Detection and treatment of micrometastatic prostate cancer before radiographic evidence have been widely studied. However, the currently used computed tomography (CT), bone scans and even multiparametric MRI lack sensitivity. Positron emission tomography/computed tomography (PET/CT) with nuclear radiotracers such as NaF, F-FDG and choline/acetate show some promise, but still miss a large proportion of recurrent disease. PET/CT with 18F-fluciclovine has been shown to improve the detection of recurrent prostate cancer and detect up to 57% of recurrences in previously treated prostate cancer, not detected by CT or bone scan.
In the presented retrospective study, the authors evaluated the ability of 18F-fluciclovine to change treatment, and also tried to identify an optimal PSA cut-off to screen for recurrent prostate cancer. Patients who received 18F-fluciclovine for recurrent PCa following treatment were analyzed, and patients with positive scans were compared to those who had negative scans. Also, a receiver-operator characteristic (ROC) curve was used to estimate the optimal PSA cut-off to predict for a positive scan.
According to the authors’ presentation, 84 patients with post-treatment suspected recurrent prostate cancer received 18F-fluciclovine PET/CT at a single institution. In the final analysis, 78 patients were included, divided into those with (n=53) and those without 18F-fluciclovine PET/CT positivity (n=25). 18F-fluciclovine was demonstrated to predict radiographic recurrence or metastatic disease in 53 patients (67.9%). The following parameters were similar between both groups: Age, number of comorbidities, mean PSA at diagnosis, Gleason score, Gleason grade group, clinical stage, treatment type received, nadir PSA, PSA velocity, and time from diagnosis to scan. The following covariates were shown to be associated with a positive scan: a higher mean PSA at the time of the scan (6.29 vs. 1.1 ng/ml, p = 0.01), receiving salvage radiotherapy to the prostatic bed (55% vs. 27%, p<0.01), any use of androgen deprivation therapy (ADT) (62% vs. 32%, p=0.016), and a higher mean number of scans since PSA began to rise (2.77 vs. 1,59, p = 0.042), as seen in table 1.
Recurrence sites included: lymph nodes in 65.8%, bone in 22.5%, prostatic bed in 9.2%, and others, such as lung and mediastinum, in 2.5%. A PSA of 0.5 ng/ml was identified from a ROC curve for detecting recurrent/metastatic disease, with a sensitivity of 81.13%, and a specificity of 71.43% (figure 1).
Recurrence sites included: lymph nodes in 65.8%, bone in 22.5%, prostatic bed in 9.2%, and others, such as lung and mediastinum, in 2.5%. A PSA of 0.5 ng/ml was identified from a ROC curve for detecting recurrent/metastatic disease, with a sensitivity of 81.13%, and a specificity of 71.43% (figure 1).
Alteration of the treatment plan occurred in 34/58 (58.6%) patients.The most common treatment alterations included directed stereotactic body radiation therapy (SBRT) (16/34, 47%), salvage surgical resection (4/34, 11.7%), and continuous ADT (3/34, 8.7%).
The authors concluded that 18F-fluciclovine PET/CT detected recurrence in almost 68% of patients with rising PSA. The most common site of recurrence was within the pelvic lymph nodes. Alteration of treatment plans occurred in 58% of the time with salvage SBRT being the most common treatment modality. Any use of salvage therapy and or ADT were associated with PET/CT positivity. Lastly, a PSA cut-off of 0.5 ng/ml was demonstrated to be a good starting point in identifying patients with recurrent prostate cancer after localized treatment. This was especially true if they have risk factors such as prior salvage therapy or use of ADT.
Presented by: Julio Chong, MD, Icahn School of Medicine at Mount Sinai
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