A Prospective Study on 18F-DCFPyL PSMA PET/CT Imaging in Biochemical Recurrence of Prostate Cancer.
Rousseau E1, Wilson D1, Lacroix-Poisson F1, Krauze A1, Chi K1, Gleave M2, McKenzie M1, Tyldesley S1, Goldenberg SL2, Bénard F1.
Author information
1
BC Cancer, Canada.
2
University of British Columbia, Canada.
Abstract
18F-DCFPyL, a prostate specific membrane antigen targeting radiotracer, has shown promise as a prostate cancer imaging radiotracer. We evaluated the safety, sensitivity and impact on patient management of 18F-DCFPyL in the settings of biochemical recurrence of prostate cancer. Methods: Subjects with prostate cancer and biochemical recurrence post radical prostatectomy/curative intent radiotherapy were included in this prospective study. The subjects underwent 18F-DCFPyL PET/CT imaging. The localisation and number of lesions were recorded. The uptake characteristics of the five most active lesions were measured. A pre- and post-test questionnaire was sent to treating physicians to assess the impact on management. Results: One-hundred and thirty subjects were evaluated. 18F-DCFPyL PET/CT localized recurrent prostate cancer in 60% (PSA ≥0.4 to <0.5), 78% (≥0.5 to <1.0), 72% (≥1.0 to <2.0), and 92% (≥2.0) of cases. Many subjects had few lesions: one lesion (40.8%), two (8.5%), three (4.6%). The number of lesions was significantly related to PSA by ANOVA analysis, but there was a large overlap in the PSA values for number of lesions categories. Total lesion uptake was also significantly related to PSA values. Change in treatment intent occurred in 65.5% of subjects. Disease stage changed in 65.5%. Management plans changed in 87.3% of subjects. Twenty-two subjects reported mild adverse events after the scan; all resolved completely. Conclusion: 18F-DCFPyL PET/CT is safe and sensitive for the localization of biochemical recurrence of prostate cancer. This test improved decision making for referring oncologists and changed management for the majority of subjects.
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Written by
tango65
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The problem is that Stephenson/Tendulkar tell us that you should start with salvage radiation at a PSA value of 0.2 ng/ml or even lower. Otherwise chances are reduced, that the treatment is curative (i.e. a stable PSA value). In this study by Rousseau they started with the PET/CT at a PSA value of 0.4 ng/ml, so according to Stephenson/Tendulkar you waited a bit too long.
On the other hand Amling reports that the PSA value will very often stabilize below 0.4 ng/ml so he suggests to define a recurrence at that cut point. Therefore many urologists prefer to wait before starting a salvage radiation.
This tudy was not designed to determine when radiotherapy should be done after BCR. I do not think they asked patients who had a prostatectomy to let their PSA get to 0.4., so they did not wait too long. I think they did not enter in the study any patients with a PSA < 0.4.
The study was designed to see the sensitivity of the technique in patients with BCR and a PSA 0.4 or higher and the impact that this type of study could have on the management of theses patients. Management was changed in many patients after a PSMA PET/CT was done. I believe this is an important finding. People with BCR should be studied with a PSMA PET/CT if possible.
I did not want to criticize the study, just to add additional information and „food for thought“. I think a PSMA PET/CT is very important in a BCR too.
If the patient's PSA value rises above 0.2 ng/ml after surgery, he has a biochemical recurrence and the Stephenson/Tendulkar studies and some guidelines recommend to do salvage radiation quickly or the chance for a curative radiation would be reduced:
At least in the study you presented, there is no information, if you should do a PSMA PET/CT below 0.4 ng/ml. So the doctor has to decide: should he start radiating now or wait until the PSA value rises above 0.4 ng/ml and then make a PSMA PET/CT? If he waits, he may reduce the chances to achieve a curative radiation. If he radiates without PSMA PET/CT he may radiate an unaffected area.
In Munich they decided to do a PSMA PET/CT when the PSA value rises above 0.2 ng/ml. You have a low chance to see mets, but sometimes you do. In the study by Perera they report a 42% chance to find mets if the PSA value is between 0–0.2 ng/ml:
Maybe I have a different point of view since I already read several studies that reported the sensitivity of a PSMA PET/CT and a few how this changed the intended treatment. So this study reports what I was convinced of before it was published.
Regarding Amling and 0.4 ng/ml: this just makes you ask whether the Stephenson/Tendulkar studies reported better results of radiation at lower PSA values simply because radiation below 0.4 ng/ml was an overtreatment in many patients. Lieng writes: „It is important to note that not all patients with a rising or detectable PSA may develop further PSA progression or clinical progression of disease, and earlier initiation of SRT may result in overtreatment of some patients“
Knowing the source that is increasing the PSA is proving to be most important for targeted treatment even if that is a systemic chemo drug. It certainly helped me and my oncologist with our game plan!
This is my belief with the newer scans and their benefit for treatment and likely, OS. The Axumin and PSMA scans provide much better info than the bone and CT scan and at an earlier window for treatment. When these scans are run at the much lower PSA scores, it is currently as close as we can get to finding people near an oligometastatic state. Can we find people in a true oligometastatic state knowing of micrometastasis and CTC's? No !!!
But....by finding met lesions earlier, we can attack the disease in a weaker state and slow progression in my opinion...Now, I am hoping for a scan where lesions can be identified below .05 PSA... That might change the game further...
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