Abstract
1458
Objectives: Physiological renal excretion of 68Ga labelled PSMA may complicate the assessment of pelvic region in prostate carcinoma, with prostatic lesion being obscured by the high radio tracer bladder activity. Thereby can lead to problems in differentiating the pelvic lymph nodes from ureteral activity and challenges in local invasion of prostate carcinoma into the surrounding structures (seminal vesicles, urinary bladder and rectum.The aim of this retrospective study was to assess the utility of diuretic 68Ga-PSMA PET/CT imaging in the loco-regional staging of locally advanced prostate carcinoma. Materials and methods : Sixty one biopsy proven prostate cancer patients with mean age of 66.7 +/- 4.9 years who underwent 68Ga-PSMA PET/CT were evaluated after approval from the institutional ethics committee. All the patients underwent whole body 68 Ga-PSMA PET/CT scan followed by two bed position post-lasix PET/CT scan. The tracer activity in the prostate, bladder, seminal vesicle, lymph nodes and ureter were evaluated in pre-lasix and post-lasix images visually (scores 0,1,2 & 3 were given for negative, equivocal, mildly positive and strongly positive ) and quantitatively by SUVmax of the tumour to background ratio( T:B ratio). Data was statistically analysed using Mann-Whitney U test and Paired t test and p value of <0.05 was considered as significant. Results:
Of the 61 patients, primary in prostate was noted in all patients. Delayed post-lasix view could better delineate prostatic lesions in 45/61 (73.7% ) of the patients demonstrated as an increase in T:B SUV values in the post-lasix views (t=2.91 ;p value = 0.005). After furosemide injection the bladder activity reduced (t= -3.84; p value = 0.0002) improving the visualisation of prostate lesions. The ureteric activity also reduced bilaterally (Right ureter t= -2.23; p value = 0.036 & Left ureter t= -4.26; p value = 0.00034) allowing better delineation of pelvic lymph nodes.Visualisation of Seminal vesicles also improved ( Right t= 2.65; p value = 0.010 & Left t= 3.22; p= 0.002 ) changing the staging of the prostate carcinoma and detection of extraprostatic extension. Detection of bladder wall invasion was detected in post-lasix view was detected in 7/61 patients with bladder wall invasion better delineated in post-lasix view. Seminal vesicle invasion (2/61 patients) and Rectal wall invasion (1/61 patients) were also detected better in delayed post-lasix scans.
Conclusions: The addition of a post-lasix view resulted in better visualisation of local prostatic lesion and detection of extraprostatic spread changing the stage of the prostate carcinoma to locally advanced prostate cancer.