Cost-effectiveness of PET imaging in clinical oncology

Positron emission tomography (PET) for staging and evaluation of response to treatment in patients with Hodgkin's disease

Forty two examinations utilizing F-18 FDG-PET were performed in 23 patients with Hodgkin's disease to study for involved lymphoma regions and compared to conventional staging procedures. Twenty stagings were performed at diagnosis of untreated Hodgkin's disease or at first relapse, and 22 restagings during and after chemoradiotherapy. At diagnosis in 5 of 20 patients PET and other procedures revealed different extranodal manifestations and in 3 patients established different clinical staging. PET seemed to be accurate in the assessment of lymphoma involvement in nodal sites. During follow up, in 10 out of 22 investigations different results and discrepancy were recorded, mostly due to the different extent of F-18-FDG metabolism in residual masses in lymphatic tissues compared to CT, X-ray or ultrasonography. The results indicate that PET may have advantages in the assessment of remissions in nodal sites. Less conclusive results were observed with regard to extranodal involvement or inflammatory disease. In conclusion PET may be sufficient for the staging of the majority of patients with Hodgkin's disease and particularly for assessing remission status in nodal sites, but PET may have disadvantages in the evaluation of extranodal lymphoma and inflammatory disease.

A Delphi study to establish national cost-effectiveness research priorities for positron emission tomography

OBJECTIVE

This study aimed to determine the key cost-effectiveness research questions relating to positron emission tomography (PET) in the UK.

METHODS

A systematic literature review was conducted to establish the existing knowledge base relating to the cost-effectiveness of PET in the various conditions for which it has been proposed. A three-round postal Delphi study of relevant individuals was used to determine the key cost-effectiveness research questions relating to PET in the UK. The content and structure of the Delphi study was informed by the results of the literature review.

RESULTS

The most important cost-effectiveness research priorities for the National Health Service (NHS) relating to PET were in the clinical areas of lung cancer, breast cancer and the assessment of myocardial viability. Gamma camera PET using coincidence imaging was highlighted as a modality whose, clinical role needed to be determined urgently.

CONCLUSION

Underlying the cost-effectiveness research priorities which were established is the need for evidence that the use of the various PET modalities as a diagnostic technique will alter patient management as compared to existing diagnostic strategies. The findings of the project provide a contemporary overview of the potential role for PET in the NHS and will be relevant to other countries.

[Managing cutaneous melanoma]

Cutaneous melanoma represents the main cause of death among skin cancers. Early diagnosis gives, for the time being, the only possibility for high rate of curative treatment. Diagnosis is based on pathological findings, and at primary tumor stage. Breslow thickness of the lesion is the best prognostic index. At local stage of the disease, treatment is precisely codified by international recommendations and consensus conferences. Follow-up after surgical treatment is also well codified. Treatment of lymph node invasion or metastatic disease is, on the other hand, less codified. Despite recent advances, especially in immunotherapy, treatment of advanced stages of melanoma remains difficult.

F-18-FDG uptake in tuberculosis

Two patients are described who showed abnormal fluorine-18 fluorodeoxyglucose (F-18 FDG) uptake that was due to benign disease, specifically tuberculous lymphadenitis and pneumonitis. The first patient had ulceration and oozing of the left nipple that was related to Paget's disease. An F-18 FDG PET, whole-body scan, which was performed for staging, showed no breast uptake. However, there was intense multifocal uptake in mediastinal, supraclavicular, and para-aortic areas that was confirmed radiologically to represent widespread lymphadenopathy. Pathologic examination of a mediastinal lymph node showed active tuberculosis. The second patient showed intense focal F-18 FDG uptake in mediastinal and supraclavicular areas and para-aortic lymphadenopathy due to non-Hodgkin's lymphoma. In addition, there was abnormal F-18 FDG lung uptake that revealed the presence of acid-fast bacilli on bronchial lavage. Intense focal F-18 FDG uptake in widespread lymphadenopathy or in the lung could be caused by infectious diseases such as tuberculosis. This possibility should be considered when whole-body scans of patients with cancer are interpreted, especially in those with a high incidence of infectious disease.

Classification and staging of melanoma

Although a standardized and uniformly accepted cancer staging system is an essential and fundamental requirement to enable meaningful comparisons across patient populations, the sometimes capricious biologic behavior of melanoma makes developing such a staging system particularly difficult. Since the earliest well-documented attempts at classifying patients with cutaneous melanoma were described more than 50 years ago, the identification of increasingly powerful prognostic factors has led to sequential modifications of the cutaneous melanoma staging system. The current AJCC staging system is based on relatively well-established prognostic factors; however, several recent reports have identified additional prognostic factors not included in the current system, and other studies support the re-evaluation of some of the currently employed staging criteria. Some of the more controversial areas include the relevance of level of invasion versus tumor thickness, optimal cutoffs for tumor thickness, importance of ulceration, the grouping of satellites with in-transit metastases, the inclusion of microsatellites and local recurrences as a separate staging criterion, the replacement of size of nodal mass with number of positive nodes, the importance of nodal metastases in more than one nodal basin, and the prognostic significance of distant metastases. Therefore, future modifications of the staging system are anticipated to better incorporate these observations. Stage-specific staging recommendations for the patient with melanoma provide the clinician with a framework to most efficiently assess extent of disease in an era of cost-conscious clinical practice. In the asymptomatic patient with primary melanoma (stage I or II), we recommend a chest roentgenogram and evaluation of alkaline phosphatase and LDH levels; extensive radiologic evaluations are not indicated, because the rate of detection in this population is extremely low. Additional staging information should also be obtained by the technique of lymphatic mapping and sentinel lymphadenectomy. For patients with local-regional disease (stage III, satellites, and local recurrence), a selective approach to imaging studies is warranted. For this patient population, we recommend complete blood count, liver function tests including alkaline phosphatase and LDH, a chest roentgenogram, and a CT scan of the abdomen. Although the yield of these tests, particularly CT of the abdomen, in detecting distant metastases in asymptomatic patients is low, they may identify false-positive abnormalities and provide an important baseline for future studies in this high-risk population. For patients with disease below the waist or in the head and neck region, we recommend CT of the pelvis and CT of the neck, respectively. Additional studies should be done only if clinically indicated. Finally, patients with known systemic disease (stage IV) should be more comprehensively evaluated, because the likelihood of detecting asymptomatic metastases is higher. Accordingly, in addition to the work-up outlined previously for stage III patients, we also perform a CT scan of the chest and MR imaging of the brain; other studies (e.g., bone scan, gastrointestinal series) are performed on the basis of symptoms.

Evaluating tumor biology and oncological disease with positron-emission tomography

The usefulness of positron-emission tomography (PET) for noninvasive assessment of several biological parameters of neoplastic tissue has been reviewed. Numerous radiotracers have been developed, whose particular distribution in the presence of cancer in vivo serves to distinguish medically relevant properties of the tumor cells with which they associate. That distribution is most accurately determined through use of a PET scanner, to localize and quantify the tracer molecules, in which have been incorporated positron-emitting isotopes. These tracers include hypoxia markers, receptor ligands, substrates for enzymatic modification by the products of expression of specific genes, and precursors of protein anabolism and carbohydrate catabolism. In addition, application of PET to evaluation of patients with some particular cancers has been examined, while placing special emphasis on the level of scientific rigor of the evidence underlying conclusions about appropriate use of PET in oncology.

A brief history of positron emission tomography (PET)

The development of positron emission tomography (PET) illustrates how advances in basic science translates into benefits for human beings. In 1930 Ernest Lawrence and co-workers conceived of the cyclotron. By 1938 Lawrence, Livingston, et al had designed a "medical cyclotron." The subsequent production of C-11, N-13, O-15, and F-18 found many uses in medical and physiologic research. The introduction of F-18 deoxyglucose represents another major step toward practical clinical use of positron-emitting tracers. We have now achieved the transition from the postulation of the existence of positrons to their use in a wide variety of diseases.

Progress in nuclear medicine imaging of cancers

Nuclear imaging is assuming an increasing role in the management of patients with cancer. A variety of new radiopharmaceuticals, several antibody or peptide based, as well as innovative uses of existing radiopharmaceuticals, mean that most nuclear medicine departments equipped with standard imaging devices can image the single photon imaging agents without difficulty.

Fluorodeoxyglucose whole-body positron emission tomography in colorectal cancer patients studied in routine daily practice

PURPOSE

To evaluate the routine clinical value of attenuation-corrected whole-body fluorodeoxyglucose positron emission tomography in colorectal cancer, a total of 59 patients who were referred for evaluation of suspected or proven colorectal cancers were studied.

METHODS

Positron emission tomography scans were recorded using a Siemens ECAT Exact 921/47.

RESULTS

Median follow-up after the positron emission tomography study was 11 (mean, 12.3; range, 1-21) months. According to computed tomography, coloscopy, and ultrasound, we recorded eight apparently false-positive results. During later follow-up, however, three of those cases, which were negative with computed tomography, magnetic resonance imaging, sonography, or laparoscopy, turned out to be true-positive instead. In 3 patients, a primary colorectal cancer was suspected; in 26 patients, a recurrence of colorectal cancer was suspected. Eight patients were studied for follow-up after the history of colorectal cancer with no suspicion of recurrence. In 12 patients, the rise of serum tumor marker concentrations was the reason for the positron emission tomography study; 12 patients with known metastatic disease were also included ("restaging"). With regard to the entire patient population, we found an overall sensitivity of 100 percent, a specificity of 67 percent, and positive and negative predictive values of 92 and 100 percent, respectively. Being merely confirmative with respect to tumor recurrence or distant metastases in the majority of patients, positron emission tomography revealed a primary tumor in one patient and confirmed metastatic foci in several patients that had not been delineated by other imaging modalities.

CONCLUSION

A whole-body positron emission tomography scan provides optimum conditions to locate metastatic lesions that might not be seen otherwise. There is a trend showing that positron emission tomography diagnostics as a consequence of early increased tumor markers is a highly sensitive combination, because computed tomography and magnetic resonance imaging were not as sensitive in early recurrences. Positron emission tomography, as performed in daily clinical practice, proved to be a powerful diagnostic tool in our subset of colorectal cancer patients.