Unfortunately I never bookmarked previous studies I've looked at (I don't claim to have read whole studies) in the past on the topic. I'll look further as it's a topic that should be addressed better on this forum but a little DuckDuckGo searching turned up the following.
This study(s) that do cover the topic somewhat if you read enough of the whole page: Simply titled "Erectile dysfunction"
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3217797/.
This next listed article doesn't seem to address the topic as directly but does include a pile of references that in all likelihood will contain information on the topic: "A prospective randomized study to optimize the dosage of trimix ingredients and compare its efficacy and safety with prostaglandin E1"
https://www.nature.com/articles/3901313.
Here's another less relevant abstract article that I'm throwing in as it seems to indicate fibrosis is often a result of an RP and VED use as well as injections are use as therapy to treat it: "Penile fibrotic changes after radical retropubic prostatectomy"
https://bjui-journals.onlinelibrary.wiley.com/doi/abs/10.1046/j.1464-410x.2000.00364.x.
I'll edit this later if I find some good stuff but I have stuff to do at the moment.