A small breast cancer detected by PET

The method and efficacy of 18F-fluorodeoxyglucose positron emission tomography/computed tomography for diagnosing the lymphatic metastasis of colorectal carcinoma

RATIONALE AND OBJECTIVES

The aim of this study was to analyze the morphologic and functional features of metastatic lymph nodes of colorectal carcinoma on (18)F-fluorodeoxyglucose positron emission tomographic (PET)/computed tomographic (CT) images and correlate these with pathologic results to explore the best diagnostic performance.

METHODS

Sixty-eight patients without any previous treatment underwent (18)F-fluorodeoxyglucose PET/CT examinations and subsequent operations. All lymph nodes were evaluated by recording short diameter and maximum standardized uptake value (SUVmax) on axial images and were carefully verified on the surgically resected specimens. The radiologic diagnostic efficacies on the basis of different diagnostic criteria were compared and evaluated with pathologic results.

RESULTS

There was a significant difference for SUVmax between metastatic and benign juxtaintestinal lymph nodes (F = 96.836, P = .000) and a correlation between size and SUVmax in metastatic juxtaintestinal lymph nodes (r = 0.352, P = .038). Diagnosing according to short diameter ≥ 10 mm and SUVmax ≥ 2.5, the sensitivity, specificity, positivity prediction value (PPV), and negative prediction value (NPV) were 10.00%, 98.26%, 66.67%, and 75.84% and 82.50%, 90.43%, 75.00%, and 93.69%, respectively. Considered together, the sensitivity, specificity, PPV, and NPV were 10.00%, 99.13%, 80.00%, and 76.00%, respectively. Receiver-operating characteristic curves showed that the best cutoff values for SUVmax and short diameter were 2.0 and 4.85 mm, respectively; the corresponding sensitivity, specificity, PPV, and NPV, were 91.43%, 87.83%, 69.57%, and 97.12% and 85.71%, 60.87%, 40.00%, and 98.2%, respectively. Considered together, the sensitivity, specificity, PPV, and NPV were 95.00%, 86.96%, 71.70%, and 98.04%, respectively.

CONCLUSIONS

Fluorine-18-fluorodeoxyglucose uptake was a more reliable indicator in diagnosing malignant juxtaintestinal lymph node of colorectal carcinoma. The optimal diagnostic efficacy could be reached by considering morphologic and functional features together.

PET and cancer screening

Various carcinomas are discovered incidentally during FDG PET study. This points to the potential use of PET as a cancer screening modality. Our experience using three PET scanners showed that PET can be performed in many individuals, and a wide variety of carcinomas can be detected at potentially curable stages. PET screening targets various organs that conventional organ-specific screening tests cannot cover. PET used simultaneously with conventional tests can prevent the overlooking of cancer, reduce false-positive results, and assist in the interpretation of CT and MR images. Thus, PET can play a supportive role when used with conventional screening tests. To reduce false-positive and false-negative results in PET screening, however, experienced PET oncologists who can differentiate between distinct physiological FDG uptake and faint abnormal FDG uptake are needed. In Japan, more than half of the PET facilities offer PET examinations for cancer screening of asymptomatic persons. Not a few individuals pay for sophisticated cancer screenings. Guidelines concerning the use of PET for cancer screening were issued by the Japanese Society of Nuclear Medicine in 2004. The guidelines provide for maintenance of study quality and warn of overselling PET screening. It is unclear how much PET contributes to sophisticated cancer screening. Data are lacking as to whether mortality is reduced by PET screening. Scientific evidence should be presented demonstrating the value of PET in cancer screening.

Evolving role of positron emission tomography in the management of patients with inflammatory and other benign disorders

Fluoro-2-deoxyglucose (FDG) positron emission tomography (PET) has evolved from a research imaging modality assessing brain function in physiologic and pathologic states to a pure clinical necessity. It has been successfully used for diagnosing, staging, and monitoring a variety of malignancies. FDG-PET imaging also is evolving into a powerful imaging modality that can be effectively used for the diagnosis and monitoring of a certain nononcological diseases. PET has been shown to be very useful in the diagnosis of osteomyelitis, painful prostheses, sarcoidosis, fever of unknown etiology, and acquired immunodeficiency syndrome. Based on recent observations, several other disorders, such as environment-induced lung diseases, atherosclerosis, vasculitis, back pain, transplantation, and blood clot, can be successfully assessed with this technique. With the development and the introduction of several new PET radiotracers, it is expected that PET will secure a major role in the management of patients with inflammatory and other benign disorders.

Nuclear medicine and breast cancer: a review of current strategies and novel therapies

While breast cancer is still increasing in frequency, new diagnostic procedures are now available to challenge existing procedures and to make diagnosis of breast cancer more accurate and reliable. Mammography remains the standard investigation to reveal disease in an asymptomatic population: it can also be used to diagnose breast cancer in symptomatic patients (e.g. those with palpable breast lumps) and for guiding fine needle aspiration (FNA). Because the majority of breast lumps are benign, the challenge is to distinguish benign from malignant lesions without the use of invasive methods and this has attracted nuclear medicine physicians and medical oncologists to investigate the role of scintigraphic procedures to identify which patients require FNA. This review attempts to shed light on the various scintigraphic methods available which are of potential practical use in the assessment of malignant breast disease as well as looking at the possible role of nuclear medicine in the treatment of advanced disease.

Detection of clinically unexpected malignant and premalignant tumors with whole-body FDG PET: histopathologic comparison

PURPOSE

To determine the clinical importance and malignant potential of unexpected abnormal foci of hypermetabolism at fluorodeoxyglucose (FDG) positron emission tomography (PET) performed for evaluation of malignancy.

MATERIALS AND METHODS

A total of 1,750 FDG PET scans were obtained to evaluate a variety of known or suspected malignancies. Each scan was evaluated for abnormal unexpected hypermetabolism based on unusual location (ie, foci that did not conform to the usual distribution of metastases given the primary tumor for which the PET scan was requested) and discrete focal nature of an abnormality. Unexpected findings were followed by pathologic confirmation and were considered clinically important if the final pathologic diagnosis was cancerous, precancerous, or noncancerous but had the potential for local destruction or systemic physiologic effects.

RESULTS

On the basis of the normal spread pattern of the primary lesion, 58 abnormal unexpected foci of hypermetabolism were identified in 53 patients. Forty-five of these abnormalities were followed up with computed tomography (CT), magnetic resonance imaging, and/or mammography, and 42 had subsequent tissue confirmation at endoscopic, CT-guided, or surgical biopsy. Of 42 histopathologically confirmed abnormalities, 30 (71%) were either malignant or premalignant tumors that differed from the cancer for which the patient was originally scanned. Nine other suspicious abnormal foci proved benign and three represented false-positive findings, with no abnormal findings at endoscopy. Three of nine nonmalignant lesions were considered clinically important because of the potential for local destruction and/or systemic effects.

CONCLUSION

The identification of unexpected foci of hypermetabolism at whole-body FDG PET may signal the presence of tumors that are unrelated to the neoplasm for which the patient was scanned. Findings of this study emphasize the need for follow-up of these abnormalities because the majority represent either malignant or premalignant neoplasms, which were not clinically apparent.

Lymph node metastasis from breast cancer diagnosed by F-18 FDG whole-body PET (case report)

We report a 48-year-old woman with lymph node (LN) metastases from breast cancer in whom diagnosis was difficult by conventional imaging methods but easy by F-18 fluorodeoxyglucose (FDG) PET. She was given a diagnosis of right breast cancer and then underwent modified radical mastectomy in December 1997. During routine CT and US studies in September 1998, a questionable LN measuring 1 cm in diameter was detected in the right supraclavicular region, but a definitive diagnosis of this LN was difficult by these tests. The patient underwent FDG PET test, which showed strong nodular activity (SUV= 7.1) in the right supraclavicular region, indicating a metastatic lesion. Moreover, an unexpected second metastatic LN lesion (SUV= 5.5) in the medial aspect of the right axillary was diagnosed by PET. The PET results were confirmed by pathological examination of the surgical specimens. FDG PET is a useful tool to detect small malignant lesions that are not easily diagnosed by conventional imaging techniques such as CT and US. It is expected that PET test will be feasible at many institutions.

Application of positron emission tomography imaging to cancer screening

Whole-body positron emission tomography (PET) with(18)F-fluorodeoxyglucose (FDG) is a diagnostic modality that can noninvasively survey the entire body and sensitively detect various cancers. In this study, we examined the potential application of whole-body PET for cancer screening in asymptomatic individuals. PET was performed in conjunction with conventional examinations including physical examination, laboratory study, ultrasonography and chest computed tomography. Between September 1994 and March 1999, 3165 asymptomatic individuals participated in 5575 screening sessions (2017 men and 1148 women; mean +/- SD age, 52.2+/-10.4 years). Follow-up periods were no less than 10 months. PET results were compared with the screening outcomes. Within 1 year after screening, malignant tumours were discovered in 67 of the 3165 participants (2.1%). PET findings were true-positive in 36 of the 67 cancers (54%). Most of the 36 patients underwent potentially curative surgery; thus a wide variety of cancers were detected by PET at potentially curable stages. However, PET findings were false-negative in 31 of the 67 patients (46%). 14 of these 31 (45%) were of urological origin. FDG PET imaging has the potential to detect a wide variety of cancers at potentially curable stages. However, PET imaging is not suited to screening test of general population because PET examination involves substantial cost.