A question about radiation resistance

[Chasbearcat999]

Last week a post was made about Decipher showing high radiation resistance. My decipher showed the same.

Quick question. If you have had SBRT and it hasn't deliver a “killing dose” to tumor, is brachytherapy a follow up option? My PSA showed rise after SBRT, (from 8.6 to 12) Ro and Mo attributed this to remain ing inflammation. One month later PSA dropped to 9.

While the drop is good, it seems that SBRT usually shows a pretty rapid decline initially followed by slow decline.

I'll be tested again in a week. Just trying to be informed when meeting with docs in a couple of weeks if things still seem odd. (such as PSA drops, but not significantly)

I did have PSMA immediately prior to SBRT that only showed PSA at site of lesion.

[Tall_Allen]

You cannot expect PSAs to drop low quickly. For me, it took 4 years to reach nadir, with bounces along the way. Imaging tells you nothing. You just have to wait.

The biologically effective dose (BED) of SBRT is very high and will overcome an radioresistance. It is rare to have a local recurrence after SBRT or HDR brachytherapy - recurrences are almost always regional or distant.

[Chasbearcat999 in reply to Tall_Allen]

Thank you Allen. That is reassuring!

[Nordman in reply to Tall_Allen]

Tall_Allen. Your use the term radio resistance, got me thinking of the following. I have read that antioxidants like vitamin c and vitamin d3 etc can have a protective effect on cells generally. High dose vitamin c can protect cells and body tissue from significant radiation doseage, and has been used for this. If these vitamins are taken during treatment or after RT, can there then be radio resistance in respect of the PCa cells? Should we therefore avoid vitamin supplementation following RT and for what duration, considering the time it takes to reach nadir?

uhn.ca/PatientsFamilies/Hea...

[Tall_Allen in reply to Nordman]

I agree. All antioxidants should be avoided and most ROs will instruct their patients of that. Prostate cancer patients should particularly avoid Vitamin E. While radiation is the most obvious contraindication, antioxidants interfere with apoptosis (the destruction of damaged cells) and immune function. All nutrients in food are safe. Vitamin D is a steroid, and is not an antioxidant, to my knowledge.

[EvFC in reply to Tall_Allen]

Are antioxidants not recommended at all with prostate cancer? Or only when undergoing radiation treatment?

[Tall_Allen in reply to EvFC]

Both. The SELECT trial proved that antioxidant supplements are harmful to people with cancer.

[Mascouche in reply to Tall_Allen]

This NIH articles calls it a membrane antioxidant:

"Vitamin D is a membrane antioxidant: thus Vitamin D3 (cholecalciferol) and its active metabolite 1,25-dihydroxycholecalciferol and also Vitamin D2 (ergocalciferol) and 7-dehydrocholesterol (pro-Vitamin D3) all inhibited iron-dependent liposomal lipid peroxidation. Cholecalciferol, 1,25-dihydroxycholecalciferol and ergocalciferol were all of similar effectiveness as inhibitors of lipid peroxidation but were less effective than 7-dehydrocholesterol; this was a better inhibitor of lipid peroxidation than cholesterol, though not ergosterol. The structural basis for the antioxidant ability of these Vitamin D compounds is considered in terms of their molecular relationship to cholesterol and ergosterol. Furthermore, the antioxidant ability of Vitamin D is compared to that of the anticancer drug tamoxifen and its 4-hydroxy metabolite (structural mimics of cholesterol) and discussed in relation to the anticancer action of this vitamin."

pubmed.ncbi.nlm.nih.gov/832....

[pd63]

I've recently had SBRT 5 sessions first psa test is 6 months, is there really any advantage for earlier testing

[Xavier10 in reply to pd63]

not really.

[ToolBeltZia]

I had SBRT and am finishing up 6 months of Orgovyx. I had a 3 moth post SBRT PSA and testosterone. My pre-trt testosterone was 517, PSA 7.7 . At 3 months post SBRT my testosterone was 14, and PSA 0.09. I know the Orgovyx is showing a likely "artificially" lo w PSA. Regardless, my RO said we will use whatever and whenever your lowest PSA is as your nadir. I did not know about the full Grid report until after my treatment. Mine was significant with "RT Sensitivity, 0.64, 32%, Resistant ". He was not concerned saying the addition of the Orgovyx, and as Tall Allen alluded to, the use of SBRT (particularly with a boost to the primary lesion) in all likelihood rendered "Radio-resistant" finding mute. Only time will tell. I am getting a 7th month PSA and testosterone, that being one month after my Orgovyx is finished. Will be interesting to see both the T and PSA values.

Stay Strong Brothers

[Chasbearcat999]

An update to this.

PSA after SBRT

[Xavier10 in reply to Chasbearcat999]

Loooks pretty good to me

[Xavier10 in reply to Xavier10]

Dr. Storey, in his substack at

protons101.substack.com/p/p...

has one of those studies graphed and as you can see where you are is within the blue area, which is good, but a little higher than the median lines of both the BCF and non-BCF, but the only thing that matters is where you end up. As Tall Allen said, it just varies from patient to patient. But I thought you would like seeing this graph that shows you in the blue area. But bounces occur, so I'm not sure you can really count on anything being accurate other than long term reductions.

[Chasbearcat999 in reply to Xavier10]

Thank you Xavier. That was very interesting!