Main Session
Sep
30
PQA 07 - Genitourinary Cancer, Patient Safety, Nursing/Supportive Care
3283 - The Performance of PET and Multiparametric MRI in Identification of Intraprostatic Tumor Deposits after Prostate Radiation Therapy
Presenter(s)
Ting Martin Ma, MD, PhD - University of Washington, Seattle, WA
T. M. M. Ma1, A. Pham2, H. Parsai3, M. Montague4, S. Rieth4, J. Bell3, R. Mangibin3, S. N. Seyedin5, and R. A. Hsi6; 1University of Washington, Seattle, WA, 2University of Washington, Department of Radiation Oncology, Seattle, WA, 3EvergreenHealth Department of Radiation Oncology, Kirkland, WA, 4Fred Hutchinson Cancer Center Peninsula, Poulsbo, WA, 5University of California, San Francisco, Department of Radiation Oncology, San Francisco, CA, 6University of Washington School of Medicine, Seattle, WA
Purpose/Objective(s):
To assess the performance of PET and multiparametric (mp) MRI scans to identify intraprostatic tumor deposits in patients previously treated with prostate radiation therapy (RT) using a systematic and targeted MR-guided transperineal prostate biopsy technique.Materials/Methods:
Thirty-three patients with a rising PSA after prior external beam RT, brachytherapy, or combined external beam RT and brachytherapy for localized prostate cancer underwent an 18F-fluciclovine or PSMA PET scan followed by mpMRI and subsequent combined systematic and targeted MRI-guided prostate biopsy using a transperineal approach. For each patient, the pre-biopsy mpMRI images were imported into a prostate biopsy planning system. Dividing the prostate into an apical and base section, a systematic array of transperineal biopsies spaced approximately 10mm apart was planned with additional biopsies targeting any mpMRI-identified PI-RADS 3, 4, or 5 lesion. Biopsy procedures were carried out under general anesthesia in the dorsal lithotomy position using a transrectal ultrasound with stepper-stabilizer and template grid. Matching of the planning mpMRI images to live ultrasound images was achieved using the template grid as a reference.Results:
Median time from completion of initial course of RT to biopsy was 5.9 years (interquartile range IQR 4.1-9.8). All 33 patients successfully underwent biopsy without post-procedure urinary obstruction or infection. Median prostate volume was 27cc (IQR 23-34). Median PSA prior to biopsy was 2.8 ng/mL (IQR 2.0-4.5). Median number of biopsy cores obtained per patient was 18 (IQR 16-20). On a per lesion basis, the overall positive predictive value (PPV) of PET scans was 90% (26/29). The PPVs of the 18F-fluciclovine and PSMA scans were 80% (8/10) and 95% (18/19), respectively. A total of 29 PI-RADS lesions were identified in the mpMRI. PPV of any PI-RADS 3-5 lesion for prostate cancer (based on pathologic confirmation) was 93% (27/29). The individual PPVs of PI-RADS 3, 4 and 5 lesions for prostate cancer were 60% (3/5), 100% (15/15), and 100% (9/9), respectively. For lesions that co-localized on both mpMRI and PET, the PPV of the combined scans was 96% (23/24). However, the sensitivities of PET, MRI and combined (lesion positive in one or both scans) were relatively low at 70%, 73% and 81%, respectively. Twenty-one percent (7/33) of patients harbored biopsy-proven prostate cancer that was not identified by either PET or MRI scan.Conclusion:
In patients with prior radiation to the prostate, an intraprostatic lesion is highly likely to be cancerous on biopsy if it is positive on either a PET or an mpMRI; the likelihood increases even more if it is positive on both scans. However, given the lower sensitivity and substantial rate of unidentified prostate cancer by either scan, the addition of systematic transperineal prostate biopsy appears necessary to most accurately identify all intraprostatic tumor deposits.