Diagnostic and prognostic impact of 18F-FDG PET/CT in follicular lymphoma

Purpose

The aim of this study was to assess the usefulness of positron emission tomography/computed tomography in staging, prognosis evaluation and restaging of patients with follicular lymphoma.

Methods

A retrospective study was performed on 45 patients with untreated biopsy-proven follicular lymphoma who underwent ¹⁸F-fluorodeoxyglucose PET/CT (FDG PET/CT) and CT before and after chemoimmunotherapy induction treatment (rituximab combined with cyclophosphamide, doxorubicin, vincristine and prednisone).

Results

PET/CT detected more nodal (+51%) and extranodal (+89%) lesions than CT. PET/CT modified Ann Arbor staging in eight patients (18%). Five patients (11%) initially considered as being early stage (I/II) were eventually treated as advanced stage (III/IV). In this study, an initial PET/CT prognostic score was significantly more accurate than the Follicular Lymphoma International Prognostic Index score in identifying patients with poor prognosis (i.e. patients with incomplete therapeutic response or early relapse). The accuracy of PET/CT for therapeutic response assessment was higher than that of CT (0.97 vs 0.64), especially due to its ability to identify inactive residual masses. In addition, post-treatment PET/CT was able to predict patients’ outcomes. The median progression-free survival was 48 months in the PET/CT-negative group as compared with 17.2 months for the group with residual uptake (p?<?10^?4).

Conclusion

FDG PET/CT is useful for staging and assessing the prognosis and therapeutic response of patients with follicular lymphoma.     

18F-FDG PET/CT imaging versus dynamic contrast-enhanced CT for staging and prognosis of inflammatory breast cancer

Purpose

Inflammatory breast cancer (IBC) is the most aggressive type of breast cancer with a poor prognosis. Locoregional staging is based on dynamic contrast-enhanced (DCE) CT or MRI. The aim of this study was to compare the performances of FDG PET/CT and DCE CT in locoregional staging of IBC and to assess their respective prognostic values.

Methods

The study group comprised 50 women (median age: 51?±?11 years) followed in our institution for IBC who underwent FDG PET/CT and DCE CT scans (median interval 5?±?9 days). CT enhancement parameters were net maximal enhancement, net early enhancement and perfusion.

Results

The PET/CT scans showed intense FDG uptake in all primary tumours. Concordance rate between PET/CT and DCE CT for breast tumour localization was 92 %. No significant correlation was found between SUVmax and CT enhancement parameters in primary tumours (p?>?0.6). PET/CT and DCE CT results were poorly correlated for skin infiltration (kappa?=?0.19). Ipsilateral foci of increased axillary FDG uptake were found in 47 patients (median SUV: 7.9?±?5.4), whereas enlarged axillary lymph nodes were observed on DCE CT in 43 patients. Results for axillary node involvement were fairly well correlated (kappa?=?0.55). Nineteen patients (38 %) were found to be metastatic on PET/CT scan with a significant shorter progression-free survival than patients without distant lesions (p?=?0.01). In the primary tumour, no statistically significant difference was observed between high and moderate tumour FDG uptake on survival, using an SUVmax cut-off of 5 (p?=?0.7 and 0.9), or between high and low tumour enhancement on DCE CT (p?>?0.8).

Conclusion

FDG PET/CT imaging provided additional information concerning locoregional involvement to that provided by DCE CT on and allowed detection of distant metastases in the same whole-body procedure. Tumour FDG uptake or CT enhancement parameters were not correlated and were not found to have any prognostic value.     

Recurrent bladder carcinoma: clinical and prognostic role of 18 F-FDG PET/CT

Aim

A small number of studies evaluated the detection rate of lesions from bladder carcinoma (BC) of 18 F-FDG PET/CT in the restaging process. However, the prognostic role of FDG PET/CT still remains unclear. The aim of the present study was to evaluate the accuracy, the effect upon treatment decision, and the prognostic value of FDG PET/CT in patients with suspected recurrent BC.

Materials and Methods

Forty-one patients affected by BC underwent FDG PET/CT for restaging purpose. The diagnostic accuracy of visually interpreted FDG PET/CT was assessed compared to histology (n?=?8), other diagnostic imaging modalities (contrast-enhanced CT in 38/41 patients and MRI in 15/41) and clinical follow-up (n?=?41). Semiquantitative PET values (SUVmax, SUVmean, SUL, MTV, TLG) were calculated using a graph-based method. Progression-free survival (PFS) and overall survival (OS) were assessed by using Kaplan-Meier curves. The risk of progression (hazard ratio, HR) was computed by Cox regression analysis by considering all the available variables.

Results

PET was considered positive in 21 of 41 patients. Of these, recurrent BC was confirmed in 20 (95 %). Sensitivity, specificity, positive predictive value, negative predictive value, and accuracy of FDG PET/CT were 87 %, 94 %, 95 %, 85 %, 90 %. AUC was 0.9 (95 %IC 0.8-1). Bayesian positive and negative likelihood ratios were 14.5 and 0.13, respectively. FDG PET/CT findings modified the therapeutic approach in 16 patients (modified therapy in 10 PET-positive patients, watch-and-wait in six PET-negative patients). PFS was significantly longer in patients with negative scan vs. those with pathological findings (85 % vs. 24 %, p?<?0.05; HR?=?12.4; p?=?0.001). Moreover, an unremarkable study was associated with a longer OS (88 % vs. 47 % after 2 years and 87 % vs. 25 % after 3 years, respectively, p?<?0.05). Standardized uptake value (SUV)max?>?6 and total lesion glycolysis (TLG)?>?8.5 were recognized as the most accurate thresholds to predict PFS (2-year PFS 62 % for SUVmax?<?6 vs. 15 % for SUVmax?>?6, p?=?0.018; 2-year PFS 66 % for TLG?<?8.5 vs. 18 % for TLG?>?8.5, p?=?0.09).

Conclusion

A very good diagnostic performance for FDG PET/CT was confirmed in patients with suspected recurrent BC. FDG PET/CT allowed for a change in treatment decision in about 40 % of cases and showed an important prognostic value in assessing PFS and OS.

     

18F-FDG PET/CT is a valuable tool for relapsing polychondritis diagnose and therapeutic response monitoring

Objectives

To retrospectively investigate the role of ¹⁸ F–fluorodeoxyglucose positron emission tomography/computed tomography (¹⁸F-FDG PET/CT) for the diagnosis and therapeutic response in relapsing polychondritis (RP) patients.

Methods

¹⁸F-FDG PET/CT findings were reviewed in six RP patients. The initial scans were performed for all patients, follow-up scans were performed during steroid therapy for five patients. Changes in the abnormal lesions and the maximal standard uptake value (SUV_max) were analyzed.

Results

The initial PET/CT scans revealed intense FDG uptake in the cartilages for all six patients. The lesions of abnormal FDG uptake were tracheal/bronchial cartilage (n = 4), costicartilage (n = 4), nasal cartilage (n = 3), cricoid cartilage (n = 3), auricular cartilage (n = 3), arytenoid cartilage (n = 3), thyroid cartilage (n = 2), hyoid cartilage (n = 1) and mediastinum lymph node (n = 1). The mean visual score and the mean SUV_max were 2.96 ± 0.20 and 4.10 ± 0.6. The intense uptake reduced or disappeared during steroid therapy for five patients, the mean visual score and the mean SUV_max were 1.58 ± 1.4 and 1.51 ± 1.4.

Conclusions

¹⁸F-FDG PET/CT enables the acquisition of both morphologic and glucose metabolic of the related cartilage structures. It plays a valuable role in assessing almost all cartilage and detecting RP, which is a better selection of a biopsy site as well as therapeutic response monitoring.     

Whole-body [18F]FDG PET/MRI vs. PET/CT in the assessment of bone lesions in oncological patients: initial results

Objectives

To compare [¹⁸?F]FDG PET/MRI with PET/CT for the assessment of bone lesions in oncologic patients.

Methods

This prospective study included 67 patients with solid tumours scheduled for PET/CT with [¹⁸?F]FDG who also underwent a whole-body PET/MRI scan. The datasets (PET/CT, PET/MRI) were rated by two readers regarding lesion conspicuity (four-point scale) and diagnostic confidence (five-point scale). Median scores were compared using the Wilcoxon test.

Results

Bone metastases were present in ten patients (15 %), and benign bone lesions in 15 patients (22 %). Bone metastases were predominantly localized in the pelvis (18 lesions, 38 %) and the spine (14 lesions, 29 %). Benign bone lesions were exclusively osteosclerotic and smaller than the metastases (mean size 6 mm vs. 23 mm). While PET/CT allowed identification of 45 of 48 bone metastases (94 %), PET/MRI allowed identification of all bone metastases (100 %). Conspicuity of metastases was high for both modalities with significantly better results using PET/MRI (p?<?0.05). Diagnostic confidence in lesion detection was high for both modalities without a significant difference. In benign lesions, conspicuity and diagnostic confidence were significantly higher with PET/CT (p?<?0.05).

Conclusions

[¹⁸?F]FDG PET/MRI shows high potential for the assessment of bone metastases by offering superior lesion conspicuity when compared to PET/CT. In hypersclerotic, benign bone lesions PET/CT still sets the reference.

Key Points

? PET/MRI and PET/CT are of equal value for the identification of disease-positive patients ? PET/MRI offers higher lesion conspicuity as well as diagnostic confidence ? PET/MRI is an attractive new alternative for the assessment of bone metastases     

Contrast between hypervascularized liver lesions and hepatic parenchyma: early dynamic PET versus contrast-enhanced CT

Objectives

To detect hypervascularized liver lesions, early dynamic (ED) ¹⁸F-FDG PET may be an alternative when contrast-enhanced (CE) imaging is infeasible. This retrospective pilot analysis compared contrast between such lesions and liver parenchyma, an important objective image quality variable, in ED PET versus CE CT.

Materials and methods

Twenty-eight hypervascularized liver lesions detected by CE CT [21 (75 %) hepatocellular carcinomas; mean (range) diameter 4.9 ± 3.5 (1–14) cm] in 20 patients were scanned with ED PET. Using regions of interest, maximum and mean lesional and parenchymal signals at baseline, arterial and venous phases were calculated for ED PET and CE CT.

Results

Lesional/parenchymal signal ratio was significantly higher (P < 0.005) with ED PET versus CE CT at the arterial phase and similar between the methods at the venous phase.

Conclusion

In liver imaging, ED PET generates greater lesional–parenchymal contrast during the arterial phase than does CE CT; these observations should be formally, prospectively evaluated.     

18F-FDG PET/CT in the characterization and surgical decision concerning adrenal masses: a prospective multicentre evaluation

Purpose

This prospective multicentre study assesses the usefulness of FDG PET/CT in characterizing and making the therapeutic decision concerning adrenal tumours that are suspicious or indeterminate in nature after conventional examinations (CE).

Methods

Seventy-eight patients (37 men, 41 women, 81 adrenal lesions) underwent FDG PET/CT after CE including CT scan, biological tests and optionally ¹³¹I-metaiodobenzylguanidine (MIBG) and/or ¹³¹I-norcholesterol scans. FDG adrenal uptake exceeding that of the liver was considered positive. PET results were not decisive. Surgery was discussed when at least one of the following criteria was found during CE: size >3 cm, spontaneous attenuation value >10 HU, heterogeneous aspect, abnormal MIBG or norcholesterol scan or hormonal hypersecretion.

Results

Following the gold standard (histology analysis or ≥9 months follow-up), 49 lesions potentially qualified for surgery (malignant = 27, benign secreting = 22) and 32 benign non-secreting lesions did not. PET was negative in 97% of non-surgical lesions and positive in 73% of potentially surgical ones which included all the malignant lesions, except 3 renal cell metastases, and 12 of 22 benign secreting lesions. The negative predictive value for malignancy was 93% (41/44) and positive predictive value for detecting surgical lesions was 97% (36/37). A high FDG uptake (maximum standardized uptake value?≥?10) was highly predictive of malignancy.

Conclusion

Adrenal FDG uptake is a good indicator of malignancy and/or of secreting lesions and should lead one to discuss surgery. If there is no prior history of poorly FDG-avid cancer, the absence of FDG uptake should avoid unnecessary removal of benign adrenal lesions.     

The role of 18F-fluoride PET-CT in the detection of bone metastases in patients with breast, lung and prostate carcinoma: a comparison with FDG PET/CT and 99mTc-MDP bone scan

Objectives

We aimed to compare the role of ¹⁸F-fluoride PET/CT, FDG PET/CT and ^99mTc-MDP bone scans in the detection of bone metastases in patients with lung, breast and prostate carcinoma.

Methods

This was a prospective study including patients for staging (S) and restaging (R). Seventy-two patients (23S, 49R) with infiltrating ductal breast carcinoma, 49 patients (25S, 24R) with prostate adenocarcinoma and 30 patients (17S, 13R) with non-small-cell lung carcinoma (NSCLC), without known bone metastases but with high risk/clinical suspicion for the same, underwent a ^99mTc-MDP bone scan, FDG PET/CT and ¹⁸F-fluoride PET/CT within 2 weeks. All scans were reviewed by two experienced nuclear medicine physicians, and the findings were correlated with MRI/thin-slice CT/skeletal survey. Histological verification was done wherever feasible.

Results

Sensitivity and negative predictive value (NPV) of ¹⁸F-fluoride PET/CT was 100 % in all three malignancies, while that of FDG PET/CT was 79 % and 73 % in NSCLC, 73 % and 80 % in breast cancer and 72 and 65 % in prostate cancer. Specificity and positive predictive value (PPV) of FDG PET/CT were 100 % in NSCLC and prostate and 97 % and 96 % in breast cancer. As compared to the ^99mTc-MDP bone scan, all parameters were superior for ¹⁸F-fluoride PET/CT in prostate and breast cancer, but sensitivity and NPV were equal in NSCLC. The MDP bone scan had superior sensitivity and NPV compared to FDG PET/CT but had low specificity and PPV.

Conclusion

To rule out bone metastases in cases where there is a high index of suspicion, ¹⁸F-fluoride PET/CT is the most reliable investigation. ¹⁸F-fluoride PET/CT has the potential to replace the ^99mTc-MDP bone scan for the detection of bone metastases.     

18F-FDG PET as a single imaging modality in pediatric neuroblastoma: comparison with abdomen CT and bone scintigraphy

Objective

The purpose of this study was to evaluate the diagnostic performance of ¹⁸F-fluoro-2-deoxy-d-glucose positron emission tomography (FDG PET) as a single imaging agent in neuroblastoma in comparison with other imaging modalities.

Methods

A total of 30 patients with pathologically proven neuroblastoma who underwent FDG PET for staging were enrolled. Diagnostic performance of FDG PET and abdomen CT was compared in detecting soft tissue lesions. FDG PET and bone scintigraphy (BS) were compared in bone metastases. Maximal standardized uptake value (SUVmax) of primary or recurrent lesions was calculated for quantitative analysis.

Results

Tumor FDG uptake was detected in 29 of 30 patients with primary neuroblastoma. On initial FDG PET, SUVmax of primary lesions were lower in early stage (I–II) than in late stage (III–IV) (3.03 vs. 5.45, respectively, p = 0.019). FDG PET was superior to CT scan in detecting distant lymph nodes (23 vs. 18 from 23 lymph nodes). FDG PET showed higher accuracy to identify bone metastases than BS both on patient-based analyses (100 vs. 94.4 % in sensitivity, 100 vs. 77.8 % in specificity), and on lesion-based analyses (FDG PET: 203 lesions, BS: 86 lesions). Sensitivity and specificity of FDG PET to detect recurrence were 87.5 % and 93.8, respectively.

Conclusion

FDG PET was superior to CT in detecting distant LN metastasis and to BS in detecting skeletal metastasis in neuroblastoma. BS might be eliminated in the evaluation of neuroblastoma when FDG PET is performed.     

F-18 FDG PET/CT in the evaluation of Takayasu arteritis: An experience from the tropics

Objective

To evaluate the performance parameters of FDG PET/CT in patients with Takayasu arteritis at diagnosis and during immunosuppression.

Methods

Retrospective analysis of 60 FDG PET/CT studies in 51 patients was performed (17 scans at diagnosis out of which 4 had follow-up scans also and 43 scans on immunosuppression). The degree of FDG uptake in the vessels was assessed visually using a 4-point scale and maximum standardized uptake value (SUVmax), SUVratio, extent of vasculitis and association with ESR were calculated.

Results

PET/CT was positive for active vasculitis in all 17 patients at diagnosis. The mean SUVmax and mean SUV ratio of the active areas were 5.1 ± 3.0 and 3.2 ± 1.9, respectively. On immunosuppression, PET scan was positive for active vasculitis in 14/43 (32.5%) scans. The mean SUVmax and mean SUVratio of the active areas were 1.7 ± 2.1 and 0.95 ± 1.2, respectively. There was significant difference between the mean SUVmax and mean SUVratio at diagnosis and on immunosuppression, respectively (P < .01). The median number of vascular segments in each uptake grade group was also statistically different (P < .01) between scans at diagnosis and on immunosuppression. The median ESR level in PET positive scans was 29 mm/hour (2-53), whereas in PET negative scans was 35.5 mm/hour (6-50) and the difference was not statistically significant.

Conclusion

FDG PET/CT showed good sensitivity to detect active vasculitis at diagnosis and during immunosuppression. The change in SUVmax between the successive FDG PET/CT scans may give an objective assessment of response to immunosuppression.     

PET/CT for staging and follow-up of pediatric nasopharyngeal carcinoma

Purpose

While FDG PET/CT for the evaluation of nasopharyngeal carcinoma (NPC) in adult patients has documented advantages and disadvantages compared with conventional imaging, to our knowledge, no studies of FDG PET/CT for the evaluation of NPC in pediatric patients have been performed. In this investigation, we studied the utility of FDG PET/CT in children with NPC.

Methods

The study group comprised 18 children with biopsy-proven NPC who underwent FDG PET/CT and MRI (total 38 pairs of images). All baseline and follow-up FDG PET/CT and MRI studies were independently reviewed for restaging of disease.

Results

The concordance between FDG PET/CT and MRI in T, N, and overall staging was 29%, 64%, and 43%, respectively. Compared with MRI, FDG PET/CT yielded lower T and overall staging and showed less cervical and retropharyngeal lymphadenopathy. The concordance between follow-up FDG PET/CT and MRI was 79% overall and 100% 9?months after therapy. In patients who achieved complete remission, FDG PET/CT showed disease clearance 3–6?months earlier than MRI. There were no false-positive or false-negative FDG PET/CT scans during follow-up.

Conclusion

FDG PET/CT may underestimate tumor extent and regional lymphadenopathy compared with MRI at the time of diagnosis, but it helps to detect metastases and clarify ambiguous findings. FDG PET/CT is sensitive and specific for follow-up and enables earlier determination of disease remission. FDG PET/CT is a valuable imaging modality for the evaluation and monitoring of NPC in pediatric patients.     

Recurrent renal cell carcinoma: clinical and prognostic value of FDG PET/CT

Purpose

The purpose of our study was 1) to evaluate the diagnostic performance of 18F-fluorodeoxyglucose (FDG) positron emission tomography (PET)/computed tomography (CT), 2) to assess the impact of FDG PET/CT on treatment decision-making, and 3) to estimate the prognostic value of FDG PET/CT in the restaging process among patients with renal cell carcinoma (RCC).

Methods

From the FDG PET/CT databases of San Raffaele Hospital in Milan, Italy, and the Veneto Institute of Oncology in Padua, Italy, we selected 104 patients with a certain diagnosis of RCC after surgery, and for whom at least 24 months of post-surgical FDG PET/CT, clinical, and instrumental follow-up data was available. The sensitivity and specificity of FDG PET/CT were assessed by histology and/or other imaging as standard of reference. Progression-free survival (PFS) and overall survival (OS) were computed using the Kaplan–Meier method. Univariate and multivariate Cox proportional hazards models were used to identify predictors of outcome.

Results

FDG PET/CT resulted in a positive diagnosis in 58 patients and a negative diagnosis in 46 patients. Sensitivity and specificity were 74 % and 80 %, respectively. FDG PET/CT findings influenced therapeutic management in 45/104 cases (43 %). After a median follow-up period of 37 months (± standard deviation 12.9), 51 (49 %) patients had recurrence of disease, and 26 (25 %) had died. In analysis of OS, positive versus negative FDG PET/CT was associated with worse cumulative survival rates over a 5-year period (19 % vs. 69 %, respectively; p <0.05). Similarly, a positive FDG PET/CT correlated with a lower 3-year PFS rate. In addition, univariate and multivariate analysis revealed that a positive scan, alone or in combination with disease stage III–IV or nuclear grading 3–4, was associated with high risk of progression (multivariate analysis = hazard ratios [HRs] of 4.01, 3.7, and 2.8, respectively; all p?<?0.05).

Conclusions

FDG PET/CT is a valuable tool both in treatment decision-making and for predicting survival and progression in patients affected by RCC.

     

PET/CT assessment in follicular lymphoma using standardized criteria: central review in the PRIMA study

Purpose

We aimed to compare the standardized central review of ¹⁸F-fluorodeoxyglucose (FDG) positron emission tomography (PET)/CT scans performed after induction therapy for follicular lymphoma (FL) in the PRIMA study (Salles et al., Lancet 377:42–51, 2011; Trotman et al., J Clin Oncol 29:3194–3200, 2011) to scan review at local centres.

Methods

PET/CT scans were independently evaluated by two nuclear medicine physicians using the 2007 International Harmonization Project (IHP) criteria (Cheson et al., J Clin Oncol 25:579–586, 2007; Juweid et al., J Clin Oncol 25:571–578, 2007; Shankar et al., J Nucl Med 47:1059–1066, 2006) and Deauville 5-point scale (5PS) criteria (Meignan et al., Leuk Lymphoma 50:1257–1260, 2009; Meignan et al., Leuk Lymphoma 51:2171–2180, 2010; Barrington et al., Eur J Nucl Med Mol Imaging 37:1824–1833, 2010). PET/CT status was compared with prospectively recorded patient outcomes.

Results

Central evaluation was performed on 119 scans. At diagnosis, 58 of 59 were recorded as positive, with a mean maximum standardized uptake value (SUV_max) of 11.7 (range 4.6–35.6). There was no significant association between baseline SUV_max and progression-free survival (PFS). Sixty post-induction scans were interpreted using both the IHP criteria and 5PS. Post-induction PET-positive status failed to predict progression when applying the IHP criteria [p?=?0.14; hazard ratio (HR) 1.9; 95 % confidence interval (CI) 0.8–4.6] or 5PS with a cut-off ≥3 (p?=?0.12; HR 2.0; 95 % CI 0.8–4.7). However, when applying the 5PS with a cut-off ≥4, there was a significantly inferior 42-month PFS in PET-positive patients of 25.0 % (95 % CI 3.7–55.8 %) versus 61.4 % (95 % CI 45.4–74.1 %) in PET-negative patients (p?=?0.01; HR 3.1; 95 % CI 1.2–7.8). The positive predictive value (PPV) of post-induction PET with this liver cut-off was 75 %. The 42-month PFS for patients remaining PET-positive by local assessment was 31.1 % (95 % CI 10.2–55.0 %) vs 64.6 % (95 % CI 47.0–77.6 %) for PET-negative patients (p?=?0.002; HR 3.3; 95 % CI 1.5–7.4), with a PPV of 66.7 %.

Conclusion

We confirm that FDG PET/CT status when applying the 5PS with a cut-off ≥4 is strongly predictive of outcome after first-line immunochemotherapy for FL. Further efforts to refine the criteria for assessing minimal residual FDG uptake in FL should provide a reproducible platform for response assessment in future prospective studies of a PET-adapted approach.     

Performance of 18F-FDG PET/CT as a postoperative surveillance imaging modality for asymptomatic advanced gastric cancer patients

Objective

The purpose of this study was to investigate the diagnostic performance of postoperative fluorine-18 fluoro-2-deoxy-d-glucose (¹⁸F-FDG) positron emission tomography/computed tomography (PET/CT) as a surveillance modality for advanced gastric cancer patients who were asymptomatic and negative by conventional follow-up.

Methods

We retrospectively collected 46 advanced gastric cancer patients who received approximately 1-year-postoperative ¹⁸F-FDG PET/CT surveillance following curative resection (mean age 60.6 ± 11.5 years). ¹⁸F-FDG PET/CT was interpreted by nuclear medicine physicians who were blind to the clinical information. Final confirmation was determined by clinical follow-up using tumor markers, conventional CT scan, upper gastrointestinal endoscopy and with/without subsequent histopathologic diagnosis.

Results

Four patients developed recurrence (8.7 %; 1 local and 3 distant recurrences). For local recurrence, ¹⁸F-FDG PET/CT found four hypermetabolic lesions and one was local recurrence. For distant recurrence, seven hypermetabolic lesions were found in six patients and true-positive was three lesions. False-positive cases were mainly turned out to be physiologic small bowel uptake. Regardless of the recurrence site, the sensitivity, specificity, positive predictive value and negative predictive value of ¹⁸F-FDG PET/CT were 100 % (4/4, 95 % confidence interval (CI) 39.6–100 %), 88.1 % (37/42, 95 % CI 73.6–95.5 %), 44.4 % (4/9, 95 % CI 15.3–77.3 %) and 100 % (37/37, 95 % CI 88.3–100 %), respectively in the patient-based analysis.

Conclusion

Our study showed good specificity of postoperative surveillance ¹⁸F-FDG PET/CT for detecting recurrence. Careful caution should be made for interpreting some false-positive hypermetabolic lesions in postoperative ¹⁸F-FDG PET/CT, especially at the local anastomosis site.     

Diagnostic performance of 18F-fluorothymidine PET/CT for primary colorectal cancer and its lymph node metastasis: comparison with 18F-fluorodeoxyglucose PET/CT

Purpose

To examine the diagnostic performance of ¹⁸F-fluorothymidine (FLT) PET/CT in primary and metastatic lymph node colorectal cancer foci in comparison with ¹⁸F-fluorodeoxyglucose (FDG) PET/CT.

Methods

The study population comprised 28 patients with 30 newly diagnosed colorectal cancers who underwent surgical resection of the primary lesion and regional lymph nodes after both FLT and FDG PET/CT. The associations between SUVmax levels and pathological factors were evaluated using the Mann-Whitney U or Kruskal-Wallis test. Differences in diagnostic indexes for detecting nodal metastasis between the two tracers were estimated using the McNemar exact or χ ² test.

Results

All 30 primary cancers (43.0?±?20.0 mm, range 14 – 85 mm) were visualized by both tracers, but none of the FLT SUVmax values exceeded the FDG SUVmax values in any of the primary cancers (6.6?±?2.4 vs. 13.6?±?5.8, p?<?0.001). The sensitivity, specificity and accuracy for detecting nodal metastasis were 41 % (15/37), 98.8 % (493/499) and 94.8 % (508/536) for FDG PET/CT, and 32 % (12/37), 98.8 % (493/499) and 94.2 % (505/536) for FLT PET/CT, respectively. The sensitivity (p?=?0.45), specificity (p?=?0.68) and accuracy (p?=?0.58) were not different between the tracers. Nodal uptake of FLT and FDG was discordant in 7 (19 %) of 37 metastatic nodes. There were ten concordant true-positive nodes of which six showed higher FDG SUVmax and four showed higher FLT SUVmax, but the difference between FDG and FLT SUVmax was not significant (5.56?±?3.55 and 3.62?±?1.45, respectively; p?=?0.22).

Conclusion

FLT has the same potential as FDG in PET/CT for the diagnosis of primary and nodal foci of colorectal cancer despite significantly lower FLT uptake in primary foci.     

Direct comparison of [18F]FDG PET/CT with PET alone and with side-by-side PET and CT in patients with malignant melanoma

Purpose

The purpose of this retrospective, blinded study was to evaluate the additional value of [¹⁸F]FDG PET/CT in comparison with PET alone and with side-by-side PET and CT in patients with malignant melanoma (MM).

Methods

A total of 127 consecutive studies of patients with known MM referred for a whole-body PET/CT examination were included in this study. PET alone, side-by-side PET and CT and integrated PET/CT study were independently and separately interpreted without awareness of the clinical information. One score each was applied for certainty of lesion localisation and for certainty of lesion characterisation. Verification of the findings was subsequently performed using all available clinical, pathological (n?=?30) and follow-up information.

Results

The number of lesions with an uncertain localisation was significantly (p?p?p?=?0.057) compared versus PET alone. Respectively, PET, side-by-side PET and CT and PET/CT showed a sensitivity of 86%, 89% and 91%, a specificity of 94%, 94% and 94%, a positive predictive value of 96%, 96% and 96% and a negative predictive value of 80%, 83% and 87%.

Conclusion

Integrated PET/CT offers a significant benefit in lesion localisation and an improvement in lesion characterisation compared with PET alone or with side-by-side PET and CT. The benefit is not as great as that reported for other tumour entities, which may be due to the high avidity of MM for [¹⁸F]FDG.     

A comparative study of FDG PET/CT and enhanced multi-detector CT for detecting liver metastasis according to the size and location

Purpose

The aim of this study was to compare the diagnosability between ¹⁸F-fluorodeoxyglucose (FDG) PET/CT and enhanced multi-detector CT (MDCT) for the detection of liver metastasis (LM) according to the size and location in liver and to evaluate standard maximum standardized uptake values (SUVmax) of all liver metastatic lesions.

Materials and methods

One hundred two consecutive patients with malignancy who underwent both FDG PET/CT and MDCT for LM evaluation were retrospectively reviewed. Among them, 56 patients with LM were enrolled in this study. LM was confirmed by follow-up imaging studies after at least 6 months or by histopathology. FDG PET/CT and MDCT images were visually analyzed using three-point scale by the consensus of two radiologists and two nuclear medicine physicians. The size and location (central vs. sub-capsular) of the all liver lesions were evaluated using MDCT images. Furthermore, SUVmax of all liver lesions on FDG PET/CT images were calculated.

Results

A total of 146 liver lesions were detected by FDG PET/CT and MDCT and 142 of the lesions were diagnosed as LM. The detection rates of MDCT and FDG PET/CT for LM by visual analysis were 77 and 78 %, respectively. There was no significant difference of detection rate according to the overall location and size of the lesions. However, FDG PET/CT was more sensitive than MDCT for detecting small and sub-capsular LM. The detection rate of FDG PET/CT for LM was 68 % by the cutoff SUVmax of 2.7.

Conclusions

Although the diagnosabilities of MDCT and FDG PET/CT for detecting LM were comparable, FDG PET/CT is superior to MDCT for detecting small LM located in the sub-capsular portion of liver.     

Comparison of integrated whole-body [11C]choline PET/MR with PET/CT in patients with prostate cancer

Purpose

To evaluate the performance of conventional [¹¹C]choline PET/CT in comparison to that of simultaneous whole-body PET/MR.

Methods

The study population comprised 32 patients with prostate cancer who underwent a single-injection dual-imaging protocol with PET/CT and subsequent PET/MR. PET/CT scans were performed applying standard clinical protocols (5 min after injection of 793?±?69 MBq [¹¹C]choline, 3 min per bed position, intravenous contrast agent). Subsequently (52?±?15 min after injection) PET/MR was performed (4 min per bed position). PET images were reconstructed iteratively (OSEM 3D), scatter and attenuation correction of emission data and regional allocation of [¹¹C]choline foci were performed using CT data for PET/CT and segmented Dixon MR, T1 and T2 sequences for PET/MR. Image quality of the respective PET scans and PET alignment with the respective morphological imaging modality were compared using a four point scale (0–3). Furthermore, number, location and conspicuity of the detected lesions were evaluated. SUVs for suspicious lesions, lung, liver, spleen, vertebral bone and muscle were compared.

Results

Overall 80 lesions were scored visually in 29 of the 32 patients. There was no significant difference between the two PET scans concerning number or conspicuity of the detected lesions (p not significant). PET/MR with T1 and T2 sequences performed better than PET/CT in anatomical allocation of lesions (2.87?±?0.3 vs. 2.72?±?0.5; p?=?0.005). The quality of PET/CT images (2.97?±?0.2) was better than that of the respective PET scan of the PET/MR (2.69?±?0.5; p?=?0.007). Overall the maximum and mean lesional SUVs exhibited high correlations between PET/CT and PET/MR (ρ?=?0.87 and ρ?=?0.86, respectively; both p?<?0.001).

Conclusion

Despite a substantially later imaging time-point, the performance of simultaneous PET/MR was comparable to that of PET/CT in detecting lesions with increased [¹¹C]choline uptake in patients with prostate cancer. Anatomical allocation of lesions was better with simultaneous PET/MR than with PET/CT, especially in the bone and pelvis. These promising findings suggest that [¹¹C]choline PET/MR might have a diagnostic benefit compared to PET/CT in patients with prostate cancer, and now needs to be further evaluated in prospective trials.     

Incremental diagnostic utility of gastric distension FDG PET/CT

Purpose

To assess the diagnostic utility of gastric distension (GD) FDG PET/CT in both patients with known gastric malignancy and those not known to have gastric malignancy but with incidental focal FDG uptake in the stomach.

Methods

This retrospective analysis included 88 patients who underwent FDG PET/CT following GD with hyoscine N-butylbromide (Buscopan®) and water ingestion as part of routine clinical evaluation between 2004 and 2014. FDG PET/CT scans before and after GD were reported blinded to the patient clinical details in 49 patients undergoing pretreatment staging of gastric malignancy and 39 patients who underwent GD following incidental suspicious gastric uptake. The PET findings were validated by a composite clinical standard.

Results

In the 49 patients undergoing pretreatment staging of gastric malignancy, GD improved PET detection of the primary tumour (from 80 % to 90 %). PET evaluation of tumour extent was concordant with endoscopic/surgical reports in 31 % (interpreter 1) and 45 % (interpreter 2) using pre-GD images and 73 % and 76 % using GD images. Interobserver agreement also improved with GD (κ?=?0.29 to 0.69). Metabolic and morphological quantitative analysis demonstrated a major impact of GD in normal gastric wall but no significant effect in tumour, except a minor increase in SUV related to a delayed acquisition time. The tumour to normal stomach SUVmax ratio increased from 3.8?±?2.9 to 9.2?±?8.6 (mean?±?SD) with GD (p?<?0.0001), facilitating detection and improved assessment of the primary tumour. In 25 (64 %) of the 39 patients with incidental suspicious gastric uptake, acquisition after GD correctly excluded a malignant process. In 10 (71 %) of the remaining 14 patients with persistent suspicious FDG uptake despite GD, malignancy was confirmed and in 3 (21 %) an active but benign pathology was diagnosed.

Conclusion

GD is a simple way to improve local staging with FDG PET in patients with gastric malignancy. In the setting of incidental suspicious gastric uptake, GD is also an effective tool for ruling out malignancy and leads to the avoidance of unnecessary endoscopy.

     

Diagnostic value of diffusion-weighted magnetic resonance imaging (DWI) compared to FDG PET/CT for whole-body breast cancer staging

Purpose

The aim of the study was to prospectively compare the diagnostic value of whole-body diffusion-weighted imaging (DWI) and FDG PET/CT for breast cancer (BC) staging.

Methods

Twenty BC patients underwent whole-body FDG PET/CT and 1.5-T DWI. Lesions with qualitatively elevated signal intensity on DW images (b?=?800 s/mm²) were rated as suspicious for tumour and mapped to individual lesions and different compartments (overall 552 lesions). The apparent diffusion coefficient (ADC) value was determined for quantitative evaluation. Histopathology, MRI findings, bone scan findings, concordant findings between FDG PET/CT and DWI, CT follow-up scans and plausibility served as the standards of reference defining malignancy.

Results

According to the standards of reference, breasts harboured malignancy in 11, regional lymph nodes in 4, M1 lymph nodes in 3, bone in 7, lung in 2, liver in 3 and other tissues in 3 patients. On a compartment basis, the sensitivity, specificity, accuracy, positive predictive value (PPV) and negative predictive value (NPV) for the detection of malignancies were 94, 99, 98, 97 and 98% for FDG PET/CT and 91, 72, 76, 50 and 96% for DWI, respectively. Of the lesions seen on DWI only, 348 (82%) turned out to be false-positive compared to 23 (11%) on FDG PET/CT. The average lesion ADC was 820?±?300 with true-positive lesions having 929?±?252 vs 713?±?305 in false-positive lesions (p?<?0.0001).

Conclusion

Based on these initial data DWI seems to be a sensitive but unspecific modality for the detection of locoregional or metastatic BC disease. There was no possibility to quantitatively distinguish lesions using ADC. DWI alone may not be recommended as a whole-body staging alternative to FDG PET(/CT). Further studies are necessary addressing the question of whether full-body MRI including DWI may become an alternative to FDG PET/CT for whole-body breast cancer staging.