Genetic Test prior to Radiation

[chral11]

Is a genetic test predictive of susceptibility to radiation therapy toxicity something that is recommended prior to starting ones therapy (SBRT)? What is this test anyway so I can ask my RO beforehand if indeed useful. Thanks.

[Tall_Allen]

A germline test will tell you if you have any rare inherited genetic diseases.

prostatecancer.news/2018/02...

A test of the genomics of your prostate biopsy may be useful if you are on active surveillance and considering getting treatment.

There are no genomic tests you need before primary therapy.

[chral11 in reply to Tall_Allen]

Thanks Allen as usual. I have noticed in reading different posts that UCLA's Amar Kishan does a genetic test prior to radiation treatment. I'm not sure if it is part of an ongoing study or a DNA test can help deciding how many fractions over what duration will be most effective while reducing side effects. I found this study on GARUDA:uclahealth.org/urology/iuo/...

I did get a Decipher test last month based on 5 month old biopsy. It was relatively low at 0.38 and within AS range. I'm still pursuing treatment though a soon as I find the right RO.

[Tall_Allen in reply to chral11]

He is doing his own trial. He is hunting for genetic biomarkers that may predict optimum radiation schedules. He expects first results in 2027.

[chral11 in reply to Tall_Allen]

Got it. So he is not changing anybody's regimen outside established guidelines yet as a result of the test!

[redonthehead in reply to Tall_Allen]

Thank you for your continued time and effort you devote to education on PCa.

Wondering if you take requests for blog articles - I'd sure like to see a writeup summarizing the various machines and tracking systems being used for SBRT, and if any have advantages over the others. Maybe include the older systems which are still in use, and potential new systems coming out.

[Tall_Allen in reply to redonthehead]

Dr Kishan has a randomized trial now between their standard VMAT (Truebeam with rapidarc) and the 1.5T MRI-guided MRIdian. Personally, I doubt whether it makes a difference for primary treatment, but we'll see. I expect there will be a difference for salvage radiation, but we'll see. The latest innovation is a PET-guided linac. Again, we'll see. The technology probably matters less than you would think.

[chral11 in reply to Tall_Allen]

Now that we've expanded this topic, can I ask your opinion Allen on PSMA scan? Do you think Pylarify PSMA PET/CT would add any value prior to initial treatment in Favorite Intermediate? Can the RO make any sense of the resulting image with a relatively high PSA? Or would the usual MRI be more useful?

[Tall_Allen in reply to chral11]

No value for PSMA PET in fav. intermediate risk PCa. No diagnostic value for MRI either, just for planning.

[chral11 in reply to Tall_Allen]

I checked with UCLA about their MRIdian Viewray's resolution. They said it is 0.35T and not 1.5T, same as other MRIdians. The centers with a Viewray do their SBRT planning on the same machine. Is 0.35T resolution on a Viewray sufficient for SBRT planning? If the radiologist that looked at my 3T MPMRI misinterpreted it and it had to be reread, how can the RO looking at 0.35T pictures do a proper plan?

[Tall_Allen in reply to chral11]

You are right - it is a 0.35T MRI at UCLA. Dr. Kishan assures me the resolution is adequate. He says it is the MRI gating that allows for tighter margins and potentially less toxicity. He is running an RCT to see if that is true. There is an Elekta Linac/MRI that uses 1.5T.