From tumor biology to clinical Pet: a review of positron emission tomography (PET) in oncology

Spatial-temporal [¹⁸F]FDG-PET features for predicting pathologic response of esophageal cancer to neoadjuvant chemoradiation therapy

PURPOSE

To extract and study comprehensive spatial-temporal (18)F-labeled fluorodeoxyglucose ([(18)F]FDG) positron emission tomography (PET) features for the prediction of pathologic tumor response to neoadjuvant chemoradiation therapy (CRT) in esophageal cancer.

METHODS AND MATERIALS

Twenty patients with esophageal cancer were treated with trimodal therapy (CRT plus surgery) and underwent [(18)F]FDG-PET/CT scans both before (pre-CRT) and after (post-CRT) CRT. The 2 scans were rigidly registered. A tumor volume was semiautomatically delineated using a threshold standardized uptake value (SUV) of ≥2.5, followed by manual editing. Comprehensive features were extracted to characterize SUV intensity distribution, spatial patterns (texture), tumor geometry, and associated changes resulting from CRT. The usefulness of each feature in predicting pathologic tumor response to CRT was evaluated using the area under the receiver operating characteristic curve (AUC) value.

RESULTS

The best traditional response measure was decline in maximum SUV (SUVmax; AUC, 0.76). Two new intensity features, decline in mean SUV (SUVmean) and skewness, and 3 texture features (inertia, correlation, and cluster prominence) were found to be significant predictors with AUC values ≥0.76. According to these features, a tumor was more likely to be a responder when the SUVmean decline was larger, when there were relatively fewer voxels with higher SUV values pre-CRT, or when [(18)F]FDG uptake post-CRT was relatively homogeneous. All of the most accurate predictive features were extracted from the entire tumor rather than from the most active part of the tumor. For SUV intensity features and tumor size features, changes were more predictive than pre- or post-CRT assessment alone.

CONCLUSION

Spatial-temporal [(18)F]FDG-PET features were found to be useful predictors of pathologic tumor response to neoadjuvant CRT in esophageal cancer.

Early FDG PET response assessment of preoperative radiochemotherapy in locally advanced rectal cancer: correlation with long-term outcome

PURPOSE

The aim of the present study is to prospectively evaluate the prognostic value of previously defined [(18)F]2-fluoro-2-deoxy-D-glucose positron emission tomography (FDG PET) criteria of early metabolic response in patients with locally advanced rectal cancer (LARC) after long-term follow-up.

METHODS

Forty-two patients with poor prognosis LARC underwent three biweekly courses of chemotherapy with oxaliplatin, raltitrexed and 5-fluorouracil modulated by levofolinic acid during pelvic radiotherapy. FDG PET studies were performed before and 12 days after the beginning of the chemoradiotherapy (CRT) treatment. Total mesorectal excision (TME) was carried out 8 weeks after completion of CRT. A previously identified cutoff value of ≥52 % reduction of the baseline mean FDG standardized uptake value (SUV(mean)) was applied to differentiate metabolic responders from non-responders and correlated to tumour regression grade (TRG) and survival.

RESULTS

Twenty-two metabolic responders showed complete (TRG1) or subtotal tumour regression (TRG2) and demonstrated a statistically significantly higher 5-year relapse-free survival (RFS) compared with the 20 non-responders (86 vs 55 %, p = .014) who showed TRG3 and TRG4 pathologic responses. A multivariate analysis demonstrated that early ∆SUV(mean) was the only pre-surgical parameter correlated to the likelihood of recurrence (p = .05).

CONCLUSION

This study is the first prospective long-term evaluation demonstrating that FDG PET is not only an early predictor of pathologic response but is also a valuable prognostic tool. Our results indicate the potential of FDG PET for optimizing multidisciplinary management of patients with LARC.

18F-Fluorodeoxyglucose positron-emission tomography (PET) can be used to assess inflammation non-invasively in Crohn's disease

BACKGROUND

Differential therapy requires repeated diagnostic assessment for mapping and monitoring of disease activity in Crohn's disease (CD).

PURPOSE

The purpose of this prospective study was to evaluate the accuracy of (18)F-fluorodexyglucose positron-emission tomography (FDG-PET) for non-invasive assessment of disease activity in CD.

METHODS

Forty-three patients with CD underwent ileocolonoscopy and hydromagnetic resonance imaging (hydro-MRI) as reference standards. In addition, FDG-PET was performed and correlated with clinical data, hydro-MRI, and endoscopy findings. Diagnostic accuracy was determined for all methods.

RESULTS

Two-hundred and forty-one bowel segments could be analyzed by all methods. Of 80 endoscopically inflamed segments in CD, FDG-PET detected 72 and hydro-MRI 53 segments. Overall sensitivity was 90 % (FDG-PET) versus 66 % (hydro-MRI), and specificity was 92.6 % versus 99 %. In the proximal ileum, hydro-MRI revealed inflammation in eight out of 49 patients and FDG-PET, also, detected all of these inflamed segments. Seventeen stenoses could be identified in 43 CD patients. With regard to assessment as inflammatory or fibrotic stenosis, there was good concordance between colonoscopy, hydro-MRI, and FDG-PET. In one case only, the nature of the stenosis was assessed differently. In contrast with leukocyte numbers and CDAI, there was significant correlation of FDG-PET activity with C-reactive protein and CDEIS levels (P = 0.019 and P = 0.007, respectively).

CONCLUSION

FDG-PET is able to detect mucosal inflammation in CD with high sensitivity and specificity and to enable proper assessment of inflammatory activity in stenoses. FDG-PET is, thus, a promising non-invasive technique for clinical management of CD.

Waldenström's macroglobulinemia harbors a unique proteome where Ku70 is severely underexpressed as compared with other B-lymphoproliferative disorders

Waldenström's macroglobulinemia (WM) is a clonal B-cell lymphoproliferative disorder (LPD) of post-germinal center nature. Despite the fact that the precise molecular pathway(s) leading to WM remain(s) to be elucidated, a hallmark of the disease is the absence of the immunoglobulin heavy chain class switch recombination. Using two-dimensional gel electrophoresis, we compared proteomic profiles of WM cells with that of other LPDs. We were able to demonstrate that WM constitutes a unique proteomic entity as compared with chronic lymphocytic leukemia and marginal zone lymphoma. Statistical comparisons of protein expression levels revealed that a few proteins are distinctly expressed in WM in comparison with other LPDs. In particular we observed a major downregulation of the double strand repair protein Ku70 (XRCC6); confirmed at both the protein and RNA levels in an independent cohort of patients. Hence, we define a distinctive proteomic profile for WM where the downregulation of Ku70—a component of the non homologous end-joining pathway—might be relevant in disease pathophysiology.

In vivo visualization of heterogeneous intratumoral distribution of hypoxia-inducible factor-1α activity by the fusion of high-resolution SPECT and morphological imaging tests

Purpose. We aimed to clearly visualize heterogeneous distribution of hypoxia-inducible factor 1α (HIF) activity in tumor tissues in vivo. Methods. We synthesized of ¹²⁵I-IPOS, a ¹²⁵I labeled chimeric protein probe, that would visualize HIF activity. The biodistribution of ¹²⁵I-IPOS in FM3A tumor-bearing mice was evaluated. Then, the intratumoral localization of this probe was observed by autoradiography, and it was compared with histopathological findings. The distribution of ¹²⁵I-IPOS in tumors was imaged by a small animal SPECT/CT scanner. The obtained in vivo SPECT-CT fusion images were compared with ex vivo images of excised tumors. Fusion imaging with MRI was also examined. Results. ¹²⁵I-IPOS well accumulated in FM3A tumors. The intratumoral distribution of ¹²⁵I-IPOS by autoradiography was quite heterogeneous, and it partially overlapped with that of pimonidazole. High-resolution SPECT-CT fusion images successfully demonstrated the heterogeneity of ¹²⁵I-IPOS distribution inside tumors. SPECT-MRI fusion images could give more detailed information about the intratumoral distribution of ¹²⁵I-IPOS. Conclusion. High-resolution SPECT images successfully demonstrated heterogeneous intratumoral distribution of ¹²⁵I-IPOS. SPECT-CT fusion images, more favorably SPECT-MRI fusion images, would be useful to understand the features of heterogeneous intratumoral expression of HIF activity in vivo.

Fluorinated ΔF508-CFTR correctors and potentiators for PET imaging

(19)F-modified bithiazole correctors and phenylglycine potentiators of the ΔF508-CFTR chloride channel were synthesized and their function assayed in cells expressing human ΔF508-CFTR and a halide-sensitive fluorescent protein. Fluorine was incorporated into each scaffold using prosthetic groups for future biodistribution imaging studies using positron emission tomography (PET). The ΔF508-CFTR corrector and potentiator potencies of the fluorinated analogs were comparable to or better than those of the original compounds.

Lymph node metastasis diagnosis using positron emission tomography with 2-[18F] fluoro-2-deoxy-D-glucose as a tracer and computed tomography in surgical cases of non-small cell lung cancer

OBJECTIVES

Positron emission tomography with 2-[18F] fluoro-2-deoxy-D-glucose as a tracer and computed tomography (FDG-PET/CT) are utilized for the diagnosis of lymph node (LN) metastasis from lung cancer. In this study, we analyzed the diagnostic ability of FDG-PET for N staging by focusing on the clinical features of false-positive (FP) and false-negative (FN) cases.

METHODS

From March 2006 to February 2010, 112 patients underwent preoperative examinations using FDG-PET/CT followed by radical resection with hilar and mediastinal dissection. We analyzed their clinicopathological characteristics based on preoperative FDG-PET/CT findings and post-operative histopathological diagnosis of resected LNs.

RESULTS

Based on the PET/CT results, 17 patients were misdiagnosed (9 FN and 8 FP). The sensitivity, specificity, accuracy and negative and positive predictive values for N1/N2 were 50.0, 94.5, 84.0, 93.0 and 58.3%, respectively, whereas those for N2 were 57.8, 90.3, 84.8, 90.3 and 61.1%, respectively. FP findings more frequently occurred in cases with elevated white blood cell (WBC) count (P=0.015) and smokers (P=0.04). In the FN group, the maximum standardized uptake value for the primary tumour was lower than that in the true-positive (TP) group (P=0.01). The short-axis sizes of 71 LNs differently diagnosed by PET/CT and histopathology findings were significantly smaller in the FN group than the TP group (P<0.001), whereas there was no difference between TP and FP. As for FN LNs in the TP group, there was no significant difference.

CONCLUSIONS

PET/CT showed a good ability to detect metastatic LNs, especially for N2 diagnosis. However, there were some limitations, especially in cases with elevated peripheral WBC count and/or smoking history.

In-vivo near-infrared optical imaging of growing osteosarcoma cell lesions xenografted in mice: dual-channel quantitative evaluation of volume and mineralization

BACKGROUND

In a previous study using a rodent osteosarcoma-grafted rat model, in which cell-dependent mineralization was previously demonstrated to proportionally increase with growth, we performed a quantitative analysis of mineral deposit formation using (99m)Tc-HMDP and found some weaknesses, such as longer acquisition time and narrower dynamic ranges (i.e. images easily saturated). The recently developed near-infrared (NIR) optical imaging technique is expected to non-invasively evaluate changes in living small animals in a quantitative manner.

PURPOSE

To test the feasibility of NIR imaging with a dual-channel system as a better alternative for bone scintigraphy by quantitatively evaluating mineralization along with the growth of osteosarcoma lesions in a mouse-xenograft model.

MATERIAL AND METHODS

The gross volume and mineralization of osteosarcoma lesions were evaluated in living mice simultaneously with dual-channels by NIR dye-labeled probes, 2-deoxyglucose (DG) and pamidronate (OS), respectively. To verify these quantitative data, retrieved osteosarcoma lesions were then subjected to ex-vivo imaging, weighing under wet conditions, microfocus-computed tomography (μCT) analysis, and histopathological examination.

RESULTS

Because of less scattering and no anatomical overlapping, as generally shown, specific fluorescence signals targeted to the osteosarcoma lesions could be determined clearly by ex-vivo imaging. These data were well positively correlated with the in-vivo imaging data (r > 0.8, P < 0.02). Other good to excellent correlations (r > 0.8, P < 0.02) were observed between DG accumulation and tumor gross volume and between OS accumulation and mineralization volume.

CONCLUSION

This in-vivo NIR imaging technique using DG and OS is sensitive to the level to simultaneously detect and quantitatively evaluate the growth and mineralization occuring in this type of osteosarcoma lesions of living mice without either invasion or sacrifice. By possible mutual complementation, this dual imaging system might be useful for accurate diagnosis even in the presence of overlapping tissues.

Comparison of FLT-PET and FDG-PET for visualization of head and neck squamous cell cancers

PURPOSE

We compared 3'[F-18]fluoro-3'-deoxythymidine (FLT) positron emission tomography (PET) and 2-deoxy-2-[F-18]fluoro-D-glucose (FDG) for PET visualization of head and neck squamous cell cancers (HNSCCs) and evaluated which might better reflect proliferative activity as indicated by the Ki-67 index.

PROCEDURES

A total of 43 patients with HNSCCs were examined with FLT-PET and FDG-PET. The PET images were evaluated qualitatively for regions of focally increased metabolism and for semiquantitative analysis the maximum standardized uptake value (SUV) was calculated.

RESULTS

For depiction of primary tumours, the sensitivity of both approaches was 100%. The mean (± SD) SUV for FLT (5.65 ± 2.96) was significantly lower than that for FDG (10.9 ± 4.91; p < 0.0001). No significant differences were found for the T category. However, the mean (± SD) FLT SUV was significantly higher in poorly than in well-differentiated tumours (6.49 ± 3.13 vs. 4.2 ± 2.08; p < 0.04). Similarly, FDG SUVs in poorly and moderately differentiated tumours (12.72 ± 4.8 and 11.46 ± 4.64) were significantly higher than in well-differentiated tumours (7.45 ± 3.51; p < 0.004 and p < 0.02). No significant correlation was observed with the Ki-67 index for either.

CONCLUSION

FLT-PET showed as high a sensitivity as FDG-PET for the detection of primary HNSCC lesions, although uptake of FLT was significantly lower than that of FDG.

Study of an image-derived SUV and a modified SUV using mouse FDG-PET

INTRODUCTION

Standard uptake value (SUV) is calculated without consideration of the differences in plasma 2-deoxy-2-[18F]fluoro-D-glucose (FDG) clearance. Its variability can be affected by changes of the amount of excreted FDG by renal function. Moreover, the estimation of SUV is quite sensitive to errors in the measurements of body weight and injected dose. This study aims to develop an image-based method to obtain an image-derived SUV (iSUV) and a modified SUV (mSUV) to overcome these problems.

METHODS

Thirty-one tumor-planted SCID mice were scanned in micro-positron emission tomography (PET) at ∼60 min post FDG injection and then scanned in micro-computed tomographic (CT). Using image-based method, the body weight and injected dose were derived from the microPET/CT images to calculate iSUV. The volumes and the total activities of FDG within the bladder and the whole-body were also obtained to calculate mSUV. For the selected targets, the iSUVs and mSUVs were compared against their corresponding SUVs.

RESULTS

Compared with SUV factor (injected dose/body weight), iSUV factor had an average percentage error of -0.7%. The linear regressions between SUV and iSUV had a slope of 0.99 with correlation coefficient of 0.95. Compared with SUV and iSUV, coefficient of variation of mSUV decreased while the tumor-to-background separation of mSUV increased.

CONCLUSIONS

Using this image-based method, the iSUV can replace SUV when the actual measurements were missing or unreliable. The mSUV can reduce the inter-subject variability and enhance the tumor-to-background separation in mouse FDG-PET studies.

FDG PET/CT evaluation of treatment response in patients with recurrent colorectal cancer

AIM

to evaluate the treatment response in patients with recurrent colorectal cancer (CRC) using FDG PET/CT.

MATERIALS AND METHODS

a total of 32 recurrent CRC patients (21 males, 11 females; mean age, 52.8 years) were included in this retrospective study. All patients underwent a baseline and follow-up FDG PET/CT scans after chemotherapy. Of 32 patients, 23 patients had follow-up carcinoembryonic antigen (CEA) levels.

RESULTS

on qualitative analysis of baseline and follow-up FDG PET/CT studies, there were 20 nonresponders and 12 were responders. On quantitative analysis, there were 19 nonresponders and 13 were responders. In responders, baseline and follow-up mean SUV(max) were 11.8 ± 10.1 and 3.7 ± 4.1, respectively (significant decrease, P = 0.001). Among nonresponders, baseline and follow-up mean SUV(max) were 8.1 ± 5.2 and 14.1 ± 9.0, respectively (significant increase, P = 0.003). There was no association between response and different factors like age, sex, diagnosis, extent of the lesions, and number of lesions.

CONCLUSION

FDG PET/CT appears to be useful modality in evaluating chemotherapy response and can differentiate responders from nonresponders in recurrent CRC patients.

Discrimination between low-grade oligodendrogliomas and diffuse astrocytoma with the aid of 11C-methionine positron emission tomography

OBJECT

The diagnostic usefulness of (11)C-methionine PET scans in gliomas is still controversial. The authors investigated the clinical significance of (11)C-methionine PET findings in preoperative diagnosis of histological type and grade.

METHODS

The tissue uptake of (11)C-methionine was assessed using PET in 70 patients with histologically confirmed intracerebral gliomas. The ratio of maximum standard uptake values in tumor areas to the mean standard uptake values in the contralateral normal brain tissue (tumor/normal tissue [T/N] ratio) was calculated and correlated with tumor type, histological grade, contrast enhancement on MR imaging, Ki 67 labeling index, and 1p/19q status.

RESULTS

The T/N ratio was significantly increased as tumor grade advanced in astrocytic tumors (WHO Grade II vs Grade III, p = 0.0011; Grade III vs Grade IV, p = 0.0007). Among Grade II gliomas, the mean T/N ratio was significantly higher in oligodendroglial tumors than in diffuse astrocytomas (DAs) (p < 0.0001). All T/N ratios for oligodendroglial tumors were ≥ 1.46, and those for DA were consistently < 1.46, with the exception of 2 cases of gemistocytic astrocytoma. The Ki 67 labeling index significantly correlated with T/N ratio in astrocytic tumors, but not in oligodendrogliomas. Oligodendroglial tumors without 1p/19q deletion had a significantly higher T/N ratio than those with the codeletion. In combination with Gd-enhanced MR imaging, 67% of nonenhanced tumors with a T/N ratio of ≥ 1.46 were proved to be Grade II oligodendrogliomas.

CONCLUSIONS

These results clearly show that (11)C-methionine PET T/N ratios in Grade II oligodendrogliomas were higher than those in DAs independently of their proliferative activity. This information contributes to preoperative differential diagnoses of histological type, especially in suspected low-grade gliomas.

18Fluoro-deoxy-glucose positron emission tomography in assessing tumor response to preoperative chemoradiation therapy for locally advanced rectal cancer

BACKGROUND

This study aims to evaluate the efficacy of (18)F-FDG PET in assessing tumor response after preoperative chemoradiation therapy (CRT) for rectal cancer.

METHODS

Maximum standardized uptake value (SUV) was measured for 37 patients who underwent (18)F-FDG PET before and 4 weeks after completion of preoperative CRT. Pre-SUV, post-SUV, the difference between pre- and post-SUV (ΔSUV), and reduction rate (RR) were correlated with tumor response.

RESULTS

A lower mean post-SUV and a higher mean RR were shown in good tumor response (T-downstaging(+) and tumor regression grade 1, 2). Considering pathologic complete response (pCR), the mean post-SUV and the mean RR were significantly different between pCR (+) patients (N = 13) and pCR (-) patients (N = 24) (2.7 vs. 4.8, P < 0.001, 73.9% vs. 58.7%, P = 0.009). With a 3.35 cut-off value for the post-SUV by receiver operating characteristic analysis, 84.6% sensitivity, 79.2% specificity, and 81.2% overall accuracy were obtained for discriminating between pCR (+) and pCR (-) (area under the curve = 0.885, P < 0.001).

CONCLUSIONS

(18)F-FDG PET is potentially useful as a method for assessing tumor response after preoperative CRT for rectal cancer. Post-SUV and RR were significantly associated with pathological treatment response, especially in pCR.

Perspectives and potential applications of nanomedicine in breast and prostate cancer

Nanomedicine is a branch of nanotechnology that includes the development of nanostructures and nanoanalytical systems for various medical applications. Among these applications, utilization of nanotechnology in oncology has captivated the attention of many research endeavors in recent years. The rapid development of nano-oncology raises new possibilities in cancer diagnosis and treatment. It also holds great promise for realization of point-of-care, theranostics, and personalized medicine. In this article, we review advances in nano-oncology, with an emphasis on breast and prostate cancer because these organs are amenable to the translation of nanomedicine from small animals to humans. As new drugs are developed, the incorporation of nanotechnology approaches into medicinal research becomes critical. Diverse aspects of nano-oncology are discussed, including nanocarriers, targeting strategies, nanodevices, as well as nanomedical diagnostics, therapeutics, and safety. The review concludes by identifying some limitations and future perspectives of nano-oncology in breast and prostate cancer management.

Strategies of assessing and quantifying radiation treatment metabolic tumor response using F18 FDG Positron Emission Tomography (PET)

The use of positron emission tomography (PET) using F18 labeled fluorodeoxyglucose (FDG) for both oncology disease staging and radiation therapy target volume delineation has steadily increased over the last decade, and FDG-PET is today readily available in all major medical centers. The goal of anti tumor treatment, including chemotherapy and/or radiation therapy is to diminish a tumor cell population, ideally to the state of total eradication. Reducing the number of viable tumor cells can lead to a reduction in anatomical tumor size, and may also be correlated with decreased FDG uptake. Efforts to assess tumor response to therapy have attempted to describe and quantify changes in glucose utilization, also referred to as metabolic tumor response. In this review, an attempt is made to present and discuss methodologies to assess and quantify tumor metabolic response to radiation therapy or chemoradiation treatment courses.

Constrictive tuberculous pericarditis diagnosed using 18F-fluorodeoxyglucose positron emission tomography: a report of two cases

We present two cases of tuberculous pericarditis that were diagnosed using 18F-fluorodeoxyglycose (18F-FDG) positron emission tomography (PET). Here, we highlight the value of 18F-FDG-PET for demonstrating tuberculous pericardial involvement as well as disease dissemination and activity. The patients received antitubercular treatment, and their symptoms and findings resolved accordingly.

Prospective study on the FDG-PET/CT predictive and prognostic values in patients treated with neoadjuvant chemoradiation therapy and radical surgery for locally advanced rectal cancer

BACKGROUND

2-[fluorine-18]fluoro-2-deoxy-D-glucose-positron emission tomography/computed tomography (FDG-PET/CT) was carried out before and after neoadjuvant chemoradiotherapy (NCRT) followed by radical surgery for locally advanced rectal cancer (LARC). The aim of this study was to define its predictive and prognostic values.

PATIENTS AND METHODS

Patients with cT3-T4 N-/+ carcinoma of medium/low rectum received daily 5-fluorouracil-based chemotherapy infusion and radiation therapy on 6-week period followed by surgery 7-8 weeks later. Tumour metabolic activity, expressed as maximum standardised uptake value (SUV-1 = at baseline and SUV-2 = pre-surgery), was calculated in the most active tumour site. Predictive and prognostic values of SUV-1, SUV-2 and Δ-SUV (percentage change of SUV-1 - SUV-2) were analysed towards pathological response (pR) in the surgical specimen and disease recurrence, respectively.

RESULTS

Eighty consecutive patients entered the study. SUV-1, SUV-2 and Δ-SUV appeared singly correlated with pR, but not one of them resulted an independent predictive factor at multivariate analysis. After a median follow-up of 44 months, 13 patients (16.2%) presented local and/or distant recurrence. SUV-2 ≤5 was associated with lower incidence of disease recurrence and resulted prognostic factor at multivariate analysis.

CONCLUSIONS

Dual-time FDG-PET/CT in patients with LARC treated with NCRT and radical surgery supplies limited predictive information. However, an optimal metabolic response appears associated with a favourable patient outcome.

Correlation between glucose transporter-1 expression and 18F-fluoro-2-deoxyglucose uptake on positron emission tomography in lung cancer

PURPOSE

The aim of this study was to determine if glucose transporter-1 (Glut1) expression correlates with (18)F-FDG ((18)F-fluoro-2-deoxyglucose) uptake on positron emission tomography (PET) in lung cancer and to examine the similarities and differences between them.

METHODS

A total of 34 patients with resected primary lung cancers were investigated in this study. There were 17 adenocarcinomas, 12 squamous cell carcinomas, and 5 cancers of other cell types. Immunohistochemical Glut1 intensity was categorized into three groups: negative, positive, and strongly positive. Glut1 frequency was defined by the proportion of positive cells among all cancer cells, and it was graded on a semiquantitative scale as 0-100% in 10% increments. The data are expressed as the mean +/- SD.

RESULTS

Maximum standardized uptake values (SUVmax) were 4.8 +/- 6.3 in "negative" Glut1 intensity cases, 4.7 +/- 3.1 in "positive" Glut1 intensity cases, and 11.2 +/- 5.2 in "strongly positive" Glut1 intensity cases. Although SUVmax correlated significantly with tumor size (correlation coefficient 0.58, P = 0.00033), Glut1 frequency did not correlate significantly with tumor size (correlation coefficient 0.18, P = 0.301). Cell type and cell differentiation correlated significantly with Glut1 expression and (18)F-FDG uptake.

CONCLUSION

Glut1 expression correlates significantly with (18)F-FDG uptake. There are similarities in cell differentiation and cell type between Glut1 expression and (18)F-FDG uptake. (18)F-FDG uptake correlates significantly with tumor size, but Glut1 expression does not.

The use of PET in assessing tumor response after neoadjuvant chemoradiation for rectal cancer

PURPOSE

To assess the correlation of 18F-FDG-PET (PET) response to pathological response after neoadjuvant chemoradiation (CRT) for locally advanced rectal cancer.

METHODS AND MATERIALS

Twenty patients with locally advanced rectal cancer were identified between 2001 and 2005. The median age was 57 years (range 37-72) with 14 males and 6 females. All patients were staged with endorectal ultrasound and/or MRI, CT, and PET. The clinical staging was T3N0M0 (16), T3N1M0 (2), and T3N0M1 (2). Restaging PET was performed after CRT, and prior to definitive surgery. The response on PET and pathology was assessed and correlated. Patient outcome according to PET response was also assessed.

RESULTS

Following CRT, a complete PET response occurred in 7 patients, incomplete response in 10, and no response in 3 patients. At surgery, complete pathological response was recorded in 7 patients, incomplete response in 10 and no response in 3. There was a good correlation of PET and pathological responses in complete responders (5/7 cases) and non-responders (3/3 cases). After a median follow-up of 62 months (range 7-73), twelve patients were alive with no evidence of disease. All patients achieving complete metabolic response were alive with no evidence of disease, while as those who had no metabolic response, all died as a result of metastatic disease.

CONCLUSIONS

PET is a promising complementary assessment tool for assessing tumor response after CRT if there is a complete or no response. PET response may also predict for outcome.

Molecular imaging (PET) of brain tumors

Despite the recognized limitations of (18)Fluorodeoxyglucose positron emission tomography (FDG-PET) in brain tumor imaging due to the high background of normal gray matter, this imaging modality provides critical information for the management of patients with cerebral neoplasms with regard to the following aspects: (1) providing a global picture of the tumor and thus guiding the appropriate site for stereotactic biopsy, and thereby enhancing its accuracy and reducing the number of biopsy samples; and (2) prediction of biologic behavior and aggressiveness of the tumor, thereby aiding in prognosis. Another area, which has been investigated extensively, includes differentiating recurrent tumor from treatment-related changes (eg, radiation necrosis and postsurgical changes). Furthermore, FDG-PET has demonstrated its usefulness in differentiating lymphoma from toxoplasmosis in patients with acquired immune deficiency syndrome with great accuracy, and is used as the investigation of choice in this setting. Image coregistration with magnetic resonance imaging and delayed FDG-PET imaging are 2 maneuvers that substantially improve the accuracy of interpretation, and hence should be routinely employed in clinical settings. In recent years an increasing number of brain tumor PET studies has used other tracers (like labeled methionine, tyrosine, thymidine, choline, fluoromisonidazole, EF5, and so forth), of which positron-labeled amino acid analogues, nucleotide analogues, and the hypoxia imaging tracers are of special interest. The major advantage of these radiotracers over FDG is the markedly lower background activity in normal brain tissue, which allows detection of small lesions and low-grade tumors. The promise of the amino acid PET tracers has been emphasized due to their higher sensitivity in imaging recurrent tumors (particularly the low-grade ones) and better accuracy for differentiating between recurrent tumors and treatment-related changes compared with FDG. The newer PET tracers have also shown great potential to image important aspects of tumor biology and thereby demonstrate ability to forecast prognosis. The value of hypoxia imaging tracers (such as fluoromisonidazole or more recently EF5) is substantial in radiotherapy planning and predicting treatment response. In addition, they may play an important role in the future in directing and monitoring targeted hypoxic therapy for tumors with hypoxia. Development of optimal image segmentation strategy with novel PET tracers and multimodality imaging is an approach that deserves mention in the era of intensity modulated radiotherapy, and which is likely to have important clinical and research applications in radiotherapy planning in patients with brain tumor.

11C-methionine PET of acute myocardial infarction

Tissue uptake of l-[methyl-(11)C]-methionine ((11)C-methionine) has been used to monitor amino acid metabolism and protein synthesis. We examined whether (11)C-methionine was retained in areas of myocardial infarction after successful reperfusion.

METHODS

Nine patients with infarction in the left anterior descendent region underwent percutaneous transluminal coronary artery intervention within 24 h and (201)Tl SPECT, (18)F-FDG PET, and (11)C-methionine PET within 2 wk of infarction onset. The standardized uptake values of the infarcted area and of the normal area were measured.

RESULTS

The (11)C-methionine images showed increased uptake in the infarcted area, whereas the (201)Tl SPECT and (18)F-FDG PET images showed decreased uptake. The highest accumulation of (11)C-methionine in the infarcted area was observed during the early phase of AMI.

CONCLUSION

(11)C-methionine uptake is elevated in infarcted areas and may reflect the early acute phase of damage healing, that is, the initial process of remodeling.

PET scan in clinically suspected paraneoplastic neurological syndromes: a 6-year prospective study in a regional neuroscience unit

BACKGROUND

The role of PET in the diagnosis of paraneoplastic neurological syndromes (PNS) has previously been reported in retrospective studies, from specialized neuro-oncology units, often selecting patients with positive paraneoplastic antibodies.

OBJECTIVES

To prospectively assess the usefulness of PET in detecting malignancy in patients clinically suspected of having PNS.

METHODS

PET was performed in patients suspected of PNS within 4 weeks of the normal CT body scan. All patients were followed up.

RESULTS

Eighty patients suspected of having PNS underwent PET. 18/80 (23%) were abnormal and suspicious of malignancy. The total number of definite and probable PNS with abnormal PET was 11/18 (61%). The total number of definite and probable PNS with a normal PET was 3/62 (5%). Only 50% of patients with biopsy-proven malignancy were positive for paraneoplastic antibodies. The prevalence of abnormal PET in patients presenting with classical PNS was 41% as opposed to 21% in patients with non-classical PNS. The sensitivity and specificity of PET in diagnosing PNS was 75% and 87% respectively.

CONCLUSIONS

PET is a valuable tool in clinically suspected PNS. Its use should not be restricted to specialized neuro-oncology units or in patients with positive paraneoplastic antibodies. Positive yield is the highest amongst patients with classical PNS.

Imaging matrix metalloproteinases in cancer

Early detection of both primary tumors and metastatic disease remains a major challenge in the diagnosis and staging of cancer. The recognition of the role of MMPs in both the growth and metastasis of tumors has guided the development not only of therapeutic strategies utilizing synthetic, small-molecule MMP inhibitors (MMPIs), but has also catalyzed methods to detect and image tumors in vivo by means of tumor-associated proteolytic activity. These imaging approaches target MMPs involved in cancer progression via contrast agents linked to MMPIs or to MMP selective and specific substrates with sensitivity enhanced by amplification during enzymatic processing. This review draws attention to a variety of strategies utilized to image MMP activity in vivo.

Significance of 18F-fluorodeoxyglucose positron-emission tomography/computed tomography for the postoperative surveillance of advanced renal cell carcinoma

OBJECTIVES

To evaluate the role of (18)F-fluorodeoxyglucose (FDG) positron-emission tomography (PET)/computed tomography (CT) for the surveillance of patients with renal cell carcinoma (RCC) who have a high risk of local recurrence or distant metastasis, by comparing the results with those of conventional imaging methods.

PATIENTS AND METHODS

Sixty-three patients with RCC had conventional imaging studies and FDG PET/CT during the follow-up after surgical treatment. Their pathological stages were T2 in 28 patients, T3a in 14, T3b in 19 and T4 in two; lymph-node or distant metastases were present in 12 patients. Suspicious recurrent or metastatic lesions were confirmed by histopathology or by clinical follow-up. The sensitivity, specificity, positive predictive value, negative predictive value and accuracy of conventional surveillance methods and FDG PET/CT were analysed. The difference in the accuracy of FDG PET/CT by nuclear grade and histological subtype of tumours was also assessed.

RESULTS

The FDG PET/CT accurately classified the presence of a recurrence or metastasis in 56 (89%) patients. FDG PET/CT had an 89.5% sensitivity, 83.3% specificity, 77.3% positive predictive value, 92.6% negative predictive value, and 85.7% accuracy in detecting recurrence or metastasis, which was not significantly different from the results with conventional methods. Moreover, the accuracy of the FDG PET/CT by nuclear grade and histological subtypes was not significantly different.

CONCLUSION

For the surveillance of high-risk RCC, FDG PET/CT had results that were as good as conventional methods and were not influenced by the nuclear grades of cancer cells. In addition, it was possible to examine all organ systems in one procedure, and there was no need for contrast agents, that can damage renal function. Therefore, FDG PET/CT might replace conventional methods.

Crude ethanol extract from babassu (Orbignya speciosa): cytotoxicity on tumoral and non-tumoral cell lines

Plant-derived substances have been considered as important sources of drugs, including antineoplasic agents. Babassu mesocarp is popularly used in Brazil as a food additive, and in popular medicine against several conditions, such as inflammations, menstrual pains and leukaemia. From babassu Orbignya speciosa (Mart.) Barb. Rodr. [Arecaceae (Palmae)] epicarp/mesocarp, an ethanol extract was prepared and named OSEME, which was tested on the viability,morphology and metabolism of several cell lines, such as the leukaemic cell lines, HL-60, K562 and the latter multidrug resistant counterpart K562-Lucena 1, the human breast cancer cell line MCF-7, the mouse fibroblast cell line 3T3-L1 and fresh human lymphocytes. OSEME promoted a dose-dependent decrease on the viability of all cells. This effect was much more pronounced on the tumoral cell lines than on non-tumoral cells, a phenomenon revealed by the dose of OSEME which promotes half of maximal effect (ID50). The decrease on viability was followed by shrinkage of cells, alteration on their morphology, and a markedly nuclear condensation. Curiously, stimulation of 6-phosphofructokinase activity (6.6-times) was observed on HL-60 cells, treated with OSEME, when compared to control treated with ethanol (vehicle). These results support evidences to suggest OSEME as a promising source of novel antineoplasic agents.

(18)F-FDG accumulation in the oral cavity is associated with periodontal disease and apical periodontitis: an initial demonstration on PET/CT

OBJECTIVE

The objective of this study was to prospectively investigate the relationship between high accumulation of 2-deoxy-2-[(18)F] fluoro-D: -glucose (FDG) in the oral cavity and dental infections on positron emission tomography/computed tomography (PET/CT).

METHODS

FDG-PET/CT scans of 103 patients who underwent a health screening were evaluated. The dental examination was performed prior to each PET/CT scan, and dental infections were assessed. Dental infections were classified into six blocks. The severity of dental caries was classified into five grades, and periodontal disease and apical periodontitis were classified into three grades. Two radiologists classified the PET images in the same manner as the dental examination. They evaluated the intensity of FDG uptake by a four-point visual PET image score for each block. The comparison of the dental examination, as a gold standard, and the visual PET image score was performed on a patient or block basis.

RESULTS

On a patient-based analysis, 21 of 103 patients (20.4%) showed PET positive findings in the oral cavity; 18 of the 21 patients (85.7%) had dental infections. On a block-based analysis, 25 of 605 blocks (4.1%) showed PET positive findings in the oral cavity; 22 of the 25 blocks (88.0%) had dental infections. On a detailed block-based analysis, a significant difference was observed between the presence of periodontal disease, or apical periodontitis and the positivity of the visual PET image findings (P < 0.01). Their severity correlated with the visual PET image score (P < 0.05).

CONCLUSIONS

Periodontal disease or apical periodontitis, but not dental caries, caused FDG accumulation in the oral cavity. This finding should be taken into account when a head and neck FDG-PET study is interpreted.

Causes and consequences of increased glucose metabolism of cancers

In this review we examine the mechanisms (causes) underlying the increased glucose consumption observed in tumors within a teleological context (consequences). In other words, we will ask not only "How do cancers have high glycolysis?" but also, "Why?" We believe that the insights gained from answering the latter question support the conclusion that elevated glucose consumption is a necessary component of carcinogenesis. Specifically we propose that glycolysis is elevated because it produces acid, which provides an evolutionary advantage to cancer cells vis-à-vis normal parenchyma into which they invade.

Utility of PET/CT imaging performed early after surgical resection in the adjuvant treatment planning for head and neck cancer

PURPOSE

To evaluate the utility of positron emission tomography (PET)/computed tomography (CT) early after surgical resection and before postoperative adjuvant radiation therapy.

METHODS AND MATERIALS

We studied a prospective cohort of 91 consecutive patients referred for postoperative adjuvant radiation therapy after complete surgical resection. Tumor histologies included 62 squamous cell and 29 non-squamous cell cancers. Median time between surgery and postoperative PET/CT was 28 days (range, 13-75 days). Findings suspicious for persistent/recurrent cancer or distant metastasis were biopsied. Correlation was made with changes in patient care.

RESULTS

Based on PET/CT findings, 24 patients (26.4%) underwent biopsy of suspicious sites. Three patients with suspicious findings did not undergo biopsy because the abnormalities were not easily accessible. Eleven (45.8%) biopsies were positive for cancer. Treatment was changed for 14 (15.4%) patients (11 positive biopsy and 3 nonbiopsied patients) as a result. Treatment changes included abandonment of radiation therapy and switching to palliative chemotherapy or hospice care (4), increasing the radiation therapy dose (6), extending the radiation therapy treatment volume and increasing the dose (1), additional surgery (2), and adding palliative chemotherapy to palliative radiation therapy (1). Treatment for recurrent cancer and primary skin cancer were significant predictors of having a biopsy-proven, treatment-changing positive PET/CT (p < 0.03).

CONCLUSIONS

Even with an expectedly high rate of false positive PET/CT scans in this early postoperative period, PET/CT changed patient management in a relatively large proportion of patients. PET/CT can be recommended in the postoperative, preradiation therapy setting with the understanding that treatment-altering PET/CT findings should be biopsied for confirmation.

Inter-observer Variations in FDG-PET Interpretation for Cancer Screening

BACKGROUND

Diagnostic guidelines for the use of 2-(fluorine 18) fluoro-2 deoxy-D-glucose (FDG)-positron emission tomography (PET) in cancer screening have yet to be established. We assessed inter-observer variability in screening FDG-PET.

METHODS

Subjects comprised 40 individuals who underwent FDG-PET and computed tomography (CT) for cancer screening. To assess various patterns of FDG uptakes, three subsets of the cases were selected: 'Cancer', 15 cases with cancer; 'Not malignant', 15 cases with suspected cancer by FDG-PET who were confirmed as cancer-free; and 'Normal', 10 cases without remarkable FDG uptake who were confirmed as cancer-free. A total of 68 lesions made up of malignancy (n = 18), benign (n = 21), and physiological FDG uptake (n = 29) were interpreted by six physicians. Each observer reviewed each case three times. Step 1 involved interpretation of PET images alone, Step 2 involved side-by-side reading of PET and CT images, and Step 3 involved re-evaluation of findings with the results of other screening tests. We assessed inter-observer agreement for each step.

RESULTS

Inter-observer agreement for all lesions at each step was moderate, compared to fair agreement for 'Normal' subjects. Inter-observer agreement of 'Cancer' and 'Not malignant' subjects in Step 1 were better than those in Step 2 and 3; however, the differences were not statistically significant.

CONCLUSION

The interpretation of FDG-PET is adequately reproducible, while that of 'Normal' subjects is less reproducible. Improvement of inter-observer variability in assessing physiological FDG uptakes requires universal reporting criteria in FDG-PET. Correlative interpretation of PET, CT and other information may require standardization in subjects with suspected cancer by FDG-PET.

Sequential FDG-PET/CT reliably predicts response of locally advanced rectal cancer to neo-adjuvant chemo-radiation therapy

PURPOSE

Prediction of rectal cancer response to preoperative, neo-adjuvant chemo-radiation therapy (CRT) provides the opportunity to identify patients in whom a major response is expected and who may therefore benefit from alternative surgical approaches. Traditional morphological imaging techniques are effective in defining tumour extension in the initial diagnostic and staging work-up, but perform poorly in distinguishing residual neoplastic tissue from scarring post CRT, when restaging the patient before surgery. Fluorine-18 fluorodeoxyglucose positron emission tomography (FDG-PET) is a promising tool for monitoring the effect of anti-tumour therapy. The aim of this study was to prospectively assess the value of sequential FDG-PET scans in predicting the response of locally advanced rectal cancer to neo-adjuvant CRT.

METHODS

Forty-four consecutive patients with locally advanced (cT3-4) primary rectal cancer and four patients with pelvic recurrence of rectal cancer were enrolled in this prospective study. Treatment consisted of external beam intensified radiotherapy (50 Gy to the posterior pelvis, 56 Gy to the tumour), chemotherapy (in most cases PVI 5-FU at 300 mg/m(2) per day) and, 8-10 weeks later, surgery with curative intent. All patients underwent FDG-PET/CT both before CRT and 5-6 weeks after completing CRT. One patient died before surgery because of acute myocardial infarction, and was therefore excluded from further analysis. Semi-quantitative measurements of FDG uptake (SUV(max)), absolute difference (DeltaSUV(max)) and percent SUV(max) difference (Response Index, RI) between pre- and post-CRT PET scans were considered. Results were correlated with pathological response, assessed both by histopathological staging of the surgical specimens (pTNM) and by the tumour regression grade (TRG) according to Mandard's criteria (patients with TRG1-2 being defined as responders and patients with TRG3-5 as non-responders).

RESULTS

Following neo-adjuvant CRT, of the 45 patients submitted to surgery, 23 (51.1%) were classified as responders according to Mandard's criteria (8 TRG1 and 15 TRG2), while the remaining 22 (48.9%) were non-responders (9 TRG3 and 13 TRG4-5). Considering all patients, the mean pre-CRT SUV(max) was 15.6, significantly higher than the mean value of 5.4 post CRT (p < 0.001). Nevertheless, when stratifying patients according to response to CRT (using Mandard's criteria), the mean RI was significantly higher in responders than in non-responders (75.9% versus 46.9%,p = 0.0015). Using a 66.2% SUV(max) decrease as the cut-off value (identified by ROC analysis) for defining response to therapy, the following parameters were obtained: 79.2% specificity, 81.2% sensitivity, 77% positive predictive value, 89% negative predictive value and 80% overall accuracy.

CONCLUSION

The results suggest the potential utility of FDG-PET as a complementary diagnostic and prognostic procedure in the assessment of neo-adjuvant CRT response of locally advanced rectal cancer. DeltaSUV(max) and RI seem the best predictors of CRT response.

Distinguishing benign from malignant gallbladder wall thickening using FDG-PET

OBJECTIVE

Because thickening of the gallbladder wall is observed not only in patients with gallbladder cancer but also in those with benign diseases such as chronic cholecystitis and gallbladder adenomyosis, it is difficult to distinguish between benign and malignant gallbladder wall thickening by conventional techniques of diagnostic imaging such as computed tomography (CT), magnetic resonance imaging (MRI), and abdominal ultrasonography (US). In the present study, we attempted to distinguish between benign and malignant gallbladder wall thickening by means of fluorine-18-fluorodeoxyglucose (FDG)-Positron emission tomography (PET).

METHODS

FDG-PET was performed in 12 patients with gallbladder wall thickening detected by CT or US, to determine whether it was benign or malignant. Emission scans were taken, beginning 45 minutes after intravenous administration of FDG, and SUV was calculated as an indicator of glucose metabolism.

RESULTS

Of the 12 patients, 4 showed positive uptake of FDG in the gallbladder wall. Of these 4 patients, 3 had gallbladder cancer. The remaining one, who had chronic cholecystitis, had false-positive findings. The other 8 patients had negative uptake of FDG in the gallbladder wall. Two of these 8 underwent surgical resection, which yielded a diagnosis of chronic cholecystitis. The other 6 patients exhibited no sign of gallbladder malignancy and have been followed without active treatment.

CONCLUSIONS

FDG-PET appears able to distinguish between benign and malignant gallbladder wall thickening.