Proton Radiation to Thoracic Vertebra

[LeeLiam]

I seem to have a recurrence after 2006 seeds and IMRT. After an Axumin scan, rhPSMA scan, and whole-body mpMRI, the only spot found is on the left pedicle (a small bone off the back of the vertebra) of the T8 vertebra. I am completely asymptomatic. My RO does both SBRT and Proton. I told him I felt the proton would be safer than SBRT as it will not leave an exit dose going through the heart and lungs. He studied the scans and agreed to do proton. I will have five fractions starting next Monday. I was wondering if anyone else has had radiation near the T8 and/or had proton radiation to the spine? If so, what should I expect as to side effects? Thanks.

[Tall_Allen]

Coincidentally, I'm currently working with a patient who is about to undergo SBRT to the posterior 8th rib, near the T8 vertebrae. He is also having SBRT to the posterior 5th rib. I asked a similar question. The dose to the lung parenchema is unavoidable, but will only affect a small bit of peripheral tissue, and will do no functional damage. The heart dose is negligible - only from reflected dose (which would occur with protons or photons). He will be getting a single dose of 18 Gy to those spots. More troubling to his RO is the dose to the S1 neural foramen and the C7 pedicle because of potential damage to the spinal cord. He is bringing in a neurological consult for those and will probably hypofractionate them across 3-5 fractions.

He will also be getting SBRT to his prostate with a small boost to the index tumor. I am more concerned with the side effects of that because he has quite a bit of cancer in his prostate and is already having some urinary symptoms from the cancer. As long as he keeps peeing, he will be fine.

[LeeLiam in reply to Tall_Allen]

TA, I don't understand "would occur with protons or photons". My understanding is the proton goes in with very low radiation until the depth where the Bragg peak occurs. No radiation is delivered past that point. In other words, no exit dose. Most of the radiation occurs in less than 1 cm diameter. It seems as long as the pedicle is more than 1 cm from the spinal chord, it should not be a problem. Is this what you understand?

[Tall_Allen in reply to LeeLiam]

Bragg peak is the theory. In actuality, it doesn't work that way. In the real world, what happens is protons are diffracted from the nozzles, spread out due to repulsion, reflected from bone, and create secondary particles forward of the beam. So far, proton toxicity seems to be no different from photon toxicity:

prostatecancer.news/2016/08...

I'm sure it is fine, it is just no better than SBRT. I'm not sure what dose limits there may be.

[LeeLiam in reply to Tall_Allen]

Thanks, TA. But I really like the last sentence "Pencil-beam proton therapy may be able to improve toxicity still further." as that is what I'll be getting at Emory. I guess a lot of things improve over the years.

[Tall_Allen in reply to LeeLiam]

I used the term "may." I haven't seen any evidence that it does that.

[LeeLiam in reply to Tall_Allen]

Yes, evidence always seems to take years.

[Tall_Allen in reply to LeeLiam]

If there was a huge difference, they would know much more quickly - I doubt that there is.

[wilcoxsaw in reply to LeeLiam]

You are correct in your understanding. Having just completed 15 proton fractions to the 6th rib, the proton particle was stopped at the lesion, and there was no dose delivered to my lung. Had I done photon radiation there would have been substantial lung involvement as well as other tissue.

Dr Rossi, at California proton, stated that he could stop the beam at the rib, with photons this would not be possible. The dosimetry plan verifies this. Rossi is well respected, perhaps the most experienced rad onc using protons in the world. His explanations support your understanding, you are correct.

My side effect was darkened skin at the entrance site. No other side effects.

Hope this helps

Scott

[LeeLiam in reply to wilcoxsaw]

Thanks, Scott. That makes me feel better. Did the doctor give you any idea how long it takes the radiation to kill the cancer? Will you be monitoring it with PSA tests?

[wilcoxsaw in reply to LeeLiam]

Hi Liam

The Dr did not state how long it would take for the protons ( also pencil beam) to kill the lesion, I had 2 areas treated, the rib and a node. Had I been treated with photons on the node there would have been radiation passing through the bowel, stomach, and spleen. With pencil beam protons there was none, and no side effects.

Along with the protons I am doing a 12 month course of ADT. We will monitor my psa every 3 months, and once the adt ends in Nov we will see what the future holds.

If the psa rises I will repeat a PSMA likely, that was how these 2 spots were located.

I am not an MD, but would guess your doctor will enter through your back to treat the pedicle. As in my case, because the lesion is close to the skin surface you might see some skin darkening. That was my only side effect, hopefully yours will be the same.

Scott

[Tall_Allen in reply to wilcoxsaw]

Did you ask to see the dose volume histogram?

[wilcoxsaw in reply to Tall_Allen]

Yep. Keep copies in case of subsequent treatment.

[Back2future in reply to Tall_Allen]

I too have bone mets in the spine. What RO subspecialty should I look for here at JH Balto? What would be the safest type (Pencil-beam proton therapy) and what dosage for the spinal cord? I am also seeing MO next week.

[Tall_Allen in reply to Back2future]

I don't think JH has a very good RO department. If you can, try to be seen by Sean Collins at Georgetown. He's much better and more experienced than anyone at JH.

[ragnar2020]

Hello LeeLiam,

I saved your post from a year ago, so now I'm curious how you're doing following your treatment. Did you use proton beam or photons? Are you happy with your results or disappointed?

Best regards,

Jeff

[LeeLiam in reply to ragnar2020]

Jeff,

I am very happy. After years of undetectable PSA, it rose to 4.4 last year, over a course of three years.

I had the five fractions of the proton beam in April 2021. No ADT, no side effects from the treatment. Interestingly, he treated the entire T8 vertebrae, not just the pedicle.

Since then my PSA has been 1.9 (08/05/21), 1.3 (10/21/21), 0.5 (02/07/22), and 0.3 (05/24/22).

The trend is my friend. I hope others do as well.

[ragnar2020 in reply to LeeLiam]

Hi LeeLiam,

I'm so happy to hear this. Last month my PSA reached .21, so I am now BCR. I had a PSMA PET CT scan last week at Dana Farber, and a small lesion was discovered on my sacrum. I'm taking Tramadol and Tylenol for that resultant pain, and I've scheduled SRT at the Roberts Proton Beam Center at UPenn. I expect the folks at UPenn to treat the spot on my sacrum too. Happy to hear that your PSA is dropping and your treatment went well.

Stay healthy,

Jeff