Surveillance Therapy - MRI vs. CT?

[S P]

Dr. Bosl at Sloan told me that never in his life had he ever seen or heard of a secondary cancer case involving CT scans. Only on paper is there the suggesting of an increased risk of secondary cancers, but in reality it just hasn't shown up. On the other hand, there is a slight chance of secondary cancers developing from radiation therapy used to treat pure seminomas, but the amount of radiation you get from CT scans is a drop in the bucket compared to that. I think I read that you get about as much radiation from a trans-continental flight as you do from a CT scan, so it's really not a concern.

[Slurpeeholic]

Dr. Bosl at Sloan told me that never in his life had he ever seen or heard of a secondary cancer case involving CT scans. Only on paper is there the suggesting of an increased risk of secondary cancers, but in reality it just hasn't shown up. On the other hand, there is a slight chance of secondary cancers developing from radiation therapy used to treat pure seminomas, but the amount of radiation you get from CT scans is a drop in the bucket compared to that. I think I read that you get about as much radiation from a trans-continental flight as you do from a CT scan, so it's really not a concern.

The idea of doctors "seeing" secondary cancer involving CT scans is a bit fuzzy to me. Is s/he saying they have never seen a person who had had several CT scans get cancer later? I doubt it. They are saying that they can't tie the cancer specifically to the CT scans. But how can you? Any given cancer diagnosis can be tied to anything - or nothing. The study cited is a pretty big study and showing a higher risk for those who had the CT scans can't be completely ignored. It has to be put in perspective, but not ignored.

[CancerSux]

The idea of doctors "seeing" secondary cancer involving CT scans is a bit fuzzy to me. Is s/he saying they have never seen a person who had had several CT scans get cancer later? I doubt it. They are saying that they can't tie the cancer specifically to the CT scans. But how can you? Any given cancer diagnosis can be tied to anything - or nothing. The study cited is a pretty big study and showing a higher risk for those who had the CT scans can't be completely ignored. It has to be put in perspective, but not ignored.

I agree entirely. We should take effort to not cite Docs, even as experienced, knowledgeable, wise, and regarded as Dr. Bosl, as gospel, especially in light of scientific support otherwise such as this extensive 18 year, 7000 patient study. Do the parameters apply? Is it a risk some are willing to take? All valid questions for each individual patient.

[Slurpeeholic]

If you include your original CT scan at diagnosis, I make that 9 total.

Maybe this is the "missing" CT scan from the regimen we discussed earlier. We were only counting the follow-up scans and not taking into account any scans performed at diagnosis.

[Paul54]

Seminoma, classic seminoma, and pure or 100% seminoma are terms used for the same thing. Classic and pure are sometimes added to differentiate germ cell seminoma from spermatocytic seminoma which is not a germ cell cancer. Seminoma makes up 40-50% of all TC diagnoses.

My oncologist at Dana Farber (Boston) has always used the Princess Margaret Hospital (Toronto) protocol rather than NCCN, although I never figured out the difference, and DF usually has at least one doctor on the advisory board of the NCCN TC group. Now in my 5th year of surveillance, my surveillance protocol was recently changed from the PMH/NCCN so that years 4 and onward deviate:

Years 1-3: 4 months; A/P CT; alternate chest CT and Xray (CT x 3 annually)

Year 4: 6 months: A/P CT; alternate chest CT and xray (CT x 2 annually)

Year 5-?: 6 months: Alternate A/P CT and chest xray (CT x 1 annually)

That adds to 12 CT's in 5 years. I think that MRI's are essentially as good as CT's depending on the skills of the radiologist, as long as time and cost are not issues. I would opt for MRI's instead on CT's if my insurance covered the difference.

[CancerSux]

Seminoma, classic seminoma, and pure or 100% seminoma are terms used for the same thing. Classic and pure are sometimes added to differentiate germ cell seminoma from spermatocytic seminoma which is not a germ cell cancer. Seminoma makes up 40-50% of all TC diagnoses.

My apologies - it is significantly more common than I had thought. I'm going to amend my previous post. Thanks Paul (I thought I had read it on the forum about is being more rare - I need to take my own advice about not repeating stuff I 'heard' without scientific confirmation. ). I did find exactly what you were writing as I was looking into it more.

[Slurpeeholic]

<snip> I think I read that you get about as much radiation from a trans-continental flight as you do from a CT scan, so it's really not a concern.

I've been wondering about statements like this one. I've also heard comparisons of radiation from CT scans being the equivalent to other daily activities, but it all seems very cavalier to me.

It's interesting that no one ever talks about the risk of radiation to airplane crew members, who commonly log over a few thousand trans-continental flights (or their equivalent) over a ten year period.

I once heard exposure from CT scans being compared to those we get from elevators. I've certainly never heard of any elevator operators from the old days being at higher risk for cancer.

When you go in for a CT scan, the technician doesn't stand anywhere near you. In fact, they go behind a specially reinforced door to avoid even being in the same room. This seems like a smart precaution, but would it really be necessary if the amount of radiation exposure for the patient were really that minor?

I'm a layman. I have no special knowledge of these things. But as long as CT technicians feel the need to be behind a protective door during scans, I'm not going to take it for granted that the risk of exposure for the person IN THE MACHINE is negligible. Studies like the one cited earlier in this thread just confirm my instinct here.

I'm not against CT scans. It's just data that needs to be put into perspective when weighing your options. Cancer is an area where you're "playing with live ammo." Every path you choose is going to have some risk.

[DARDEVIL]

Hey Tracy, how are you ?
May be I haven t been precise enough, cause even if I repeat what I ve heard from some specialists, I conclude by saying I am very concerned to the point I plan to continue my follow-up with some MRIs and chest X rays for the 2nd year.
I also made a mistake : the dose for a ct scan chest abdo and pelv for a fit person is around 17 msv with new generation equipment and the maximum dose recommended for many medical organisations is 100 msv in five years ...
So Tracy, you can see how I try to get involved,
By the way, concerning those persons in the study more than 45 years old : were the smokers, good eaters etc....I mean do we have all the parameters ?
And (that s because my english is not my first language at all) how many persons got a secondary cancer among 7000 persons ? I didn t catch it .
But I would be glad to get a radiologist s opinion.

Hope to read you

[ukboyuk]

Health workers who administer even xrays shield themselves because cumulative exposure even from x-rays is bad.

In fact, even x-rays are far from safe. Now when you consider that a CT is like taking hundreds (maybe more) x-rays at once (CT is roughly speaking, fine slices of x-rays to make a 3-d picture) then no doubt a CT is a heavy dose, relatively speaking.

[CancerSux]

By the way, concerning those persons in the study more than 45 years old : were the smokers, good eaters etc....I mean do we have all the parameters ?

Dardevil, from what I can tell, when they ran a program to decipher statistically significant trends (usually SAS or SPSS), only age came out with the CT scans. They likely have a history where smoking is recorded, but probably not eating habits, so I don't know. It is a good point that there could be other co-founding factors, but over 7000+ patients, those factors would hopefully be fairly evenly distributed. It is important to note that these patients were not randomized in their choices, they were just followed for secondary cancers (i.e. it was not equally balanced groups between active surveillance and treatment (surgery/RT/chemo).

how many persons got a secondary cancer among 7000 persons ? I didn t catch it .

It was 306 for the active surveillance group and 233 for the other group, so 539 out of 7301 men for a rate of ~7.4% (I checked my math this time )

[Slurpeeholic]

The way they reported this data is a little confusing. The study "examined the cases of 7,301 men diagnosed between 1988 and 2006," but when they quoted the data, they did it on a base of 10,000:

Chamie’s research found that more patients who have been on active surveillance will be diagnosed with secondary malignancies after 15 years than will patients who received aggressive lymph node surgery or chemotherapy. Statistical analysis determined that of 10,000 patients put on active surveillance, 306 would get secondary malignancies, versus 233 if they had the surgery alone. That translates into 73 additional secondary malignancies. And while 73 may not seem like a big number, of the men who underwent surgery, only 50 died of testicular cancer.

So my reading is that 3.06% (306/10000) of those in active surveillance would get secondary malignancies versus 2.33% if they had had surgery alone. The reason the raw data would be different than the reported data is that they do statistical analysis to even out the risk factors in each of the groups. For example, if more people in the surveillance group were >45, they would try to correct for this in the analysis.

So, the impact of surveillance itself is 0.73% (3.03% - 2.33%), according to the article.

[indymike]

That clarification is correct, per my understanding. That the 15 or more CT scan regimen increased secondary cancers by .73% across a statistically significant sampled population.

That is .7% total increase, but if you look at it in terms of "basis points" or what your baseline chance of getting a secondary cancer is, then that increases your chance of a secondary cancer by ~30% over the chance you would have if you DIDN'T get CT scans.

One could argue that ~30% of "near zero" is still "near zero".

To the point about a CT scan being compared to the radiation of an airplane trip - I have never heard that. However, I have seen it documented that a CT scan is on the order of 400 times the radiation of a chest X-ray. It is also the equivalent to 5.3 years worth of "ambient" radiation that one gets from just living on the surface of the earth (radon gas, cosmic rays, etc). I shudder to think that my CT surveillance regimen of 15 scans would give me the equivalent of ~75 years of ambient radiation exposure!

Bear in mind that every single errant wave of energy penetrating your body carries with it the chance of disrupting cellular replication and starting the chain reaction that leads to cancer.

Why I have grown concerned is that I work in the healthcare industry, for a maker of medical products. My research showed that the use of CT in the US has exploded, with over 80 million CTs per year currently. I know from experience the influence that pharma and device makers can have on "standard of care". I began my research on this, because I was amazed that my local hospitals were offering $49 heart CT scans - passing these things out like they are popcorn.

Like so many therapies, I don't believe we have a long-enough backlog of data to demonstrate the harmful effects. The study in my original post is the first such indication I've seen. Bear in mind that radiation was first-line adjuvant therapy until evidence of secondary cancers started to emerge.

[K&R]

Perspective

Here is a source you might find useful to put the relative radiation exposure levels into perspective. http://www.xrayrisk.com/index.php. They include comparison levels for air travel and background radiation. Reference to source material is available on the "About" page.

That translates into 73 additional secondary malignancies. And while 73 may not seem like a big number, of the men who underwent surgery, only 50 died of testicular cancer.

This statement is only comparing the number of men who followed surveillance, got diagnosed (assumed treated) with a secondary cancer (no data on mortality) versus those who did an RPLND and died from the TC anyway (assuming additional treatment in case of relapse). To me it is more a piece of data about choosing between RPLND and surveillance, than about choosing to drastically cut back on CTs for anyone on surveillance.

There is no data here (and little elsewhere) about the mortality of those who don't do surveillance for whatever reason. CT has some risk that we need to be aware of and manage, but we're doing them for an important reason. For me the additional 0.7% risk of a secondary cancer is worth earning the 99+% cure rate for TC.


Kevin

[indymike]

Agree that active surveillance is well worth the 99% curability of metastasis of TC is detected.

My question is: what should be the mode of active surveillance? CT scan, which is now proven to add to your odds of a secondary cancer, or MRI, which evidently does not have the same effects?

[CancerSux]

That clarification is correct, per my understanding. That the 15 or more CT scan regimen increased secondary cancers by .73% across a statistically significant sampled population.

It' not quite right - the study followed 7301 men and extrapolated their values to indicate the # that are 'at risk' out of 10,000 because it is a more metric #, more comprable to other literature and easier to compare across studies. The 233 and 306 were ACTUAL men out of the 7301, so the 'additional' 73 men is ~1% of the total population.

The fact that these were men >45 was telling also - as we age we are less capable of repairing DNA damage, more likely to see slower cellular growth and activity, etc.

There is no data here (and little elsewhere) about the mortality of those who don't do surveillance for whatever reason. CT has some risk that we need to be aware of and manage, but we're doing them for an important reason. For me the additional 0.7% risk of a secondary cancer is worth earning the 99+% cure rate for TC.

Those who don't do surveillance are difficult to follow on a clinical study, but yes, the increase in 1% of secondary (and likely treatable/curable) malignancy seems minor, but should be taken into consideration. There are ongoing trials looking at lower frequency of imaging for similar 'efficacy' and lower risks (One is in England, I believe)