Concerns about prostate swelling in Sbrt Treatment,could the tumor be outside of treatment zone

[Marc196404]

Hi, I would like to introduce myself, I am Marc, 60 years old and I live in Europe.

Prostate cancer Gleason 3+4 diagnosed in 04/24.

I am very grateful that this forum exists.

I am fortunate that there is a Cyberknife center 20 miles away from me and where treatment is now scheduled for November.

I have a few concerns regarding procedures at the center in question, and a question in general, but in my opinion it is a topic that should not be underestimated.

1.They don't use Space Oar here because they feel that the benefits don't outweigh the disadvantages.

2. They proceed according to the empty bladder protocol because it is apparently easier to repeat safely, my planning CT and MRI were also carried out this way.

3.My tumor (8mm) is located at the rear left inside edge of the prostate capsule.

There is a study that says that the prostate swells by around 15% after the first Sbrt treatment, mainly in length, which in my case would be around 4-6mm. The question is, if the tumor will not be outside of the treatment zone during the following treatments!?

I would be very grateful for advice.

Very kind regards

[Tall_Allen]

CyberKnife uses several tools to accurately track the prostate to minimize misses. At the start of each session, cone beam CT aligns the fiducials with plan. Then, during the treatment, stereo X-rays are used to realign them before the robot delivers each beam. The plan acknowledges that there may be swelling by treating a margin of ~5 mm around the prostate. Because accuracy is so important, your radiation oncologist must carefully draw the contours of the prostate into the plan image.

Some are experimenting with "adaptive planning" that changes the plan (not just the actual delivery) as the prostate swells. There are MR linacs that facilitate this. The goal is to decrease the margin and thereby lower toxicity to healthy tissues.

SpaceOAR does less than the hype the manufacturers put out. It only decreases late-term rectal side effects, but late-term rectal side effects seldom occur (less than 5%). It is dangerous when there is extracapsular extension near the rectum. And there is a small risk of rectal ulcers.

Some radiation oncologists question the need for water in the bladder. I would like to see a randomized trial of urinary side effects with and without it.

[Marc196404 in reply to Tall_Allen]

Dear Allen,

Many thanks for the competent and detailed answer. This was very helpfull for me.It is sometimes hard to get a Dr for additional questions…

In attachment a small study about different bladder protocolls.For me,it does‘nt seems that logic that a full bladder pushs the rektum away from prostate.

Kind regards

search.app/HaLj7TmrfwEMZt2X9

[Marc196404 in reply to Tall_Allen]

Many thanks for the competent and detailed answer. This was very helpfull for me.It is sometimes hard to get a Dr for additional questions…

In attachment a small study about different bladder protocolls.For me,it does‘nt seems that logic that a full bladder pushs the rektum away from prostate.

Kind regards

search.app/HaLj7TmrfwEMZt2X9

[Tall_Allen in reply to Marc196404]

The purpose is to lift the bladder away from the prostate and restrict prostate motion during treatment. It has nothing to do with the rectum.

redjournal.org/article/S036...

[Marc196404 in reply to Tall_Allen]

This article might be intresting to,saying that full bladder could move small intestins away from radiation zone….

search.app/XNt1McHJQ5B5pKNf8

[Tall_Allen in reply to Marc196404]

Small intestine is not an organ at risk unless whole pelvic radiation.

[Laguy01]

You should as your doc. My experience is my docs used the hydrogel spacer but it was not installed good, according to the oncologist, he proceeded with proton radiation anyway. He said it was not worth going back thru the procedure to have it re-done. I am having 28 treatments and have 10 left. Initially he said he was radiating a area the size of a sheet of paper to include my lymph nodes. Starting today he is radiating just prostate. Your doctor might be doing the same thing. I am also on hormone therapy (well on hold due to one medicine causing my liver enzymes to gov way up), but should be back on schedule soon. Talk to your doctor.