Positron emission tomography in oncology. General acceptance of its role is overdue

Relapse after more than 20 years of follow-up for epithelial ovarian carcinoma

BACKGROUND

Very late relapse of ovarian cancer is unusual and may present with atypical symptoms.

CASES

We diagnosed 3 cases of relapse occurring after more than 20 years of follow-up. In the first case, the first recurrence was diagnosed by an appendicitis syndrome. With the second recurrence, small pelvic nodules were detected by fluorodeoxyglucose scintigraphy, whereas other imaging method results were negative. In the second case, a nodule in the axilla revealed the recurrence, and imaging methods confirmed multiple metastasis. In the third case, the patient presented with paroxysmal abdominal pain, and fluorodeoxyglucose scintigraphy showed a tiny lesion.

CONCLUSION

Late relapses of ovarian cancer raise the issue of regrowth of dormant cells or the development of a new primary cancer. The absence of family history and BRCA gene mutations in these 3 patients favor late recurrence. Fluorodeoxyglucose scintigraphy was useful for diagnosis, particularly of small lesions not visible by classic imaging methods.

Detection of lung cancer with positron coincidence gamma camera using fluorodeoxyglucose in comparison with dedicated PET

OBJECTIVE

Dual-head gamma cameras with sodium iodide (NaI) detectors operated in coincidence mode provide a new approach for imaging with positron-labeled tracers. The purpose of this study was to evaluate the feasibility of FDG imaging with positron coincidence detection gamma camera (PCD) in detecting lung tumor in comparison with FDG imaging with the dedicated positron emission tomography (PET).

METHODS AND MATERIAL

Twenty-six lesions of 13 patients with suspected lung cancer were studied with both FDG PET and FDG PCD on the same day. Pulmonary lesions were analyzed visually and semi-quantitatively using the ratio of target-to-background counts (T/B ratio).

RESULTS AND CONCLUSIONS

FDG PCD and FDG PET could detect visually 21 lesions (80.8%) and 23 lesions (88.0%), respectively. The mean T/B ratio and standard deviation (S.D.) of FDG PCD was 4.6 +/- 3.9, significantly lower than that of FDG PET (11.4 +/- 6.6, P<0.001). When pulmonary lesions were no more than 2.0 cm in diameter, the sensitivity of FDG PCD was 37.5%, significantly inferior to that of FDG PET (62.5%, P<0.001). There was no statistically significant difference of the sensitivity between the FDG PCD and FDG PET in lesions of more than 2.0 cm in diameter. FDG PCD with uniform attenuation correction was clinically available in detecting lung cancer. However, the sensitivity for small lesions less than 2.0 cm was limited. The application of measured attenuation correction and scatter correction may to be needed to improve the detectability of FDG PCD, especially for detecting small lung cancer.

Oncological diagnosis using positron coincidence gamma camera with fluorodeoxyglucose in comparison with dedicated PET

The purpose of this study was to compare the utility of a dual-head positron coincidence detection gamma camera (PCD) with that of dedicated positron emission tomography (PET) in the imaging of various malignancies using (18)F-fluorodeoxyglucose (FDG). 25 patients with known or suspected malignancies at various sites underwent imaging with both methods, and diagnostic performance on a lesion basis was compared. Tumour lesions were analyzed visually and semi-quantitatively using the ratio of tumour-to-background counts (T/B ratio). FDG PCD and FDG PET visually detected 34 (72.3%) lesions and 37 (78.7%) lesions, respectively. The mean T/B ratio and standard deviation (SD) of FDG PCD was 3.5+/-3.3, significantly lower than that of FDG PET (8.4+/-7.1, p<0.001). When tumour lesions were less than 2.0 cm in diameter, the sensitivity of FDG PCD was 37.5%, significantly inferior to that of FDG PET (50.0%, p<0.01). Sensitivity between FDG PCD and FDG PET in lesions of more than 2.0 cm diameter showed no statistically significant difference. This study indicates that FDG imaging with a dual-head coincidence detection gamma camera can provide suitable diagnostic performance for lesions greater than 2.0 cm diameter, but performed significantly worse than dedicated PET for lesions smaller than this.

Positron emission tomography for staging and management of malignant melanoma

BACKGROUND

The incidence of malignant melanoma is rising; it now has an incidence of ten per 100 000 per annum in the UK. The development of metastases is unpredictable, but prognosis is linked directly to the initial stage at diagnosis. Positron emission tomography (PET) can allow the detection of malignant cells at a relatively early stage.

METHODS

A review of the literature was undertaken by searching the Medline database for the period 1980-2000 without any language restrictions.

RESULTS

The overall sensitivity and specificity of PET are 74-100 and 67-100 per cent respectively. PET has a reduced sensitivity and specificity for thinner lesions (less than 1 x 5 mm). Comparison with computed tomography and magnetic resonance imaging has shown a higher sensitivity and specificity for PET in all regions of the body except the thorax.

CONCLUSION

Currently the accepted indication for PET is recurrent melanoma when surgical intervention is being considered. However, other potential indications include the detection of occult or distant metastasis at initial presentation and the clarification of abnormal radiological findings at follow-up. The routine use of PET for American Joint Commission on Cancer stage I or II disease is of uncertain benefit and is not indicated at present.

Extending positron emission tomography scan utility to high-risk neuroblastoma: fluorine-18 fluorodeoxyglucose positron emission tomography as sole imaging modality in follow-up of patients

PURPOSE

Although positron emission tomography (PET) with fluorine-18 fluorodeoxyglucose ((18)F-FDG) has a major impact on the treatment of adult cancer, the reported experience with extracranial tumors of childhood is limited. We describe a role for PET in patients with neuroblastoma (NB).

PATIENTS AND METHODS

In 51 patients with high-risk NB, 92 PET scans were part of a staging evaluation that included iodine-123 or iodine-131 metaiodobenzylguanidine (MIBG) scan, bone scan, computed tomography (and/or magnetic resonance imaging), urine catecholamine measurements, and bone marrow (BM) examinations. The minimum number of tests sufficient to detect NB was determined.

RESULTS

Of 40 patients who were not in complete remission, only 1 (2.5%) had NB that would have been missed had a staging evaluation been limited to PET and BM studies, and 13 (32.5%) had NB detected by PET but not by BM and urine tests. PET was equal or superior to MIBG scans for identifying NB in soft tissue and extracranial skeletal structures, for revealing small lesions, and for delineating the extent and localizing sites of disease. In 36 evaluations of 22 patients with NB in soft tissue, PET failed to identify only two long-standing MIBG-negative abdominal masses. PET and MIBG scans showed more skeletal lesions than bone scans, but the normally high physiologic brain uptake of FDG blocked PET visualization of cranial vault lesions. Similar to MIBG, FDG skeletal uptake was diffusely increased with extensive or progressing BM disease but faint or absent with minimal or nonprogressing BM disease.

CONCLUSION

In the absence or after resolution of cranial vault lesions, and once the primary tumor is resected, PET and BM tests suffice for monitoring NB patients at high risk for progressive disease in soft tissue and bone/BM.

Positron emission tomography using 2-[(18)F] fluoro-2-deoxy-D-glucose in the diagnosis of uterine leiomyosarcoma: a case report

The preoperative diagnosis of uterine leiomyosarcoma (LMS) is very difficult. Magnetic resonance (MR) imaging is usually used for it; however, precise diagnosis by MR imaging is limited to typical LMS with coagulative tumor cell necrosis. We presented a case of LMS that was diagnosed preoperatively by positron emission tomography (PET) using 2-[(18)F] fluoro-2-deoxy-D-glucose (FDG).

Positron emission tomography with (18)F-fluorodeoxyglucose of uterine sarcoma: a comparison with magnetic resonance imaging and power Doppler imaging

OBJECTIVE

The effectiveness of positron emission tomography with (18)F-fluorodeoxyglucose (FDG-PET) for diagnosis of uterine sarcoma was evaluated in comparison to the effectiveness of magnetic resonance (MR) imaging and power Doppler imaging.

METHOD

The cases of five Osaka City University Hospital patients diagnosed with uterine sarcoma based on histopathological examination, in whom FDG-PET, MR imaging, and power Doppler imaging studies had been performed preoperatively, were reviewed. A comparative study of the usefulness of these three imaging modalities for diagnosis of sarcoma was conducted. Tumors comprised three leiomyosarcomas, one endometrial stromal sarcoma, and one carcinosarcoma.

RESULTS

FDG-PET examinations were 100% positive for the five sarcomas; MR imagings were 80% positive (four of five cases), and US was 40% positive (two of five cases). The mean standardized uptake value of the sarcomas was 4.5 +/- 1.3.

CONCLUSION

The sarcoma lesions were clearly imaged by FDG-PET. FDG-PET may be a most useful diagnostic method for uterine sarcoma.

Imaging of malignant lymphomas with F-18 FDG coincidence detection positron emission tomography

PURPOSE

The authors evaluated the utility of F-18 fluorodeoxyglucose (FDG) coincidence detection (CoDe) positron emission tomography (PET) for staging, post-treatment evaluation, and follow-up assessment of patients with malignant lymphomas.

MATERIALS AND METHODS

Fifty-eight patients with histologically proved malignant lymphomas (4 Hodgkin's disease, 54 non-Hodgkin's lymphoma) underwent CoDe PET using F-18 FDG. CoDe PET was performed using a dual-head gamma camera equipped with coincidence detection circuitry. Of the 87 CoDe PET studies, 26 were performed for staging, 38 for post-treatment evaluation, and 23 for follow-up evaluation of recurrence. The entire trunk, from the cervical to the inguinal regions, or selected regions were scanned with the patient in the supine position. No attenuation correction was made and reconstruction was performed using filtered back-projection rather than iterative reconstruction. CoDe PET findings were compared with corresponding results of computed tomographic (CT) and magnetic resonance imaging (MRI), tissue biopsy, or clinical follow-up.

RESULTS

For staging, 52 sites were positive on CoDe PET or CT-MRI. CoDe PET detected 49 sites (94%), and CT-MRI showed 47 sites (90%). CoDe PET detected five more lymphomatous lesions and missed three lesions. For post-treatment evaluation, CoDe PET showed a positive predictive value of 100% and a negative predictive value of 83%, but the validated cases numbered only 11. For follow-up for recurrence, CoDe PET had a negative predictive value of 90%, but frequent false-positive findings were noted in the head and neck region as a result of underlying inflammatory changes.

CONCLUSIONS

For staging, FDG CoDe PET alone without attenuation correction is not sensitive enough to be used as an independent imaging method, especially for small abdominal lesions. However, it appears to be an accurate method for assessing residual disease and for patient follow-up.

Positron emission tomography in the clinical staging of patients with Stage I and II testicular germ cell tumors

OBJECTIVES

To evaluate the accuracy of fluorodeoxyglucose positron emission tomography (PET) compared with computed tomography (CT) staging in patients with Stage I and II testicular germ cell tumors (GCTs).

METHODS

From January 1995 to July 1997, in 37 patients with clinical Stage (CS) I (n = 25) and CS II (n = 12) GCT (24 nonseminomas, 13 seminomas), PET and CT were compared in the initial staging. After PET, the patients with nonseminomatous GCT were staged surgically by retroperitoneal lymph node dissection and the patients with seminomatous GCT were followed up clinically.

RESULTS

Correct staging by PET was achieved in 34 of 37 patients compared with correct CT staging in 29 of 37 patients. Of 10 metastatic lesions, 7 and 4 were detected by PET and CT, respectively. PET did not show false-positive signals. PET was unable to detect vital cancer with a maximal diameter less than 0.5 cm or teratoma at any size.

CONCLUSIONS

PET was useful for detecting viable tumor in lesions that are visible on CT scan and, thus, it may omit false-positive CS II lesions. However, PET was not able to identify mature teratoma. In this study, PET did not improve the staging in patients with CS I tumor.

Noninvasive detection of inguinofemoral lymph node metastases in squamous cell cancer of the vulva by L-

In the majority of patients with early stage squamous cell cancer (SCC) of the vulva, an inguinofemoral lymphadenectomy is performed (in retrospect) for diagnostic reasons: exclusion of inguinofemoral lymph node metastases. The morbidity of this procedure, however, is significant. The aim of the present study was to evaluate noninvasive detection of inguinofemoral lymph node metastases by positron emission tomography (PET) using L-[1-11C]-tyrosine (TYR) as tracer. In patients with SCC of the vulva, scheduled for resection of the primary tumor and uni- or bilateral inguinofemoral lymphadenectomy, results of preoperative palpation of the groins and TYR-PET imaging were compared with histopathology. PET imaging was performed using two different methods. In a first group (n = 16), nonattenuation corrected 'whole body' scans were performed, and in a second group (n = 9), attenuation corrected static emission scans. Sensitivity, specificity, accuracy, and positive and negative predictive value for palpation were 62%, 89%, 82%, 67%, and 87% per groin. Sensitivity, specificity, accuracy, and positive and negative predictive value for TYR-PET were calculated for the two methodologies separately and overall. There were no significant differences. Overall values were 53%, 95%, 94%, 33%, and 98% per lymph node and 75%, 62%, 65%, 41% and 88% per groin. Detection of inguinofemoral lymph node metastases by TYR-PET is not superior to palpation. Neither palpation nor TYR-PET is able to adequately predict or exclude presence of inguinofemoral lymph node metastases in patients with SCC of the vulva.

Metabolic imaging by positron emission tomography in oncology

Positron emission tomography (PET) is a novel method in nuclear medicine to image metabolism in vivo. A wide range of physiological tracers labelled with positron emitters are available for dynamic measurements of various physiological and pathological functions of the body. PET is nowadays widely used for cardiological and neurological studies in health and disease. Oncological applications are under eager investigations. In particular, the detection of viable residual and recurrent tumour is a difficult clinical challenge which is expected to be solved by PET, while the altered metabolism related to cancer can also be studied.