World Journal of Nuclear Medicine

: 2012  |  Volume : 11  |  Issue : 3  |  Page : 154--159

ICRT-Abstracts of Oral Presentations


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Efficacy of Different Protocols of Radioiodine Therapy for Treatment of Toxic Nodular Goiter: Systematic Review and Meta-analysis of the Literature

S. R. Zakavi, H. Rakni, R. Sadeghi, Z. Mousavi

Nuclear Medicine Research Centre, Mashhad University of Medical Sciences, Mashhad, Iran

Hyperthyroidism is a common disorder all over the world. While multinodular goiter is the second most common etiology of hyperthyroidism and radioiodine therapy is the most commonly accepted treatment for these patients, there is no consensus on optimum dose of radioiodine. Fixed dose is very easy to use while calculation of delivered dose is time consuming. The aim of this meta-analysis is to evaluate two main methods of radioiodine dose determination in toxic nodular goiter, namely, calculated versus fixed dose and high versus low dose of radioiodine treatment. We searched MEDLINE and SCOPUS databases for clinical trials (randomized or non-randomized) that compared two different methods of iodine administration in toxic nodular goiter (multinodular or single nodule). The trials were classified into two groups: those that compared fixed versus calculated dosimetry method and those assessed high fixed dose versus low fixed dose method. Treatment response was defined as euthyroidism or hypothyroidism 1 year after radioiodine administration. We calculated the odds ratio and risk difference of treatment response as well as permanent hypothyroidism as outcome variables. Random effects model was used for data pooling. The search yielded 2393 articles of which 1936 articles were irrelevant. After excluding animal studies, review articles, and editorials, 172 relevant articles remained for eligibility analysis. Two randomized and five non-randomized clinical trials met the eligibility criteria for meta-analysis. Patients with toxic nodular goiter who were treated according to calculated method had 8.4% higher rate of cure (odds ratio = 1.58, P = 0.059) and only 0.9% more permanent hypothyroidism (odds ratio = 1.01, P = 0.9) compared to patients with fixed dose method. The total amount of administered radioiodine was lower in calculated method compared to fixed dose method. Patient treated with fixed high dose had 18.1% more cure rate (odds ratio = 4.6, P < 0.001) and 20.9% more permanent hypothyroidism (odds ratio = 3.34, P < 0.001) compared to patients treated by fixed low dose protocols. Our study showed that calculated radioiodine therapy is preferred to fixed dose method in patients with toxic nodular goiter. High dose methods are associated with more response and more hypothyroidism.


Early Radioiodine Ablation Post Thyroidectomy with Recombinant TSH Stimulation and its Impact on Performance Status, versus Thyroxin Abstinence Protocol in Differentiated Thyroid Carcinoma: Initial Results of a Randomized Prospective Clinical Trial

P. S. Choudhury, A. Purthi, A. K. Dewan, T. Pradhan, A. Goel, V. Chauhan

Nuclear Medicine and Surgical Oncology (H & N Services), Rajiv Gandhi Cancer Institute and Research Centre, Delhi, India

Background: The current standard practice of I-131 (radioiodine) ablation post thyroidectomy in thyroid carcinoma requires 4-5 weeks for physiological stimulation of thyroid stimulating hormone (TSH), which affects the quality of life (QOL) due to severe hypothyroid symptoms. Few reports are available in the literature regarding pharmacological stimulation of TSH and its utility in ablation of residual tissue.

Aims and Objectives: A prospective study was conducted to assess the feasibility and utility of recombinant TSH (r-TSH) injection to facilitate ablation of residual tissue with radioactive iodine, immediately post thyroidectomy, in differentiated thyroid carcinoma and its impact on performance status as compared to standard prolonged thyroxine abstinence.

Materials and Methods: In our randomized trial, we compared two thyrotropin stimulation methods, namely, r-TSH within 10-12 days post surgery during one hospital stay (group I) and thyroxine abstinence for 4-5 weeks (group II). Inclusion criteria were age of 18 years or older, total/near-total thyroidectomy performed for differentiated thyroid carcinoma, and tumor-node-metastasis (TNM) stage, ascertained on pathological examination (p) of a surgical specimen, of pT1-T3, N0/N1, and no iodine contamination. Patients with distant metastasis on presentation or locally advanced (T4) primary tumor were excluded from the study. r-TSH was obtained as a sterile non-pyrogenic lyophilized product reconstituted with sterile water for injection. 0.9 mg was injected intramuscularly on two consecutive days (24 h interval). Serum TSH assay was done on the 3 rd day prior to therapeutic radioiodine administration. Usual replacement dose of thyroxine was continued (Group I). Diagnostic whole-body I-131 scan followed by ablative dose of radioiodine was administered in group II. Radioiodine (I-131) with administered activities ranging from 45 to 68 mCi (mean dose of 55 and 59 mCi, respectively) was used for ablation. QOL assessment was done using standard Eastern co-operative oncology group (ECOG) criteria in both the groups. Response to radioiodine treatment was assessed after 6 months by whole-body radioiodine scintigraphy, neck ultrasonography, and measurement of stimulated thyroglobulin. End points used for current analysis were the rate of success of ablation and QOL during and after ablation. Relevant statistical analysis was performed. The protocols were approved by the institutional review board (ethics committee). Results: Nineteen patients (7 males and 12 females) who underwent radioiodine ablation during March 2011-May 2012 were included in the analysis. 89% had papillary carcinoma. Eight patients (mean age 57.38 ± 14.85 years) and 11 patients (mean age 41.73 ± 12.87 years) were randomized to group I and II, respectively. Adequate TSH response was seen (>80 mIU/ml). Avid I-131 concentration in the thyroid bed with no evidence of distant metastasis was seen in the post-therapy scans in all patients. Total ablation of residual tissue was seen in six patients (two patients yet to undergo follow-up scan) with thyroglobulin levels <1 ng/ml in 5 (>10 ng/ml in 1 with total ablation on scan) in group I and in nine patients with thyroglobulin levels <1 ng/ml in group II (P = 0.719). Partial ablation was seen in 0 and 2 patients in group I and II, respectively (P = 0.202). No statistically significant difference was seen in response rates between the two groups. The ECOG score was 0-1 and 2-3 in group I and II, respectively. There was statistically significant difference in QOL between the two groups (P = 0.0005).

Conclusion: Our results show that ablation of residual thyroid tissue is feasible immediately post thyroidectomy by r-TSH stimulation and has the same outcome as compared to the standard thyroxine withdrawal which is universally practiced. No morbid symptoms of hypothyroidism post r-TSH stimulation resulted in better compliance, performance status, and QOL, with patients being able to go back to their normal routine much earlier.


Clinical Significance of Measurement of Serum Antithyroglobulin Antibodies (ATgAb) in the Follow-up of Differentiated Thyroid Carcinoma

J. Irfan, K. Mir, S. Fatima

Nuclear Medicine, Nuclear Medicine, Oncology and Radiotherapy Institute (NORI), Islamabad, Pakistan

Background: Despite the excellent prognosis, recurrence rate of differentiated thyroid carcinoma (DTC) is 20-40%. That is why long-term follow-up with sensitive tests is needed. Tg measurement is important for follow-up after surgery in patients with DTC and for detection of persistent or recurrent thyroid cancer, but in the presence of antiTg autoantibody (ATgAb), a negative Tg result is most likely false negative. So, recent guidelines recommend assessing ATgAb, with simultaneous measurement of serum Tg, every 6-12 months after surgery. Persistence of ATgAb after treatment or increasing ATgAb concentration indicates persistent or recurrent DTC.

Materials and Methods: A total of 90 patients (18 males and 72 females) of DTC who have undergone total thyroidectomy along with I-131 ablation, with TSH stimulated Tg <2 ng/ml were included in this study. Serial assessment of Tg and ATgAb level was done in those patients. Conclusion and results were extracted after comparison of ATgAb level with available imaging modalities, i.e., whole-body scan (WBS), ultrasound, chest X-ray (CXR), bone scintigraphy, computed tomography (CT), and magnetic resonance imaging (MRI), and response to therapy.

Results: Out of total 90 patients, (63.3% papillary Ca, 36.7% follicular Ca), patients with increased ATgAb of >20 numbered 39 (43%). There was no significant difference in gender (P < 0.48) or multifocality (P < 0.04) between ATgAb-positive and ATgAb-negative groups. Compared with ATgAb-negative group, a greater number of ATgAb-positive patients had lymph nodal metastasis (P < 0.004) and extrathyroidal extension (P < 0.002). Further analysis of the data showed that raised ATgAb levels and disease status are very well correlated, i.e., P>0.05. Out of 39 patients, 7 patients (17.98%) with positive ATgAb showed recurrence whereas only 2 (3.92%) of 51 patients with negative ATgAb had recurrence during the follow-up (P< 0.028). Recurrence rate was 0% in group I, 10% in group II, and 45% in group III. No significant correlation of gender, multifocality, lymph nodal metastasis, or extrathyroidal extension was noted among groups I, II, and III.

Conclusion: ATgAb is also a tumor marker that increases when tumor is present and decreases when the tumor has been destroyed. There is a statistically significant correlation between the complete disappearance of thyroid tissue and that of ATgAb, so serial measurement of ATgAb levels in the follow-up of patients of differentiated thyroid cancer is as important as the measurement of Tg level.


Consequences of Misadministration in Handling of Radiopharmaceuticals

A. K. Shukla

Department of Nuclear Medicine, Sanjay Gandhi Postgraduate Institute of Medical Sciences, Lucknow, India

The term "misadministration" in Nuclear Medicine refers to the probable events in routine practice of nuclear medicine that may lead to preventable potential exposures to patients. However, consequential outcome of such occurrences and their real-time impact would remain unpredictable. Major events causing misadministration include administering a radiopharmaceutical to a wrong patient or wrong radiopharmaceutical/activity to a patient. In addition, it also includes the unjustified investigation (involving use of radiopharmaceuticals) on pregnant or lactating patients. Incorrect or inappropriate route of administration of radiopharmaceutical also constitutes an event of misadministration. Major causes of misadministration have been identified to be improper communication, busy work routines, stressors, lack of training, and local rules, as well as inadequate or no quality assurance system in place. In order to minimize or prevent the occurrence of events leading to misadministration, it is necessary to identify the initiating events and contributing factors/causes. A comprehensive safety analysis also needs to be undertaken to identify as to what can go wrong in the entire course of application, including the steps involved in various procedure protocols. The factors outlined to be responsible for misadministration could lead to accidental exposures and consequential outcome of such occurrences and their real impact would remain unpredictable. In a broader sense, these may lead to increased radiation dose to patient as well as radiation workers involved, increased cost to mitigate the consequences arising thereof, inconvenience to patients due to multiple visits for repeat procedures, and finally delayed diagnosis. The events of misadministration in nuclear medicine can be enlisted as: wrong identification of patients, administration of wrong radiopharmaceuticals, wrong route of administration, wrong activity, pregnant women, and lactating women.


Experience with 177Lu-EDTMP Regarding Improvement in Quality of Life and Bone Pain Palliation

G. Jameel, J. Zaknun, S. Saeed, J. Irfan, S. Fatima, S. Tufail

Nuclear Medicine, Nuclear Medicine Oncology and Radiotherapy Institute, Islamabad, Pakistan

Objectives: To evaluate the pain palliating effect of Lu-177 EDTMP and to assess the beneficial effect on improving mobility and quality of life of patients with known disseminated skeletal metastases. Different doses of Lu-177 EDTMP were used (1300-2600 MBq) and doses were repeated to compare the effects of doses on pain palliation.

Materials and Methods: Thirty-one patients of carcinoma of the prostate and carcinoma of the breast (male:female ratio of 23:9) with skeletal metastases were enrolled and Lu-177 EDTMP was injected after formulation and quality control. 177Lu-EDTMP images were acquired on dual-head gamma camera, at 30 min, 24 h, and 48 h to determine tracer distribution. Pain palliation was recorded by means of a pain dairy submitted on each follow-up visit. The recording comprised a visual analogue score (VAS) 0-10, increase or decrease in use of analgesics over the period of time, and mobility. Karnofsky score was performed at every follow-up visit as a standard of quality of life till 4 months post-injection, on weeks 1, 2, and 4 and at months 2, 3, and 4. The complete blood counts (CBC) were assessed and closely monitored for any toxic effects.

Results: In 85% of patients, irrespective of the stage of disease and dose of Lu-177 EDTMP used, there was improvement in pain as was monitored by VAS which dropped from 8 to 4 (50% improvement) within 1 week post-therapy. The results were statistically analyzed as various parameters and scores were used to assess increase in mobility, use of analgesics, and quality of life. The results showed more than 20% improvement in Karnofsky score in 80% of patients within 2 weeks post-therapy. All blood toxicity parameters were monitored and analyzed, and only 1 patient out of 31 showed grade II toxicity.

Conclusions: The results indicate that Lu-EDTMP can be used in skeletal metastatic pain for pain alleviation and improvement in quality of life. This can be achieved without increase in toxicity to compromise patients' safety. 177Lu-EDTMP is an effective and safe therapeutic radiopharmaceutical for pain palliation of disseminated skeletal disease in prostate and breast cancer at activities up to 2600 MBq. (Research Support: CRP-E13033, International Atomic Energy Agency)


Hydroxyapatite Particles Labeled with Beta-Emitting Lanthanoids for Radiosynovectomy

M. Sohaib

Department of Medical Sciences, Pakistan Institute of Engineering and Applied Sciences, Islamabad, Pakistan

Rationale: Radiation synovectomy is used when chronic inflammatory synovitis is refractory to conventional pharmaceutical therapy. This procedure employs particulate substances labeled with beta-emitting radionuclides, which are injected into joint space to restore synovial lining. Tissue penetration of beta particles depends upon their energies such that high energy is for large joints and low energy for smaller joints. Hydroxyapatite (HA) is a naturally occurring compound and one of the particle options that can be labeled with a beta-emitting radiometal for radiosynovectomy. In the current study, we labeled these particles with four beta-emitting lanthanoids (Lutitium-177, Samarium-153, Yttrium-90, and Holmium-166) having various beta energies and evaluated them in knees of animal model.

Materials and Methods: All these beta-emitting lanthanoids were prepared by (n, g) reaction at PARR -1 (PINSTECH) and were tagged to HA at Isotope Production Division, PINSTECH, Islamabad. Radiochemical quality control of these was performed by paper chromatography. Particle size of HA was determined using laser particle size analyzer at Department of Chemical and Materials Engineering, PIEAS, Islamabad. Their in vivo bio-evaluation studies were carried out in rabbit models at Department of Medical Sciences, PIEAS, Islamabad. Each labeled HA was injected in knee joints of two rabbits, which were evaluated visually for leakage. Half-lives of radiopharmaceuticals were determined from disappearance of activity from the joints. The data were then used to measure percent leakages from the joints and biological half-lives.

Results: 95% of the particles of HA were in the range of 0.614-6.096 mm, 80% being in the ideal range (2-10 mm). No particle was seen below 0.2 mm. Lu-177, Sm-153, Y-90, and Ho-166 were produced with good radionuclide purity. They were adequately tagged with HA having labeling yields of 97.4%, 99.9%, 99.5%, and 99.8%, respectively. No leakage from the knees of rabbits of any of the agents was seen visually in gamma camera studies. Half-lives of the Lu-177 HA, Sm-153 HA, Y-90 HA, and Ho-166 HA in rabbit 1 and 2 were 153.2 h and 155.0 h, 44.3 h and 45.3 h, 65.2 h and 61.3 h, and 27.2 h and 26.0 h, respectively. Biological half-lives of these agents were 140.1, 106.4, 211.3, and 148.5 days, respectively.

Conclusion: Lu-177 HA, Sm-153 HA, Y-90 HA, and Ho-166 HA can be obtained with high labeling yields and have minimal leakages from the joint space, hence are suitable for radiosynovectomy.


A Pilot Study to Evaluate the Effectiveness of Radiosynoviorthesis of Sacro-Iliac joints with Rhenium-186

M. Vereb, L. Kaliska, K. Liepe

Nuklearmedizin, Klinikum Kassel, Kassel, Germany

Purpose: Intraarticular injected beta-emitting radionuclide [radiosynoviorthesis (RSO)] is an established form of therapy in persistent inflammatory joint diseases. It is safe, accepted, and has a good documented procedure. Standard use of radiosynoviorthesis is known in rheumatic and psoriatic arthritis and also in other different types of joint diseases such as mono-, oligo-, and polyarthritis, hemophilic arthritis, pigment villonodular synovitis, and lymes boreliosis. Commercially available ones are: Ytrium-90 recommended for knees; Erbium-169 recommended for metacarpal/metatarsophalangeal and interphalangeal joints; and Rhenium-186 recommended for hip/shoulders, elbow, wrist/ankle, and subtalar joints. According to literature review, the improvement of joint pain after RSO was noticed in periods longer than 2 years in 40-90% of cases, independent of the affected joint and type of arthropathy. At present, there are no available data in the literature concerning application of RSO in the case of aseptic sacroiliitis, what is the inflammatory disease of one-joint or both-sacroiliac joint, most frequently seen in psoriatic arthritis, spondylopathy or HLA-B 27 positivity. The disease usually manifests 5-10 years after existence of disease. Without suitable treatment, the illness will progress and lead to degenerative changes, often also with immobilization. Diagnosis is based on clinical data, laboratory tests, and diagnostic imaging. However, the assessment of disease is not easy to make. Our target is to evaluate the effectiveness of RSO in sacro-iliac joints based on favorable experience with RSO in persistent inflammatory joint diseases.

Materials and Methods: Inflammatory joint disease of sacro-iliac joints was confirmed by hyperperfusion of sacro-iliac joints on two-phase bone scintigraphy. 74 MBq of Rhenium-186 in volume of 0.2-0.4 ml after 2 ml, of Lidocaine (2%), was applied to the sacro-iliac joint under C-arm fluoroscopy in prone position, whereby the pelvis region was elevated by underlying pillow. Rhenium-186 applic ation was followed by patient immobilization, which is recommended for next 2 days during hospitalization of patient. The selection of radiopharmaceutical was empiric, according to the physical properties of the radionuclide. The evaluation of positive effects of RSO was done by subjective scoring of patient about pain relief [according to 10° visual analogue scale (VAS) of pain]. Acceptable result was considered as decrease of pain minimally in 2° of VAS. As objective measurement of good result, we used two-phase bone scintigraphy with improvement of hyperperfusion of sacro-iliac joint on follow-up scan.

Preliminary Results: Six sacro-iliac joints were treated in four patients with known history of persistent inflammatory joint disease (1x rheumatic arthritis, 2x psoriatic arthritis, 1x polyarthritis) and with hyperperfusion of sacro-iliac joints documented by two-phase bone scintigraphy. All patients underwent multiple RSO of extremity joints with excellent effect. Tolerance of RSO in sacro-iliac joints was excellent in all patients. No complications were observed after injection of radionuclide Rhenium-186. Preliminary results showed that all patients experienced early pain remission in more than 2° of VSA, which started usually on 2 nd day after injection and lasted until 3 months (till present). The objective evaluation of therapy effect will be made in next 3 months.

Conclusion: Application of Rhenium-186 to sacro-iliac joints in persistent sacroiliitis was followed by prompt pain remission, which lasted minimally for 3 months. No side effects were observed. Preliminary data are promising for future utilization of RSO in sacro-iliac joints. Our present data are the first available data about RSO in persistent sacroiliitis. The assessment of the study is not finished yet. In the near future, results will be supplemented with objective evaluation of disease stage by two-phase bone scintigraphy. Our intention is to involve more patients in the study and confirm positive therapeutic effect of RSO in inflammatory sacroiliac joints.


Radiation Synovectomy with Yttrium (90Y) Citrate in Rheumatoid Arthritis Patients-5 Years of Follow-up

L. Jaukovic, B. Ajdinovic, Z. Andjelkovic, S. Dugonjic

Military Medical Academy, Institute of Nuclear Medicine, Belgrade, Serbia

Background: Radiation synovectomy is the radionuclide therapy of joint synovitis by intraarticular injection of radionuclides in colloidal form.

Aim: The aim of this study was to evaluate the therapeutic effects of application of Yttrium (90Y) citrate in colloidal suspension for local injection in radiosynovectomy of the knees.

Materials and Methods: During a period of 10 years, radiation synovectomy was performed in 155 knee joints of 110 rheumatoid arthritis patients who failed the intraarticular therapy with corticosteroids. In 45 patients, both knees were treated. The majority of patients had mild to moderate radiological damage. Severe radiological damage was an exclusion criterion. Radiation synovectomy was applied using 185 MBq 90Y citrate per joint. Therapeutic effects were assessed using clinical evaluation (the patient's and physician's global assessment of the effect of therapy joint pain, swelling, and the range of motion). Echosonography was additionally used in therapy assessment of 35 joints. Effects were classified as successful therapy (A), partially successful (B), failure (C), and were considered as positive (A + B) and negative (C).

Results: After 1 year, the results of evaluation were valuable in 139 out of 155 treated knees and in 112, 98, 84, and 62 joints after 2, 3, 4, and 5 years of follow-up, respectively. Complete remission of synovitis in the period of 1-3 years was achieved in 50-55% of joints, and the positive effects were observed in 70-80% of treated joints. At the end of 5 years follow-up period, the percentage of joints with complete remission decreased to 40. Treatment failure after the first year was observed in 19% (27/139) of joints. The number of joints with C effect increased over time, reaching 39% at the end of follow-up period. Recurrence of synovitis was observed in 30, 25, and 21% of joints with C effect after 2, 3, and 4 years of follow-up, respectively.

Conclusion: These results confirm the clinical efficacy of synoviorthesis using 90Y citrate in rheumatoid arthritis-diseased knee joints with 3 years positive effects in 70-80% of treated joints.


Cis-Diamminedichloroplatinum (II) Enhancement of Antitumor Effect of In-111-labeled N-myc Antisense Oligonucleotides in Nude Mouse-grown Human Neurobalstoma

N. Watanabe, M. Yoshizumi, K. Endo

Department of Radiological Sciences, Gunma Prefectural College of Human Sciences, Maebashi, Japan

Auger electrons are able to create breaks in mRNA (messenger ribonucleic acids), giving them possible therapeutic utility against malignant tumor. The antitumor effect of combined use of In-111-labeled N-myc antisense oligonucleotides and cis-diamminedichloroplatinum (II) (CDDP) was investigated in human neuroblastoma intraperitoneally transplanted to BALB/c athymic mice. The effects of In-111-labeled N-myc antisense oligonucleotides against human neuroblastoma cells and transplanted to athymic nude mice were found elsewhere. The response of the tumor to CDDP was relevant to the dose administered. Regression of the tumor was observed when CDDP was administered at about 5 mg/kg/injection. The retardation of tumor growth was observed in the group to which CDDP was administered at about 2 mg/kg/injection. When CDDP was administered with In-111-labeled N-myc antisense oligonucleotides, regression of the tumor was observed in the group treated with In-111-labeled N-myc antisense oligonuclotides, and the retardation of tumor growth was observed in the group treated with In-111-labeled N-myc antisense oligonucleotides at the lower doses. These results indicate that CDDP enhances the antitumor effect of In-111-labeled N-myc antisense oligonucleotides against transplanted neuroblastoma in BALB/c athymic mice.


46-Ki-67 and/or 18 FDG PET/CT? Which do we Need for Qualifying Patients to Peptide Receptor Radionuclide Therapy?

J. Kunikowska, L. Krolicki, D. Pawlak

Nuclear Medicine Department, Medical University of Warsaw, Warsaw, Poland

Background: Peptide Receptor Radionuclide Therapy (PRRT) using radiolabeled somatostatin analogs is a treatment option for patients with disseminated neuroendocrine tumors (NET). Grading of NET is based on histochemical characteristics of primary tumors, but metastatic lesions could be different and have higher Ki-67. The aim of the study was to assess Ki-67 and 18FDG PET/CT in response to the tandem 90Y/177Lu-DOTATATE therapy in patients with overexpression of somatostatin receptors.

Materials and Methods: Twenty-four patients with disseminated NET were included in the study prospectively. Before treatment, PET/CT on scanner Biograph 64 TruePoint (Siemens Medical Solutions) was performed 60 min after 300-370 MBq 18FDG injection and 60-80 min post injection of 120-185 MBq 68Ga-DOTATATE. The period between both studies was no longer than 4 weeks. Treatment was based on tandem therapy protocol: 1:1 90Y/177Lu-DOTATATE with activity 3.7 GBq/m2 body surface area in 3-5 cycles, with amino acid infusion for nephroprotection. The histopathology examinations with the proliferation index Ki-67 (MIB1) were done.

Results: All patients had positive 68Ga-DOTATATE study in all defined lesions. In the group of NET patients with Ki-67 < 2% (G1), 18FDG was positive in 25% of cases with SUV max 8.3 ± 4.2. In the group of NET patients with Ki-67 2-20% (G2), 18FDG was positive in 75% of cases with SUV max 9.6 ± 9.7. Patients with NET G2 and negative 18FDG study had Ki-67 4-5%. Time to progression (TTP) was 29.9 months in 18FDG-positive patients and it was not reached in 18FDG-negative group. In patients with NET G1, TTP was 26.5 months, and in patients with NET G2, TTP was 29.9 months (P > 0.05). The median overall survival (OS) time in all groups was not reached. Progression after PRRT in NET G1 group was observed in 25% of cases and in NET G2 group in 50% cases. Independent of the Ki-67 index, progression was observed in 75% of patients with 18FDG-positive study and only in 25% of patients with 18FDG-negative study. All patients presented progression when 18FDG uptake was observed in all metastases.

Conclusions: Not only Ki-67 but also 18FDG PET/CT results seem to be helpful parameters for qualifying patients with NET G2 to PRRT. Due to limited number of patients, future studies and observations are still needed.