Prediction of response to neoadjuvant chemotherapy by sequential F-18-fluorodeoxyglucose positron emission tomography in patients with advanced-stage ovarian cancer

PET/CT imaging in gynecologic malignancies: a critical overview of its clinical impact and our retrospective single center analysis

Gynecologic cancers represent a major global healthcare problem since they are associated with a significant mortality and morbidity. Over the last decade, considerable efforts have been spent in the development and optimization of novel diagnostic modalities to achieve an early diagnosis, aid in choosing appropriate treatment, improving long term surveillance, with the ultimate goal of increasing survival of gynecologic cancer patients. A growing body of evidence defines PET/CT as one of the most powerful tools for tumor, nodal and metastasis (TNM) cancer staging both in pre-treatment and in post treatment follow-up settings. At any phase of cancer evaluation, detection of metastasis represents one of the most critical impediments to the cure of tumor; traditional diagnostic imaging modalities, such as computed tomography (CT), are frequently found to inadequately stage the tumor, based on subsequent outcomes. As a consequence, patients may undergo pointless surgery for disease that could be treated with local medical therapies. In the setting of restaging, the ability to describe primary lesion, lymph nodes, possible metastases to peritoneum, bone, liver, lungs and brain renders PET/CT a potential alternative for a series of tests, including bone scanning, MRI or ultrasound, diagnostic CT, lymph node surgical sampling, that need to be used in combination in order to obtain a level of clinical confidence. In this review, we describe, the theoretical advantage and prognostic implications of PET/CT in the management of gynecologic cancer patients.

Preoperative [F]FDG PET/CT predicts recurrence in patients with epithelial ovarian cancer

OBJECTIVE

To determine whether [(18)F]FDG uptake on PET/CT imaging before surgical staging has prognostic significance in patients with epithelial ovarian cancer (EOC).

METHODS

Patients with EOC were imaged with integrated PET/CT before surgical staging. Hypermetabolic lesions were measured as the standardized uptake value (SUV) in primary and metastatic tumors. SUV distribution was divided into two regions at the level of umbilicus, and the impact of the ratio between above and below umbilicus (SUV(location) ratio) on progression-free survival (PFS) was examined using Cox proportional hazards regression.

RESULTS

Between January 2004 and December 2009, 55 patients with EOC underwent preoperative PET/CT. The median duration of PFS was 11 months (range, 3 to 43 months), and twenty (36.4%) patients experienced recurrence. In univariate analysis, high SUV(location) ratio (p=0.002; hazard ratio [HR], 1.974; 95% confidence interval [CI], 1.286 to 3.031) was significantly associated with recurrence. Malignant mixed mullerian tumor compared with endometrioid histology was also shown to have significance. In multivariate analysis, high SUV(location) ratio (p=0.005; HR, 2.418; 95% CI, 1.1315 to 4.447) and histology (serous, mucinous, and malignant mixed mullerian tumor compared with endometrioid type) were significantly associated with recurrence. Patients were categorized into two groups according to SUV(location) ratio (<0.3934 vs. ≥0.3934), and the Kaplan-Meier survival graph showed a significant difference in PFS between the groups (p=0.0021; HR, 9.47, log-rank test).

CONCLUSION

SUV distribution showed a significant association with recurrence in patients with EOC, and may be a useful predictor of recurrence.

Serum HE4 Profile During Primary Chemotherapy of Epithelial Ovarian Cancer

OBJECTIVE

Human epididymis protein 4 (HE4) is a promising novel serum biomarker for the detection of early-stage epithelial ovarian cancer (EOC) and for the differential diagnosis between benign and malignant ovarian tumors. The objective of the present study was to determine the value of HE4 for monitoring the response to primary therapy in patients with advanced disease.

METHODS

Serum HE4 and cancer antigen (CA) 125 levels of 10 patients with advanced EOC and one patient with adenocarcinoma of unknown origin were measured preoperatively and during first-line chemotherapy. Seven patients were treated with primary surgery and six cycles of chemotherapy. Response to treatment was evaluated 4 weeks after the completion of chemotherapy using computed tomography. Four patients received neoadjuvant chemotherapy (NACT) before surgery. To evaluate the early response to chemotherapy, changes in serum biomarker levels were compared with metabolic changes of tumors during NACT as detected by positron emission tomography/computed tomography.

RESULTS

The profile of HE4 during primary chemotherapy was in line with radiologic and clinical responses. In the neoadjuvant chemotherapy group, HE4 correlated better with the radiologic response than CA 125.

CONCLUSION

Assessment of serum HE4 may improve the reliability of response evaluation during chemotherapy for serous epithelial ovarian cancer.

Prognostic significance of mediastinal 18F-FDG uptake in PET/CT in advanced ovarian cancer

PURPOSE

To evaluate the prognostic significance of increased mediastinal (18)F-FDG uptake in PET/CT for the staging of advanced ovarian cancer.

METHODS

We retrospectively evaluated patients managed for FIGO stage III/IV ovarian cancer between 1 January 2006 and 1 June 2009. Patients were included if they had undergone (18)F-FDG PET/CT and surgery for initial staging. Exclusion criteria were age younger than 18 years, inability to undergo general anaesthesia, recurrent ovarian cancer, and borderline or nonepithelial malignancy. Whole-body PET/CT was performed after intravenous (18)F-FDG injection. The location of abnormal hot spots and (18)F-FDG maximal standard uptake values (SUV(max)) were recorded. We compared the complete cytoreduction and survival rates in groups defined based on mediastinal (18)F-FDG uptake and SUV(max) values. Kaplan-Meier curves of overall survival and disease-free survival were compared using the log-rank test. Hazard ratios with their 95% confidence intervals were computed. Adjusted hazard ratios were obtained using a multivariate Cox model.

RESULTS

We included 53 patients, of whom 17 (32%) had increased mediastinal (18)F-FDG uptake. Complete cytoreduction was achieved in 14 (87.5%) of the 16 patients managed with primary surgery and in 21 (75%) of the 28 patients managed with interval surgery. Complete cytoreduction was achieved significantly more often among patients without increased mediastinal (18)F-FDG uptake (80.6% vs. 35.3%; p = 0.001). Disease-free survival was comparable between the two groups. By univariate analysis, overall mortality was significantly higher among patients with increased mediastinal (18)F-FDG uptake (hazard ratio 5.70, 95% confidence interval 1.74-18.6). The only factor significantly associated with overall survival by multivariate analysis was complete cytoreduction (adjusted hazard ratio 0.24, 95% confidence interval 0.07-0.89).

CONCLUSION

Increased mediastinal (18)F-FDG uptake was common in patients with advanced ovarian cancer. However, complete cytoreduction, which was significantly more frequent among patients without mediastinal (18)F-FDG uptake, was the only factor independently associated with survival.

PET/CT allows stratification of responders to neoadjuvant chemotherapy for high-grade sarcoma: a prospective study

PURPOSE

The aim of the present study was to determine whether metabolic reduction is capable of reflecting the histopathologic response and outcome after neoadjuvant chemotherapy in patients with high-grade sarcoma.

PATIENTS AND METHODS

Forty-two patients with histologically proven high-grade sarcoma underwent neoadjuvant chemotherapy followed by surgical resection. Quantitative F-18 fluorodeoxyglucose (F-18-FDG) positron emission tomography (PET)/computed tomography scans were acquired before and after the first cycle and after completion of neoadjuvant chemotherapy. Standardized uptake values (SUVs) and metabolic reduction rates were compared with histopathologic response, progression-free survival, and overall survival.

RESULTS

Baseline SUVmax was 10.9 ± 3.6 (range, 3.8-19.6). Therapeutic effect resulted in 10 patients (24%) with a satisfactory response and in 32 patients (76%) with an unsatisfactory response after completion of neoadjuvant chemotherapy. The SUV decreased to 7.8 ± 3.4 after the first cycle (t1) of chemotherapy and to 5.2 ± 3.4 after completion (t2) of chemotherapy. Histopathologic response and percentage SUV (t2) reduction rate were independent predictors of progression-free survival and overall survival in the multivariate analyses.

CONCLUSION

Metabolic reduction after neoadjuvant chemotherapy evaluated by F-18 FDG PET or computed tomography can be used for stratification of the histopathologic response in patients with high-grade sarcoma.

MR-PET fusion imaging in evaluating adnexal lesions: a preliminary study

PURPOSE

The objective of this preliminary study was to examine the effects of combined magnetic resonance/positron emission tomography (MR-PET) evaluation in the morphofunctional characterisation of ovarian lesions.

MATERIALS AND METHODS

From June 2008 to September 2010, we evaluated 24 patients (mean age 44±10 years; range 24-74) with ovarian lesions incidentally detected on ultrasonography (US) and/or multislice computed tomography (CT). All patients underwent MR imaging of the pelvis and total-body CT-PET. PET and MR images were subsequently fused at postprocessing using specific anatomical criteria. Results were compared with the histological examination.

RESULTS

Of the 24 examined lesions, 19 were malignant and five were benign on histological examination. MR, CT-PET and MR-PET sensitivity was 84%, 74% and 94%, respectively and specificity 60%, 80% and 100%, respectively. Positive (PPV) and negative predictive (NPV) values were 93% and 44% for CT-PET, 89% and 50% for MR and 100% and 83% for MR-PET, respectively.

CONCLUSIONS

Pelvic MR-PET fusion imaging provides advantages in terms of sensitivity and especially specificity compared with MR imaging or CT-PET alone. The added value of this fusion imaging modality lies in combining the benefits of the morphological evaluation provided by MR imaging and the metabolic assessment provided by PET.

Repeatability of SUV measurements in serial PET

PURPOSE

The standardized uptake value (SUV) is a quantitative measure of FDG tumor uptake frequently used as a tool to monitor therapeutic response. This study aims to (i) assess the reproducibility and uncertainty of SUV max and SUV mean, due to purely statistical, i.e., nonbiological, effects and (ii) to establish the minimum uncertainty below which changes in SUV cannot be expected to be an indicator of physiological changes.

METHODS

Three sets of measurements were made using a GE Discovery STE PET/CT Scanner in 3D mode: (1) A uniform 68Ge 20 cm diameter cylindrical phantom was imaged. Thirty serial frames were acquired for durations of 3, 6, 10, 15, and 30 min. (2) Esser flangeless phantom (Data Spectrum, approximately 6.1 L) with fillable thin-walled cylinders inserts (diameters: 8, 12, 16, and 25 mm; height: approximately 3.8 mm) was scanned for five consecutive 3 min runs. The cylinders were filled with 18FDG with a 37 kBq/cc concentration, and with a target-to-background ratio (T/BKG) of 3/1. (3) Eight cancer patients with healthy livers were scanned approximately 1.5 h post injection. Three sequential 3 min scans were performed for one bed position covering the liver, with the patient and bed remaining at the same position for the entire length of the scan. Volumes of interest were drawn on all images using the corresponding CT and then transferred to the PET images. For each study (1-3), the average percent change in SUV mean and SUV max were determined for each run pair. Moreover, the repeatability coefficient was calculated for both the SUV mean and SUV max for each pair of runs. Finally, the overall ROI repeatability coefficient was determined for each pair of runs.

RESULTS

For the 68Ge phantom the average percent change in SUV max and SUV mean decrease as a function of increasing acquisition time from 4.7 +/- 3.1 to 1.1 +/- 0.6%, and from 0.14 +/- 0.09 to 0.04 +/- 0.03%, respectively. Similarly, the coefficients of repeatability also decrease between the 3 and 30 min acquisition scans, in the range of 10.9 +/- 3.9% - 2.6 +/- 0.9%, and 0.3 +/- 0.1% - 0.10 +/- 0.04%, for the SUV max and SUV mean, respectively. The overall ROI repeatability decreased from 18.9 +/- 0.2 to 6.0 +/- 0.1% between the 3 and 30 min acquisition scans. For the l8FDG phantom, the average percent change in SUV max and SUV mean decreases with target diameter from 3.6 +/- 2.0 to 1.5 +/- 0.8% and 1.5 +/- 1.3 to 0.26 +/- 0.15%, respectively, for targets from 8-25 mm in diameter and for a region in the background (BKG). The coefficients of repeatability for SUV max and SUV mean also decrease as a function of target diameter from 7.1 +/- 2.5 to 2.4 +/- 0.9 and 4.2 +/- 1.5 to 0.6 +/- 0.2, respectively, for targets from 8 mm to BKG in diameter. Finally, overall ROI repeatability decreased from 12.0 +/- 4.1 to 13.4 +/- 0.5 targets from 8 mm to BKG in diameter. Finally, for the measurements in healthy livers the average percent change in SUVmax and SUV mean were in the range of 0.5 +/- 0.2% - 6.2 +/- 3.9% and 0.4 +/- 0.1 and 1.6 +/- 1%, respectively. The coefficients of repeatability for SUV max and SUV men are in the range of 0.6 +/- 0.7% - 9.5 +/- 12% and 0.6 +/- 0.7% - 2.9 +/- 3.6%, respectively. The overall target repeatability varied between 27.9 +/- 0.5% and 41.1 +/- 1.0%.

CONCLUSIONS

The statistical fluctuations of the SUV mean are half as large as those of the SUV max in the absence of biological or physiological effects. In addition, for clinically applicable scan durations (i.e., approximately 3 min) and FDG concentrations, the SUV max and SUV mean have similar amounts of statistical fluctuation for small regions. However, the statistical fluctuations of the SUVmean rapidly decrease with respect tothe SUVmax as the statistical power of the data grows either due to longer scanning times or as the target regions encompass a larger volume.

Interleukin-6 as a therapeutic target in human ovarian cancer

PURPOSE

We investigated whether inhibition of interleukin 6 (IL-6) has therapeutic activity in ovarian cancer via abrogation of a tumor-promoting cytokine network.

EXPERIMENTAL DESIGN

We combined preclinical and in silico experiments with a phase 2 clinical trial of the anti-IL-6 antibody siltuximab in patients with platinum-resistant ovarian cancer.

RESULTS

Automated immunohistochemistry on tissue microarrays from 221 ovarian cancer cases showed that intensity of IL-6 staining in malignant cells significantly associated with poor prognosis. Treatment of ovarian cancer cells with siltuximab reduced constitutive cytokine and chemokine production and also inhibited IL-6 signaling, tumor growth, the tumor-associated macrophage infiltrate and angiogenesis in IL-6-producing intraperitoneal ovarian cancer xenografts. In the clinical trial, the primary endpoint was response rate as assessed by combined RECIST and CA125 criteria. One patient of eighteen evaluable had a partial response, while seven others had periods of disease stabilization. In patients treated for 6 months, there was a significant decline in plasma levels of IL-6-regulated CCL2, CXCL12, and VEGF. Gene expression levels of factors that were reduced by siltuximab treatment in the patients significantly correlated with high IL-6 pathway gene expression and macrophage markers in microarray analyses of ovarian cancer biopsies.

CONCLUSION

IL-6 stimulates inflammatory cytokine production, tumor angiogenesis, and the tumor macrophage infiltrate in ovarian cancer and these actions can be inhibited by a neutralizing anti-IL-6 antibody in preclinical and clinical studies.

Sequential FDG-PET/CT as a biomarker of response to Sunitinib in metastatic clear cell renal cancer

PURPOSE

To test the hypothesis that sequential (18)F-fluorodeoxyglucose-positron emission tomography/computed tomography (FDG-PET/CT) is a correlative marker in metastatic clear cell renal cancer (mRCC), patients were treated with sunitinib. Three sequential scans were conducted to determine whether the timing of the investigation was relevant.

EXPERIMENTAL DESIGN

Forty-four untreated mRCC patients were enrolled into this prospective phase II study. (18)F-FDG-PET/CT scans were conducted before (n = 44) and after 4 weeks (n = 43) and 16 weeks (n = 40) of sunitinib given at standard doses. The primary endpoint was to correlate FDG-PET/CT response (20% reduction in SUV(max)) at 4 and 16 weeks with overall survival (OS).

RESULTS

Forty-three (98%) patients had FDG-PET/CT avid lesions at diagnosis (median SUV(max) = 6.8, range: <2.5-18.4). In multivariate analysis, a high SUV(max) and an increased number of PET-positive lesions correlated with shorter OS [HR: 3.30 (95% CI: 1.36-8.45) and 3.67 (95% CI: 1.43-9.39), respectively]. After 4 weeks of sunitinib, a metabolic response occurred in 24 (57%) patients, but this did not correlate with progression-free survival (HR for responders = 0.87; 95% CI: 0.40-1.99) or OS (HR for responders = 0.80; 95% CI: 0.34-1.85). After 16 weeks of treatment, disease progression on FDG-PET/CT occurred in 28% (n = 12) patients which correlated with a decreased OS and PFS [HR = 5.96 (95% CI: 2.43-19.02) and HR = 12.13 (95% CI: 3.72-46.45), respectively].

CONCLUSIONS

Baseline FDG-PET/CT yields prognostic significant data. FDG-PET/CT responses occur in the majority of patients after 4 weeks of therapy; however, it is not until 16 weeks when the results become prognostically significant.

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.

Metabolomics in urogenital cancer

Although in recent decades the development of many drugs against cancer has been witnessed, the morbidity and mortality for the most prevalent urogenital cancer have not been significantly reduced. A key task in cancer medicine is to detect the disease as early as possible. In order to achieve this, many new technologies have been developed for cancer biomarker discovery. Monitoring fluctuations of certain metabolite levels in body fluids, such as urine, has become an important way to detect early stages in carcinogenesis. Moreover metabolomic approaches are likely to be used to screen for potential diagnostic and prognostic biomarkers of urogenital cancer. In future work, these potential biomarkers should be further validated with a large enough patient cohort to achieve earlier diagnosis not only of urogenital cancer, but also other malignancies. Moreover, the improvement of patient prognosis will be another aim of such investigations. This novel metabolomic approach has the potential to provide more information about the pathophysiological status of an organism and distinguish precancerous and cancerous stages.

Assessment of tumoricidal efficacy and response to treatment with 18F-FDG PET/CT after intraarterial infusion with the antiglycolytic agent 3-bromopyruvate in the VX2 model of liver tumor

The purpose of this study was to determine the effects of 3-bromopyruvate (3-BrPA) on tumor glucose metabolism as imaged with (18)F-FDG PET/CT at multiple time points after treatment and compare them with those after intraarterial control injections of saline.

METHODS

Twenty-three New Zealand White rabbits implanted intrahepatically with VX2 tumors were assigned to 1 of 2 groups: 14 rabbits were assigned to the treatment group (TG) and 9 to the saline control group (SG). All animals were infused with 25 mL of either 1.75 mM 3-BrPA or saline over 1 h via a 2-French catheter, which was secured in the hepatic artery. For PET/CT, the animals were injected with 37 MBq of (18)F-FDG at 1 d before treatment and 2 h, 24 h, and 1 wk after treatment. Tumor size, tumor and liver maximal standardized uptake value (SUV(max)), and tumor-to-background ratios were calculated for all studies. Seven TG and 5 SG animals were sacrificed at 1 wk after treatment for histopathologic analysis.

RESULTS

Intense (18)F-FDG uptake was seen in untreated tumors. A significant reduction in tumor SUV(max) was noted in TG animals, when compared with SG animals, at 1 wk after treatment (P = 0.006). The tumor-to-liver background ratio in the TG animals, compared with the SG animals, was significantly reduced as early as 24 h after treatment (P = 0.01) and remained reduced at 1 wk (P = 0.003). Tumor SUV(max) increased from the baseline levels at 7 d in controls (P = 0.05). The histopathologic analysis of explanted livers revealed increased tumor necrosis in all TG samples. There was a significant inverse correlation (r(2) = 0.538, P = 0.005) between the percentage of tumor necrosis on histopathology and tumor SUV(max) on (18)F-FDG PET at 7 d after treatment with 3-BrPA.

CONCLUSION

Intraarterial injection of 3-BrPA resulted in markedly decreased (18)F-FDG uptake as imaged by PET/CT and increased tumor necrosis on histopathology at 1 wk after treatment in the VX2 rabbit liver tumor. PET/CT appears to be a useful means to follow antiglycolytic therapy with 3-BrPA.

Potential role of coregistered photoacoustic and ultrasound imaging in ovarian cancer detection and characterization

Currently, there is no adequate technology to detect early stage ovarian cancers. Most of the cancers in the ovary are detected when the cancer has already metastasized to other parts of the body. As a result, ovarian cancer has the highest mortality of all gynecologic cancers with a 5-year survival rate of 30% or less. Thus, there is an urgent need to improve the current diagnostic techniques. Photoacoustic imaging (PAI) is an emerging modality with a great potential to assist ultrasound for detecting ovarian cancer noninvasively. In this article, we report the first study of coregistered ultrasound and PAI of 33 ex vivo human ovaries. An assessment of the photoacoustic images has revealed light absorption distribution in the ovary, which is directly related to the vasculature distribution and amount. Quantification of the light absorption levels in the ovary has indicated that, in the postmenopausal group, malignant ovaries showed significantly higher light absorption than normal ones (P = .0237). For these two groups, we have obtained a sensitivity of 83% and a specificity of 83%. This result suggests that PAI is a promising modality for improving ultrasound diagnosis of ovarian cancer.

Metabolic imaging allows early prediction of response to vandetanib

The RET (rearranged-during-transfection protein) protooncogene triggers multiple intracellular signaling cascades regulating cell cycle progression and cellular metabolism. We therefore hypothesized that metabolic imaging could allow noninvasive detection of response to the RET inhibitor vandetanib in vivo.

METHODS

The effects of vandetanib treatment on the full-genome expression and the metabolic profile were analyzed in the human medullary thyroid cancer cell line TT. In vitro, transcriptional changes of pathways regulating cell cycle progression and glucose, dopa, and thymidine metabolism were correlated to the results of cell cycle analysis and the uptake of (3)H-deoxyglucose, (3)H-3,4-dihydroxy-L-phenylalanine, and (3)H-thymidine under vandetanib treatment. In vivo, the tumor metabolism under vandetanib was monitored by small-animal PET of tumor-bearing mice.

RESULTS

Vandetanib treatment resulted in the transcriptional downregulation of various effector pathways with consecutive downregulation of cyclin expression and a G(0)/G(1) arrest. In vitro, vandetanib treatment resulted in the decreased expression of genes regulating glucose, 3,4-dihydroxy-L-phenylalanine, and thymidine metabolism, with a subsequent reduction in the functional activity of the corresponding pathways. In vivo, metabolic imaging with PET was able to assess changes in the tumoral glucose metabolism profile as early as 3 d after initiation of vandetanib treatment.

CONCLUSION

We describe a metabolic imaging approach for the noninvasive detection of successful vandetanib treatment. Our results suggest that PET may be useful for identifying patients who respond to vandetanib early in the course of treatment.

Instrumentation factors affecting variance and bias of quantifying tracer uptake with PET/CT

PURPOSE

The variances and biases inherent in quantifying PET tracer uptake from instrumentation factors are needed to ascertain the significance of any measured differences such as in quantifying response to therapy. The authors studied the repeatability and reproducibility of serial PET measures of activity as a function of object size, acquisition, reconstruction, and analysis method on one scanner and at three PET centers using a single protocol with long half-life phantoms.

METHODS

The authors assessed standard deviations (SDs) and mean biases of consecutive measures of PET activity concentrations in a uniform phantom and a NEMA NU-2 image quality (IQ) phantom filled with 9 months half-life 68Ge in an epoxy matrix. Activity measurements were normalized by dividing by a common decay corrected true value and reported as recovery coefficients (RCs). Each experimental set consisted of 20 consecutive PET scans of either a stationary phantom to evaluate repeatability or a repositioned phantom to assess reproducibility. One site conducted a comprehensive series of repeatability and reproducibility experiments, while two other sites repeated the reproducibility experiments using the same IQ phantom. An equation was derived to estimate the SD of a new PET measure from a known SD based on the ratios of available coincident counts between the two PET measures.

RESULTS

For stationary uniform phantom scans, the SDs of maximum RCs were three to five times less than predicted for uncorrelated pixels within circular regions of interest (ROIs) with diameters ranging from 1 to 15 cm. For stationary IQ phantom scans from 1 cm diameter ROIs, the average SDs of mean and maximum RCs ranged from 1.4% to 8.0%, depending on the methods of acquisition and reconstruction (coefficients of variation range 2.5% to 9.8%). Similar SDs were observed for both analytic and iterative reconstruction methods (p > or = 0.08). SDs of RCs for 2D acquisitions were significantly higher than for 3D acquisitions (p < or =s 0.008) for same acquisition and processing parameters. SDs of maximum RCs were larger than corresponding mean values for stationary IQ phantom scans ( < or = 0.02), although the magnitude of difference is reduced due to noise correlations in the image. Increased smoothing decreased SDs ( < or =s 0.045) and decreased maximum and mean RCs (p < or = 0.02). Reproducibility of GE DSTE, Philips Gemini TF, and Siemens Biograph Hi-REZ PET/CT scans of the same IQ phantom, with similar acquisition, reconstruction, and repositioning among 20 scans, were, in general, similar (mean and maximum RC SD range 2.5% to 4.8%).

CONCLUSIONS

Short-term scanner variability is low compared to other sources of error. There are tradeoffs in noise and bias depending on acquisition, processing, and analysis methods. The SD of a new PET measure can be estimated from a known SD if the ratios of available coincident counts between the two PET scanner acquisitions are known and both employ the same ROI definition. Results suggest it is feasible to use PET/CTs from different vendors and sites in clinical trials if they are properly cross-calibrated.

Gynecological cancers

The clinical problems raised in patients presenting with all forms of gynecological malignancy are currently addressed using conventional cross-sectional imaging, usually MRI. In general, F-18 FDG PET-CT has not been shown to have a clinical role in any of these cancers at presentation, although studies are under way to use this form of metabolic imaging to predict prognosis and the response to treatment. Although F-18 FDG PET-CT is superior to conventional imaging techniques, it is only moderately sensitive in demonstrating lymph node metastasis preoperatively, and is inadequate for local staging of patients with endometrial cancer. In ovarian cancer, F-18 FDG PET-CT provides an accurate assessment of the extent of disease, particularly in areas difficult to assess for metastases by CT and MRI such as the abdomen and pelvis, mediastinum, and supraclavicular region. F-18 FDG PET-CT is a sensitive method of detecting pelvic and para-aortic lymph nodal disease in cervical cancer, and appears to be superior to MRI and CT despite the limitations in identifying small foci of disease. In the main, as elsewhere in patients with cancer, the value of PET-CT is in identifying and defining the extent of recurrent disease, in distinguishing between posttreatment fibrosis and recurrence, and possibly in monitoring response to therapy.

In vivo imaging in cancer

Imaging has become an indispensable tool in the study of cancer biology and in clinical prognosis and treatment. The rapid advances in high resolution fluorescent imaging at single cell level and MR/PET/CT image registration, combined with new molecular probes of cell types and metabolic states, will allow the physical scales imaged by each to be bridged. This holds the promise of translation of basic science insights at the single cell level to clinical application. In this article, we describe the recent advances in imaging at the macro- and micro-scale and how these advances are synergistic with new imaging agents, reporters, and labeling schemes. Examples of new insights derived from the different scales of imaging and relevant probes are discussed in the context of cancer progression and metastasis.

PET imaging for pediatric oncology: an assessment of the evidence

Positron emission tomography (PET) has shown potential benefits when used in therapeutic clinical trials for children with cancer. However, existing trials are limited in scope with small numbers of patients and varied observations, making accurate conclusions about the usefulness of PET scanning impossible. This review examines PET and its applications in pediatric oncology. While evidence is limited, there appears to be a basis for rigorous evaluation of this imaging modality before widespread application without validation from clinical trials.

Present and future of FDG-PET/CT in ovarian cancer

Integrated FDG-PET/CT has been used successfully for the diagnosis, staging, restaging, therapy monitoring and prognostic prediction of ovarian cancer as well as various other malignant tumors. Compared with conventional PET/non-contrast CT images, combined PET/contrast-enhanced CT images with intravenous iodine contrast medium and sufficient radiation dose may contribute to a more accurate diagnosis with higher confidence. In the future, tracers other than FDG and integrated PET/MRI will be realized. We herein review the place and role of FDG-PET/CT in the management of ovarian cancer, discussing its usefulness and limitations in the imaging of these patients.

Early repeated 18F-FDG PET scans during neoadjuvant chemoradiation fail to predict histopathologic response or survival benefit in adenocarcinoma of the esophagus

This study evaluated the role of (18)F-FDG PET as an early predictor of histopathologic response to neoadjuvant chemoradiotherapy and overall survival in patients with adenocarcinoma of the esophagus undergoing multimodal therapy.

METHODS

Thirty-seven patients with locally advanced adenocarcinoma of the esophagus underwent pretreatment and an intratreatment (18)F-FDG PET scan in the second week of a 6-wk regimen of neoadjuvant chemoradiotherapy. Histopathologic response and overall survival were correlated with percentage change in (18)F-FDG uptake (%Δmaximum standardized uptake value [%ΔSUVmax]).

RESULTS

In 16 patients (43%), treatment induced a histopathologic response (<10% viable tumor cells), which was associated with a significant (P < 0.05) survival benefit. The optimal reduction in (18)F-FDG uptake, which separated histopathologic responders and nonresponders, was a -26.4% ΔSUVmax (receiver-operating-characteristic curve analysis). At this separation, sensitivity, specificity, positive predictive value, negative predictive value, and accuracy (area under the receiver operating characteristic curve) were 62.5%, 71.4%, 62.5%, 71.4%, and 67.4%, respectively, for intratreatment (18)F-FDG PET scans. Kaplan-Meier survival analysis of (18)F-FDG PET responders (>26.4% reduction in SUVmax), compared with (18)F-FDG PET nonresponders (<26.4% reduction in SUVmax), revealed no survival benefit for responders (P = 0.6812).

CONCLUSION

The %ΔSUVmax during the second week of induction chemoradiation did not correlate either with histopathologic response or with survival. Our results show that, in contrast to published reports on neoadjuvant chemotherapy, combined chemoradiotherapy in patients with adenocarcinoma of the esophagus lowers the predictive accuracy of early repeated (18)F-FDG PET in identifying histopathologic responders and those with chances for increased survival below clinically applicable levels.

The Roles of Fluorodeoxyglucose-PET/Computed Tomography in Ovarian Cancer: Diagnosis, Assessing Response, and Detecting Recurrence

The potential roles of fluorodeoxyglucose positron emission tomography/computed tomography imaging in ovarian cancer include noninvasive characterization of an ovarian mass, staging, and treatment planning. This article assesses these roles for predicting and monitoring response to treatment, restaging, and early diagnosis of recurrence.

Early reduction of glucose uptake after cisplatin treatment is a marker of cisplatin sensitivity in ovarian cancer

Cisplatin is an effective chemotherapeutic agent for ovarian cancer, but the sensitivity of cancers differs in individual cases. Because cisplatin is reported to suppress glucose uptake, we investigated the correlation between glucose uptake and sensitivity to the drug. A fluorescent derivative of D-glucose, 2-NBDG (2-[N-(7-nitrobenz-2-oxa-1,3-diaxol-4-yl) amino]-2-deoxyglucose), was used to evaluate glucose uptake. Two ovarian cancer cell lines, SKOV-3 as a relatively resistant line and OVCAR-3 as a relatively sensitive line, were analyzed. Both cell lines had a decreased number of cells accompanied by cell death 24 h after cisplatin treatment, but not at 3 h. In contrast, glucose uptake was decreased 3 h after high-dose cisplatin treatment, which correlated with the sensitivity to the drug at 24 h. The protein levels of glucose transporter 1 (GLUT1) did not change with cisplatin treatment. In contrast, the membrane localization of GLUT1 disappeared after cisplatin treatment. Other cisplatin-resistant cell lines did not show an early decrease in glucose uptake after cisplatin treatment. The early decrease in glucose uptake and later cell death also correlated in cultured cancer cells from ovarian cancer patients. Thus, the decrease in glucose uptake at an early time point after high dose cisplatin treatment reflected cisplatin chemosensitivity in ovarian cancer cells. Measuring glucose uptake might be useful as a rapid evaluation of cisplatin chemosensitivity in ovarian cancer patients.

Usefulness of interim FDG-PET after induction chemotherapy in patients with locally advanced squamous cell carcinoma of the head and neck receiving sequential induction chemotherapy followed by concurrent chemoradiotherapy

PURPOSE

Induction chemotherapy (ICT) has been used to select patients for organ preservation and determine subsequent treatments in patients with locally advanced squamous cell carcinoma of the head and neck (LASCCHN). Still, the clinical outcomes of LASCCHN patients who showed response to ICT are heterogeneous. We evaluated the efficacy of interim 18-fluoro-2-deoxy-glucose positron emission tomography (FDG-PET) after ICT in this specific subgroup of LASCCHN patients who achieved partial response (PR) after ICT to predict clinical outcomes after concurrent chemoradiotherapy (CCRT).

METHODS AND MATERIALS

Twenty-one patients with LASCCHN who showed PR to ICT by Response Evaluation Criteria In Solid Tumors before definitive CCRT were chosen in this retrospective analysis. FDG-PET was performed before and 2-4 weeks after ICT to assess the extent of disease at baseline and the metabolic response to ICT, respectively. We examined the correlation of the metabolic response by the percentage decrease of maximum standardized uptake value (SUVmax) on the primary tumor or lymph node after ICT or a specific threshold of SUVmax on interim FDG-PET with clinical outcomes including complete response (CR) rate to CCRT, progression-free survival (PFS), and overall survival (OS).

RESULTS

A SUVmax of 4.8 on interim FDG-PET could predict clinical CR after CCRT (100% vs. 20%, p=0.001), PFS (median, not reached vs. 8.5 mo, p<0.001), and OS (median, not reached vs. 12.0 months, p=0.001) with a median follow-up of 20.3 months in surviving patients. A 65% decrease in SUVmax after ICT from baseline also could predict clinical CR after CCRT (100% vs. 33.3%, p=0.003), PFS (median, not reached vs. 8.9 months, p<0.001) and OS (median, not reached vs. 24.4 months, p=0.001) of the patients.

CONCLUSION

These data suggest that interim FDG-PET after ICT might be a useful determinant to predict clinical outcomes in patients with LASCCHN receiving sequential ICT followed by CCRT.

Ovarian Cancer: The Role of Functional Imaging as an End Point in Clinical Trials

The Gynaecological Cancer InterGroup conducts collaborative trials in gynecologic cancer and also aims to develop standards that can be used to strengthen all aspects of study methodology. There is an urgent need to develop more refined imaging end points that can be used as early treatment response biomarkers in ovarian cancer. Therefore, the Gynaecological Cancer InterGroup commissioned an expert position paper on the role of functional imaging as an end point in clinical trials in ovarian cancer. In this position paper, we state the limitation of current anatomical imaging methods used in clinical trials, highlight the potential of functional imaging, and provide key recommendations on the use of functional imaging as an end point in ovarian cancer clinical trials.

Present and future of PET and PET/CT in gynaecologic malignancies

OBJECTIVES

To review the published data in literature on patients affected by gynaecological malignancies to establish the role of (18)F-FDG positron emission tomography (PET) and PET/CT in comparison to conventional imaging (CI).

MATERIALS AND METHODS

All papers specifically addressed to the role of (18)F-FDG PET and PET/CT in gynaecological malignancies published on PubMed/Medline, in abstracts from the principal international congresses, in the guidelines from national Societies that had appeared in literature until November 2009 were considered for the purpose of the present study.

RESULTS AND CONCLUSIONS

The use of (18)F-FDG PET, and even more of (18)F-FDG PET/CT, is increasing in the follow up of patients with gynaecologic malignancies and suspected recurrent disease: there is evidence in the literature that (18)F-FDG PET/CT has a higher sensitivity than CI in depicting occult metastatic spread. An interesting issue is represented by patients with ovarian cancer with an increase of the specific biomarker, CA-125, and negative/inconclusive findings at CI. The use of (18)F-FDG PET in differential diagnosis and staging is more controversial, but there is some evidence that a baseline PET examination performed before commencing therapy, for staging purpose, is also useful to evaluate the response to chemoradiation treatment. In several papers it has been suggested a relevant role of (18)F-FDG PET/CT in evaluating the entity of response to treatment and therefore to plan the subsequent therapeutic strategy.

Prediction of patient outcome with 2-deoxy-2-[18F]fluoro-D-glucose-positron emission tomography early during radiotherapy for locally advanced cervical cancer

INTRODUCTION

It is difficult to assess the individual response of locally advanced cervical cancer to chemoradiation therapy during the course of treatment. We have investigated the predictive value of positron emission tomography (PET) with 2-deoxy-2-[18F]fluoro-D-glucose (FDG) early during treatment in relation to progression-free survival.

METHODS

This prospective single-center clinical trial included women with locally advanced cervical cancer from 2004 to 2008. 2-Deoxy-2-[18F]fluoro-D-glucose-PET/computed tomography was performed at baseline, during the third week of treatment and, finally, 3 months after the completion of treatment. The images were evaluated visually, semiquantitatively with the maximum standardized uptake value, and by calculating the metabolic rate of FDG. Thirty-two patients were eligible for full evaluation.

RESULTS

The median follow-up time was 28 months (range, 5-53 months). Visual metabolic complete response on FDG-PET, after a mean irradiation dose of 23 Gy (range, 16-27 Gy), was found in 7 patients, none of which relapsed. Eleven of the 25 patients with remaining malignant hypermetabolism on the second FDG-PET relapsed. Neither maximum standardized uptake value nor metabolic rate of FDG could further discriminate between patients with low risk and patients with high risk of relapse. The follow-up FDG-PET performed 3 months after the completion of treatment identified a group of patients with poor prognosis.

CONCLUSIONS

In conclusion, FDG-PET early during chemoradiation therapy identified a small number of patients with an excellent prognosis. However, FDG-PET at this early point in time during treatment failed to predict the outcome for most patients. Future clinical trials to determine the optimal timing of predictive FDG-PET are thus warranted.

A comparison between radiolabeled fluorodeoxyglucose uptake and hyperpolarized (13)C-labeled pyruvate utilization as methods for detecting tumor response to treatment

Detection of early tumor responses to treatment can give an indication of clinical outcome. Positron emission tomography measurements of the uptake of the glucose analog, [(18)F] 2-fluoro-2-deoxy-D-glucose (FDG), have demonstrated their potential for detecting early treatment response in the clinic. We have shown recently that (13)C magnetic resonance spectroscopy and spectroscopic imaging measurements of the uptake and conversion of hyperpolarized [1-(13)C]pyruvate into [1-(13)C]lactate can be used to detect treatment response in a murine lymphoma model. The present study compares these magnetic resonance measurements with changes in FDG uptake after chemotherapy. A decrease in FDG uptake was found to precede the decrease in flux of hyperpolarized (13)C label between pyruvate and lactate, both in tumor cells in vitro and in tumors in vivo. However, the magnitude of the decrease in FDG uptake and the decrease in pyruvate to lactate flux was comparable at 24 hours after drug treatment. In cells, the decrease in FDG uptake was shown to correlate with changes in plasma membrane expression of the facilitative glucose transporters, whereas the decrease in pyruvate to lactate flux could be explained by an increase in poly(ADP-ribose) polymerase activity and subsequent depletion of the NAD(H) pool. These results show that measurement of flux between pyruvate and lactate may be an alternative to FDG-positron emission tomography for imaging tumor treatment response in the clinic.

Molecular probes for the in vivo imaging of cancer

Advancements in medical imaging have brought about unprecedented changes in the in vivo assessment of cancer. Positron emission tomography, single photon emission computed tomography, optical imaging, and magnetic resonance imaging are the primary tools being developed for oncologic imaging. These techniques may still be in their infancy, as recently developed chemical molecular probes for each modality have improved in vivo characterization of physiologic and molecular characteristics. Herein, we discuss advances in these imaging techniques, and focus on the major design strategies with which molecular probes are being developed.

Predicting the response of advanced cervical and ovarian tumors to therapy

The management of advanced cervical and ovarian cancers remains a significant challenge as many women fail to respond to recommended therapy, resulting in disease progression and ultimately patient death. Because of tumor heterogeneity, it is rare for all cancers of a particular type to respond to a specific therapy; and, as a result, many patients receive treatment from which they derive little or no benefit, leading to increased morbidity and undue costs. A marker that could rapidly predict or forecast disease outcome would clearly be beneficial in allowing the administration of a tailored regime for each patient while reducing toxicity and cost. Traditional prognostic factors of tumor size, grade, and stage are not ideal for predicting patient outcome, whereas the use of in vitro assays to detect chemosensitivity or resistance has not yet translated into routine clinical practice. Similarly, biomarkers and tumor markers vary in their predictive ability. DNA array technology offers great promise in predicting the response to therapy based on gene expression profiles, and can allow for targeted therapies against specific molecular alterations that cause disease. Imaging techniques, particularly those with the ability to characterize biological tissues and provide functional, structural, and molecular information, have the potential to noninvasively integrate physical and metabolic information. These include F-18-fluorodeoxyglucose positron emission tomography, dynamic contrast-enhanced magnetic resonance imaging, and diffusion weighted magnetic resonance imaging, all techniques that attempt to evaluate and predict therapy response and so influence clinical outcome. This review examines different methods of predicting the response to treatment in advanced cervical and ovarian tumors.

TARGET AUDIENCE

Obstetricians & Gynecologists, Family Physicians.

LEARNING OBJECTIVES

After completion of this article, the reader should be able to describe why prediction of response to therapy for cervical and ovarian cancers is important, describe obstacles to use of in vitro assays to predict outcomes for therapy for ovarian and cervical cancers, and explain potentially new predictive markers.

Surveillance of patients after initial treatment of ovarian cancer

The surveillance of ovarian cancer patients after initial treatment is a challenging question in clinical practice. Serum CA 125 assay, physical examination, and imaging examinations have been employed with different time schedules for the follow-up of asymptomatic patients. Rising serum CA 125 levels may precede the clinical detection of relapse in 56-94% of cases with a median lead time of 3-5 months. An ongoing randomised phase III European trial is comparing the benefits of early administration of chemotherapy based on serum CA 125 assay alone versus delaying treatment until clinical or radiological detection of recurrent disease. Physical examination, with or without ultrasound, is very useful for the surveillance of these patients, since approximately 25-50% of relapses involve the pelvis. Additional radiological imaging techniques, such as computed tomography (CT) and magnetic resonance imaging (MRI), are usually performed in asymptomatic patients with rising CA 125 levels as well as in patients with suspicious symptoms or signs. Integrated positron emission tomography (PET) and CT scanners (PET/CT) can identify recurrent disease in tissues that appear normal at CT imaging as well as metastatic lesions intimately associated with the bowel wall that are difficult to detect with CT or MRI, so that in most series PET/CT has a higher diagnostic reliability than that of conventional imaging techniques. Moreover, PET/CT can disclose unusual supra-diaphragmatic spreading of the disease and may be very helpful for treatment planning, especially for the selection of patients suitable for secondary surgical cytoreduction. A prospective, randomised trial of therapeutic interventions based on stratification by PET/CT disease status could elucidate the real impact of this diagnostic procedure in the management of patients with recurrent ovarian cancer.

18F-FDG PET/CT imaging for an early assessment of response to sunitinib in metastatic renal carcinoma: preliminary study

PURPOSE

Sunitinib is a new standard for the treatment of metastatic renal-cell carcinoma (RCC). We evaluated the accuracy of 18-fluorodeoxyglucose-positron emission tomography/computed tomography (FDG-PET/CT) in assessing early response to this antiangiogenic drug, which cannot be obtained with conventional CT.

PROCEDURES

Patients had an FDG-PET/CT at baseline and another one for follow-up at the end of the first cycle (at day 42). For each examination, all lesions were registered and the maximum standardized uptake value (SUV(max)) was measured. The metabolic response on PET at day 42 was assessed, using European Organization for Research and Treatment of Cancer criteria. Morphologic response on CT at day 84 (after two cycles), using Response Evaluation Criteria in Solid Tumors criteria, was used as the reference standard. The long-term outcome was assessed by the progression-free survival.

RESULTS

Twelve (12) patients who completed at least two cycles of sunitinib were assessed. The SUV(max) for the lesions with the highest uptake ranged between 2.9 and 11.8 for the 12 patients (mean = 6.3). Early PET/CT findings, after one cycle of sunitinib, were consistent with later CT results in 9 patients of 11 assessable patients: 1 patient progressed on PET and CT, 7 patients had stable disease, and 1 had a partial response. The other 2 patients had a metabolic partial response on PET and stable disease on CT. However, 1 patient achieved a partial response later in follow-up, suggesting that metabolic early changes are an indication of sunitinib activity.

CONCLUSION

FDG-PET/CT seems to be an interesting tool for the early evaluation of response to sunitinib in metastatic RCC. Larger studies are needed to confirm these preliminary results and establish a prognostic value for PET/CT.

Monitoring response to therapeutic interventions in patients with cancer

Positron emission tomography (PET) and PET/computed tomography (CT) with the glucose analog (18)F-fluorodeoxyglucose (FDG) are increasingly used to assess response to therapy in patients, and there is converging evidence that changes in glucose utilization during therapy can be used to predict clinical outcome. Today, integrated PET/CT systems have mainly replaced stand-alone PET devices, providing the opportunity to integrate morphologic information and functional information. However, the use of PET/CT systems also gives rise to methodological challenges for the quantitative analysis of PET scans for treatment monitoring. Recently published single-center studies demonstrate that FDG-PET and FDG-PET/CT have been successfully used for monitoring of tumor response to cytotoxic therapy in a variety of tumor entities. The potential early identification of nonresponding tumors provides an opportunity to alter treatment regimens according to the individual chemosensitivity of the tumor tissue. In this article, we review the methodological background to monitoring of cancer treatment with PET/CT, the diagnostic and prognostic performance of PET/CT for predicting tumor response with the glucose analog FDG in various tumor entities, and the clinical potential of new imaging probes. In addition, the future direction of research and clinical applications is discussed.

A Case Report Demonstrating Unambiguous Clinical Utility of Pet/CT Scanning in Recurrent Ovarian Cancer

There has been discussion and debate in the medical literature regarding the clinical value of PET/CT scans in ovarian cancer, particularly focusing on evidence whether the technology is of predictive versus solely prognostic utility. In the somewhat unusual case reported here, the results of the PET/CT scan were extremely helpful in developing a rational management strategy. The case emphasizes the critical need to specifically address the issue of whether data generated from an expensive diagnostic test will be useful in an individual patient's management before it is obtained.

Positron emission tomography in ovarian cancer: 18F-deoxy-glucose and 16alpha-18F-fluoro-17beta-estradiol PET

The most frequently used molecular imaging technique is currently 18F-deoxy-glucose (FDG) positron emission tomography (PET). FDG-PET holds promise in the evaluation of recurrent or residual ovarian cancer when CA125 levels are rising and conventional imaging, such as ultrasound, CT, or MRI, is inconclusive or negative. Recently, integrated PET/CT, in which a full-ring-detector clinical PET scanner and a multidetector helical CT scanner are combined, has enabled the acquisition of both metabolic and anatomic imaging data using one device in a single diagnostic session. This can also provide precise anatomic localization of suspicious areas of increased FDG uptake and rule out false-positive PET findings. FDG-PET/CT is an accurate modality for assessing primary and recurrent ovarian cancer and may affect management. FDG-PET/CT may provide benefits for detection of recurrent of ovarian cancer and improve surgical planning. And FDG-PET has been shown to predict response to neoadjuvant chemotherapy and survival in advanced ovarian cancer. This review focuses on the role of FDG-PET and FDG-PET/CT in the management of patients with ovarian cancer. Recently, we have evaluated 16α-18F-fluoro-17β-estradiol (FES)-PET, which detects estrogen receptors. In a preliminary study we reported that FES-PET provides information useful for assessing ER status in advanced ovarian cancer. This new information may expand treatment choice for such patients.

From RECIST to PERCIST: Evolving Considerations for PET response criteria in solid tumors

The purpose of this article is to review the status and limitations of anatomic tumor response metrics including the World Health Organization (WHO) criteria, the Response Evaluation Criteria in Solid Tumors (RECIST), and RECIST 1.1. This article also reviews qualitative and quantitative approaches to metabolic tumor response assessment with (18)F-FDG PET and proposes a draft framework for PET Response Criteria in Solid Tumors (PERCIST), version 1.0.

METHODS

PubMed searches, including searches for the terms RECIST, positron, WHO, FDG, cancer (including specific types), treatment response, region of interest, and derivative references, were performed. Abstracts and articles judged most relevant to the goals of this report were reviewed with emphasis on limitations and strengths of the anatomic and PET approaches to treatment response assessment. On the basis of these data and the authors' experience, draft criteria were formulated for PET tumor response to treatment.

RESULTS

Approximately 3,000 potentially relevant references were screened. Anatomic imaging alone using standard WHO, RECIST, and RECIST 1.1 criteria is widely applied but still has limitations in response assessments. For example, despite effective treatment, changes in tumor size can be minimal in tumors such as lymphomas, sarcoma, hepatomas, mesothelioma, and gastrointestinal stromal tumor. CT tumor density, contrast enhancement, or MRI characteristics appear more informative than size but are not yet routinely applied. RECIST criteria may show progression of tumor more slowly than WHO criteria. RECIST 1.1 criteria (assessing a maximum of 5 tumor foci, vs. 10 in RECIST) result in a higher complete response rate than the original RECIST criteria, at least in lymph nodes. Variability appears greater in assessing progression than in assessing response. Qualitative and quantitative approaches to (18)F-FDG PET response assessment have been applied and require a consistent PET methodology to allow quantitative assessments. Statistically significant changes in tumor standardized uptake value (SUV) occur in careful test-retest studies of high-SUV tumors, with a change of 20% in SUV of a region 1 cm or larger in diameter; however, medically relevant beneficial changes are often associated with a 30% or greater decline. The more extensive the therapy, the greater the decline in SUV with most effective treatments. Important components of the proposed PERCIST criteria include assessing normal reference tissue values in a 3-cm-diameter region of interest in the liver, using a consistent PET protocol, using a fixed small region of interest about 1 cm(3) in volume (1.2-cm diameter) in the most active region of metabolically active tumors to minimize statistical variability, assessing tumor size, treating SUV lean measurements in the 1 (up to 5 optional) most metabolically active tumor focus as a continuous variable, requiring a 30% decline in SUV for "response," and deferring to RECIST 1.1 in cases that do not have (18)F-FDG avidity or are technically unsuitable. Criteria to define progression of tumor-absent new lesions are uncertain but are proposed.

CONCLUSION

Anatomic imaging alone using standard WHO, RECIST, and RECIST 1.1 criteria have limitations, particularly in assessing the activity of newer cancer therapies that stabilize disease, whereas (18)F-FDG PET appears particularly valuable in such cases. The proposed PERCIST 1.0 criteria should serve as a starting point for use in clinical trials and in structured quantitative clinical reporting. Undoubtedly, subsequent revisions and enhancements will be required as validation studies are undertaken in varying diseases and treatments.

A prototype hybrid intraoperative probe for ovarian cancer detection

A novel prototype intraoperative system combining positron detection and optical coherence tomography (OCT) imaging has been developed for early ovarian cancer detection. The probe employs eight plastic scintillating fiber tips for preferential detection of local positron activity surrounding a central scanning OCT fiber providing volumetric imaging of tissue structure in regions of high radiotracer uptake. Characterization measurements of positron sensitivity, spatial response, and position mapping are presented for Tl(204)/Cs(137) sources as well as 18F-FDG. In conjunction with co-registered frequency domain OCT measurements the results demonstrate the potential for a miniaturized laparoscopic probe offering simultaneous functional localization and structural imaging for improved early cancer detection.

The role of 18F-FDG PET in assessing therapy response in cancer of the cervix and ovaries

For locally advanced cervical cancer, the current literature supports the use of (18)F-FDG PET for assessing treatment response 3 mo after the completion of concurrent chemoradiation. (18)F-FDG PET can provide reliable long-term prognostic information for these patients and, in the future, may be used to guide additional therapy. Investigational areas include the use of (18)F-FDG PET for monitoring response during radiotherapy and chemotherapy in the metastatic and neoadjuvant settings. For ovarian masses, the performance of (18)F-FDG PET in the detection of borderline tumors is limited, and the presence of physiologic (18)F-FDG uptake in normal ovaries of premenopausal women poses another limitation. Preliminary data suggest that the performance of (18)F-FDG PET and (18)F-FDG PET/CT is superior to that of CT alone in initial staging, but the sensitivity of both in the detection of carcinomatosis is limited. Preliminary data also suggest that (18)F-FDG PET may be promising for early prediction of response to chemotherapy and for prediction of response after the completion of chemotherapy. (18)F-FDG PET and (18)F-FDG PET/CT are most helpful in the evaluation of patients with suspected recurrent ovarian carcinoma, especially when CA-125 levels are rising and CT findings are normal or equivocal. PET and CT are complementary, and PET/CT should be used when available. Preliminary data suggest that the addition of (18)F-FDG PET/CT to the evaluation of these patients changes management in approximately a third and reduces overall treatment costs by accurately identifying patients who will or will not benefit from surgery.

Measuring response with FDG-PET: methodological aspects

The use of fluorodeoxyglucose positron emission tomography (FDG-PET) for the evaluation of tumor response to chemotherapy and radiation therapy has been studied in a number of malignancies. By imaging tumor metabolism and therapy-related changes, FDG-PET has demonstrated advantages over anatomical imaging in the assessment of treatment response. More recent investigations have indicated that FDG-PET can predict tumor response early during the course of therapy, potentially allowing for early treatment adjustments. The aim of this review is to provide oncologists with a basic knowledge of the practical aspects of PET quantification for treatment.

18F-FDG PET and PET/CT in the evaluation of cancer treatment response

Multimodality imaging, as represented by its greatest exponent, PET/CT, has a firm place in the evaluation of a patient presenting with cancer. With 18F-FDG, PET/CT is rapidly becoming the key investigative tool for the staging and assessment of cancer recurrence. In the last 5 y, PET/CT has also gained widespread acceptance as a key tool used to demonstrate early response to intervention and therapy. In this setting, a major clinical need is being addressed with 18F-FDG PET/CT, because of its inherent ability to demonstrate (before other markers of response) if disease modification has occurred. This review presents available evidence to this effect.