Quantitative PET/CT could improve prostate cancer treatment
Men suffering from prostate cancer have a very high chance of developing bone metastases, making it imperative to track and effectively treat local and distant tumors, especially in castrate-resistant cases. Metabolic imaging with FDG PET could provide a biomarker for predicting patients’ survival, which has been found to be a beneficial indicator in the prognosis of patients with this highly variable disease, according to a study published June 19 in the Journal of Nuclear Medicine.
Hossein Jadvar, MD, PhD, vice chair of radiology at Keck School of Medicine of USC, University of Southern California in Los Angeles, and colleagues evaluated the effectiveness of quantitative FDG PET/CT, and specifically parameters of tracer uptake for assessing overall survival of castrate-resistant metastatic prostate cancer.
“An important unmet need in this clinical context is the optimal selection and sequencing of various drug options guided by the most informative outcome measures to provide maximum benefit to individual patients,” wrote Jadvar et al. “Given the proclivity of prostate cancer to metastasize to bone, and the limitations of existing imaging tools for assessment of bone metastases, evaluating response quantitatively has been difficult.”
About one in six men in developing countries are expected to develop prostate cancer. Now that prostate-specific antigen screening is available, metastatic disease is present in about 4 percent of patients who are newly diagnosed, but a high percentage of these will progress to recurrent cancer and eventual metastases. The castrate-resistant form of the disease is considered incurable and is the primary cause of mortality for these patients.
“A recognized and relevant outcome measure in castrate-resistant metastatic prostate cancer is overall survival (OS), which may be useful for guiding and optimizing treatment decisions,” wrote the authors. “OS may be predicted by several clinical, laboratory, and imaging parameters. However, given the remarkable heterogeneity of disease in terms of prognosis, a quantitative patient-specific imaging-based predictive model of OS will be of significant clinical value.”
For this prospective study, 87 men with a median age of 68 years presenting with castrate-resistant metastatic prostate cancer were imaged with F-18 FDG PET/CT and underwent a follow up to assess OS. Of the 87 subjects, 29 were on chemotherapy and the other 58 were on chemotherapy after having recurrent disease following hormone therapy. Bone metastases were found in 73 out of 87 cases, or about 84 percent. Patients were followed up a median of 22 months after imaging. At follow up, 61 of the original 87 patients had died. Median OS was 16.5 months and the probability of OS at 24 months was about 39 percent. After completion of a univariate analysis, the hazard ratios associated the sum of the maximum standard uptake value (SUVmax), average SUVmax and max SUVmax were calculated at about 1.01, 1.13 and 1.11, respectively.
“Sum of SUVmax derived from 18F-FDG PET/CT contributes independent prognostic information on OS in men with castrate-resistant metastatic prostate cancer, and this information may be useful in assessing the comparative effectiveness of various conventional and emerging treatment strategies,” wrote the researchers.
Further studies including clinical trials will need to be conducted to demonstrate the sum of SUVmax beneficial in quantifying patient survival and for better patient selection and assessment for both conventional and investigational prostate cancer therapies.