Helen Almquist

Concordance between four European centres of PET reporting criteria designed for use in multicentre trials in Hodgkin lymphoma

PurposeTo determine if PET reporting criteria for the Response Adapted Treatment in Hodgkin Lymphoma (RATHL) trial could enable satisfactory agreement to be reached between ‘core’ laboratories operating in different countries.MethodsFour centres reported scans from 50 patients with stage II–IV HL, acquired before and after two cycles of Adriamycin/bleomycin/vinblastine/dacarbazine. A five-point scale was used to score response scans using ‘normal’ mediastinum and liver as reference levels. Centres read scans independently of each other. The level of agreement between centres was determined assuming (1) that uptake in sites involved at diagnosis that was higher than liver uptake represented disease (conservative reading), and (2) that uptake in sites involved at diagnosis that was higher than mediastinal uptake represented disease (sensitive reading).ResultsThere was agreement that the response scan was ‘positive’ or ‘negative’ for lymphoma in 44 patients with a conservative reading and in 41 patients with a sensitive reading. Kappa was 0.85 (95% CI 0.74–0.96) for conservative reading and 0.79 (95% CI 0.67–0.90) for sensitive reading. Agreement was reached in 46 and 44 patients after discussion for the conservative and sensitive readings, respectively.ConclusionThe criteria developed for reporting in the RATHL trial are sufficiently robust to be used in a multicentre setting.

Combined (18) F-fluorocholine and (18) F-fluoride positron emission tomography/computed tomography imaging for staging of high-risk prostate cancer.

Study Type – Diagnosis (cohort)

PET-CT for staging and early response: results from the Response-Adapted Therapy in Advanced Hodgkin Lymphoma study

International guidelines recommend that positron emission tomography-computed tomography (PET-CT) should replace CT in Hodgkin lymphoma (HL). The aims of this study were to compare PET-CT with CT for staging and measure agreement between expert and local readers, using a 5-point scale (Deauville criteria), to adapt treatment in a clinical trial: Response-Adapted Therapy in Advanced Hodgkin Lymphoma (RATHL). Patients were staged using clinical assessment, CT, and bone marrow biopsy (RATHL stage). PET-CT was performed at baseline (PET0) and after 2 chemotherapy cycles (PET2) in a response-adapted design. PET-CT was reported centrally by experts at 5 national core laboratories. Local readers optionally scored PET2 scans. The RATHL and PET-CT stages were compared. Agreement among experts and between expert and local readers was measured. RATHL and PET0 stage were concordant in 938 (80%) patients. PET-CT upstaged 159 (14%) and downstaged 74 (6%) patients. Upstaging by extranodal disease in bone marrow (92), lung (11), or multiple sites (12) on PET-CT accounted for most discrepancies. Follow-up of discrepant findings confirmed the PET characterization of lesions in the vast majority. Five patients were upstaged by marrow biopsy and 7 by contrast-enhanced CT in the bowel and/or liver or spleen. PET2 agreement among experts (140 scans) with a κ (95% confidence interval) of 0.84 (0.76-0.91) was very good and between experts and local readers (300 scans) at 0.77 (0.68-0.86) was good. These results confirm PET-CT as the modern standard for staging HL and that response assessment using Deauville criteria is robust, enabling translation of RATHL results into clinical practice.

Quantitative SPECT by attenuation correction of the projection set using transmission data: evaluation of a method.

A method for measuring attenuation coefficients in single-photon emission tomography (SPECT) is described and evaluated, together with a method for attenuation correction using these measured attenuation coefficients. Build-up, caused by scattered photons, is corrected for by a simple substitution in the algorithms. Transmission studies are performed with a99mTc- or57Co flood source, and emission phantom studies with99mTc line sources. The method is evaluated with variable but well-defined phantoms. The result is accurate attenuation coefficients for different densities, dimensions and geometries, and an accuracy of corrected emission activities of better than ∓ 10% in most cases. The present limitations of the method for attenuation correction are discussed.

Clinical implication of down-scatter in attenuation-corrected myocardial SPECT

BackgroundInterpretation of myocardial perfusion single photon emission computed tomography (SPECT) studies is hampered by attenuation artifacts. Attenuation correction methods with simultaneous emission and transmission are now commercially available. However, it has been observed in clinical practice that attenuation correction without down-scatter correction in a 1-day rest/stress myocardial perfusion protocol may lead to serious interpretation errors. Therefore the aim of this study was to study errors resulting from down-scatter under realistic conditions, thus providing a background for the assessment of further corrections.Methods and ResultsForty-six patients underwent myocardial perfusion scintigraphy in a 1-day technetium 99m-tetrofosmin rest-stress SPECT protocol, with a moving 153Gd line-source device for attenuation correction without down-scatter correction. Short-axis slices were quantified as inferior/anterior, septal/lateral, and apical/remainder count ratios. The changes at rest (350 MBq) and exercise (900 MBq) induced by attenuation correction were studied. Attenuation correction gave differences in apparent perfusion between rest and exercise not seen before correction The gender differences in inferior-anterior ratio were greatly reduced after correction at rest but remained at exercise. A torso phantom study indicated that these results were due to under-correction at exercise because of down-scatter.ConclusionsDown-scatter results in an underestimation of attenuation in simultaneous emission and transmission, if not accurately accounted for. Particularly, a high-dose study compared with a low-dose study, as in the 1-day protocol, might cause serious interpretation errors.

[F-18]Fluorodeoxyglucose - positron emission tomography/computed tomography improves staging in patients with high-risk muscle-invasive bladder cancer scheduled for radical cystectomy

Abstract Objective. The aim of this study was to evaluate the clinical use of [18F]fluorodeoxyglucose-positron emission tomography/computed tomography (FDG-PET/CT) in addition to conventional preoperative radiological investigations in a defined group of patients with high-risk muscle-invasive bladder cancer. Materials and methods. In total, 103 patients with high-risk muscle-invasive bladder cancer defined as stage T3/T4 disease or as stage T2 with hydronephrosis or high-risk histological features, who were provisionally scheduled to undergo cystectomy, were prospectively recruited to the study. The patients were referred to FDG-PET/CT in addition to standard preoperative investigation with computed tomography (CT). The final treatment decision was reached at a multidisciplinary conference based on all available information including the FDG-PET/CT findings. Results. Compared to CT alone, FDG-PET/CT provided more supplemental findings suggesting malignant manifestations in 48 (47%) of the 103 patients. The additional FDG-PET/CT findings led to an altered provisional treatment plan in 28 out of 103 patients (27%), detection of disseminated bladder cancer and subsequent cancellation of the initially intended cystectomy in 16 patients, and identification of disseminated disease and treatment with induction chemotherapy before radical cystectomy in 12 patients. Conclusions. Preoperative FDG-PET/CT changed the treatment plan for a considerable proportion (27%) of the present patients. Accordingly, such examination can potentially improve the preoperative staging of cystectomy patients with high-risk features, and may also reduce the number of futile operations in patients with advanced disease who are beyond cure.

Radiotherapy response in head and neck cancer – evaluation of the primary tumour site

Abstract Conclusion: PET-CT scans seem to be sufficient to rule out residual tumour at the primary site. Patients with positive or equivocal PET findings should be scheduled for endoscopy with biopsy or a second PET-CT scan. Objectives: Assessment of remission at the primary site, in patients treated with organ preservation therapy with curative intent, is important to identify residual tumours requiring treatment with salvage surgery. The aim of this study was to evaluate the diagnostic accuracy of fluorodeoxyglucose positron emission tomography (FDG-PET) after radiotherapy with or without chemotherapy in assessing primary site response in patients with head and neck cancer. Methods: A total of 82 patients, with a positive baseline PET-CT scan before start of treatment, were evaluated with a PET-CT scan 6–7 weeks post-radiotherapy and with a clinical examination/endoscopy with or without biopsy 1–2 weeks later. The majority of patients had p16-positive oropharyngeal tumours. Results: Post-treatment, 77% of the patients had no visible hypermetabolism. If equivocal PET scans are regarded as positive, the sensitivity, specificity, negative (NPV) and positive predictive value (PPV) and accuracy were 100%, 78%, 100%, 6% and 78%, respectively. Eight patients suffered from relapses involving the primary site during the 9-month follow-up.

Performance of simultaneous emission-transmission systems for attenuation-corrected SPEct: a method for validation applied to two camera systems

Several commercially available systems for attenuation correction in single photon emission computed tomography (SPECT) based on a transmission scan have been introduced that vary in performance. A test procedure for attenuation correction in SPECT is described and applied to two principally different gamma camera systems (the Siemens Multispect 3 triple-headed system [3HS] and the ADAC Genesys Vertex double-headed system [2HS]). The test procedure was based on geometrically well-defined phantoms. A torso phantom was used to illustrate the attenuation correction methods. The test procedure can be used without detailed knowledge of or access to the algorithms used for attenuation correction. The influence on the transmission measurement of radioactivity in a phantom was higher for the 2HS than for the 3HS. The 3HS produced satisfactory attenuation maps and corrected emission count rates to a constant value independent of phantom density and size. With the 2HS, there was a progressive decrease in the correction of emission count rates with increasing phantom density, and about 30% lower corrected count rates in the large compared with the small phantom. A decrease in measured attenuation coefficients in the vicinity of an emission source was demonstrated in large but not small phantoms. A likely explanation is erroneous correction of downscatter into the transmission energy window. This study demonstrates the need for independent evaluation of systems for attenuation correction in SPECT.

A prospective study of positron emission tomography for evaluation of neck node response 6 weeks after radiotherapy in patients with head and neck squamous cell carcinoma.

The purpose of this study was to evaluate if a positron emission tomography (PET) scan, 6 weeks after radiotherapy (RT), adequately selects patients in whom a neck node dissection can be omitted. Primary endpoints were isolated neck recurrences and overall survival (OS).

[18F]Fluorodeoxyglucose-positron emission tomography/computed tomography response evaluation can predict histological response at surgery after induction chemotherapy for oligometastatic bladder cancer

Abstract Objective: Patients with limited metastatic and locally advanced bladder cancer have a poor prognosis, and no definite treatment recommendations exist. However, long-term survival is possible for selected patients if surgery is combined with multiple courses of chemotherapy (i.e. induction chemotherapy). Patients with tumours that are insensitive to chemotherapy probably have little to gain from subsequent extensive surgery. The aim of this study was to evaluate sequential FDG-PET/CT examinations as an indicator of chemotherapy response. Materials and methods: Between 2007 and 2015, 50 patients with oligometastatic invasive bladder cancer selected for induction chemotherapy underwent two FDG-PET/CT examinations: the first before the start of chemotherapy and the second after three courses of cisplatinum-based combination chemotherapy. Responders were given up to six courses of chemotherapy. FDG-PET/CT response was correlated with histological response in excised lymph-node metastases. Results: Three patients showed progression to incurable disease during chemotherapy and another two patients did not undergo surgery, for medical reasons. Lymphadenectomy was performed in the remaining 45 patients, of whom 43 had lymph-node metastasis. FDG-PET/CT prediction of the histological nodal chemotherapy response was correct in 37 (86%) of those 43. The second FDG-PET/CT examination identified four out of nine non-responders. For response, the sensitivity, specificity, and positive and negative predictive values for FDG-PET/CT accuracy were 37 out of 37 (100%), one out of six (17%), 37 out of 42 (88%) and one out of one (100%), respectively. Conclusions: Repeated FDG-PET/CT seems to predict histological response. However, with the histological response criteria used in this study, five non-responders were not identified by the second FDG-PET/CT investigation.