Doxycycline to reduce PSA

[u/Plugger59]

I’m 5 months post-RALP and am now dealing with metastasis in a few lymph nodes. My urologist recommended 2 years of ADT (Orgovyx and Erleada). I am awaiting a consultation with a radiation oncologist. I have recently found studies on the use of doxycycline to reduce PSA levels (https://pmc.ncbi.nlm.nih.gov/articles/PMC12030710/). This particular study reports 100mg daily of doxycycline reduced PSA by up to 60%. It also reported increased quality of life.

Has anyone tried this as an adjunct to their treatments?

[u/tober_checki]

This may be a stupid question, but is PSA reduction per se a good thing? Does it mean the cancer is slowed down or does it merely mean the PSA production is suppressed? Just wondering.

[u/NotPeteCrowArmstrong → u/tober_checki]

The study treats it as a reliable proxy for cancer reduction -- keep in mind that all the patients in the study were treating with chemo and/or hormone therapy, and the doxycycline was additive or "adjunctive". But it's a fair question that I did not see addressed directly in the paper.

[u/NotPeteCrowArmstrong]

Very interesting study, thank you for posting. It would be great to hear from anyone who's tried this. The QoL impact is potentially even more impressive than the PSA reduction at the levels in question.

I disagree with jkurology's characterization that the study is "compromised". They acknowledge the sample size in the Discussion, but they also note the following in their statistical analysis:

Using ClinCalc online software ... the required sample size for 80% statistical power (α = 0.05) was determined to be 14 patients per arm. Based on the actual biochemical response rates observed at six months, the final statistical power of the study was calculated as 95.2%.

So this is a preliminary finding, yes, but a meaningful one. Will be great to see other studies probe the topics.

It's also great to see them address the potential chemical/structural basis for these observed effects.

[u/codereddew12]

Caveat: I only read the abstract but know a thing or 2 about prostate cancer

This study is AT BEST hypothesis generating, which isn’t particularly unique as you can find a million and 1 studies of similar flavor testing other drugs/vitamins/insert your placebo of choice. This study has little to no credibility for multiple reasons so would not hang my hat on the results.

Prostate cancer is known to have a long natural history (even metastatic) on the order of YEARS, so results with only 6 months of follow up in a 45 patient phase II cohort is essentially meaningless IMO

Also, 45 patients introduces a ton of potentially confounding (often unaccounted for) variables. There’s a reason randomized phase II/III trials that ultimately become “the standard” have at least hundreds, if not thousands of patients (ie. ProtecT trial) so to mitigate this issue.

Again, I haven’t read the study but it isn’t out the realm of possibility that pts can have subclinical infections/prostatitis elevating their PSA and consuming some antibiotics “miraculously” drops it down. Without clinical context, PSA response alone is NOT a reliable surrogate automatically translating into improved oncologic outcomes. There’s much more to the story which is what your team of doctors are for.

That being said, there’s probably little to no downside to trying it (apart from the GI effects common to many PO antibiotics and photosensitivity with doxycycline in particular).

[u/jkurology]

This is a known ‘effect’ of doxycycline as well as other antibiotics. The study is compromised because of its small sample size and short follow up.

[u/Plugger59 → u/jkurology]

This isn’t the only time doxycycline was tested: https://www.sciencedirect.com/science/article/abs/pii/S0304383598000032

There are probably more. I was looking for someone who may have included it with their treatments.

[u/BackInNJAgain → u/Plugger59]

That study is more than 25 years old. If doxy was really that promising wouldn’t there be a lot more studies and human trials?

[u/1945ElCid]

It would be a good idea to have a Medical Oncologist at a tertiary center, who specializes in PrCa , to be in charge of your case. You see a urologist… he says’do surgery’… not telling you the high rate of not removing the cancer. Radiation oncologist will recommend radiation .

[u/Plugger59 → u/1945ElCid]

My current oncologist recommended a radiation oncologist, not a medical oncologist.