged lady presenting with neck swelling for years, who on pre-surgery work-up was diagnosed to harbor metastatic nodal and lung lesions. Post-thyroidectomy and neck dissection, she was diagnosed with HCTC. Post-surgery, none of the lesions concentrated radioactive-iodine (RAI) sufficiently but showed FDG avid lesions as mediastinal nodes, lung nodules, solitary lytic sternal lesions, and unusual bilateral paraaortic abdominal nodes. She was put on tyrosine kinase inhibitor (sorafenib) and showed disease stabilization for the initial 3 years, but multiple toxicity symptoms while on sorafenib therapy that needed multiple dose adjustments. Over the period of the subsequent year, she developed significant disease progression with liver involvement. She was shifted to lenvatinib, which she tolerated well. The functional imaging profile with unusual metastatic sites, the aggressive clinical presentation and disease course of RAI refractory HCTC over 4 years on tyrosine kinase inhibitor therapy, and the role of molecular FDG-PET/CT imaging in disease monitoring and clinical management of such case is presented.

We herein illustrate a case of benign tenosynovial giant cell tumor, which was incidentally detected as FDG-avid lesion on PET/CT in a patient with radioiodine refractory thyroid cancer, with predominantly non-iodine concentrating disease. The lesion was followed up clinically and with local MRI annually for subsequent 3 years. The utility of hybrid PET-CT imaging, the non-iodine concentration of the tumor along with clinical knowledge, and findings on other imaging and pathological modalities in answering and diagnosing incidental benign musculoskeletal tumors in a patient with known thyroid malignancy are presented here.

A rare and fatal life-threatening case of necrotizing fasciitis (initially presenting with skin-deep superficial lesions and clinical suspicion of paraneoplastic syndrome) is described, who was finally diagnosed with the help of fluorodeoxyglucose-positron emission tomography (FDG-PET)/computed tomography (CT) as more extensive infectious process. A 36-year-old male presented with bilaterally symmetrical cutaneous lesions involving lower limbs that rapidly progressed to ulcerative lesions and pancytopenia. In view of suspicion of paraneoplastic manifestation, the patient underwent 18F-FDG-PET/CT to rule out any underlying malignancy. The FDG-PET/CT findings confirmed hypermetabolism circumferentially along the fasciae of bilateral lower extremities while sparing muscles and subcutaneous fat from below the knee till toe with diffused hypermetabolic marrow, and no evidence of focal disease suggesting malignancy. Biopsy turned out to be superficial necrolytic fasciitis. The patient's condition deteriorated and, 20 days following the scan, the patient succumbed secondary to severe pancytopenia and hypotension. The case raises the importance of high degree of suspicion and prompt diagnosis of this condition, where FDG-PET/CT imaging can play a valuable complimentary role. Such awareness could be lifesaving due to early optimal treatment in the disease course.

Endocrine neoplasms and malignancies are a diverse group of tumors with varied clinical, histopathologic, and functional features. These tumors vary from sporadic to hereditary, isolated entities to multiple neoplastic syndromes, functioning and non functioning tumors, unifocal locally invasive, and advanced to multifocal tumors with disseminated distant metastases. The presence of various specific biomarkers and specific receptor targets serves as valuable tools for diagnosis, prognosis, and management. PET-CT with FDG and a multitude of novel and specific radiotracers towards specific therapeutic targets mandates personalization of their use, so as to ensure maximum clinical benefit in the management of these neoplasms.

Determining the choice and the goal is key element for decision-making of a systemic radionuclide therapy. They should be clearly defined in deciding and individualizing the dose and regimen. For iodine-131 metaiodobenzylguanidine (131I-mIBG) therapy, the important considerations during dose fractionation include disease burden, tumor biology, functional symptoms, and associated comorbidities, all of which are important determinants for the intent and course of treatment. Herein, we present the case of a 67-year-old elderly female with highly functional metastatic recurrent extra-adrenal pheochromocytoma (presenting 42 years after the primary surgery and 32 years following excision of pararenal recurrence) with multiple comorbidities including single kidney and borderline renal compromise, treated successfully with a relatively lower dose of 131I-mIBG (cumulative dose of 22.2 GBq in four cycles with a mean dose of 5.7 GBq per therapy cycle). The excellent tumor burden reduction, hormonal tumor marker response, and most importantly asymptomatic status could be achieved with the administered dose. On follow-up, none of the pretherapeutic parameters (including renal function) showed any further derangement compared with the baseline during next 24 months following the treatment. All cycles were well tolerated with only reversible hematological toxicity that normalized without any active intervention. The report is intended to provide some guidance for future therapeutic regimens.

Introduction: [177Lu]Lu-prostate-specific membrane antigen (PSMA)-617 has emerged as a promising radiopharmaceutical for targeting PSMA in metastatic castrate-resistant prostate carcinoma (mCRPC). ...

Objective The aim of present study was to determine and compare the overall response rates, progression-free survival (PFS), overall survival (OS), and clinical toxicity of the combination of 177Lu-PSMA-617 radioligand therapy (PRLT) and abiraterone acetate (AA) versus 177Lu-PSMA-617 PRLT as monotherapy in metastatic castration-resistant prostate cancer (mCRPC) patients. Materials and methods The mCRPC patients who received at least one cycle of 177 Lu-PSMA-617 PRLT with or without AA therapy, were included and analyzed in the present study. The patients were divided into two major groups. Group 1 received only 177 Lu-PSMA PRLT and Group 2 received combined 177 Lu-PSMA PRLT + AA therapy. Therapeutic dose of 177 Lu-PSMA-617 PRLT was 4.4-5.55 GBq per patient per cycle administered at intervals of 10-12 weeks in both groups. The Group 2 patients additionally received a dose of 1000 mg of AA once daily and 5 mg of prednisone twice daily. Treatment response in two groups was evaluated under four broad categories (a) symptomatic, (b) biochemical (serum prostate-specific antigen level), (c) objective molecular imaging (68 Ga-PSMA-11 and 18 F-FDG PET/CT), and (d) objective anatomical imaging (computed tomography). For assessing treatment response, patients in two groups were categorized into responders (complete response [CR], partial response [PR], and stable disease [SD]) and nonresponders (progressive disease [PD]). The Kaplan-Meier product-limit method was used to calculate PFS and OS following first 177 Lu-PSMA PRLT in the two groups. Univariate analysis was used to compare the patients' characteristics in two groups using a χ2 or Fisher exact test. The Kaplan-Meier curves of PFS and OS between two groups were compared by using the log-rank test (p Results A total of 58 mCRPC patients (Group 1, 38 patients and Group 2, 20 patients) were included in this study analysis. The clinical and demographic characteristics of these patients (age, Gleason score, FDG avid disease, metastatic disease burden, and average number of 177 Lu-PSMA PRLT cycles) in two groups were compared and found to be similar (p > 0.05). Post-treatment, symptomatic, biochemical, molecular, and anatomic imaging responders were found in 22 patients (58%) and 17 patients (85%), 22 patients (58%) and 16 patients (80%), 19 patients (54%) and 14 patients (78%), and 19 patients (54%) and 14 patients (78%) in Group 1 and Group 2, respectively. The median PFS of 7 months and median OS of 8 months were documented in Group 1, whereas median PFS was not reached and median OS of 16 months registered in Group 2. Transient hematological toxicity of Grades 1 and 2 was found in total seven patients (five patients in Group 1 and two patients in Group 2). On comparison of the treatment outcome between two groups, significant p value was found for symptomatic responders (58% in Group 1 vs. 85% in Group 2), median PFS (7 months in Group 1 vs. not reached in Group 2), and median OS (8 months in Group 1 vs. 16 months in Group 2), with better outcome in Group 2 patients for these variables. Conclusion In the present study, the combination of 177 Lu-PSMA-617 PRLT and AA therapy showed significant improvement in mCRPC patients' symptomatic response, PFS, and OS as compared to 177 Lu-PSMA-617 PRLT monotherapy.

This overview describes the basic characteristics and chemistry, production and the clinical applications and use of radiopharmaceuticals pertaining to radiosynoviorthesis (RSO). In each of the case scenarios, the physical and clinical parameters that serve as determinants and govern the choice of a particular radionuclide employed for RSO are discussed. References have been drawn on the fundamentals of RSO where applicable, including a brief review of the principles and mechanism of action, the indication and efficacy of RSO in different disease conditions and suggestions set out by the current guideline recommendations.

Aleukemic leukemia cutis (ALC) is a rare condition with a relatively poor prognosis, clinically presenting as skin and subcutaneous nodules commonly involving head and neck region with discrete atypical leukemic cells infiltrating in the skin on histopathology. The lesions on the genital area skin are seldom reported. A 49-year-old male presented with joint pains and multiple subcutaneous nodules clinically with biopsy proving it as leukemia cutis. Bone marrow aspiration and biopsy were suggestive of normocellular myeloid preponderant bone marrow with mild increase in eosinophils. The 18F-fluorodeoxyglucose positron emission tomography/computed tomography (18F-FDG PET/CT) revealed metabolically active FDG avid ill-defined soft tissue attenuation involving the entire length of penile shaft with central necrotic area, diffuse scrota skin thickening, and lateral compartment muscles of left leg, in addition to multiple hypermetabolic metastatic lymph nodes, and diffuse hypermetabolic marrow in humerii and femora. Despite prompt investigations and initiation of management, the patient succumbed in 15 days post-FDG PET/CT. The present report depicts an atypical case of ALC, with FDG PET-CT showing extensive and unusual sites of disease involvement, emphasizing its potential role in ALC.

Objective: To evaluate the efficacy, toxicity and survival of salvage peptide receptor radionuclide therapy (PRRT) with indigenous, direct-route 177Lu-labelled-DOTATATE in metastatic Nueroendocrine tumor (NET) patients who showed an objective response or disease stabilization following initial course of 177Lu-DOTATATE PRRT cycles and eventually developed progressive disease after a time-interval of more than 1 year; the variables influencing survival and response of salvage PRRT were also examined. Methods: A total of 26 progressive metastatic NET patients who received salvage PRRT with indigenous 177Lu-DOTATATE, were evaluated. Response was assessed under three broad categories as clinical symptomatic, biochemical and imaging (both molecular and morphological imaging). The Kaplan–Meier product-limit method was used to calculate progression-free survival (PFS) and overall survival (OS). Toxicity of salvage PRRT was evaluated by NCI-CTCAE v. 5.0 criteria (included complete blood counts, renal and liver function tests). Association between various variables and response and survival were analyzed using the χ2 test. Results: Out of the 26 patients, the complete follow-up data were not available for four patients, where only survival information was available. Thus, a total of 22 patients (median age: 55 years, range: 38–68 years, 12 men and 10 women) were included and analyzed retrospectively in study. The cumulative dose of initial course of PRRT (I-PRRT) with indigenous 177Lu-DOTATATE ranged from 800 mCi (29.6 GBq) to 1231 mCi (45.54 GBq) per patient {mean administered cumulative dose of 964 mCi (35.66 GBq) per patient}, and the salvage PRRT with indigenous 177Lu-DOTATATE comprised of a mean dose of 170 mCi (6.29GBq) per patient. The disease control rate of 68.1%, 77.3%, 63.6% and 63.6% were observed after salvage PRRT on clinical symptomatic, biochemical, molecular and morphological imaging response respectively. The median PFS after salvage PRRT was 17 months. The median OS was not attained after I-PRRT (OS-i) and salvage PRRT (OS-s). Estimated OS-i rate was 68% at 108 months and OS-s rate was 82% at 18 months. None of the patients developed Grade 3/4 hematotoxicity, nephrotoxicity and hepatotoxicity or AML/MDS after I-PRRT and salvage PRRT at median follow-up of 72 months and 12 months respectively. The highest level of toxicity was Grade 2 [seen as reversible anemia, thrombocytopenia and nephrotoxicity in 3 (13.5%), 1 (4.5%) and 2 patients (9%) respectively]. The significant p-value was not observed for any variable association. Conclusion: With limited therapeutic options available for progressive NET after I-PRRT and in the absence of high-grade toxicity after 177Lu-DOTATATE salvage PRRT, retreatment with PRRT may be considered as a relatively safe therapeutic option for these patients. Advances in knowledge: This study examined salvage retreatment PRRT with indigenous “direct-route” 177Lu-DOTATATE and registered its safety and survival benefits, indicating this could be an effective therapeutic option in this clinical setting.

Background and Aim: The employment of prostate-specific membrane antigen (PSMA)-based PET-CT imaging has grown rapidly over the recent years. The aim of the present study was to estimate the lesional uptake across the different levels of molecular imaging PSMA (miPSMA) expression score along with normal physiological concentration of 68Ga-PSMA-11 in a cohort of mCRPC patients including their temporal variation on delayed imaging. Materials and Methods: Fifty patients of mCRPC who were being evaluated for 177Lu-PSMA PRLT, and underwent 68Ga-PSMA-11 PET-CT for evaluation of disease status, were retrospectively evaluated. The mean age of the patients undergoing the scan was 67.5 ± 8 years (52-84 years) with an average serum PSA level of 401 ± 1353 ng/ml (0.098-9235.13 ng/ml) at the time of scanning. All patients underwent standard 68Ga-PSMA-11 PET-CT at 65 minutes post-injection on an average (60-90 mins). Tumoral analysis (n = 50) was undertaken to see their correlation with miPSMA expression score and their uptake values. The physiological tracer distribution was estimated by placing a spherical VOI of fixed diameter of 1 cm for smaller organs (in the regions of submandibular glands, parotid glands, lacrimal glands, tubarial glands, renal cortices, blood pool and bowel) and 3 cm for larger organs (liver and spleen). Standardised uptake value maximum (SUVmax) and mean (SUVmean) were estimated for each of the regions. Tumor-to-spleen (T/S), tumor-to-liver (T/L) and tumor-to-parotid (T/P) ratios were calculated for each lesion. A subgroup of 16 patients underwent a delayed scan at 135 mins post injection on average (120 – 150 mins), for whom an additional analysis was performed to evaluate the effect of delayed imaging on uptake values and ratios. Results: The maximum uptake was observed in renal cortices followed by salivary glands, bowel, spleen, liver, lacrimal glands and blood pool in the descending order. The average SUVmax with SD of the organs are as: 37.7 ±22.1 for renal cortices, 15.4 ±7.3 for submandibular glands, 14.4 ± 7.1 for parotid glands, 9.4± 4.9 for spleen, 6.2 ± 3.7 for lacrimal glands, 5.9± 2.3 for liver, 5.3 ± 1.41 for tubarial glands, 13.8 ±7.6 for bowel, and 2.4 ±1.9 for blood pool. The average SUVmax of miPSMA expression score 2 was 10.33 ± 3.27 (6.46 - 17) and 38.21 ± 25.9 (7.68 – 119.08) for score 3. The average tumor-to-spleen (T/S) and tumor-to-parotid (T/P) ratios for score 2 lesions were 1.21 ± 0.44 (0.48 – 2.04) and 0.6 ± 0.18 (0.39- 0.87) respectively. The average T/S and T/P ratios for score 3 lesions were 5.05 ± 4.46 (1.25 – 20.89) and 3.15 ± 2.09 (1.06 – 9.45) respectively. The average SUVmax of index score 3 lesions was 18.85 which increased to 26.24 on delayed imaging with statistically significant difference (P = 0.0001). However, the T/L, T/S and T/P ratios did not show any significant change. The temporal variation of normal organs showed that the SUVmax was significantly increased in delayed scan in salivary (submandibular and parotid) and lacrimal glands, and renal cortices, while the SUVmean significantly increased in spleen and liver, parotid, tubarial and lacrimal glands and not significant in other organs. Conclusion: Thus, the reference ranges of normal organs (physiological uptake) and tumor lesions for uptake and ratios for miPSMA score 2 and score 3 were documented and established in the present study, based upon which a consensus on standard reference range can be proposed for all quantitative assessment values on 68Ga-PSMA-11 PET-CT. The temporal variation trends of the lesions and reference organs should be kept in mind for delayed acquisitions, the T/S, T/Lor T/P ratios could serve as better markers for such scenarios.

A patient of differentiated follicular thyroid carcinoma with unusual sites of metastases is illustrated with 131I and 18F-fluorodeoxyglucose positron emission tomography/computed tomography (18F-FDG PET/CT) imaging findings. The described case harbored extremely rare metastasis to the urinary bladder with multi-organ metastatic disease (including unusual sites of right bronchus and hepatic metastases). There was inter-lesional heterogeneity among the metastatic lesions with regard to the 131I and FDG uptake in the aforementioned lesions. The detection of such heterogeneity has important implications for patient management in metastatic differentiated thyroid carcinoma.