RT Journal Article
SR Electronic
T1 Initial experience with 11C-acetate PET/CT in management of recurrent prostate cancer under an Expanded Access IND.
JF Journal of Nuclear Medicine
JO J Nucl Med
FD Society of Nuclear Medicine
SP 1558
OP 1558
VO 57
IS supplement 2
A1 John Kindler
A1 Jack Thygesen
A1 Steven Westphal
A1 Mark Tann
A1 Thomas Gardner
A1 John Cox
A1 Gary Hutchins
A1 Mark Green
A1 James Fletcher
YR 2016
UL http://jnm.snmjournals.org/content/57/supplement_2/1558.abstract
AB 1558Objectives The primary objective is to retrospectively relate our initial experience in the use of 11C-acetate under an FDA authorized Expanded Access IND in the management of prostate cancer patients presenting with suspected recurrence.Methods Seventy-seven patients previously diagnosed with primary prostate cancer and identified as having biochemical relapse after primary treatment were referred for whole-body 11C-acetate PET/CT imaging from June 2013 until present. Scans were obtained on a 128-slice time-of-flight Siemens mCT scanner after injection of an average dose of 35 (±5.5) mCi. CT contrast enhancement (CE) was achieved in all exams with Isovue 370 i.v. A subset of patients (26) also had a forty-minute delayed PET acquisition. A positive scan, indicative of recurrence, was defined as focal increased uptake corresponding to either: i) a lymph node that was in the appropriate drainage bed and, if comparisons were available, not stable in size, or ii) soft tissue in the prostate bed, that, if comparisons were available, was new/growing or enhancing on CECT. The PET findings were correlated with the results of biopsy or directly with bone scintigraphy, or conventional radiography, when available, as well as the concurrent CECT. Patient information including: demographics, prior therapy, PSA values, post scan therapy, and therapeutic outcomes were also collected on patients where available.Results In this communication we report the results of implementing a more rigid interpretation criteria that includes consideration of prior and current CECT findings; the relationship of a positive scan to lesion derived SUVbw as well as PSA and lesion size. Of the 77 patients referred for 11C-acetate PET/CT, 53 were identified as having a positive scan. 48/53 positive scans had lesions concerning for malignancy located within the pelvis. The average SUVbw for lesions considered to be malignant was 15.4 (±8.6) compared to 6.1 (±1.1) for benign lesions, and was statistically significant (p=0.04). The percentage of negative scans (58%) exceeded that of positive scans (28%) for PSA values ≤ 1.5. Only 9% of the lesions on positive scans suspected of being malignant were < 5mm in diameter, where as 39% of them were between 5-10 mm in diameter. 26/53 had forty minute delayed acquisition scans. Within those 26 delayed studies, there were 36 malignant lesions and 55 benign lesions (e.g. reactive inguinal nodes) identified. The observed washout at 40-minutes did not further discriminate benign and malignant lesions, with clearances of 36.8% (±10.0%) and 42.8% (±10.3%)respectively. Clinician notes following 11C-acetate PET/CT scans cited the exam results as support for their treatment decision in 90% of patients.Conclusions In our experience 11C-acetate is effective in identifying the location of disease recurrence especially in patients with PSA > 1.5 and lesions larger than 5mm. The implementation of more rigid interpretation criteria that considers prior CECT findings as well as the concurrent CECT component of the PET/CT exam provided additional information to assist in confidently classifying focal tracer uptake as benign or malignant. 11C-acetate clearance as assessed by delayed imaging did not demonstrate improved differentiation of malignant versus benign lesions.