Rectal spacer with radiation - is it worthwhile?

It might be worthwhile if you have a history of rectal problems, but it rarely seems to make much of a difference. The challenge is to identify those for whom it will make a difference. I think a visit to a proctologist before one has radiation is a good idea. Those with internal hemorrhoids or a history of bowel information might benefit. Otherwise, it's pricey and adds anesthesia.

Here's the data (read the comments too, which includes an update based on the full text):

SpaceOAR hydrogel decreases rectal radiation dose, but is it worthwhile?

- Allen

Allen - very interesting study. Given how bad the post RT symptoms were for me I wish I had a time machine so I could be a test subject. I've had internal hemorrhoids for years, but always manageable with basic home treatment. If there was a way to identify the high risk group, I think this would have been something I would have seriously considered.

Given the amount of pain and discomfort I've had in the last six months, I'd say the extra cost and risk would be worth any reduction in that. It is a line of research that I think has some possiblity in some cases like mine. The question I don't completely understand is how to clinically identify cases like me.

I also think it would be good for guys having RT to get an evaluation by a proctologist (even a sigmoidoscopy or colonoscopy) would be a good idea as a part of routine screening and baselining. In my case, I've often wondered if I would have had few bowel issues with LDR brachy (surgery would have been very risky on me, but it's possible with the right surgeon it might have worked).

Interesting study,
Andrew

Have you guys ever looked at your dose/volume histogram? You can call your RO's office and ask them to print out a color copy of it.

If you don't know what one is, here's what mine looked like:
Allen's Dose/Volume Histogram - click on picture #3

It is an essential planning document done for everyone getting external beam radiation or HDR brachy (there must be some kind of equivalent for LDR brachy). Your RO sets "dose constraints" for organs at risk (bladder, rectum and femurs). The computer figures out how to deliver the radiation so that the prostate gets the right dose, while the organs at risk get less than the dose constraints he sets.

For example, it's been found that if more than 17% of the rectal volume receives 65 Gy or more, there is a significant increase in late term rectal bleeding. So a typical set of rectal IMRT dose constraints might be:

(1) no more than 10% of the rectal volume gets 70 Gy or more
(2) no more than 20% of the rectal volume gets 65 Gy or more
(3) no more than 40% of the rectal volume gets 40 Gy or more

And if you look at your Dose/Volume Histogram, the curve should be below those cut points. Sometimes it's impossible because of anatomic considerations, and sometimes they are far exceeded for the same reason. I was very impressed by LupronJim's Dose/Volume Histogram (the constraints are different for SBRT) because he was treated on a state-of-the-art linac (TrueBeam with RapidArc) and anatomic considerations also made his rectal dose drop off amazingly quickly.

It's one clue as to whether the toxicity you suffered was due to too high a dose delivered, or your innate sensitivity to radiation.

- Allen

Andrew,

It sounds like you had "mild hypofractionation." While you had only 26 treatments instead of 44, they increased your dose per treatment from 1.8 Gy to 2.5 Gy. In terms of biologic effect, those are equivalent. If you're interested, they can easily print out a copy for you.

- Allen