Correlation of [11C]choline PET-CT with time to treatment and disease-specific survival in men with recurrent prostate cancer after radical prostatectomy.

AIM: Radiotherapy following radical prostatectomy should be considered in men with high risk features who have a life expectancy of more than 10 years. So far no effect on prostate cancer specific survival has been proven by 3 randomized controlled trials (RCTs) on adjuvant radiotherapy. At present the optimal timing of radiotherapy is not defined. Identifying the site of recurrence is difficult at low PSA levels. [11C]choline PET-CT studies in biochemical recurrent prostate cancer after prostatectomy show a higher frequency of (false) negative cases compared to restaging after EBRT. It is uncertain if this reflects low volume of disease and/or low grade as biopsies fail to prove recurrent cancer in 50% of cases. We followed the clinical course of men with recurrent prostate cancer after radical prostatectomy and investigated treatment and survival. PET-CT data were correlated with clinical data, PSA kinetics and disease specific and overall survival. We also studied relative survival comparing an age matched group from the Central Dutch Statistical Office (CBS). METHODS: Sixty-four patients underwent [11C]choline PET-CT on PSA relapse. All patients were initially treated with radical prostatectomy and reached PSA nadir of <0.1 ng/mL. Recurrent disease was defined as PSA increase <0.2 ng/mL after nadir. Patients were either treated with watchful waiting, salvage radiotherapy and/or androgen deprivation therapy based on individual assessments by the treating urologists. Statistic: χ2, log-rank and Mann-Whitney-U tests were used to compare the [11C] choline PET/CT groups. RESULTS: The 64 patients had median PSA of 1.4 ng/mL. Median follow-up period of patients was 50 (6-124) months. Ten patients died during the course of follow-up of which 5 due to metastasized disease. No significant differences were seen in age, time to recurrence, total PSA at recurrence and PET-CT results. Patients with abnormal PET had higher PSAVel (median 3.09 ng/mL/yr versus 10.17, P=0.002) and shorter PSADT (med 4.83 months vs. 0.53, P=0.016). Median time to treatment was significantly lower in the PET-CT negative group. Age of patients at death from the whole group did not differ from the age of death in an age matched group. Disease specific survival was significantly higher in the PET-CT negative group (P=0.05). CONCLUSION: [11C]choline PET-CT showed that a negative PET/CT correlated with a higher disease specific survival and a lower treatment rate in men with a biochemical recurrence after radical prostatectomy. Overall survival of the total group was equal to the age matched cohort emphasizing the limited effect of a biochemical recurrent prostate cancer on overall survival. The optimum timing (adjuvant or early salvage) must be answered in running trials before adjuvant RT is used as standard of care.

PET/CT and radiotherapy in prostate cancer.

Radiotherapy is one of the corner stone treatments for patients with prostate cancer. Especially for locally advanced tumors radiotherapy +/- adjuvant androgen deprivation treatment is standard of care. This brings up the need for accurate assessment of extra prostatic tumor growth and/or the presence of nodal metastases for selection of the optimal radiation dose and treatment volume. Morphological imaging like transrectal ultra sound, computed tomography (CT) and magnetic resonance imaging (MRI) are routinely used but are limited in their accuracy in detecting extra prostatic extension and nodal metastases. In this article we present a structured review of the literature on positron emission tomography (PET)/CT and radiotherapy in prostate cancer patients with emphasis on: 1) the pretreatment assessment of extra prostatic tumor extension, nodal and distant metastases; 2) the intraprostatic tumor characterization and radiotherapy treatment planning; and 3) treatment evaluation and the use of PET/CT in guidance of salvage treatment. PET/CT is not an appropriate imaging technique for accurate T-staging of prostate cancer prior to radiotherapy. Although macroscopic disease beyond the prostatic capsule and into the periprostatic fat or in seminal vesicle is often accurately detected, the microscopic extension of prostate cancer remains undetected. Choline PET/CT holds a great potential as a single step diagnostic procedure of lymph nodes and skeleton, which could facilitate radiotherapy treatment planning. At present the use of PET/CT for treatment planning in radiotherapy is still experimental. Choline PET based tumor delineation is not yet standardized and different segmentation-algorithms are under study. However, dose escalation using dose-painting is feasible with only limited increases of the doses to the bladder and rectum wall. PET/CT using either acetate or choline is able to detect recurrent prostate cancer after radiotherapy but stratification of patients for any local salvage treatment has not been addressed in the current literature.

What is the value of emission tomography studies in patients with a primary glioblastoma multiforme treated by 192Ir brachytherapy?

BACKGROUND: We studied the use of (201)Thallium SPECT and L-[1-(11)C]-tyrosine PET in patients with a primary glioblastoma multiforme treated with (192)Ir brachytherapy after surgery and external beam radiation therapy. We hypothesised that the patients most likely to benefit from further surgery after deterioration would be those with radiation necrosis and would be recognised by a negative emission tomography scan. METHODS: Twenty-one patients underwent (201)Thallium SPECT performed before brachytherapy, and this was repeated in 19 patients when recurrence was suspected. Nine patients also underwent a PET scan at the same time. Nine patients underwent a second operation. FINDINGS: SPECT and PET were highly concordant concerning the prediction of radionecrosis and/or tumour recurrence. Repeat surgery did not lead to a significant increase in survival. There was no significant association between the duration of survival and tumour-to-background ratio but the number studied was small. Both SPECT and PET showed highly active lesions, which were proved to be recurrent tumour by clinical and histological follow-up. CONCLUSION: Although PET and SPECT are both highly sensitive in detecting active tumour tissue, emission tomography was not clinically valuable in the investigation of patients with a primary glioblastoma treated with brachytherapy.

Cortico-thalamic activation in generalized status epilepticus, a PET study.

In a patient with a refractory generalized convulsive status epilepticus, the ictal distribution of regional cerebral glucose was assessed with positron emission tomography (PET). Synchronized seizure activity in the EEG was associated with bilateral metabolic activation of medial sensorimotor regions, anterior cingulate cortex, striatum and thalamus. This pattern with focal cortical activation supports the concept that a cortical focus may drive epilepsy, while the thalamus mediates synchronization of neuronal activity as reflected in the EEG.

Acute effects of thalamotomy and pallidotomy on regional cerebral metabolism, evaluated by PET.

The subacute effect of thalamotomy and pallidotomy on regional cerebral metabolism was studied by means of Positron Emission Tomography (PET). In this way we aimed to identify the pattern of functional deafferentiation following a specific lesion in the basal ganglia. The cerebral distribution of 2-[18F]fluoro 2-deoxy-D-glucose (FDG) uptake at 1-2 weeks after operation was compared with the uptake before operation. Analysis of the changes was done by statistical parametric mapping (SPM). Thalamotomy resulted in a reduction of FDG uptake in predominantly the lateral prefrontal- and the parietal cortex, whereas pallidotomy affected only uptake in the (pre)frontal cortex. The absence of change in the primary sensory-motor cortex after either surgical procedure may suggest that, in man, the motor portions of the thalamus exert a predominantly indirect influence on the human motor cortex.

FDG-PET to evaluate response to hyperthermic isolated limb perfusion for locally advanced soft-tissue sarcoma.

UNLABELLED: We investigated FDG-PET in patients undergoing hyperthermic isolated limb perfusion (HILP) with rTNF-alpha, rIFN-gamma and melphalan for locally advanced soft-tissue sarcoma of the extremities. METHODS: Twenty patients (11 women, 9 men; aged 18-80 yr, mean age 49 yr) were studied. FDG-PET studies were performed before, 2 and 8 wk after HILP. After the final PET study, the tumor was resected and pathologically graded. Patients with pathologically complete response (pCR) showed no viable tumor after treatment. Those with pathologically partial response (pPR) showed various amounts of viable tumor in the resected specimens. RESULTS: Seven patients showed a pCR (35%) and 12 patients showed a pPR (60%). In one patient, pathological examination was not performed (5%). The pre-perfusion glucose consumption in the pCR group was significantly higher than in the pPR group (p<0.05). Visual analysis of the PET images after perfusion showed a rim of increased FDG uptake around the core of absent FDG uptake in 12 patients. The rim signal contained a fibrous pseudocapsule with inflammatory tissue in the pCR group, viable tumor was seen in the pPR group. The glucose consumption in the pCR group at 2 and 8 wk after perfusion had decreased significantly (p<0.05) in comparison to the glucose consumption in the pPR. CONCLUSION: Based on the pretreatment glucose consumption in soft-tissue sarcomas, one could predict the probability of a patient achieving complete pathological response after HILP. FDG-PET indicated the pathological tumor response to HILP, although the lack of specificity of FDG, in terms of differentiation between an inflammatory response and viable tumor tissue, hampered the discrimination between pCR and pPR.

Contribution of magnetic resonance spectroscopic imaging and L-[1-11C]tyrosine positron emission tomography to localization of cerebral gliomas for biopsy.

Proton magnetic resonance spectroscopic imaging (1H-MRSI) and positron emission tomography with the tracer L-[1-11C]tyrosine (11C-TYR) were used to localize gliomas for biopsy or resection. This is especially helpful in cases of low-grade gliomas, if these lesions are not visualized by contrast-enhanced computed tomographic and magnetic resonance imaging scans. The clues to improved localization are provided by changes in tissue metabolite contents, such as elevation of phosphocholine, indicating cellular proliferation; decrease of N-acetylaspartate, denoting loss of neurons (as these are replaced by tumor cells); and elevation of lactate, pointing to the prevalence of glycolysis, as observed in many tumors. These data on tissue metabolite content have been obtained in vivo in the patient by proton magnetic resonance spectroscopy; metabolite maps derived from these data then visualize the distribution of the various metabolites over the section of the brain under investigation. Alternatively, localization of a tumor may be achieved by means of positron emission tomography depicting the pattern of uptake of the amino acid tracer 11C-TYR, as it tends to be incorporated in the process of cellular proliferation and protein biosynthesis. Five cases are presented as examples.