First-in-Humans PET Imaging of Tissue Factor in Patients with Primary and Metastatic Cancers Using 18F-labeled Active-Site Inhibited Factor VII (18F-ASIS): Potential as Companion Diagnostic

Tissue factor (TF) expression in cancers correlates with poor prognosis. Recently, the first TF-targeted therapy was approved by the U.S. Food and Drug Administration for cervical cancer. To unfold the potential of TF-targeted therapies, correct stratification and selection of patients eligible for treatments may become important for optimization of patient outcomes. TF-targeted PET imaging based on ¹⁸F-radiolabeled active-site inhibited versions of the TF natural ligand coagulation factor VII (¹⁸F-ASIS) has in preclinical models convincingly demonstrated its use for noninvasive quantitative measurements of TF expression in tumor tissue. ¹⁸F-ASIS PET imaging thus has the potential to act as a diagnostic companion for TF-targeted therapies in the clinical setting. Methods: In this first-in-humans trial, we included 10 cancer patients (4 pancreatic, 3 breast, 2 lung, and 1 cervical cancer) for ¹⁸F-ASIS PET imaging. The mean and SD of administered ¹⁸F-ASIS activity was 157 ± 35 MBq (range, 93-198 MBq). PET/CT was performed after 1, 2, and 4 h. The primary objectives were to establish the safety, biodistribution, pharmacokinetics, and dosimetry of ¹⁸F-ASIS. Secondary objectives included quantitative measurements of SUVs in tumor tissue with PET and evaluation of the correlation (Pearson correlation) between tumor SUV_max and ex vivo TF expression in tumor tissue. Results: Administration of ¹⁸F-ASIS was safe, and no adverse events were observed. No clinically significant changes in vital signs, electrocardiograms, or blood parameters were observed after injection of ¹⁸F-ASIS. Mean ¹⁸F-ASIS plasma half-life was 3.2 ± 0.6 h, and the radiotracer was predominantly excreted in the urine. For injection activity of 200 MBq of ¹⁸F-ASIS, effective whole-body dose was 4 mSv and no prohibitive organ-specific absorbed doses were found. Heterogeneous radiotracer uptake was observed across patients and within tumors. We found a trend of a positive correlation between tumor SUV_max and ex vivo TF expression (r = 0.84, P = 0.08, n = 5). Conclusion: ¹⁸F-ASIS can be safely administered to cancer patients for PET imaging of TF expression in tumors. The trial marks the first test of a TF-targeted PET radiotracer in humans (first-in-class). The findings represent important first steps toward clinical implementation of ¹⁸F-ASIS PET imaging of TF expression.

Deep learning for Dixon MRI-based attenuation correction in PET/MRI of head and neck cancer patients

Background

Quantitative whole-body PET/MRI relies on accurate patient-specific MRI-based attenuation correction (AC) of PET, which is a non-trivial challenge, especially for the anatomically complex head and neck region. We used a deep learning model developed for dose planning in radiation oncology to derive MRI-based attenuation maps of head and neck cancer patients and evaluated its performance on PET AC.

Methods

Eleven head and neck cancer patients, referred for radiotherapy, underwent CT followed by PET/MRI with acquisition of Dixon MRI. Both scans were performed in radiotherapy position. PET AC was performed with three different patient-specific attenuation maps derived from: (1) Dixon MRI using a deep learning network (PET_Deep). (2) Dixon MRI using the vendor-provided atlas-based method (PET_Atlas). (3) CT, serving as reference (PET_CT). We analyzed the effect of the MRI-based AC methods on PET quantification by assessing the average voxelwise error within the entire body, and the error as a function of distance to bone/air. The error in mean uptake within anatomical regions of interest and the tumor was also assessed.

Results

The average (± standard deviation) PET voxel error was 0.0 ± 11.4% for PET_Deep and −1.3 ± 21.8% for PET_Atlas. The error in mean PET uptake in bone/air was much lower for PET_Deep (−4%/12%) than for PET_Atlas (−15%/84%) and PET_Deep also demonstrated a more rapidly decreasing error with distance to bone/air affecting only the immediate surroundings (less than 1 cm). The regions with the largest error in mean uptake were those containing bone (mandible) and air (larynx) for both methods, and the error in tumor mean uptake was −0.6 ± 2.0% for PET_Deep and −3.5 ± 4.6% for PET_Atlas.

Conclusion

The deep learning network for deriving MRI-based attenuation maps of head and neck cancer patients demonstrated accurate AC and exceeded the performance of the vendor-provided atlas-based method both overall, on a lesion-level, and in vicinity of challenging regions such as bone and air.

Robustness and Generalizability of Deep Learning Synthetic Computed Tomography for Positron Emission Tomography/Magnetic Resonance Imaging-Based Radiation Therapy Planning of Patients With Head and Neck Cancer

Purpose

Radiotherapy planning based only on positron emission tomography/magnetic resonance imaging (PET/MRI) lacks computed tomography (CT) information required for dose calculations. In this study, a previously developed deep learning model for creating synthetic CT (sCT) from MRI in patients with head and neck cancer was evaluated in 2 scenarios: (1) using an independent external dataset, and (2) using a local dataset after an update of the model related to scanner software-induced changes to the input MRI.

Methods and Materials

Six patients from an external site and 17 patients from a local cohort were analyzed separately. Each patient underwent a CT and a PET/MRI with a Dixon MRI sequence over either one (external) or 2 (local) bed positions. For the external cohort, a previously developed deep learning model for deriving sCT from Dixon MRI was directly applied. For the local cohort, we adapted the model for an upgraded MRI acquisition using transfer learning and evaluated it in a leave-one-out process. The sCT mean absolute error for each patient was assessed. Radiotherapy dose plans based on sCT and CT were compared by assessing relevant absorbed dose differences in target volumes and organs at risk.

Results

The MAEs were 78 ± 13 HU and 76 ± 12 HU for the external and local cohort, respectively. For the external cohort, absorbed dose differences in target volumes were within ± 2.3% and within ± 1% in 95% of the cases. Differences in organs at risk were <2%. Similar results were obtained for the local cohort.

Conclusions

We have demonstrated a robust performance of a deep learning model for deriving sCT from MRI when applied to an independent external dataset. We updated the model to accommodate a larger axial field of view and software-induced changes to the input MRI. In both scenarios dose calculations based on sCT were similar to those of CT suggesting a robust and reliable method.

64Cu-DOTATATE PET in Patients with Neuroendocrine Neoplasms: Prospective, Head-to-Head Comparison of Imaging at 1 Hour and 3 Hours After Injection

⁶⁴Cu-DOTATATE PET/CT imaging 1 h after injection is excellent for lesion detection in patients with neuroendocrine neoplasms (NENs). We hypothesized that the imaging time window can be extended up to 3 h after injection without significant differences in the number of lesions detected. Methods: From a prospective study, we compared, on a head-to-head basis, sets of ⁶⁴Cu-DOTATATE PET/CT images from 35 patients with NENs scanned 1 and 3 h after injection of 200 MBq of ⁶⁴Cu-DOTATATE. The number of lesions on both PET scans was counted and grouped according to organs or regions and compared with negative binomial regression. Discordant lesions (visible on only the 1-h images or only the 3-h ⁶⁴Cu-DOTATATE PET images) were considered true if found on simultaneous CT or later MR, CT, or somatostatin receptor imaging. We measured lesion SUV_max, reference normal-organ or -tissue SUV_mean, and tumor-to-normal-tissue ratios calculated from SUV_max and SUV_mean Results: We found 822 concordant lesions (visible on both 1-h and 3-h ⁶⁴Cu-DOTATATE PET) and 5 discordant lesions, of which 4 were considered true. One discordant case in 1 patient involved a discordant organ system (lymph node) detected on 3-h but not 1-h ⁶⁴Cu-DOTATATE PET that did not alter the patient's disease stage (stage IV) because the patient had 11 additional concordant liver lesions. We found no significant differences between the number of lesions detected on 1-h and 3-h ⁶⁴Cu-DOTATATE PET. Throughout the 1- to 3-h imaging window, the mean tumor-to-normal-tissue ratio remained high in all key organs: liver (1 h: 12.6 [95% confidence interval (CI), 10.2-14.9]; 3 h: 11.0 [95%CI, 8.7-13.4]), intestines (1 h: 24.2 [95%CI, 14.9-33.4]; 3 h: 28.2 [95%CI, 16.5-40.0]), pancreas (1 h: 42.4 [95%CI, 12.3-72.5]; 3 h: 41.1 [95%CI, 8.7-73.4]), and bone (1 h: 103.0 [95%CI, 38.6-167.4]; 3 h: 124.2 [95%CI, 57.1-191.2]). Conclusion: The imaging time window of ⁶⁴Cu-DOTATATE PET/CT for patients with NENs can be expanded from 1 h to 1-3 h without significant differences in the number of lesions detected.

Metal artefact reduction for accurate tumour delineation in radiotherapy

BACKGROUND AND PURPOSE

Two techniques for metal artefact reduction for computed tomography were studied in order to identify their impact on tumour delineation in radiotherapy.

MATERIALS AND METHODS

Using specially designed phantoms containing metal implants (dental, spine and hip) as well as patient images, we investigated the impact of two methods for metal artefact reduction on (A) the size and severity of metal artefacts and the accuracy of Hounsfield Unit (HU) representation, (B) the visual impact of metal artefacts on image quality and (C) delineation accuracy. A metal artefact reduction algorithm (MAR) and two types of dual energy virtual monochromatic (DECT VM) reconstructions were used separately and in combination to identify the optimal technique for each implant site.

RESULTS

The artefact area and severity was reduced (by 48-76% and 58-79%, MAR and DECT VM respectively) and accurate Hounsfield-value representation was increased by 22-82%. For each energy, the observers preferred MAR over non-MAR reconstructions (p < 0.01 for dental and hip cases, p < 0.05 for the spine case). In addition, DECT VM was preferred for spine implants (p < 0.01). In all cases, techniques that improved target delineation significantly (p < 0.05) were identified.

CONCLUSIONS

DECT VM and MAR techniques improve delineation accuracy and the optimal of reconstruction technique depends on the type of metal implant.

18 F-FDG PET/CT for planning external beam radiotherapy alters therapy in 11% of 581 patients

BACKGROUND

¹⁸ F-FDG PET/CT (FDG PET/CT) used in radiotherapy planning for extra-cerebral malignancy may reveal metastases to distant sites that may affect the choice of therapy.

AIM

To investigate the role of FDG PET/CT on treatment strategy changes induced by the use of PET/CT as part of the radiotherapy planning. 'A major change of treatment strategy' was defined as either including more lesions in the gross tumour volume (GTV) distant from the primary tumour or a change in treatment modalities.

METHODS

The study includes 581 consecutive patients who underwent an FDG PET/CT scan for radiotherapy planning in our institution in the year 2008. All PET/CT scans were performed with the patient in treatment position with the use of immobilization devices according to the intended radiotherapy treatment. All scans were evaluated by a nuclear medicine physician together with a radiologist to delineate PET-positive GTV (GTV-PET).

RESULTS

For 63 of the patients (11%), the PET/CT simulation scans resulted in a major change in treatment strategy because of the additional diagnostic information. Changes were most frequently observed in patients with lung cancer (20%) or upper gastrointestinal cancer (12%). In 65% of the patients for whom the PET/CT simulation scan revealed unexpected dissemination, radiotherapy was given - changed (n = 38) or unchanged (n = 13) according to the findings on the FDG PET/CT.

CONCLUSION

Unexpected dissemination on the FDG PET/CT scanning performed for radiotherapy planning caused a change in treatment strategy in 11% of 581 patients.

Abstract P5-01-04: uPAR PET imaging in breast cancer: First-in-humans studies using 64Cu-DOTA-AE105 and 68Ga-NOTA-AE105

Objective

The urokinase-type plasminogen activator receptor (uPAR) is a well-established prognostic biomarker in many cancer types including breast cancer (BC). Numerous studies using immunohistochemically evaluation of uPAR expression in tissue samples from BC patients have shown that not only is uPAR consistently overexpressed, but also carries strong prognostic value and is associates with overall survival. Accordingly, uPAR is an obvious target for identifying BC and for phenotyping aggressiveness in BC. Using whole body Positron Emission Tomography (PET) imaging rather than tissue specimens circumvents possible sampling error and allows for staging. Our objective was therefore to perform first-in-humans studies of uPAR-specific PET imaging in BC using either 64Cu-DOTA-AE105 or 68Ga-NOTA-AE105

Methods

Six patients with BC and scheduled for surgery were included. Prior to operation, patients were either PET/CT scanned 1, 3 and 24 h after injection of the uPAR PET ligand 64Cu-DOTA-AE105 (n=3; half life of 64Cu: 13 h) or PET/CT scanned 10 min, 1 h or 2 h after injection of 68Ga-NOTA-AE105 (n=3; half life of 68Ga: 1 h). PET Images were visually analyzed for visible tumor uptake of 64Cu-DOTA-AE105 or 68Ga-NOTA-AE105 and Standardized Uptake Values (SUV) were obtained by manually drawing volumes of interest (VOIs) around the primary tumor as well as identified metastases. Results are given as SUVmax. Tumor-to-background ratios relative to liver, kidney, blood and muscle were also calculated. Surgical tumor specimens were obtained from all patients during subsequent surgery. In addition to routine pathological examination, tissue was analyzed for ex vivo uPAR expression as target validation.

Results

Both primary tumors and metastases were visually detectable. For 64Cu-DOTA-AE105 SUVmax values were 2.9–4.0., and 2.9-4.0 after 1 and 3 h, respectively. Tumor-to-background ratios after 1 h were 0.91 (tumor-liver), 1.65 (tumor-kidney), 0.96 (tumor-blood) and 8.9 (tumor-muscle), respectively. Tumor-to-background ratios after 3 h were 0.50 (tumor-liver), 0.96 (tumor-kidney), 4.2 (tumor-blood) and 11.4 (tumor-muscle), respectively. Ex vivo analysis by immunohistochemistry confirmed uPAR expression in all primary cancer lesions. For 68Ga-NOTA-AE105, SUVmax was 5.0, 3.8 and 4.2 after 10 min, 1 h and 3 h, respectively (first patient analyzed). Tumor-to-background ratios after 10 min were 2.8 (tumor-liver), 0.4 (tumor-kidney), 1.6 (tumor-blood) and 8.4 (tumor-muscle), respectively. Tumor-to-background ratios after 1 h were 3.2 (tumor-liver), 0.6 (tumor-kidney), 1.7 (tumor-blood) and 7.1 (tumor-muscle), respectively.

Conclusion

This is the first study in humans using PET imaging of uPAR in BC. Both primary tumors and metastases were clearly visible with robust PET tracer uptake and a high and sufficient contrast between tumors and background. Our data supports continuation into phase II clinical studies using uPAR PET for staging and risk stratification, which potentially may be used for selection of treatment strategy in BC.

Citation Format: Kjaer A, Persson M, Skovgaard D, Brandt-Larsen M, Christensen C, Madsen J, Nielsen CH, Loft A, Berthelsen AK, Kroman N, Højgaard L. uPAR PET imaging in breast cancer: First-in-humans studies using 64Cu-DOTA-AE105 and 68Ga-NOTA-AE105. [abstract]. In: Proceedings of the Thirty-Eighth Annual CTRC-AACR San Antonio Breast Cancer Symposium: 2015 Dec 8-12; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2016;76(4 Suppl):Abstract nr P5-01-04.

Prospective phase II trial of image-guided radiotherapy in Hodgkin lymphoma: benefit of deep inspiration breath-hold

BACKGROUND

Long-term Hodgkin lymphoma (HL) survivors have an increased risk of late cardiac morbidity and secondary lung cancer after chemotherapy and mediastinal radiotherapy. In this prospective study we investigate whether radiotherapy with deep inspiration breath-hold (DIBH) can reduce radiation doses to the lungs, heart, and cardiac structures without compromising the target dose.

PATIENTS AND METHODS

Twenty-two patients (14 female, 8 male), median age 30 years (18-65 years), with supra-diaphragmatic HL were enrolled and had a thoracic PET/CT with DIBH in addition to staging FDG-PET/CT in free breathing (FB) and a planning CT in both FB and DIBH. For each patient an involved-node radiotherapy plan was done for both DIBH and FB, and the doses to the lungs, heart, and female breasts were recorded prospectively. Mean doses to the heart valves and coronary arteries were recorded retrospectively. Patients were treated with the technique yielding the lowest doses to normal structures.

RESULTS

Nineteen patients were treated with DIBH and three with FB. DIBH reduced the mean estimated lung dose by 2.0 Gy (median: 8.5 Gy vs. 7.2 Gy) (p < 0.01) and the mean heart dose by 1.4 Gy (6.0 Gy vs. 3.9 Gy) (p < 0.01) compared to FB. The lung and heart V20Gy were reduced with a median of 5.3% and 6.3%. Mean doses to the female breasts were equal with FB and DIBH.

CONCLUSION

DIBH can significantly decrease the estimated mean doses to the heart and lungs without lowering the dose to the target in radiotherapy for patients with mediastinal HL.

Recurrences after intensity modulated radiotherapy for head and neck squamous cell carcinoma more likely to originate from regions with high baseline [18F]-FDG uptake

BACKGROUND AND PURPOSE

To analyze the recurrence pattern in relation to target volumes and (18)F-fluorodeoxyglucose (FDG) uptake on positron emission tomography in head and neck squamous cell carcinoma (HNSCC) patients treated with definitive chemoradiation.

MATERIAL AND METHODS

520 patients received radiotherapy for HNSCC from 2005 to 2009. Among 100 patients achieving complete clinical response and a later recurrence, 39 patients with 48 loco-regional failures had a recurrence CT scan before any salvage therapy. The estimated point of origin of each recurrence was transferred to the planning CT by deformable image co-registration. The recurrence position was then related to the delineated target volumes and iso-SUV-contours relative to the maximum standard uptake value (SUV). We defined the recurrence density as the total number of recurrences in a sub-volume divided by the sum of that volume for all patients.

RESULTS

54% (95% CI 37-69%) of recurrences originated inside the FDG-positive volume and 96% (95% CI 86-99%) in the high dose region. Recurrence density was significantly higher in the central target volumes (P<0.0001) and increased with increasing FDG avidity (P=0.036).

CONCLUSIONS

The detailed pattern-of-failure data analysis suggests that most recurrences occur in the FDG PET positive areas or the solid tumor.

Failure-probability driven dose painting

PURPOSE

To demonstrate a data-driven dose-painting strategy based on the spatial distribution of recurrences in previously treated patients. The result is a quantitative way to define a dose prescription function, optimizing the predicted local control at constant treatment intensity. A dose planning study using the optimized dose prescription in 20 patients is performed.

METHODS

Patients treated at our center have five tumor subvolumes from the center of the tumor (PET positive volume) and out delineated. The spatial distribution of 48 failures in patients with complete clinical response after (chemo)radiation is used to derive a model for tumor control probability (TCP). The total TCP is fixed to the clinically observed 70% actuarial TCP at five years. Additionally, the authors match the distribution of failures between the five subvolumes to the observed distribution. The steepness of the dose-response is extracted from the literature and the authors assume 30% and 20% risk of subclinical involvement in the elective volumes. The result is a five-compartment dose response model matching the observed distribution of failures. The model is used to optimize the distribution of dose in individual patients, while keeping the treatment intensity constant and the maximum prescribed dose below 85 Gy.

RESULTS

The vast majority of failures occur centrally despite the small volumes of the central regions. Thus, optimizing the dose prescription yields higher doses to the central target volumes and lower doses to the elective volumes. The dose planning study shows that the modified prescription is clinically feasible. The optimized TCP is 89% (range: 82%-91%) as compared to the observed TCP of 70%.

CONCLUSIONS

The observed distribution of locoregional failures was used to derive an objective, data-driven dose prescription function. The optimized dose is predicted to result in a substantial increase in local control without increasing the predicted risk of toxicity.

Preoperative PET/CT in early-stage breast cancer

BACKGROUND

The aim of this study was to assess the diagnostic and therapeutic impact of preoperative positron emission tomography and computed tomography (PET/CT) in the initial staging of patients with early-stage breast cancer.

PATIENTS AND METHODS

A total of 103 consecutive patients with newly diagnosed operable breast cancer with tumors ≥2 cm were independently examined preoperatively with conventional assessment (mammography, breast/axillary ultrasound, chest X-ray and blood samples) and PET/CT with no prior knowledge of the other.

RESULTS

PET/CT identified a primary tumor in all but three patients (97%). PET/CT solely detected distant metastases (ovary, bones and lung) in 6 patients and new primary cancers (ovary, lung) in another two patients, as well as 12 cases of extra-axillary lymph node involvement. In 15 patients (15%), extra-axillary malignancy was detected by PET/CT only, leading to an upgrade of initial staging in 14% (14/103) and ultimately a modification of planned treatment in 8% (8/103) of patients.

CONCLUSIONS

PET/CT is a valuable tool to provide information on extra-axillary lymph node involvement, distant metastases and other occult primary cancers. Preoperative (18)F-fluorodeoxyglucose-PET/CT has a substantial impact on initial staging and on clinical management in patients with early-stage breast cancer with tumors ≥2 cm.

Interobserver delineation variation in lung tumour stereotactic body radiotherapy

OBJECTIVES

In radiotherapy, delineation uncertainties are important as they contribute to systematic errors and can lead to geographical miss of the target. For margin computation, standard deviations (SDs) of all uncertainties must be included as SDs. The aim of this study was to quantify the interobserver delineation variation for stereotactic body radiotherapy (SBRT) of peripheral lung tumours using a cross-sectional study design.

METHODS

22 consecutive patients with 26 tumours were included. Positron emission tomography/CT scans were acquired for planning of SBRT. Three oncologists and three radiologists independently delineated the gross tumour volume. The interobserver variation was calculated as a mean of multiple SDs of distances to a reference contour, and calculated for the transversal plane (SD(trans)) and craniocaudal (CC) direction (SD(cc)) separately. Concordance indexes and volume deviations were also calculated.

RESULTS

Median tumour volume was 13.0 cm(3), ranging from 0.3 to 60.4 cm(3). The mean SD(trans) was 0.15 cm (SD 0.08 cm) and the overall mean SD(cc) was 0.26 cm (SD 0.15 cm). Tumours with pleural contact had a significantly larger SD(trans) than tumours surrounded by lung tissue.

CONCLUSIONS

The interobserver delineation variation was very small in this systematic cross-sectional analysis, although significantly larger in the CC direction than in the transversal plane, stressing that anisotropic margins should be applied. This study is the first to make a systematic cross-sectional analysis of delineation variation for peripheral lung tumours referred for SBRT, establishing the evidence that interobserver variation is very small for these tumours.

A prospective comparison of 18F-FDG PET/CT and CT as diagnostic tools to identify the primary tumor site in patients with extracervical carcinoma of unknown primary site

BACKGROUND

The aim of the present study was to evaluate prospectively the diagnostic value of (18)F-fluorodeoxyglucose positron emission tomography/computed tomography ((18)F-FDG PET/CT) and conventional CT regarding the ability to detect the primary tumor site in patients with extracervical metastases from carcinoma of unknown primary (CUP) site.

PATIENTS AND METHODS

From January 2006 to December 2010, 136 newly diagnosed CUP patients with extracervical metastases underwent (18)F-FDG PET/CT. A standard of reference (SR) was established by a multidisciplinary team to ensure that the same set of criteria were used for classification of patients, that is, either as CUP patients or patients with a suggested primary tumor site. The independently obtained suggestions of primary tumor sites using PET/CT and CT were correlated with the SR to reach a consensus regarding true-positive (TP), true-negative, false-negative, and false-positive results.

RESULTS

SR identified a primary tumor site in 66 CUP patients (48.9%). PET/CT identified 38 TP primary tumor sites and CT identified 43 TP primary tumor sites. No statistically significant differences were observed between (18)F-FDG PET/CT and CT alone in regard to sensitivity, specificity, and accuracy.

CONCLUSION

In the general CUP population with multiple extracervical metastases (18)F-FDG PET/CT does not represent a clear diagnostic advantage over CT alone regarding the ability to detect the primary tumor site.

Standardized FDG uptake as a prognostic variable and as a predictor of incomplete cytoreduction in primary advanced ovarian cancer

INTRODUCTION

In patients with advanced ovarian cancer undergoing preoperative PET/CT, we investigated the prognostic value of SUV in the primary tumor and we evaluated the value of SUV for predicting incomplete primary cytoreduction (macroscopic residual tumor).

MATERIAL AND METHODS

From September 2004 to August 2007, 201 consecutive patients with a pelvic tumor and a Risk of Malignancy Index (RMI) > 150 based on serum CA-125, ultrasound examinations and menopausal state, underwent PET/CT within two weeks prior to standard surgery/debulking of a pelvic tumor. At two-year follow-up (August 15, 2009) the association between SUV and overall survival/cytoreductive result were analyzed in 60 ovarian cancer patients (58 stage III and two stage IV).

RESULTS

At inclusion median age was 62 years (range 35-85 years); 97% (58/60) had a performance status ≤2; 42% (25/60) underwent complete debulking (no macroscopic residual tumor); median SUV(max) was 13.5 (range 2.5-39.0). Median follow-up was 30.2 months. At follow-up 57% (34/60) were alive and 43% (26/60) had died from ovarian cancer. SUV(max) in patients alive was not statistically different from SUV(max) in dead patients (p=0.69), and SUV(max) was not correlated with the amount of residual tumor after surgery (p=0.19). Using univariate Cox regression analysis, residual tumor was a significant prognostic variable (p=0.001); SUV(max) was not a statistically significant prognostic variable (p=0.86).

DISCUSSION

FDG uptake (SUV(max)) in the primary tumor of patients with advanced ovarian cancer was not a prognostic variable and the FDG uptake did not predict complete cytoreduction after primary surgery. Future prospective clinical trials will need to clarify if other PET tracers can serve as prognostic variables in ovarian cancer.

Abstract P5-01-08: Preoperative Positron Emission Tomography/Computed Tomography (PET/CT) and 18F-Fluorodeoxyglucose (18F-FDG) Compared with Conventional Assessment in Patients with Early Primary Breast Cancer: Preliminary Results of a Prospective Study

Background: The prognosis and clinical management of patients with newly diagnosed breast cancer depends on the extent of disease. The aim of this study was to compare the diagnostic and therapeutic impact of preoperative PET/CT, using 18F-FDG in the initial extra-axillary staging of patients with early breast cancer, to the results of conventional assessment. One hundred patients are planned enrolled. We here report the results of the first fifty consecutive patients.

Patients and methods: Fifty consecutive patients with newly diagnosed early operable breast cancer with tumors ≥2 cm were examined preoperatively with conventional assessment (mammography, breast/axilla ultrasound, chest x-ray and blood samples) and PET/CT. Conventional assessment and PET/CT were evaluated independently with no prior knowledge of the other. Distant metastases/new primary cancers found on PET/CT were confirmed histologically, by other imaging modalities or with at least 1 year of follow-up.

Results: The mean age was 56 ± 11 years. PET/CT identified primary tumor in all but two patients (96%). Nine cases of extra-axillary lymph node involvement were solely revealed by PET/CT in the internal mammary chain (n=7) and the supraclavicular region (n=2). Additionally, PET/CT solely detected distant metastasis (ovary, bone) in two patients and new primary cancers (ovary, lung) in another two patients. Two patients (4%) had non-malignant focal uptake of 18F-FDG confirmed with histologic biopsies (schwannoma, colon adenoma).

In 12 patients (24%) extra-axillary malignancy was detected by PET/CT only, leading to an upgrade of initial staging in 20% (10/50) of patients and ultimately a modification of planned treatment in 4 (8%) patients. No patient was down staged by PET/CT.

Conclusion: PET/CT is a valuable tool to provide information on extra-axillary lymph node involvement, distant metastases and other occult primary cancers. Preoperative 18F-FDG-PET/CT has a substantially impact on initial staging and on clinical management in patients with early stage breast cancer.

Citation Information: Cancer Res 2010;70(24 Suppl):Abstract nr P5-01-08.

Methodologies for localizing loco-regional hypopharyngeal carcinoma recurrences in relation to FDG-PET positive and clinical radiation therapy target volumes

BACKGROUND

Focal methods to determine the source of recurrence are presented, tested for reproducibility and compared to volumetric approaches with respect to the number of recurrences ascribed to the FDG-PET positive and high dose volumes.

MATERIAL AND METHODS

Six patients treated for hypopharyngeal squamous cell carcinoma were extracted from archives. Inclusion criteria were: FDG-PET/CT for primary radiotherapy planning and clinical complete remission followed by loco-regional relapse. CT scan at the time of recurrence was also required. The recurrence volume was delineated in the follow-up scans by a radiologist. Putative points of origin (PO) of the recurrence were determined by two strategies 1) defined by an oncologist or 2) as the center-of-volume (COV) of the recurrence. The most likely recurrence point of origin on the treatment planning scan was also determined. All expert based points of origin were repeated to estimate reproducibility. The recurrence volume and PO were propagated to the treatment planning scan using a rigid transformation. Relations of the PO to target volumes, radiation doses and therapy-points-of-origin were quantified. For the volumetric methods, the overlap of the recurrence volume and target volumes was used to determine the source of the recurrence.

RESULTS

All recurrences were located in-field, but the volumetric approaches tended to designate fewer recurrences in the PET positive volume (25% for the 95% threshold, 95% confidence interval (CI):3-65%) than the observer-based methods (50% for the COV and both expert evaluations on the recurrence scan, 95% CI: 16-84%). The reproducibility of the expert POs is better on the recurrence scan than on the therapy scan.

CONCLUSION

Volumetric approaches favor large target volumes as the source of the recurrence, thus underestimating the number of recurrences originating in the PET positive volume. Expert based and COV approaches on the recurrence scan are the most reproducible methods to determine the PO.

Nasopharyngeal carcinoma. Treatment planning with IMRT and 3D conformal radiotherapy

The study was undertaken in order to compare dose plans for intensity-modulated radiotherapy (IMRT) with 3D conformal radiotherapy (3D-CRT) dose plans in patients with nasopharyngeal carcinoma (NPC). Clinical data from 20 consecutive patients treated with IMRT are presented. For 11 patients 3D-CRT plans were made and compared to the IMRT plans with respect to doses to the planning target volumes (PTVs) and to organs at risk (OARs). For comparison of the conformation of dose to defined target volumes the conformity index (CI) was used. Target volume coverage and critical organ protection were significantly improved with IMRT compared to 3D-CRT. One-year loco-regional control, distant metastasis-free survival, and overall survival were 79%, 72%, and 80%. Two patients have had recurrence in the clinical target volume (CTV) only and seven patients have relapsed in distant organs and/or in head-and-neck areas outside the target areas. The study confirms that IMRT is superior to 3D-CRT in the treatment of NPC. As locoregional control of NPC improves we are facing an increasing number of recurrences outside the irradiated area.

PET/CT and histopathologic response to preoperative chemoradiation therapy in locally advanced rectal cancer

PURPOSE

The objective of this study was to investigate the possibility of using positron emission tomography/computer tomography to predict the histopathologic response in locally advanced rectal cancer treated with preoperative chemoradiation.

METHODS

The study included 30 patients with locally advanced rectal adenocarcinoma treated with a combination of radiotherapy and concurrent Uftoral (uracil, tegafur) and leucovorine. All patients were evaluated by positron emission tomography/computer tomography scan seven weeks after end of chemoradiation, and the results were compared to histopathologic tumor regression as the "standard." The pathologic response was quantified by tumor regression grade.

RESULTS

Positron emission tomography/computer tomography correctly identified six of eight patients (specificity 75 percent) with complete pathologic response. However, the sensitivity of positron emission tomography/computer tomography was only 45 percent and the accuracy 53 percent. The positive and negative predictive values were 83 and 33 percent, respectively.

CONCLUSIONS

We conclude that positron emission tomography/computer tomography performed seven weeks after the end of chemoradiation is not able to predict the histopathologic response in locally advanced rectal cancer. There is an obvious need for other complementary methods especially with respect to the low sensitivity of positron emission tomography/computer tomography.

Prediction of suboptimal primary cytoreduction in primary ovarian cancer with combined positron emission tomography/computed tomography--a prospective study

OBJECTIVE

To prospectively identify combined PET/CT predictors of incomplete/suboptimal primary cytoreduction in advanced ovarian cancer.

METHODS

From September 2004 to March 2007, 179 patients with a Risk of Malignancy Index (RMI) >150 based on serum CA-125, ultrasound examinations and menopausal state, underwent PET/CT within 2 weeks prior to standard surgery/debulking of a pelvic tumor. Ten PET/CT features were identified and evaluated as predictors of cytoreduction in 54 patients with advanced ovarian cancer.

RESULTS

Complete cytoreduction (no macroscopic residual disease) was achieved in 35% and optimal cytoreduction (<1 cm residual disease) was achieved in 56%. Using univariate analysis, predictors of incomplete cytoreduction were large bowel mesentery implants (LBMI) (P<0.003), pleural effusion (P<0.009), ascites (P<0.009) and peritoneal carcinosis (P<0.01). LBMI (P<0.03) and ascites (P<0.05) were also predictors of suboptimal cytoreduction. Using multivariate analysis, LBMI was the only independent predictor of incomplete cytoreduction (P=0.004) and no predictor of suboptimal cytoreduction was found.

CONCLUSION

PET/CT predictors of cytoreduction were found. But they should not be used to withhold patients form primary cytoreductive surgery. We suggest PET/CT as a supplementary image modality prior to surgery in primary OC patients whenever accurate and comprehensive preoperative evaluation of primary tumor and metastases is desired.

Contrast-enhanced FDG-PET/CT vs. SPIO-enhanced MRI vs. FDG-PET vs. CT in patients with liver metastases from colorectal cancer: a prospective study with intraoperative confirmation

BACKGROUND

The choice of imaging before liver surgery is debated regarding the use of magnetic resonance (MR) imaging, computed tomography (CT), and positron emission tomography (PET). No studies have compared contrast-enhanced PET/CT with superparamagnetic iron oxide (SPIO)-enhanced MR imaging.

PURPOSE

To compare PET/CT with superparamagnetic iron oxide (SPIO)-enhanced MR imaging, PET, and CT in the detection of liver metastases (LM) and extrahepatic tumor from colorectal cancer (CRC).

MATERIAL AND METHODS

Thirty-five patients with suspected LM underwent PET/CT with a contrast-enhanced CT protocol and SPIO-enhanced MR imaging. Readers independently analyzed images from MR imaging, PET/CT, and the CT part and PET part of the PET/CT study. Imaging findings were compared with surgical and histological findings.

RESULTS

Lesion-by-lesion sensitivity and accuracy for liver lesions was 54% and 77% for PET alone, 66% and 83% for PET/CT, 82% and 82% for SPIO-enhanced MR imaging, and 89% and 77% for CT alone, respectively. CT and SPIO-enhanced MR imaging were less specific but significantly more sensitive than PET (P<0.0001). For extrahepatic tumor, sensitivity and specificity was 83% and 96% for PET/CT and 58% and 87% for CT, respectively.

CONCLUSION

CT and SPIO-enhanced MR imaging are more sensitive but less specific than PET in the detection of LM. PET/CT can detect more patients with extrahepatic tumor than CT alone.

The diagnostic value of PET/CT for primary ovarian cancer—A prospective study

OBJECTIVES

To prospectively evaluate the diagnostic value of combined PET/CT in detecting a malignant tumor in patients with no previous cancer history, presenting with a pelvic mass.

METHODS

From September 2004 to March 2006, 101 patients (median age=60 years, range=24-85 years) with a Risk of Malignancy Index (RMI)>150 based on serum CA-125, ultrasound examinations (US) and menopausal state, were referred to PET/CT within 2 weeks prior to standard surgery/debulking of a pelvic tumor. Histological specimens from 97 patients were evaluated and the histological diagnoses were compared to the PET/CT results to calculate the diagnostic value of PET/CT in differentiating between malignant and borderline/benign tumors. Four patients refrained from surgery or biopsy.

RESULTS

The average serum CA-125 in the 97 studied patients was 784 U/ml (range=22-9665 U/ml). PET/CT demonstrated areas of abnormally increased metabolic activity considered highly suspicious for malignant tumor in 60 patients (62%). In 37 patients (38%) the tumors were considered benign on PET/CT. Histopathology showed benign tumors in 40 patients and malignant tumors in 57 patients. The sensitivity and specificity for PET/CT in diagnosing a malignant pelvic tumor were 100% (57/57) and 92.5% (37/40), respectively (P<0.00005).

CONCLUSION

Combined PET/CT demonstrates high diagnostic value in identifying primary ovarian cancer in patients with a pelvic mass of unknown origin and RMI>150. We suggest PET/CT as the image modality of choice when US shows a pelvic tumor and additional information prior to surgery is needed.

A prospective study of PET/CT in initial staging of small-cell lung cancer: comparison with CT, bone scintigraphy and bone marrow analysis

BACKGROUND

Small-cell lung cancer (SCLC) accounts for 15%-20% of all lung cancer cases. Accurate and fast staging is mandatory when choosing treatment, but current staging procedures are time consuming and lack sensitivity.

PATIENTS AND METHODS

A prospective study was designed to examine the role of combined positron emission tomography/computed tomography (PET/CT) compared with standard staging (CT, bone scintigraphy and immunocytochemical assessment of bone marrow biopsy) of patients with SCLC. Thirty-four consecutive patients were included. Twenty-nine patients received initial PET/CT.

RESULTS

PET/CT caused change of stage in 5/29 (17%). Excluding patients with unconfirmed findings or pleural effusion, the sensitivity for accurate staging of patients with extensive disease was the following: for standard staging 79%, PET 93% and PET/CT 93%. Specificity was 100%, 83% and 100%, respectively.

CONCLUSION

The results from this first study on PET/CT in SCLC indicates that PET/CT can simplify and perhaps even improve the accuracy of the current staging procedure in SCLC. A larger clinical trial, preferably with consequent histological confirmation in case of discordance, however, is warranted.

PET/CT imaging in response evaluation of patients with small cell lung cancer

There is an increasing amount of evidence on the usability of PET in response evaluation of non-small cell lung cancer. However, data on SCLC is scarce and mainly retrospective. This prospective study assesses the use of PET (positron emission tomography) and PET/CT in response evaluation of patients with small cell lung cancer (SCLC).

METHODS

Assignment of early and final response was compared between PET, PET/CT, and CT in 20 patients with SCLC. Final response as assigned by CT (RECIST) served as reference.

RESULTS

At response evaluation after one cycle of chemotherapy major disagreement (responder versus non-responder) between PET and CT in predicting final response was seen in 1 of 12 patients. At final response evaluation major disagreement between PET, PET/CT and CT was seen in 2 of 19 patients (11%). All measurements of FDG-uptake were significantly correlated to size and changes in size as measured by CT. A significant difference in relative change in tumour FDG-uptake and volume was found between responding and non-responding patients. No significant difference was found between a visual and semi-quantitative analysis of PET.

CONCLUSION

Response evaluation of SCLC by PET/CT is feasible, but it is uncertain whether it adds further information to evaluation by RECIST, thus further studies and standardization of methods are needed.

PET/CT with intravenous contrast can be used for PET attenuation correction in cancer patients

PURPOSE

If the CT scan of a combined PET/CT study is performed as a full diagnostic quality CT scan including intravenous (IV) contrast agent, the quality of the joint PET/CT procedure is improved and a separate diagnostic CT scan can be avoided. CT with IV contrast can be used for PET attenuation correction, but this may result in a bias in the attenuation factors. The clinical significance of this bias has not been established. Our aim was to perform a prospective clinical study where each patient had CT performed with and without IV contrast agent to establish whether PET/CT with IV contrast can be used for PET attenuation without reducing the clinical value of the PET scan.

METHODS

A uniform phantom study was used to document that the PET acquisition itself is not significantly influenced by the presence of IV contrast medium. Then, 19 patients referred to PET/CT with IV contrast underwent CT scans without, and then with contrast agent, followed by an 18F-fluorodeoxyglucose whole-body PET scan. The CT examinations were performed with identical parameters on a GE Discovery LS scanner. The PET data were reconstructed with attenuation correction based on the two CT data sets. A global comparison of standard uptake value (SUV) was performed, and SUVs in tumour, in non-tumour tissue and in the subclavian vein were calculated. Clinical evaluation of the number and location of lesions on all PET/CT scans was performed twice, blinded and in a different random order, by two independent nuclear medicine specialists.

RESULTS

In all patients, the measured global SUV of PET images based on CT with IV contrast agent was higher than the global activity using non-contrast correction. The overall increase in the mean SUV (for two different conversion tables tested) was 4.5+/-2.3% and 1.6+/-0.5%, respectively. In 11/19 patients, focal uptake was identified corresponding to malignant tumours. Eight out of 11 tumours showed an increased SUVmax (2.9+/-3.1%) on the PET images reconstructed using IV contrast. The clinical evaluation performed by the two specialists comparing contrast and non-contrast CT attenuated PET images showed weighted kappa values of 0.92 (doctor A) and 0.82 (doctor B). No contrast-introduced artefacts were found.

CONCLUSION

This study demonstrates that CT scans with IV contrast agent can be used for attenuation correction of the PET data in combined modality PET/CT scanning, without changing the clinical diagnostic interpretation.