A recent clinical trial, published in The Lancet, has shown that a PSMA PET scan using Ga-68-PSMA-11 can detect more cancerous sites than the currently approved Axumin PET Scan in the same men who have experienced a recurrence.

This prospective clinical trial included 50 men. All 50 of the subject men had a post-prostatectomy PSA rise from 0.2- 2.0 ng/ml. The trial found the following:

Total Detected Cancerous Sites

Ga-68-PSMA-11 56%

Axumin 26%

Cancerous Sites Detected in the Prostate Bed

Ga-68-PSMA-11 14%

Axumin 18%

Cancerous Sites Detected in the Pelvic lymph nodes

Ga-68-PSMA-11 38%

Axumin 8%

Cancerous Sites Detected in the Extra-pelvic lesions

Ga-68-PSMA-11 16%

Axumin 0%

We should note that the two scans performed equally well in men who had their recurrence only in the prostate bed. However, the trial also showed that the PSMA PET scan detected more cancerous pelvic lymph nodes and non-regional metastases.

One of the important take-home messages is that we can attribute more prostate cancer recurrences to pelvic lymph nodes (stage N1) and extra-pelvic metastases (stage M) than to cancer in the prostate bed. This finding indicates that when you have salvage radiation treatment, it might be beneficial to have whole pelvic radiation over just salvage prostate bed radiation.

The possible exception to this, as indicated by the SPPORT Trial, would be in men who still have a very low PSA when they have salvage treatment.

Although it is confusing, these results are specific only to the Ga-68-PSMA-11 Scan. Currently, there is another PSMA-based PET scan, the DCFPyL Scan which is still actively recruiting men, so we don’t know how this scan will function against the other two discussed in this post.

https://www.thelancet.com/journals/lanonc/article/PIIS1470-2045(19)30415-2/fulltext