EBRT 6 weeks with SBRT vs EBRT 9 weeks

[Dave78717]

My doctor recommended 6 weeks of EBRT with, I think just 3 cyber knife "boosts" (SBRT) to treat PC in my prostate and some in the lymph nodes. My insurance want me to do a 9 week treatment of EBRT. They want to deny the SBRT. Any opinions on what is better or worse about one or the other? A Space Oar would be used as well.

[Tall_Allen]

LOL that your insurance actually wants to pay out more.

Your RO should appeal. ASTRO has given a strong recommendation to hypofractionation:

prostatecancer.news/2018/10...

The SBRT boosts to cancer detected in the prostate and lymph nodes was recently found to be beneficial in the FLAME trial:

ascopubs.org/doi/full/10.12...

I assume you will be getting whole pelvic radiation and 2 years of ADT as well (possibly with hormone therapy intensification).

[Dave78717 in reply to Tall_Allen]

Thanks, very nice articles - especially the 2nd one. What do you mean it would pay out more? 3 more weeks of EBRT is less than the cost of 3 SBRT boosts?

[Tall_Allen in reply to Dave78717]

Much more. They pay by the number of treatments: 9 weeks costs a lot more than 6 weeks. There is no need to do the SBRT boosts with CyberKnife. He can do simultaneous integrated boosts (SIB) in 3 fractions with the same VMAT platform that he is using for IMRT to the whole pelvic area. That way, insurance does not need to approve treatment with a separate device.

I may be misunderstanding what you are talking about - there is nothing in your profile about your diagnosis or treatment plan.

[Dave78717 in reply to Tall_Allen]

My profile should show PC and that I went to India for Lu177. It was not very successful for me. So I see from above, its more about achieving the same result with the same equipment, using it in a different way.

I have to find out what a VMAT platform is. I thought the plan for me was EBRT not IMRT. It looks like IMRT implies VMAT. I need to find out if this is IMRT or EBRT for me.

[Nusch in reply to Dave78717]

VMAT is a special kind of IMRT with 360-degrees capabilities. As far as I understood this. It’s all EBRT (E for external).

[Tall_Allen in reply to Dave78717]

Thanks. I read it and understand the issues much better now. Please ignore what I previously wrote - I thought it was your first treatment First, some definitions may help:

EBRT=external beam radiation therapy. ALL kinds of external beam are included (it only excludes brachytherapy)

IMRT=intensity modulated radiation therapy. It is a very precise way of delivering EBRT. In the US, all EBRT prostate cancer treatments are IMRT. Precision is guaranteed by INTERfractional cone beam CT. It is usually distinguished from SBRT, (although technically, SBRT is intensity modulated too); it usually means conventionally fractionated (1.8-2.0 Gy per treatment) or moderately hypofractionated (2.5-3.5 Gy per treatment).

SBRT, SABR, or CyberKnife is extreme hypofractionation (dose delivered in 2-5 treatments at > 5 Gy per treatment. Uses INTRAfractional tracking to get the intense dose delivered without excess toxicity. Platforms for delivering SBRT include CyberKnife (robotic), VMAT (arc delivery), or MRI tracking using Viewray MRIdian or Elekta Unity. All of them can also be used with lower fractionation (IMRT) too.

It seems like you are attempting salvage radiation both within the prostate and in pelvic lymph nodes. When one pelvic lymph node is found to be cancerous on a PSMA PET/CT, there are many more sites that are undetectable (PSMA false negative rates (sensitivity) are about 50-60%), so they have to treat the entire pelvic lymph node area, which has recently been expanded. This is usually achieved with 45-55 Gy delivered at 1.8 Gy per fraction (=25-30 treatments). They will give a little extra radiation (SIB) to those lymph nodes detected as cancerous on PET scans.

As for the sites of recurrence within the prostate, PSMA PET scans can give ambiguous readings, especially if the SUV max isn't sufficiently high. This is because the PSMA PET scans in widespread use are urinarily excreted, so there are false positives in the prostate. It is prudent to also have an mpMRI read by a radiologist accustomed to reading HIFU-treated prostate tissue. If you really want confidence a biopsy can confirm the imaging.

Now that we are getting long-term data on HIFU, it appears that recurrences do occur in the treatment zone as well as near it and on the contralateral side. You can confirm with a biopsy. It may be best to treat the entire prostate with salvage SBRT or salvage HDR brachytherapy.

[Nusch]

Did you do PSMA Pet?If yes, what are the findings? Oligo or more? Within pelvic? LN only? SUV-max? I can only compare with my case. But if you provide more input, there are experts in this forum who can provide advice.

[Dave78717 in reply to Nusch]

I know my case pretty well and yes I did a PET PSMA - thanks

[CurrentSEO]

Hi Dave,

FYI. I just did one week ago my 3rd Lu—177 in Austria and RO there told me that from his experience patients who did any type of EBRT to prostate or prostate bed not long before or after Lu-177 had much higher level of side effects in the next two years, especially with kidneys function.

[Dave78717 in reply to CurrentSEO]

Good to know. What is defined as "not long after"? My 3rd Lu was 2/28/2022. I wonder if there is some reasoning. I'm relatively healthy and young at 60.

[CurrentSEO in reply to Dave78717]

I think it is more like one after another, my guess will be few (2-4) months prior or after. He said that it is from his patients observations, I guess you can bring logic and reasoning to everything, but it is just his observations for now.

Also to keep in mind in Europe they have much more experiences in combining or sequencing EBRT and Lu-177 than in the States.

That was enough for me personally not to consider EBRT to the prostate for at-least 6 months after Lu-177 if at all (I have my priorities that might be different from yours). Wanted to let you know that there is another angle to consider in your decision.

I’m sorry that your Lu-177 treatments did not go as expected, however I assume you did not do comparison of two PET/CT scans FDG and PSMA to check if you have discordant Mets or spots in the prostate prior to Lu-177. Discordance might be one of the reasons why Lu-177 did not work in you as expected.

Now you are planing to make your decision about feasibility of whole pelvic radiation based on PSMA PET/CT. What if you do also FDG PET/CT to check if you do not have any FDG+ but PSMA- spread beyond pelvic area? I hope you don’t, but if you do, pelvic radiation will be pointless as far as curative intent concerns.

You mays as well consider to stay few months on ADT to shrink prostate and 6 months after your last Lu-177 go ahead with EBRT. Also with extended pelvic radiation, please do analyze well chances to be “cured” and possible side effects. Sometimes we rush to be “cured” and underestimate or ignore very real consequences.

I personally for myself would not do whole pelvic radiation (that my opinion and it is not based on trials or proven evidence, or science, but only on friendly conversations with couple of experienced ROs, so do not take it as any kind of advice) . Besides possibility of horrendous very real side effects, by killing all your pelvic area lymphatic system, we eliminate the ability of lymphatic system in this area to detain cancerous cells spread from prostate area and if (most likely when) recurrence happens it happens in far distance sites all over the body. One of the arguments of ROs that they “did a good job” when cancer spreads all over the body… is that none of cancer is found in pelvic area… that is supposed to be comforting I guess. It is debated that some cancer in lymph nodes might actually spread cancer and some might detain and protect from cancer spreading and no one really knows which one in particular does what and do they switch and when from detaining cancerous cells and protecting body from cancer spread to actually spreading it.

But all of the above that is no way a recommendation to you to postpone your EBRT, you need to make your decisions based on your priorities, just wanted to give you different perspectives.

[Dave78717]

Thanks for your input. I will try and absorb it all. - Dave