Difference between 1 Rad of radiation vs. 2 Rads - 1254706

dandelion
Posts:2

I have been on a clinical trial for just over two years, but it may be coming to an end soon. My doctors are anxious to publish the results. The criteria of the trial required an initial PET, and thereafter, PETS were suppose to be "optional". I have a PET scan scheduled next week, but have said I do not want another PET and wanted instead a regular CT as I usually have. Why? Two reasons: I am concerned about the large amounts radiation I have had, and may continue to need, and am also concerned about reaching my limits of insurance. My doctor said it would be OK to have a CT. However, when I received the appointment reschedule, I was scheduled for 2 Rads of radiation instead of the usual 1 Rad.

So, I guess my questions now is: 1) What is the radiation difference between 1 Rad and 2 Rads? 2) How much of a radiation difference is there between 2 Rads and a PET?

Thank you so very much for your help and for all you do!!

Ceryle

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Reply # - March 13, 2013, 10:57 AM

catdander
Posts:

This is a common question on Grace and there are many discussions on the forums as well as blog posts written. This is one such blog post there are further reading options at the end of the post. http://cancergrace.org/cancer-101/2012/06/21/radiation-exposure-from-me…
Take a moment to search the site for some of the discussions on the forums. This is a search result on radiation CT (note that you may need to log out to access this search result or use the search engine depending on your browser). http://cancergrace.org/search-results?q=radiation%20poisoning%20CT%20PET

In the article linked below Dr. Ella Kazerooni, professor of radiology and the director of the Division of Cardiothoracic Radiology at the University of Michigan said, ""In a pure PET scan, when people do throw out a number, is about 5 to 7 millisieverts." That, at least, gives us an idea." from, http://www.annarbor.com/health/candid-cancer-evaluating-radiation-risk-…
When she says pure PET I assume she means a PET without the added low res CT which you'd need to add at least a couple or 5 mSv.
I think since the trial you're on has you going through repeated stereotactic radiation procedures you would have had much more radiation compared to the amount you get in the scans.

I look forward to seeing those trial outcomes. Just curious though. I have seen people on trial drugs after the data is presented. I wonder why this is different and are taking you off the treatment.

I will ask a doctor to comment.

Hopes for the best,
Janine
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Reply # - March 13, 2013, 11:12 AM

dr. weiss
Posts: 206

Typically, studies keep treating individual patients as long as they are benefitting. A study can "end" in terms of analyzing data without stopping treating an individual patient who is benefitting. I'm afraid that I don't know much about radiation dose in CTs to comment on that. Generally, they're getting lower dose over time with improvements in technology.

Reply # - March 18, 2013, 01:14 PM

dandelion
Posts: 2

Hi Janine, Dr. Weiss, and Dr. West,

I’m sorry to be so slow back to you. The information you sent was very helpful and does lessen my concern. I did ask the xray department about the difference between 1 Rad and 2. The answer is that “there’s practically no difference in amounts.” My scan will be in about a week, so I’ll find out more then.

Janine, you asked a question about why the trial may stop soon, and would like to clarify. There have been two additional radiation treatments I’ve had, but not included in the bio. Sometimes it’s hard to keep it all straight.. My initial radiation was a high-dose trial. Thinking more is better, instead of the usual 54gy, I was given 37 treatments at 74gy. It didn’t make any difference, though, I had a stroke a week after it ended and then became Stage 4 six mos later. Then there was another place on my left rib 3 years ago, and had SBRT. A lot of radiation.

I think what my doctor might be referring to is that the last scan showed that the rt. adrenal gland might be starting up again. I was treated two years ago and either the cancer is coming back or it’s trying to regrow. If cancer, it may not be possible to radiate it again which could very possibly stop the trial. Other than that, I’m not sure what else is going on … but I’ll be finding out soon.

Thanks again much much for your help and knowledge,

Ceryle

Reply # - March 18, 2013, 01:56 PM

laya d.
Posts: 714

Hi Ceryle:

I don't have anything to add here, but just wanted to wish you lots of luck. . .and hope that what your docs are seeing is not a progression of your cancer - - but some benign explanation. Please keep us posted.

Laya

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