Abstract
1077
Objectives: As a functional imaging modality, PET/CT can provide molecular or metabolic changes within cells, superior to those conventional anatomical imaging such as CT or MRI. PET/CT with FDG has now become the mainstay for the imaging evaluation of several cancers, involving diagnosis, staging, guided biopsy, radiation treatment planning, and prognostication. However its value in prostate cancer has been somewhat controversial, it is often considered to be not useful and not routinely performed in prostate cancer. Recent studies demonstrated that 18F-FDG PET/CT might indeed be useful in specific phases of prostate cancer, especially for aggressive primary prostate tumors (Gleason score>7). Therefore, in our study we hypothesized that 18F-FDG PET/CT might be useful for evaluation of high-risk prostate cancer, with an emphasis on the detection of metastatic disease.
Methods: The study included 89 patients who underwent transrectal ultrasound guided (TRUS) biopsy and 18F-FDG PET/CT before primary treatment. All patients were confirmed by pathological assessment, and 10 patients were further diagnosed to be positive with neuroendocrine biomarkers (synaptophysin and chromogranin A). The preoperative serum prostate-specific antigen (PSA) level was also obtained. The patients with Gleason score蠅8 or PSA 蠅20 ng/ml were regarded to be at high-risk level, and these two estimates were the cutoff values between low and high level groups. The 18F-FDG PET/CT findings were correlated with the clinicopathologic features.
Results: Of all included patients, 68 were at high-risk level while 21 patients at low-risk level. With regarded to the metastatic lesions, 29 patients have pelvic lymph node metastasis, and 31 patients have distant metastasis involving bone (29), lung (9), cervical lymph nodes (6), liver (1), and adrenal gland (1). As shown in Table 1, the patients with high PSA (蠅20) have higher SUVmax compared to those with low PSA (<20) (4.35±1.61 vs. 3.48±1.32 respectively, p<0.05), while the difference of SUVmax between high Gleason score (蠅8) and low Gleason score (<8) was not statistically significant (p>0.05). For the evaluation of pelvic lymph node metastasis, 18F-FDG PET/CT revealed more lesions in high PSA group with the detection rate (DR) of 46.0%, compared to that of low PSA group (17.95%) (p<0.05). The same trend was showed in high Gleason score group and low Gleason score group (DR: 50.0% for high score group vs. 12.82% for low score group, p<0.05). With regard to detecting distant metastasis, the DR was 50.0% in high PSA group while 15.38% in low PSA group (p<0.05). Patients with high Gleason score have more distant lesions presented on PET/CT (28/50) compared to those with low Gleason score (3/39) (p<0.05). Overall, for high risk prostate cancer, the detection rate of 18F-FDG PET/CT in identifying metastatic lesions was significantly higher than that for low risk prostate cancer. For the patients with Gleason score 7, the 3+4 group has less regional lymph node metastases and distant metastases in comparison to 4+3 group. In addition, 18F-FDG PET/CT detected 70% of lymph node metastases and 60% of distant metastases in 10 patients with neuroendocrine prostate cancer while it only identified 27.8% of lymph node metastases and 31.6% of distant metastases in 79 patients with non-neuroendocrine tumors.
Conclusion: Current results indicated that 18F-FDG PET/CT may be useful in imaging evaluation of metastatic extent in high risk prostate cancer, and might help clinicians formulate appreciate treatment plan. In addition, for patients with neuroendocrine prostate cancer, 18F-FDG PET/CT also has clinical utility in the detection of metastatic disease. Research Support: This study was supported by National Natural Science Foundation of China (Grant No.81471692).