Metabolic Imaging of Prostate Cancer Reveals Intrapatient Intermetastasis Response Heterogeneity to Systemic Therapy

Although intrapatient heterogeneity of prostate cancer (PCa) has recently been characterized via genomic and transcriptomic studies, the heterogeneity of systemic treatment responses has yet to be reported or imaged. Our objective was to evaluate the intrapatient intermetastasis response to systemic treatment among patients with metastatic PCa. We evaluated the metabolic response for each individual metastatic lesion (n=165) in 15 patients with metastatic PCa who underwent ¹⁸F-fluorodeoxyglucose positron emission tomography/computed tomography before and at least 3 mo after initiation of a systemic therapy that did not change in that period. Intermetastasis heterogeneity was defined as opposite metabolic responses for at least two metastases from the same compartment (bone or soft tissue) between the two time points. We found intrapatient intermetastasis response heterogeneity in 40% of the cases in our retrospective series. Our results suggest that systemic therapies can induce heterogeneous responses among individual metastases in patients with PCa, supporting the polyclonal evolution of PCa in advanced disease. Molecular imaging may thus be useful in identifying clinical resistance early after therapy initiation and could also allow targeted biopsy of resistant clones for molecular analysis.

PATIENT SUMMARY

Systemic therapies can lead to heterogeneous responses in individual metastases of prostate cancer in a patient. Molecular imaging may be useful for identifying heterogeneity and could allow targeted biopsy for molecular analysis or therapy.

High (18)F-FDG uptake in urinary calculi on PET/CT: An unrecognized non-malignant accumulation

AIM

To assess the high (18)F-fluorodeoxyglucose ((18)F-FDG) uptake in urinary calculi on positron-emission tomography/computed tomography (PET/CT).

METHODS

In this study, (18)F-FDG PET/CT examinations were retrospectively reviewed from November 2013 to February 2016 in a single center, and patients with high (18)F-FDG uptake in urinary calculi were identified. The following data were collected from each patient, including age, sex, primary disease, method to verify the urinary calculus, and imaging characteristics of the calculus.

RESULTS

A total of 2758 PET/CT studies (2567 patients) were reviewed, and 52 patients with urinary calculi were identified, in which 6 (11.5%, 6/52) patients (5 males, 1 female, age 34-73 years, median age 60.5 years) demonstrated high (18)F-FDG uptake in the urinary calculi. Among the 6 patients, 3 patients had bladder calculi, 2 patients had renal calculi, and 1 patient had both bladder and renal calculi. The size of the urinary calculi varied from sandy to 19mm on CT. The maximal Hounsfield units of the calculi ranged from 153 to 1078. The SUVmax of the calculi on the routine PET/CT scan ranged from 11.7 to 143.0. Delayed PET/CT scans were performed on 4 patients, which showed the calculi SUVmax increasing in 2 patients, while decreasing in the other 2 patients. One patient with bladder calculus underwent a follow-up PET/CT, which showed enlargement of the calculus as well as the increased SUVmax.

CONCLUSION

This study shows an uncommon high (18)F-FDG uptake in urinary calculi. Recognition of this non-malignant accumulation in urinary calculi is essential for correct interpretation of PET/CT findings.

Characterizing the normative profile of 18F-FDG PET brain imaging: sex difference, aging effect, and cognitive reserve

The aim of this study was to investigate findings of positron emission tomography with 18F-fluorodeoxyglucose (18F-FDG PET) in normal subjects to clarify the effects of sex differences, aging, and cognitive reserve on cerebral glucose metabolism. Participants comprised 123 normal adults who underwent 18F-FDG PET and a neuropsychological battery. We used statistical parametric mapping (SPM8) to investigate sex differences, and aging effects. The effects of cognitive reserve on 18F-FDG uptake were investigated using years of education as a proxy. Finally, we studied the effect of cognitive reserve on the recruitment of glucose metabolism in a memory task by dichotomizing the data according to educational level. Our results showed that the overall cerebral glucose metabolism in females was higher than that in males, whereas male participants had higher glucose metabolism in the bilateral inferior temporal gyri and cerebellum than females. Age-related hypometabolism was found in anterior regions, including the anterior cingulate gyrus. These areas are part of the attentional system, which may decline with aging even in healthy elderly individuals. Highly educated subjects revealed focal hypermetabolism in the right hemisphere and lower recruitment of glucose metabolism in memory tasks. This phenomenon is likely a candidate for a neural substrate of cognitive reserve.

Role of positron emission tomography-computed tomography in gastrointestinal malignancies

Positron emission tomography (PET) has proved itself to be valuable in the evaluation of patients with a wide array of gastrointestinal (GI) malignancies. Subsequent development of fusion imaging with PET and computed tomography (PET-CT) scanners has significantly advanced the capabilities of imaging by combining the functional data of the(18)F-labeled glucose analogue fluorodeoxyglucose (FDG) with the conventional anatomic data provided by CT. This article reviews the evolving role of FDG PET-CT imaging in the initial assessment and monitoring of GI tumors. Specific applications are discussed, and normal variants and benign findings frequently encountered during PET-CT of the GI tract are reviewed.

Hypoxia stimulates 18F-fluorodeoxyglucose uptake in breast cancer cells via hypoxia inducible factor-1 and AMP-activated protein kinase

INTRODUCTION

Hypoxia can stimulate (18)F-fluorodeoxyglucose (FDG) uptake in cultured cells. A better understanding of the underlying molecular mechanism is required to determine the value of FDG for studying tumour hypoxia.

METHODS

The effect of hypoxia on FDG uptake, and key proteins involved in glucose transport and glycolysis, was studied in MCF7 and MDA231 breast cancer cell lines.

RESULTS

Hypoxia induced a dose- and time-dependent increase in FDG uptake. The FDG increase was transient, suggesting that FDG uptake is only likely to be increased by acute hypoxia (<24 h). Molecular analysis indicated that hypoxia upregulated glut1 and 6-phosphofructo-2-kinase, key proteins involved in regulating glucose transport and glycolysis, and that these changes were induced by Hypoxia-Inducible factor 1 (HIF1) upregulation and/or AMP-activated protein kinase activation.

CONCLUSIONS

FDG may provide useful information about the oxygenation status of cells in hypoxic regions where HIF1 upregulation is hypoxia-driven.

Evaluation of ¹⁸F-FDG and ¹⁸F-FLT for monitoring therapeutic responses of colorectal cancer cells to radiotherapy

In order to compare the efficacy of (18)F-fluorothymidine (FLT) and (18)F-fluorodeoxyglucose (FDG) for monitoring early responses to irradiation, two human colorectal cancer (CRC) cell lines SW480 and SW620, which were derived from the primary lesions and the metastatic lymph node, underwent X-ray irradiation of 0, 10, or 20 Gy and were examined at 0, 24 and 72 h After irradiation, reduced proliferation of both SW480 and SW620 cells was observed in a dose-dependent manner (P<0.001), G0-G1 arrest was also noted in both cell types after 72 h in the 20 Gy group (P<0.001). Although increased apoptosis was observed in both cell lines after irradiation (P<0.001), a greater percentage of SW480 cells underwent apoptosis in response to irradiation than SW620 cells. Increased Hsp27 and decreased integrin β3, Ki67 and VEGFR2 expression was observed over time via immunocytochemistry and Western blot analysis (P<0.001), however, no significant changes were noted in response to irradiation. Finally, reduced uptake of (18)F-FLT by SW480 or SW620 cells was observed at 24-h post-irradiation, however, reduced (18)F-FDG uptake was only observed after 72 h. Therefore, we conclude that (18)F-FLT is a more suitable positron emission tomography (PET) tracer for monitoring early responses to irradiation in primary and metastatic lymph node CRC cells.