Pacemaker

[Haybrant]

I have a young guy with ICM and medullary thyroid s/p thyroidectomy+ bilat neck dissection (lots of positive nodes) that I am treating to bilateral neck/upper mediastinum. He has a ICD in place for idiopathic cardiomyopathy for a few years. The ICD has never gone off. The manufacturer recommends no more than 5 Gy going to the pacemaker. Planning showed us just below 500; put a tld on at start of treatment and totaled up it would go to 5.19 Gy over the course of treatment. Do you guys have rec's in this case. We tried a bunch of different beam arrangements and this was the best we were getting. Device rep came out and interrogated today; is that necessary on a daily or weekly basis? Waiting to hear back from his EP. Thanks

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[Gfunk6]

ALARA, but don't compromise target coverage. You were correct to use the manufacturer's recommendation, but we all understand that the published max dose is very likely far lower than would render the device non-functional. In these scenarios, I always have a device rep perform an interrogation at the end of radiotherapy course.

 

[Haybrant]

ALARA, but don't compromise target coverage. You were correct to use the manufacturer's recommendation, but we all understand that the published max dose is very likely far lower than would render the device non-functional. In these scenarios, I always have a device rep perform an interrogation at the end of radiotherapy course.

Thanks GFunk, much appreciated.

 

[seper]

My institution has a policy to never exceed manufacturer's dose limits for ICD/pacemaker. I think it's wise.

 

[mpdoc2]

My institution has a policy to never exceed manufacturer's dose limits for ICD/pacemaker. I think it's wise.

I agree with GFunk. Of course institutions have these policies but it's usually written by someone with neither knowledge of this patient's cancer nor of the device. Just like the folks who wrote the meaningless "meaningful use".

 

[Pointless]

If you want to be extra cautious, you could interrogate weekly rather than at the end of the course. Otherwise, I agree with what has been stated.

 

[ramsesthenice]

I have a young guy with ICM and medullary thyroid s/p thyroidectomy+ bilat neck dissection (lots of positive nodes) that I am treating to bilateral neck/upper mediastinum. He has a ICD in place for idiopathic cardiomyopathy for a few years. The ICD has never gone off. The manufacturer recommends no more than 5 Gy going to the pacemaker. Planning showed us just below 500; put a tld on at start of treatment and totaled up it would go to 5.19 Gy over the course of treatment. Do you guys have rec's in this case. We tried a bunch of different beam arrangements and this was the best we were getting. Device rep came out and interrogated today; is that necessary on a daily or weekly basis? Waiting to hear back from his EP. Thanks

I can't quote data (I'm on vacation) but out chief of physics pointed out recently that all of the data showing damage to AICDs or pacers was with 10 MV or higher photons. I'm not saying blast away with 6s but I would make sure to keep anything close to the device to 6s.

Agree with Gfunk.

 

[mpdoc2]

I can't quote data (I'm on vacation) but out chief of physics pointed out recently that all of the data showing damage to AICDs or pacers was with 10 MV or higher photons. I'm not saying blast away with 6s but I would make sure to keep anything close to the device to 6s.

Agree with Gfunk.

It's because of the neutrons that's thought to interfere with the pacemaker.

 

[rymd]

Here is the paper your chief of physics is probably referring to. MDAnderson experience, published in JAMA Oncology. http://oncology.jamanetwork.com/article.aspx?articleid=2342048

"All single-event upsets occurred during neutron-producing RT, at a rate of 21%, 10%, and 34% per neutron-producing course for CIEDs, pacemakers, and implantable cardioverter-defibrillators, respectively. No single-event upsets were found among 178 courses of non–neutron-producing RT. Incident CIED dose did not correlate with device malfunction"

And incident to this discussion: "Given the lack of correlation between CIED malfunction and incident dose observed up to 5.4 Gy, invasive CIED relocation procedures in these settings can be minimized."

 

[ramsesthenice]

It's because of the neutrons that's thought to interfere with the pacemaker.

Exactly. Our policy now is that we only use 6s for the entire plan when someone has a cardiac device. I don't think we have ever had a problem.

I understand your concern. I wouldn't want to go over the manufacturers "recommendation" even if it's complete BS. If anything happens to that damn thing in the next 6 months you will be blamed. As a matter of CYA, if I were you I may shave the inferior portion of your nodal (as long as there is no gross disease in proximity) fields from the last frx or two just to get that number under 500 cGy.

 

[seper]

Exactly. There is always an option of moving ICD to axilla (low morbidity ambulatory procedure) or shutting it off before XRT altogether.

Exactly. Our policy now is that we only use 6s for the entire plan when someone has a cardiac device. I don't think we have ever had a problem.

I understand your concern. I wouldn't want to go over the manufacturers "recommendation" even if it's complete BS. If anything happens to that damn thing in the next 6 months you will be blamed. As a matter of CYA, if I were you I may shave the inferior portion of your nodal (as long as there is no gross disease in proximity) fields from the last frx or two just to get that number under 500 cGy.

 

[Palex80]

The Germans have a guideline published.
http://www.ncbi.nlm.nih.gov/pubmed/25739476

 

[Pewl]

For some reason a 2Gy limit to pacemakers sticks in my mind from residency. But, I do agree with abiding by the manufacturer's stated limit and having it interrogated frequently during the course of treatment. The JAMA article is interesting because it would make sense that neutrons contribute to the significant dose in pacemakers.

 

[seper]

Nice German guideline. Very strict.

 

[jezyk]

Late to the party but depending on beam arrangement, ask the planner to see if placing a 0.5-1.0cm bolus over the pacemaker would help.

 

[EffectiveZed]

Late to the party but depending on beam arrangement, ask the planner to see if placing a 0.5-1.0cm bolus over the pacemaker would help.

The dose to the pacemaker is likely due to patient internal scatter, which would be unaffected by bolus.

For some reason a 2Gy limit to pacemakers sticks in my mind from residency. But, I do agree with abiding by the manufacturer's stated limit and having it interrogated frequently during the course of treatment. The JAMA article is interesting because it would make sense that neutrons contribute to the significant dose in pacemakers.

There is a medical physics task group report on pacemakers (AAPM TG 34) that recommends not exceeding 2 Gy unless the manufacturer provides its own, higher dose limit. From what I've seen, most manufacturers either provide no guidance or recommend limiting the device to 5 Gy.