How long to wait in between scans ?

Tom:

Very interesting question. I'm not sure there is an answer. I assume the big danger is the cumulative radiation. So, the danger is really a function of the totality of radiation you have received. So, again, bit sure if the spacing between zaps matters.

Hopefully someone with more knowledge will comment.

I would think an RO would know the answer

Mel

I'm a little confused about what you're asking. Perhaps if you could include a signature, describe your current situation, and why you are interested in getting scans done (i.e., what is the treatment decision you are trying to support).

How frequently you get a scan depends upon the decision you are trying to support. For example, if you are trying to determine whether it is worthwhile having another round of docetaxel, you'd have a bone scan to see if your bone mets responded to the first round.

Full body CT scans and PET/CT scans give quite a bit of radiation, so you only want to do them when you need them - they are not for information only. Bone scans alone don't give much radiation, but they are often combined with full body CTs which do. MRIs don't give any radiation at all. Of course, if you have multiple metastases, it hardly matters if you get some radiation -- the extra radiation won't reduce your survival.

As part of my monitoring in addition to PSA tests I have CT, MRI and Bone scans done every 6 months due to my Intraductal Carcinoma which does not have a marker like PSA that can indicate what's happening. The only way we will know is by scans. None of the Dr.'s have ever mentioned being concerned about radiation from these. Since it's such an aggressive cancer they probably don't care about the extra radiation as Allen stated.

Allen, will try to clarify about the situation related to our questions about
scans and fine tune the original questions:
(If there are other threads that deal with this then pointers to them would be
great and if so, really no need for replying to this one.

1. Background
`

Several guys from support group friends - similar but not identical
situations as to recurrence after imrt and when/if to get scans
in context of seeing if its spread outside the prostate and as part of dr
diagnosis of if or when adt might start.

a. all of us have had imrt as only treatment.
All of us were gleason 7, some 4+3 and some 3+4.

b. after a few years, psa started rising and for one person, psa is now just over
the 2.0 recurrence value (2.0 since nadir was <.1), whereas for another its already
at 3.1 (which is 1.0 past their recurrence value of 2.1)

c. assumptions here are that both a bone scan and a separate ct of abdomen and
pelvis with and without contrast are needed at certain times to try to detect if its
spread to bones or soft tissues. And that both these scans would be needed
within so relativelly short amount of time of each other.

and that the bone scan to be done would be the PET/CT Na F18, and not the
more accurate ones done at Mayo or Arizona.

** I don't know if the regular CT are still used for these purposes anymore,
or if regular CT is done just if bone scans are positive, but for now assuming
both are normal scans for these situations.
please let me know if thats not true anymore.


d. The new PET/CT Axumin F18 scan is just starting to be available in our area
but only a few have been done and so think waiting until there is more
expertise there in it would be better. I think that the Axumin scan might
show things in both the bones and soft tissues but for now our questions
are in context of the PET/CT bone scan and regular CT.


2. The two questions

a. Our first question really is a safety one after all -
how long are folks told they should wait between having a ct with contrast and a
bone scan (ie the PET NaF scan) -- since both of those will be needed as part of
the initial (and perhaps followup) scans ?

That is, should it be some weeks or
months in between each of them ?

Am asking since there will be a lot of radiation from these 2 scans in a
relatively short amount of time ? (esp since the CT will be with and without
contrast and the bone scan does a partial CT in addition to the PET/Na F.

but I don't know if waiting just a few months is helpful anyway,
since have seen radiation figures from these scans stated as
giving 5-7 years of normal background radiation for each of them.

But in any case, if both are needed as part of a set of scans,
I realize one can't keep waiting to get the 2nd one done.


b. The second question relates to how long is the time doctors usually use in between subsequent sets of scans (bone scan and regular CT = a set) that are requested for men who have already had an initial set
of scans which were negative
but the doctors still want to track these men with further scans ?

The question here would be related to
men who are not on ADT yet and are still not at the PSA where doctors feel starting ADT might be appropriate for men whose scans are still negative ?
(am talking here about doctors who don't recommend ADT at recurrence value
itself and I realize criteria for starting ADT can be controversial and not
trying at all to start this discussion here)

Is the in between frequency for these repeat sets of scans usually some fixed amount of time like 3 months, 6 months, 1 year,

or is it based on patient psa or psadt values ?


And if its based on some time frame, like 6 months or a year,
is it because of radiation safety concerns or just that they feel those timeframes are
a proper time to wait to still keep tracking whats going on in the bones and
soft tissue ?

(Maybe the same guidelines are used for men on ADT and who might have had
positive scans, but I was trying to focus the question more.)

Allen,

Thanks for the information. Am guessing then that in the world of recurrence
and tracking for mets or seeing effectiveness of treatment, that radiation dosage
effects and thus waiting a long time between scans to let time pass is not
a top consideration ?

And maybe its just not doable or logical anyway - that is if the radiation dose
of a regular CT is equivalent to 5 years of background radiation
(am remembering from some charts I saw)

or that dose of a PET/CT is 7 years equivalent

then no way could/should one wait that long to get a next scan if indeed further scans are needed.

And even if the regular CT (where I live done in a separate place from the
PET/CT/bone scans) - even if one waited a few months after the CT to do
the PET/CT/bone scan, it would certainly not be any safer than if it were
all done on the same day - since the CT (with and without contrast)
is equivalent to 5 years background radiation.


I realize its not that drs or patients might not be concerned about radiation dosage,
but that the need for the scans overrides any safety concerns
and I guess that additional radiation is just part of the overall risks and potential
side effects of using the tools.

Again, sorry for such long postings, but am a lot clearer now.