Bone met reirradiation

[Lamount]

Just saw a follow-up patient I did 50/5 to a small met in the (deep) clavicular head for. Skin dose constrained. Excellent response to treatment, no skin issues.

I have always wondered about the standard of giving sub-ablative doses (30-35 in 5) when doing SBRT for oligiomets. Are people really seeing myositis as a complication? If superficial doses can be kept <30, Is that the concern for dose-reducing in soft tissue and bones vs. blasting away mets in lung, liver, etc? We do 50 in 5 for lung lesions abutting ribs all the time without blinking an eye.

Depending on the site, I worry about toxicity (chest wall pain, sacral insufficiency fractures ect…). I am less tolerant of toxicity in metastatic patients… so I am more likely to be conservative.

Plus the data show that “sub ablative” (27/3 30-35/5) doses to bone mets have excellent local control… 80-90% at 1-2 yr

I interpret these data to suggest that perhaps bone mets are more radiosensitive than lung mets… which wouldn’t be that surprising, given how much local environment affects tumor biology.
To flip the question around, if there are data that lower doses are effective, why go higher?

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[evilbooyaa]

Just saw a follow-up patient I did 50/5 to a small met in the (deep) clavicular head for. Skin dose constrained. Excellent response to treatment, no skin issues.

I have always wondered about the standard of giving sub-ablative doses (30-35 in 5) when doing SBRT for oligiomets. Are people really seeing myositis as a complication? If superficial doses can be kept <30, Is that the concern for dose-reducing in soft tissue and bones vs. blasting away mets in lung, liver, etc? We do 50 in 5 for lung lesions abutting ribs all the time without blinking an eye.

Sure skin is a consideration but the risk of inducing fracture from purposeful bone radiation to 50/5 is also a factor. We're not purposefully treating the rib to 50/5 in a lung case. If it's a T3N0 then you're going to cure and you're OK with cracking someone's rib to do it.

If you radiate the hell out of a met in the clavicle and it breaks, you have not helped the patient, especially for palliation. Especially when 30/3 or 35/5 have shown excellent control...

 

[deleted1116990]

To flip the question around, if there are data that lower doses are effective, why go higher?

Because you are talking about the "defintiopalliative" paradigm. What is the patient's life expectancy and do you want to ablate it or palliate it? Pick one.

If you want to use a low dose and palliate it fine. Do that. If returns you can re-irradiate it.
Alternatively, you can ablate it. My thinking is that if there is no OAR concern besides the bone or muscle the tumor itself is in, then why not kill the gross disease as untreated gross disease will surely result in a fracture or muscle pain.

A failure after a defintiopalliative treatment puts you in a tough spot if there is a failure.

Many of the patients who you can justify SBRT for mets are prostate patients with good survival, and that is a histology where 35-40 can be considered definitive, so not really an issue and I agree no point going to 50 in them. In my case, the patient was a NSCLC with excellent health otherwise, Life expectancy reasonably beyond 1-2 years.

I am presently re-irradiating a large 40/5 bone failure done by another rad onc (endometrial histology, no other sites of disease for many years). Burned a lot of bridges with that. Going to 30/5 and dose reducing over the retreated area to 20/5 to not toast brachial plexus. I am confident she will outlive the control I can give her with this.