Positron emission tomography scanning in gynecologic and breast cancers

Positron Emission Tomography (PET) in Oncology

Since its introduction in the early nineties as a promising functional imaging technique in the management of neoplastic disorders, FDG-PET, and subsequently FDG-PET/CT, has become a cornerstone in several oncologic procedures such as tumor staging and restaging, treatment efficacy assessment during or after treatment end and radiotherapy planning. Moreover, the continuous technological progress of image generation and the introduction of sophisticated software to use PET scan as a biomarker paved the way to calculate new prognostic markers such as the metabolic tumor volume (MTV) and the total amount of tumor glycolysis (TLG). FDG-PET/CT proved more sensitive than contrast-enhanced CT scan in staging of several type of lymphoma or in detecting widespread tumor dissemination in several solid cancers, such as breast, lung, colon, ovary and head and neck carcinoma. As a consequence the stage of patients was upgraded, with a change of treatment in 10%-15% of them. One of the most evident advantages of FDG-PET was its ability to detect, very early during treatment, significant changes in glucose metabolism or even complete shutoff of the neoplastic cell metabolism as a surrogate of tumor chemosensitivity assessment. This could enable clinicians to detect much earlier the effectiveness of a given antineoplastic treatment, as compared to the traditional radiological detection of tumor shrinkage, which usually takes time and occurs much later.

PET, PET/CT, and PET/MR Imaging Assessment of Breast Cancer

This review focuses mainly on clinical applications of PET/CT in patients with breast cancer. It discusses the role of 2-[18F]-fluoro-2-deoxy-D-glucose (FDG) PET/CT (and FDG PET) in the diagnosis and initial staging of breast cancer, in monitoring the response of disease to chemotherapy, and in identifying metastatic and recurrent disease. In addition, it discusses the role of MR imaging and potential future hybrid modalities such as PET/MR imaging.

18F-FDG PET/CT evaluation of patients with ovarian carcinoma

PURPOSE

The role of F-FDG PET has been studied in ovarian carcinoma, but its sensitivity and specificity calculations are based on dedicated PET acquisition, not PET/CT in the majority of the published studies. Therefore, we were prompted to review our experience with PET/CT in the management of patients with ovarian carcinoma.

MATERIALS AND METHODS

This is a retrospective study of 43 women with ovarian carcinoma, 27-80 years old (average: 53.9+/-7.8), who had whole-body PET/CT at our institution from 1 January 2003 to 31 August 2006. We reviewed the patients' outcomes from medical records and compared them to the interpretation of the PET/CT scans. Sensitivity and specificity were calculated using a 2 x 2 table with pathology results (79.1% of the patients) or clinical follow-up (20.9% of the cases) as the 'gold standard'. Confidence interval (CI) estimations were performed using the Wilson score method.

RESULTS

All patients had advanced stage ovarian cancer and the study was requested for re-staging. A total of 60 scans were performed: 30 patients had one scan, nine patients had two scans and four patients had three scans. The administered doses of F-FDG ranged from 381.1 to 769.6 MBq (average: 569.8+/-73.3). PET/CT had a sensitivity of 88.4% (95% CI: 75.1-95.4) and a specificity of 88.2% (95% CI: 64.4-97.9) for detection of ovarian cancer. The SUV max of the detected lesions ranged from 3 to 27 (average: 9.4+/-5.9). The CA-125 tumor marker ranged from 3 to 935 kU/ml (average: 265.2) in patients with positive scans and 4-139 kU/ml (average: 17.1) in patients with negative scans. This difference was statistically significant (P value: 0.0242).

CONCLUSION

This study confirms the good results of F-FDG PET/CT for identification of residual/recurrent ovarian cancer, as well as for distant metastases localization. PET/CT should be an integral part in evaluation of patients with high-risk ovarian cancer or rising values of tumor markers (CA-125), prior to selection of the most appropriate therapy.

Characterization of an intraperitoneal ovarian cancer xenograft model in nude rats using noninvasive microPET imaging

MicroPET is a noninvasive imaging modality that can potentially track tumor development in nude rats using the radiotracer fluorine 18-fluorodeoxyglucose (18F-FDG). Our goal was to determine whether microPET, as opposed to more invasive techniques, could be used to noninvasively monitor the development of ovarian cancer in the peritoneal cavity of nude rats for monitoring treatment response in future studies. Female nude rats were inoculated intraperitoneally with 36 million NIH:OVCAR-3 cells. Imaging was carried out at 2, 4, 6, or 8 weeks postinoculation. Each rat was fasted overnight and intravenously injected with 11.1 MBq (300 μCi) of18F-FDG in 0.2 mL of saline. Thirty minutes following injection, the rats were placed in the microPET and scanned for 30 min. After imaging, rats were euthanized for ascites and tissue collection for biodistribution and histopathologic correlation. Standard uptake values (SUVs) of18F-FDG within the peritoneal cavity were also calculated from regions of interest analysis of the microPET images. MicroPET images showed diffuse increased uptake of18F-FDG throughout the peritoneal cavity of tumor rats (mean SUV = 4.64) compared with control rats (mean SUV = 1.03). Ascites gathered from tumor-bearing rats had increased18F-FDG uptake as opposed to the peritoneal fluid collected from control rats. Biodistribution data revealed that the percent injected dose per gram (% ID/g) was significantly higher in tumor-bearing rats (6.29%) than in control rats (0.59%) in the peritoneal lymph nodes. Pathology verified that these lymph nodes were more reactive in tumor-bearing rats. By 6 weeks, some rats developed solid masses within the peritoneum, which could be detected on microPET images and confirmed as tumor by histopathology.18F-FDG uptake in these tumors at necropsy was 2.83% ID/g. These results correlate with previous invasive laparoscopic studies of the same tumor model and demonstrate that microPET using18F-FDG is a promising noninvasive tool to localize and follow tumor growth in an intraperitoneal ovarian cancer model.

Clinical significance of N-acetyl-L-aspartate resonance in ovarian mucinous cystadenoma

Magnetic resonance spectroscopy (MRS) provides a noninvasive measurement of the biochemistry of living tissue. We report spectroscopy analysis of a 26-year-old woman affected by right ovarian lesion diagnosed as mucinous cystadenoma. MRS was performed by the point-resolved spectroscopy technique with a long echo time (TE) (136 msec). MRS measurements were performed on the two distinct component of the right ovarian tumor. The classification of metabolite peaks area in this study was performed according to the technique described by Okada et al. The features of proton MRS studies are discussed. As well as strongly elevated lactate and N-acetyl-L-aspartate signals, the tumor spectrum showed lipid resonances. Proton MRS imaging may be helpful for the investigation of the underlying pathophysiology of ovarian mucinous cystadenomas.

Molecular imaging in breast cancer

Since the 1960s, bone scanning has played a major role in the management of breast cancer. In the last decade, however, the role of radionuclide molecular imaging has expanded significantly in the clinical management of breast cancer because of fluorodeoxyglucose positron emission tomography, mammoscintigraphy, and sentinel lymph node techniques. Molecular imaging also is instrumental in drug development,gene therapy, and in basic science research of breast cancer. This article provides a comprehensive review of the role of molecular imaging of breast cancer in clinical practice and reports on the current state of research in this field.

New modalities in detection of recurrent ovarian cancer

PURPOSE OF REVIEW

The vast majority of women diagnosed with ovarian cancer and subsequently treated with debulking surgery and adjuvant chemotherapy will ultimately relapse. As is the case with primary diagnosis, detection of recurrent ovarian cancer is limited due to lack of sensitivity and specificity. Specific guidelines for surveillance of this disease are controversial, partly because evidence to support such guidelines is scant and partly because the management of identified recurrences continues to be of minimal success. Subsequently, whether early detection actually can make a difference is not necessarily made clear in the literature. However, there are advances in radiological and molecular biology technology that may offer new possibilities in cancer surveillance. This review will outline the latest evidence to address their use in ovarian cancer.

RECENT FINDINGS

Most of the recent literature involving detection of recurrent ovarian cancer addresses the use of positron emission tomography. There are also some data addressing the use of magnetic resonance imaging and computed tomography in this arena. Data pertaining to other modalities such as biological markers are limited. Ca-125 is the accepted assay used for ovarian cancer surveillance, but other options are introduced that may hold promise for the future.

SUMMARY

A review of the recent literature concerning ovarian cancer surveillance techniques offers few new definitive avenues. While radiological technology and discoveries in detection assays are noteworthy, their potential impact on surveillance appears to be minimal at this time. Low sensitivity and specificity, along with expense, continue to be limiting factors.

The choice of the correct imaging modality in breast cancer management

This brief overview discusses which of the diagnostic options are more reliable and effective for breast cancer imaging with a view to avoiding the unjustified use of techniques that are suboptimal. The technological development of diagnostic imaging has been very impressive, and both radiological (mammography, ultrasonography, computed tomography, magnetic resonance imaging) and nuclear medicine tools (bone scan, planar and SPECT scintigraphy, sentinel node biopsy, positron emission tomography) have helped to overcome past limitations in the detection of small lesions. Furthermore, new approaches have been developed that permit successful differential diagnosis of doubtful lesions and rapid identification of systemic metastases, and allow non-invasive characterisation of the biology of cancer tissue. There is evidence that these advances may have helped in optimising therapeutic strategies. Importantly, the metabolic information provided by nuclear medicine procedures may be combined with the anatomical data supplied by radiological techniques in order to assist in predicting tumour response, planning radiotherapy and monitoring patient outcome. It is difficult to formulate conclusive diagnostic guidelines for application in the work-up of breast cancer, because while the role of some examinations, such as mammography and ultrasonography, is well established, that of others, such as magnetic resonance imaging and positron emission tomography, is still a matter of debate. There is a need for further prospective evaluations with appropriate clinical trials designed to evaluate the impact of these approaches in improving survival and quality of life.