Biodistribution and first clinical results of 18F-SiFAlin-TATE PET: a novel 18F-labeled somatostatin analog for imaging of neuroendocrine tumors.

INTRODUCTION: PET/CT using 68Ga-labeled somatostatin analogs (SSA) targeting somatostatin receptors (SSR) on the cell surface of well-differentiated neuroendocrine tumors (NET) represents the clinical reference standard for imaging. However, economic and logistic challenges of the 68Ge/68Ga generator-based approach have disadvantages over 18F-labeled compounds. Here, we present the first in-human data of 18F-SiFAlin-TATE, a novel 18F-labeled, SSR-targeting peptide. The aim was to compare the intra-individual biodistribution, tumor uptake, and image quality of 18F-SiFAlin-TATE to the clinical reference standard 68Ga-DOTA-TOC. METHODS: Thirteen patients with NET staged with both 68Ga-DOTA-TOC and 18F-SiFAlin-TATE PET/CT have been included in this retrospective analysis. We compared the biodistribution in normal organs and tumor uptake of NET lesions by SUVmean and SUVmax measurement for tracers. Additionally mean and max tumor-to-liver (TLR) and tumor-to-spleen ratios (TSR) have been calculated by division of SUVmean and SUVmax of tumor lesions by the SUVmean of the liver and spleen, respectively. Additionally, image quality was visually rated by 5 blinded readers and an intra-class correlation (ICC) analysis on inter-observer agreement has been performed. RESULTS: Compared with 68Ga-DOTA-TOC, the biodistribution of 18F-SiFAlin-TATE showed somewhat higher, however, statistically not significant higher uptake in the liver, spleen, and adrenal glands. Significantly higher uptake was observed in the kidneys. Tumor uptake was higher in most tumor lesions with significantly higher uptake in common metastatic sites of NET including the liver (SUVmax 18.8 ± 8.4 vs. 12.8 ± 5.6; p < 0.001), lymph nodes (SUVmax 23.8 ± 20.7 vs. 17.4 ± 16.1; p < 0.001) and bone (SUVmax 16.0 ± 10.1 vs. 10.3 ± 5.7; p < 0.01) for 18F-SiFAlin-TATE. The high tumor uptake resulted in favorable TLR and TSR, comparable with that of 68Ga-DOTA-TOC. The ICC analysis on the inter-observer agreement on image quality was substantial and almost perfect. Image quality was rated as excellent in most cases in both 68Ga-DOTA-TOC and 18F-SiFAlin-TATE PET. CONCLUSION: The favorable characteristics of 18F-SiFAlin-TATE with a high image quality, the kit-like labeling procedure, and the promising clinical performance enable improved logistics and diagnostic possibilities for PET imaging of NET. Our first clinical results warrant further systematic studies investigating the clinical use of 18F-SiFAlin-TATE in NET patients.

[Quantification of immunohistochemical expression of somatostatin receptors in neuroendocrine tumors using 68Ga-DOTATATE PET/CT]. / Quantifizierung der Somatostatinrezeptorexpression neuroendokriner Tumoren mit der (68)Ga-DOTATATE-PET/CT.

PURPOSE: The immunohistochemical expression of somatostatin receptor (SSTR) subtype 2 was compared to quantitative (68)Ga-DOTATATE PET in neuroendocrine tumors (NET). MATERIAL AND METHODS: In 27 patients suffering from metastatic NET the expression of somatostatin receptors (SSTR, score 0-3) and the Ki-67 index were assessed. The immunohistochemical findings were compared with the (68)Ga-DOTATATE PET uptake in these tumors using the SUV(max) (standardized uptake value). Both values were compared with the Ki-67 proliferation index. RESULTS: The SUV(max) in NET without SSTR expression was significantly lower compared to those with SSTR expression (p <0.05), even though 3 out of 5 NETs with a score of 0 showed a high uptake of (68)Ga-DOTATATE. The SUV(max) correlated significantly (r=0.40, p <0.05) with the score of immunohistochemical SSTR expression (negative, score 0, moderate, score 1 and high, scores 2 and 3). The Ki-67 index correlated inversely with the SSTR expression score (r=-0.42, p <0.05), but not significantly with the SUV(max) (r=-0.33, p=0.11). CONCLUSION: (68)Ga-DOTATATE uptake was moderately correlated with the results of immunohistochemical SSTR analyses. However, SSTR negative NET may show high uptake of (68)Ga-DOTATATE.

Assessment of residual tumour by FDG-PET: conventional imaging and clinical examination following primary chemotherapy of large and locally advanced breast cancer.

BACKGROUND: The aim of this was to evaluate FDG-PET (2-(fluorine-18)-fluoro-2-deoxy-D-glucose positron emission tomography) for assessment of residual tumour after primary chemotherapy of large and locally advanced breast cancer in comparison with conventional imaging modalities. METHODS: In a prospective multicentre trial, 99 patients underwent one or more breast imaging modalities before surgery in addition to clinical examination, namely, FDG-PET (n=89), mammography (n=47), ultrasound (n=46), and magnetic resonance imaging (MRI) (n=46). The presence of residual tumour by conventional imaging, dichotomised as positive or negative, and the level of FDG uptake (standardised uptake values, SUV) were compared with histopathology, which served as the reference standard. Patients with no residual tumour or only small microscopic foci of residual tumour were classified as having minimal residual disease and those with extensive microscopic and macroscopic residual tumour tissue were classified as having gross residual disease. RESULTS: By applying a threshold SUV of 2.0, the sensitivity of FDG-PET for residual tumour was 32.9% (specificity, 87.5%) and increased to 57.5% (specificity, 62.5%) at a threshold SUV of 1.5. Conventional imaging modalities were more sensitive in identifying residual tumour, but had a low corresponding specificity; sensitivity and specificity were as follows: MRI 97.6 and 40.0%, mammography 92.5 and 57.1%, ultrasound 92.0 and 37.5%, respectively. Breast MRI provided the highest accuracy (91.3%), whereas FDG-PET had the lowest accuracy (42.7%). CONCLUSIONS: FDG-PET does not provide an accurate assessment of residual tumour after primary chemotherapy of breast cancer. Magnetic resonance imaging offers the highest sensitivity, but all imaging modalities have distinct limitations in the assessment of residual tumour tissue when compared with histopathology.

Whole-body MRI at 1.5 T and 3 T compared with FDG-PET-CT for the detection of tumour recurrence in patients with colorectal cancer.

The purpose of this study was to assess the diagnostic accuracy of whole-body MRI (WB-MRI) at 1.5 T or 3 T compared with FDG-PET-CT in the follow-up of patients suffering from colorectal cancer. In a retrospective study, 24 patients with a history of colorectal cancer and suspected tumour recurrence underwent FDG-PET-CT and WB-MRI with the use of parallel imaging (PAT) for follow-up. High resolution coronal T1w-TSE and STIR sequences at four body levels, HASTE imaging of the lungs, contrast-enhanced T1w- and T2w-TSE sequences of the liver, brain, abdomen and pelvis were performed, using WB-MRI at either 1.5 T (n = 14) or 3 T (n = 10). Presence of local recurrent tumour, lymph node involvement and distant metastatic disease was confirmed using radiological follow-up within at least 5 months as a standard of reference. Seventy seven malignant foci in 17 of 24 patients (71%) were detected with both WB-MRI and PET-CT. Both investigations concordantly revealed two local recurrent tumours. PET-CT detected significantly more lymph node metastases (sensitivity 93%, n = 27/29) than WB-MRI (sensitivity 63%, n = 18/29). PET-CT and WB-MRI achieved a similar sensitivity for the detection of organ metastases with 80% and 78%, respectively (37/46 and 36/46). WB-MRI detected brain metastases in one patient. One false-positive local tumour recurrence was indicated by PET-CT. Overall diagnostic accuracy for PET-CT was 91% (sensitivity 86%, specificity 96%) and 83% for WB-MRI (sensitivity 72%, specificity 93%), respectively. Examination time for WB-MRI at 1.5 T and 3 T was 52 min and 43 min, respectively; examination time for PET-CT was 103 min. Initial results suggest that differences in accuracy for local and distant metastases detection using FDG-PET-CT and WB-MRI for integrated screening of tumour recurrence in colorectal cancer depend on the location of the malignant focus. Our results show that nodal disease is better detected using PET-CT, whereas organ disease is depicted equally well by both investigations.

Restaging of patients with lymphoma. Comparison of low dose CT (20 mAs) with contrast enhanced diagnostic CT in combined [18F]-FDG PET/CT.

AIM: Assessment of the clinical benefit of i.v. contrast enhanced diagnostic CT (CE-CT) compared to low dose CT with 20 mAs (LD-CT) without contrast medium in combined [(18)F]-FDG PET/CT examinations in restaging of patients with lymphoma. PATIENTS, METHODS: 45 patients with non-Hodgkin lymphoma (n=35) and Hodgkin's disease (n=10) were included into this study. PET, LD-CT and CE-CT were analyzed separately as well as side-by-side. Lymphoma involvement was evaluated separately for seven regions. Indeterminate diagnoses were accepted whenever there was a discrepancy between PET and CT findings. Results for combined reading were calculated by rating indeterminate diagnoses according the suggestions of either CT or PET. Each patient had a clinical follow-up evaluation for >6 months. RESULTS: Region-based evaluation suggested a sensitivity/specificity of 66/93% for LD-CT, 87%/91% for CE-CT, 95%/96% for PET, 94%/99% for PET/LD-CT and 96%/99% for PET/CE-CT. The data for PET/CT were obtained by rating indeterminate results according to the suggestions of PET, which turned out to be superior to CT. Lymphoma staging was changed in two patients using PET/CE-CT as compared to PET/LD-CT. CONCLUSION: Overall, there was no significant difference between PET/LD-CT and PET/CE-CT. However, PET/CE-CT yielded a more precise lesion delineation than PET/LD-CT. This was due to the improved image quality of CE-CT and might lead to a more accurate investigation of lymphoma.

Influence of PET/CT-introduction on PET scanning frequency and indications. Results of a multicenter study.

AIM: To evaluate the influence of the introduction of combined PET/CT scanners into clinical routine. This investigation addresses the quantitative changes between PET/CT and stand alone PET. METHODS: The study included all examinations performed on stand alone PET- or PET/CT-scanners within 12 month prior to and after implementation of PET/CT. The final data analysis included five university hospitals and a total number of 15 497 exams. We distinguished exams on stand alone tomographs prior to and after installation of the combined device as well as PET/CT scans particularly with regard to disease entities. Various further parameters were investigated. RESULTS: The overall number of PET scans (PET and PET/CT) rose by 146% while the number of scans performed on stand alone scanners declined by 22%. Only one site registered an increase in stand alone PET. The number of exams for staging in oncology increased by 196% while that of cardiac scans decreased by 35% and the number of scans in neurology rose by 47%. The use of scans for radiotherapy planning increased to 7% of all PET/CT studies. The increase of procedures for so-called classic PET oncology indications was moderate compared to the more common tumors. An even greater increase was observed in some rare entities. CONCLUSIONS: The introduction of PET/CT led to more than a doubling of overall PET procedures with a main focus on oncology. Some of the observed changes in scanning frequency may be caused by a rising availability of new radiotracers and advancements of competing imaging methods. Nevertheless the evident increase in the use of PET/CT for the most common tumour types demonstrates its expanding role in cancer staging. The combination of molecular and morphologic imaging has not only found its place but is still gaining greater importance with new developments in technology and radiochemistry.

Combined use of 64-slice computed tomography angiography and gated myocardial perfusion SPECT for the detection of functionally relevant coronary artery stenoses. First results in a clinical setting concerning patients with stable angina.

AIM: In patients with stable angina pectoris both morphological and functional information about the coronary artery tree should be present before revascularization therapy is performed. High accuracy was shown for spiral computed tomography (MDCT) angiography acquired with a 64-slice CT scanner compared to invasive coronary angiography (ICA) in detecting "obstructive" coronary artery disease (CAD). Gated myocardial SPECT (MPI) is an established method for the noninvasive assessment of functional significance of coronary stenoses. Aim of the study was to evaluate the combination of 64-slice CT angiography plus MPI in comparison to ICA plus MPI in the detection of hemodynamically relevant coronary artery stenoses in a clinical setting. PATIENTS, METHODS: 30 patients (63 +/- 10.8 years, 23 men) with stable angina (21 with suspected, 9 with known CAD) were investigated. MPI, 64-slice CT angiography and ICA were performed, reversible and fixed perfusion defects were allocated to determining lesions separately for MDCT angiography and ICA. The combination of MDCT angiography plus MPI was compared to the results of ICA plus MPI. RESULTS: Sensitivity, specificity, negative and positive predictive value for the combination of MDCT angiography plus MPI was 85%, 97%, 98% and 79%, respectively, on a vessel-based and 93%, 87%, 93% and 88%, respectively, on a patient-based level. 19 coronary arteries with stenoses > or =50% in both ICA and MDCT angiography showed no ischemia in MPI. CONCLUSION: The combination of 64-slice CT angiography and gated myocardial SPECT enabled a comprehensive non-invasive view of the anatomical and functional status of the coronary artery tree.

[Imaging in the early diagnosis of changes in the hand of patients suffering from rheumatoid arthritis. Is ultrasound a true alternative for low-field magnetic resonance scanning, 3-phase bone scintigraphy and conventional x-rays?]. / Bildgebende Verfahren in der Frühdiagnostik rheumatischer Veränderungen der Hände. Ist die Sonographie eine echte Alternative zur Niederfeld-MRT, 3-Phasen-Skelettszintigraphie und Projektionsradiographie?

PURPOSE: Besides the use of conventional x-rays in the diagnostic work-up of initial changes in patients suffering from rheumatoid arthritis (RA), 3-phase bone scintigraphy (3P-Sz) is as well established as magnetic resonance imaging (MRI). The aim of this study was to compare the diagnostic value of ultrasound of the hands with proven methods such as conventional x-rays, low-field MRI and 3P-Sz. METHODS: A total of 30 patients were studied using a 1 day protocol with ultrasound, 3P-Sz, MRI and x-ray of the hands. Images were visually assessed by two blinded nuclear medicine physicians and radiologists and classified as RA typical and non-RA typical changes. All methods were compared to the summarized findings interpreted by a rheumatologist after 2 years. RESULTS: Of the 30 patients, 19 presented with clinical symptoms of initial changes due to rheumatoid arthritis. Ultrasound revealed 14/19 patients with the correct diagnosis. Conventional x-rays indicated 11/19 patients, while 3P-Sz (100%) and low-field MRI (95%) showed high sensitivity. It was possible to differentiate between inflammation and inconspicuous findings. CONCLUSIONS: An experienced examiner can use ultrasound effectively for the initial diagnosis of RA. Based on its low cost, ultrasound is a valid alternative to conventional x-rays.

[Preoperative imaging of Charcot neuroarthropathy: Does the additional application of (18)F-FDG-PET make sense?]. / Präoperative Bildgebung bei diabetisch-neuropathischer Osteoarthropathie: Ist der zusätzliche Einsatz von (18)F-FDGPET sinnvoll?

UNLABELLED: With about 4 million diabetics in germany and presumed inclination over the following years the treatment of diabetic complications like diabetic foot will become an even more important point. The management of Charcot's foot has undergone fundamental change in the last few years. Formerly, treatment was almost exclusively limited to non surgical measures; since the late 1990's, however, current practice has shifted to early, stage-appropriate surgical therapy. The aim of the present prospective study was to investigate the value of positron emission tomography (PET) in the pre-operative work-up of Charcot's foot. PET were compared to magnetic resonance tomography (MRI). PATIENTS, METHODS: MRI and PET imaging were used as part of the preoperative work-up in 18 patients with Type II diabetes mellitus. The diagnosis of Charcot's foot requiring surgical treatment were made on the basis of clinical and radiologic criteria. RESULTS: Of 46 Charcot's lesions confirmed at surgery, 44 and 35 were detected by means of PET and MRI, respectively. PET can be used in the work-up of patients with metal implants where the MRI does not show adequate findings. PET shows the areas of detritus formation exhibit only moderately increased glucose metabolism and at visual interpretation do not usually impression as typical for acute osteomyelitis. Average SUV values stood at 1.2 (range: 0.5-2.9). CONCLUSIONS: The differentiation between Charcot's lesions and florid osteomyelitis provides the surgeon with important additional information, which is often unavailable from MRI. Because of this important additional data, PET could be considered preferable to morphologic imaging (CT, projection radiography) in the preoperative work-up of Charcot's foot.

[Diagnosis of initial changes in patients suffering from rheumatoid arthritis. Two years follow up control with a low-field magnetic resonance scanner, 3-phase bone scintigraphy and conventional x-ray]. / Frühdiagnostik rheumatischer Veränderungen der Hände: Verlaufsbeobachtung über 2 Jahre mittels Niederfeld-Magnetresonanztomographie, 3-Phasen-Skelettszintigraphie und Projektionsradiographie.

UNLABELLED: Besides conventional x-ray, in the diagnostic work up of initial changes in patients suffering from rheumatoid arthritis (RA), 3-phase bone scintigraphy (3P-Sz) is as well established as magnetic resonance imaging (MRI). The AIM of this study was to compare the diagnostic value of a newly developed low field MRI with proven methods such as conventional x-ray and 3P-Sz. PATIENTS, METHODS: 42 patients were studied using a one days protocol with 3P-Sz, MRI, and x-ray of the hands with yearly follow up examinations. Images were visually assessed by two blinded nuclear medicine physicians and radiologists and classified as RA-typical and non-RA-typical changes. All methods were compared to the summarised findings interpreted by a rheumatologist in consideration of the Ritchie articular index as gold-standard. RESULTS: 24/42 patients presented with clinical symptoms of initial changes by rheumatoid arthritis. Conventional x-ray revealed in 20/24 patients within the correct diagnosis in the study period. On the other hand 3P-Sz and low field MRI concordantly showed all 24 patients with initial changes due to RA. Time of detection showed variations with a tendency to later findings by conventional x-ray. CONCLUSIONS: In the diagnostic work up of initial changes conventional x-ray should be the first choice in imaging. Our findings suggest that MRI represents an equally sensitive method for the diagnosis of initial changes due to RA in the region of the hands as compared to the 3P-Sz. The limitation of the low field MRI is the small field of view, so we prefer 3P-Sz or high field MRI in the diagnosis of patients with suspected RA.

[Comparison of high resolution whole-body MRI using parallel imaging and PET-CT. First experiences with a 32-channel MRI system]. / Hochauflösendes Ganzkörpertumorstaging unter Verwendung paralleler Bildgebung im Vergleich zur PET-CT. Erste Erfahrungen auf einem 32-Kanal-MRT-System.

PURPOSE: To compare the accuracy in the detection and staging of various malignant tumors with high resolution whole-body MRI using parallel imaging with whole-body dual-modality PET-CT. PATIENTS AND METHODS: Preliminary results of an interim analysis from a prospective, blinded study are presented, in which 20 patients (mean age 59 years, range 27-77 years) with different oncological diseases underwent whole-body dual modality FDG-PET-CT screening for tumor search or staging in case of confirmed or suspected metastatic disease. All patients also underwent whole-body MRI imaging with the use of parallel imaging (iPAT). High-resolution coronal T1w- and STIR-sequences of 5 body levels with 512 x 512 matrix, axial fast T2w imaging of lung and abdomen (HASTE), contrast-enhanced dynamic and static T1w-sequences of liver, brain, abdomen, and pelvis were performed. Using a 32-channel whole-body MRI scanner (Magnetom Avanto, Siemens Medical Solutions) with a total field of view of 205 cm and free table movement, all patients could be covered from head to toe within one examination. With this technique, high spatial resolution and acceptable scanning times could be obtained. Two experienced radiologists read the MRI-scans, one radiologist and one nuclear scientist read PET-CT scans, each in consensus in a clinical setting. Delineation of the primary tumor (T-stage) or recurrent tumor, pathologic lymph node involvement, as well as degree and localization of metastatic disease, was assessed using PET-CT as standard of reference. RESULTS: Metastases from gastrointestinal tumor (25%) and breast cancer (25%), genitourinary tumor (15%) and malignant melanoma (15%) were detected. In 4/20 patients the primary tumor was identified, 2/20 patients showed recurrent tumor. Of 140 malignant lesions detected by PET-CT, 124 lesions were detected with MRI, resulting in a sensitivity of 89% at a specificity of 86%. In malignant lymph node detection, sensitivity of MRI was 83% and specificity 85%. CONCLUSION: Whole-body MRI is a promising technique in the detection of primary tumor and metastatic disease. Sensitivity in the assessment of lymph node metastases seems to be limited. With the use of parallel imaging (iPAT), dedicated high-resolution whole-body MRI is possible within acceptable scanning times.

Breast cancer: monitoring response to neoadjuvant chemotherapy using Tc-99m sestamibi scintimammography.

BACKGROUND: Aim of the study was to assess the value of scintimammography using Tc-99m sestamibi in the evaluation of tumor response to neoadjuvant chemotherapy. MATERIAL ANS METHODS: Results were calculated for 9 patients undergoing neoadjuvant chemotherapy. Scintimammography using 740 MBq Tc-99m sestamibi was performed before, during and after chemotherapy, and sestamibi uptake was scored visually and semiquantitatively to evaluate tumor response. RESULTS: In the case of complete response (n = 3) sestamibi uptake decreased 8 days after beginning neoadjuvant chemotherapy and normalized in the following course. Focal uptake decreased more slowly in patients with partial response (n = 3), who showed clear, persisting tracer accumulation after therapy. The patients without response (n = 3) showed a persisting high tumor activity even after chemotherapy was completed. CONCLUSIONS: The preliminary data suggest that in contrast to other imaging modalities scintimammography appears to yield early information regarding tumor response to neoadjuvant chemotherapy.

[Breast scintigraphy using 99mTc-sestamibi--use and limitations]. / Die Szintigraphie der Mamma mit 99mTc-Sestamibi--Indikationen und Limitationen.

AIM: Until now scintimammography did not achieve any definite role in the assessment of breast lesions. Purpose of this study was to elaborate its use as well as the limitations of scintimammography after 500 examinations completed. METHODS: Scintigraphic findings were correlated with the histopathologic outcome of 219 patients, who underwent surgery or biopsy for histopathological confirmation. The results were determined with respect to palpability of the lesion and tumour size. Additionally, a distinct analysis was performed for the patient subpopulation with indeterminate results of previously performed physical examination, mammography, and sonography. RESULTS: Overall sensitivity for scintimammography was 82.1% at a specificity of 87.5%. For palpable lesions sensitivity was 91.7% which was evidently higher as compared to 64.9% for non palpable lesions. For palpable lesions specificity was 81.1% and 88.6% for non palpable lesions. According to tumour size sensitivity ranged between 65.2% for carcinoma with a diameter < 1 cm and 93.7% for carcinoma > 1 cm. In the patients subgroup with indeterminate preliminary diagnosis (n = 143) sensitivity decreased to 71.7% at a specificity of 87.8%. Patients undergoing neoadjuvant chemotherapy showed decreasing sestamibi uptake as early as 8 days after therapy if tumour response was evident. However, small residual invasive tumours in patients with complete remission could not be visualised. CONCLUSION: Scintimammography is neither suited for screening, nor early diagnosis of breast cancer, nor for the further evaluation of small and unclear mammographic findings. Scintimammography should not be used whenever histopathological clarification of a suspicious lesion is necessary. It is useful to further investigate patients with unclear or probably benign findings in physical examination and/or mammography and to monitor tumour response to neoadjuvant chemotherapy.

[Correlation of FDG-PET and MRI/CT with histopathology in primary diagnosis, lymph node staging and diagnosis of recurrency of head and neck cancer]. / Korrelation von FDG-PET und MRT/CT mit der Histopathologie in Primärdiagnostik, Lymphknotenstaging und Rezidivdiagnostik von Kopf-Hals-Tumoren.

AIM: Correct staging of head and neck cancer is important for the patient's prognosis and further therapeutic strategies. Aim of the present study was to investigate the diagnostic value of FDG-PET regarding the pre-surgical diagnosis of primary tumor and cervical lymph node metastases, the diagnosis of tumour recurrence, and the localisation of unknown primary, further to compare the results to those of morphological imaging modalities (CT/MRI) and to correlate the results of both methods with histopathological findings. PATIENTS/METHODS: 115 patients (pts) (72 x primary diagnosis, 37 x recurrence, and 6 x unknown primary) underwent FDG-PET (ECAT EXACT HR+) and CT or MRI. Results were correlated with histopathological findings in terms of detection of primary and recurrent tumors as well as lymph node metastases. RESULTS: Regarding the pre-surgical diagnosis, sensitivity and specificity for identifying primary tumors were 85 % and 100 % for PET and 88 % and 75 % for CT/MRI, respectively. Accuracy was 86 % for PET and 87 % for CT/MRI. Sensitivity and specificity for detecting primary lymph node involvement were 71 %/86 % for PET and 74 %/57 % for CT/MRI, resulting in an accuracy of 77 % with PET and 68 % with morphological imaging. In 23 pts histopathology revealed pT1 stages with tumor diameters < 12 mm. In 8 pts CT/MRI and in 10 pts PET failed to identify these small primary lesions. Detecting tumor recurrence (n = 37) PET showed a higher sensitivity (83 %), specificity (76 %) and accuracy (78 %) compared to CT/MRI (sensitivity: 67 %; specificity: 52 %; accuracy: 57 %). In 4/6 pts with unknown primary, imaging was able to identify a primary lesion (3/4 in FDG-PET, 2/4 in CT/MRI), in 2/6 patients even in the follow-up no primary tumor was found. CONCLUSIONS: FDG-PET provides only minor additional information to morphological imaging concerning diagnosis of primary tumors. At a similar level of sensitivity, however, it seems to be more specific regarding the lymph node involvement. PET seems to be superior to CT/MRI in detecting tumor recurrence as well as occult primary tumors in pts with known cervical lymph node metastases.

Comparison of dynamic MR imaging of the breast and sestamibi scintimammography for evaluation of indeterminate mammographic lesions.

The aim of this study was to compare Tc-99m sestamibi scintimammography and dynamic contrast-enhanced MR imaging for the evaluation of indeterminate mammographic lesions. Forty patients with questionable mammographic findings were included in a prospective study. Thirty lesions were non-palpable. Mean lesion size was 1.6+/-0.7 cm (range 0.5-3.5 cm). Scintigraphy was considered as malignant when focal tracer accumulation was present. In MR imaging, lesions were classified according to their signal intensity time course: no enhancement or steady enhancement with low signal intensity (M0); steady enhancement with high signal intensity (M1); or rapid enhancement with plateau (M2) or washout (M3). Lesions classified as M2 or M3 were considered as suspicious for malignancy. Histopathologic evaluation was performed in 24 lesions. In 16 cases lesions were classified as benign from follow-up examinations (mean 24 months). Malignancies were proven in 14 patients (9 invasive carcinomas, 5 ductal carcinoma in situ). Sensitivity of MR imaging was 12 of 14 (86%) and sensitivity of scintimammography was 8 of 14 (57%). One of 26 benign lesions was false positive at MR imaging. Scintigraphy showed no false-positive results. In conclusion, magnetic resonance imaging provided high accuracy in evaluation of indeterminate mammographic lesions. Sensitivity of scintimammography was too low in detecting small carcinomas.

18F-FDG PET and 99mTc-sestamibi scintimammography for monitoring breast cancer response to neoadjuvant chemotherapy: a comparative study.

Presurgical neoadjuvant chemotherapy has shown promise in the treatment of locally advanced breast carcinoma (LABC). Response assessment by clinical examination and mammography is difficult. This study evaluated and compared fluorine-18 fluorodeoxyglucose positron emission tomography (18F-FDG-PET) and technetium-99m sestamibi scintimammography (SMM) as potential methods for the early assessment of tumour response to neoadjuvant chemotherapy in patients with LABC. Seven patients underwent PET and SMM [planar and single-photon emission tomography (SPET)] before beginning chemotherapy, after the first and second cycles of chemotherapy and after completing chemotherapy prior to surgery. PET and SMM results were evaluated visually and semi-quantitatively by calculating standardised uptake values (SUV) and tumour/lung ratios in the initial and subsequent studies. The findings were correlated with the initial clinical and mammographic findings and the final histopathological diagnoses. There was a highly significant correlation between SUVmean, SUVmax and the tumour/lung ratio determined with SMM-SPET in the studies performed before and during neoadjuvant chemotherapy. All three patients with complete remission showed decreasing FDG and sestamibi uptake as early as 8 days after therapy. In the presurgical study, increased sestamibi and FDG uptake was no longer evident. Three patients had partial remission with clearly reduced but persisting focal FDG and sestamibi uptake after neoadjuvant therapy. One patient who did not respond to therapy had unchanged intense tracer uptake during chemotherapy that was evident with both techniques. An early decline in glucose metabolism or sestamibi uptake 8 days after beginning therapy did not necessarily predict complete tumour remission in the further course of chemotherapy. On the other hand, increased tracer uptake after the first cycle did not exclude a partial tumour response. After the second chemotherapeutic cycle both techniques were able to distinguish between complete and partial/no response. There was a good correlation between preoperative FDG and sestamibi uptake and the histopathologically determined tumour size. However, small residual invasive tumours in patients with clinically complete remission could not be visualised with either technique. The preliminary data demonstrate that sestamibi SMM is as useful as FDG-PET for the monitoring of tumour response to neoadjuvant chemotherapy.