Explaining the Gallium 68 DOTATATE PET with Thomas Hope, MD

Explaining the Gallium 68 DOTATATE PET with Thomas Hope, MD


That is a question that I think depends
a lot on the individual patient, which is probably true about everything
we’ll discuss here today, obviously. Um, so we use a Gallium 68 PET, depending on the clinical need. And
what I mean by that is, let’s say we have a patient who we will
stay to the Gallium 68 PET and I think every patient in general deserves
a Gallium 68 pet initially, right? To show us where the
extent of the disease is, so we know where all of the
disease is, it’s in the liver, it’s in the bone marrow, it’s in the
small bowel, it’s in the lymph nodes. So we know where the disease is.
Once we know where the disease is, we will then use a conventional imaging
modality that’s specific to that. So if it’s in the lymph nodes, CT
is the best to follow the patient. It’s in the liver, we’ll follow it with
an eovist MRI. If it’s in the bones, and that’s the one odd circumstance, we will typically follow them with a CT
with intermittent Gallium DOTATATE PETs. Right? So the, the frequency of the Gallium DOTATATE
in that one and unique setting, is more frequent. Now if you have disease in the liver
and we’re following with a liver MR. Okay? And we are then, there’s
progression, stuff is growing. We then will decide if we need a DOTATATE
PET depending on whether or not you as an individual patient are being
considered for PRRT. Does that make sense? So the DOTATATE PET is used pretty much
at the time of whether or not we want to consider PRRT, peptide
receptor radionuclide therapy, or if we’re concerned that there’s more
progression than we’re seeing on the DOTATATE PET. So to see whether or not there’s osseous
disease that’s not being diagnosed on the liver MRI. Uh, and then in some
patients will get intermittent, every couple of years, DOTATATE PETs just to make sure we’re
not missing a bigger picture change. But the conventional imaging is much
better at looking for changes in size over time compared to DOTATATE PET. I don’t
know. It’s a hard question to answer, but hopefully that
helped out a little bit. That’s a good question. Um, it’s sort of a hard question to answer
in the sense that, as a patient, I’m not sure how you would ever know this
information before you get imaged. Um, most sites don’t say my scanner is this
type and it’s this many years old and has these technological advances. So it’s not like a
widely appreciated fact, but technology does matter and as
new pet scanners are introduced, technology does improve. So as a first
statement, I would say that Gallium, the agent, Gallium 68 DOTATATE is
identical no matter where you are. So the imaging agent, the radiopharmaceutical will be the
same no matter where you’re imaged. So it doesn’t matter from the injectable. The radioactive agent you’re getting
is going to be identical everywhere. Now the scanner does differ obviously
between sites and so there’s been many technological advances over the years, going
from non-time-of-flight to time-of-flight scanners. Uh, and then there’s different things
you can do in terms of reconstruction parameters. And then also the way you
acquire the image, how long you image for, etc., Can actually make a difference. Uh, most centers nowadays I would say
use time-of-flight scanners, uh, and use three minutes of imaging
per bed. This is maybe too specific. If you have that in general, the diagnostic ability will remain
equivalent across majority of sites. Um, that being said, you know, the majority of patients this
doesn’t make a huge difference in. And what I mean by that is the detection
ability of your scanner is for very small sites of metastases. Um, and so what you’re looking for, if you’re a patient who
has no evidence of disease, you might be able to see a very, very small site of disease that you
couldn’t see with a different scanner. But typically that doesn’t make a
clinical difference. Um, when you, we all know, or we all know… In general, we assume that patients who
have no evidence of disease
after surgical resection or treatment will recur. The rate of recurrence is about a
hundred percent over about 10 years. It’s just when will that recurrence occur. So detecting that recurrence super
early on by detecting a little site of disease, shouldn’t make a big difference in the
management of the individual patient. And what I mean by that is you shouldn’t
be getting surgery to treat this or get systemic therapy. Uh, you
should just wait over time, see how fast your disease is growing
and talk with your oncologist about the best way to manage that
site of disease. Um, so although there is
detectability differences, and I study that and I look at that,
from an individual patient perspective, what you really want to know
is bulkiness of disease, how much of it there is to try to
determine whether or not you should get surgery or get PRRT and those decisions
are made based on larger metastases, which should be easily detected, uh, using
whatever PET scanner is at your site. I hope that answers that question. So there are lots of documents and papers
we’ve written to support the use of DOTATATE PET or even in general, I
would say somatostatin receptor PET. One thing you have to remember is DOTATOC
was approved a couple of weeks ago. So that’s now FDA
approved. So for example, NCCN guidelines endorses
the use of DOTATATE PET. Uh, we wrote an appropriate use criteria that
was published in 2017 delineating when DOTATATE PET should be used. And the motive for doing that was
to use it to provide a resource, to provide to insurance companies. Uh, so I think those two guideline documents
can be provided to insurance companies. Now, the way the end of
that question was phrased, which was my insurance
company denied it this year, suggests a I had one last
year or the year before. Um, and I think that gets down to how
frequently you should have a DOTATATE PET. And so you don’t need to get a DOTATATE
PET every year or something like that. And so unless you have a clinical
need for the DOTATATE PET, which is in our AUC, and
we wrote out, you know, nine different clinical indications and
times where you should consider using DOTATATE PET. And that’s why we wrote that document to
provide ammunition for you to go to your insurance company and say, Hey,
I fit indication nine here. And it clearly states that, you know, in this circumstance I should be
able to get into a DOTATATE PET. That’s the general idea. But you know, every insurance company is different
and they push back differently and it’s very hard to give a blanket statement
that this is how you get your insurance company to pay for it. But, uh, I think over time this has become much
easier than it used to be. I would say, four years ago, three years ago, this was actually really a big issue
and it’s becoming less of a problem over time. And where do those documents live
again? That’s a good question. So NCCN guidelines, uh,
those, if you go to nccn.org, there’s a website and type, you just type NCCN and
neuroendocrine tumor into Google, it will take you to their documents
and so you can register. It’s a PDF. It’s like a hundred
and some page long PDF. And in there it recommends
DOTATATE PET and DOTATOC PET. And then the AUC for SNMMI. So, again,
if you type in maybe my name, AUC, SNMMI, that lives on the SNMMI website. That is a good question.
Um, so in general, insurance companies don’t pay for second
readings. Uh, it’s not always true, but I would say it’s a general
true statement. So the question is, if you got a formal reading and you are
doubtful of it or you think there’s a mistake, how would you
go about doing that? Um, so I think the best way to do it is
probably to ask your oncologist. So, um, most oncologists work in a
hospital system of some sort, and they’re radiologists who
work in that hospital system. So the oncologists could request that
the radiologists they work with go back and reinterpret or read
it. Uh, so for example, here at UCSF and this is
not an uncommon thing, we have a neuroendocrine tumor board
and we can provide formal reviews to reinterpret outside studies
that are reviewed at UCSF. Um, and I’m assuming the majority of centers
that have neuroendocrine tumor boards can do the same. Uh, so that, that’s,
I’d say the two ways to do it. So through a tumor board.
Um, and if you are concerned, I think having your case reviewed at a
neuroendocrine specific tumor board is really an important thing for you to do. And I’m sure many people have come onto
this streaming thing and talked about the role of a multidisciplinary tumor
board and I think that’s a great environment through which to get
second opinions on imaging reads. Yeah. So if you get diagnosed
with neuroendocrine tumor, uh, and you had a CT or an MR and your surgeon
takes out your primary tumor and you have some lymph nodes
and they’re taken out, and then you’re after surgery three to
six months later and you never had a Gallium 68 PET, you should definitely
have a Gallium 68 PET at that time. I think it’s very helpful for your
treating oncologist to know the extent of disease and where it is. And that again, is approved in our
appropriate use criteria. So if your insurance company
is giving you a problem, I think that document
can be helpful for that. If you had a Gallium 68
DOTATATE PET before surgery, then you have surgery, you know
where your disease is or isn’t, I’m not sure there’s a role for repeating
the somatostatin receptor PET soon thereafter. So you might consider
repeating it a couple years later. Uh, if you know where your disease is, you
can follow with conventional imaging, and then if there’s
suspicion of progression, then you can consider
repeating a DOTATATE pet. But you don’t need one immediately after
if you’ve already had a DOTATATE PET. Well, I think we’re now hopefully in an
era where the Octreoscan doesn’t exist. Although I would love to know,
I can see your comments show up, so if you don’t have DOTATATE or
DOTATOC PET available in your area, just make a comment because I’d love to
know how many people actually don’t have access to somatostatin
receptor PET. But historically, and we should couch in
historical phrases now, the Octreoscan is the original version
of imaging of the somatostatin receptor. So the Octreoscan is in
essence, is you take octreotide, which again was used for symptomatic
control of neuroendocrine tumors, hormonal secretions that would
decrease that. You label, in essence, octreotide with indium 111. Indium
is a type of radionuclide, an atom, that decays by giving
off, in this case photons, and you can image the
photons using a SPECT CT. So the main differences between octreotide
and DOTATATE are based on the type of energy it gives off, which in this case
is gamma photons versus DOTATATE PET, of which Gallium 68
gives off a positron. Uh, and because of the
differences in energies, you use a different type
of technology to image it. And so Gallium 68 DOTATATE is imaged
using a PET CT, or a PET scanner. And a PET scanner has
very good sensitivity. So it’s much better than a SPECT
CT at detecting where disease is. So, these aren’t things that
most people think about, but the technology itself really
does impact the image quality. And so that results in some significant
differences between the two imaging. So DOTATATE PET has better sensitivity,
it sees smaller lesions better, and it has a much better ability to
see osseous disease, for example. It also has the ability
to quantitate the uptakes, so you can measure how much
of the dose goes there. It has a lower radiation dose. And I think maybe the single biggest and
most important benefit is that DOTATATE PET is imaged one hour after injection
versus the next day for an Octreoscan. So if you’re a patient,
you get your injection, you start your imaging one hour later,
and then you’re done an hour afterwards. Whereas with an octreoscan, oftentimes
patients would come back the next day, then you’d get imaging with the SPECT CT, and then even some patients have to
come back a day later depending on if there’s uptake in the colon.
So it could be a multi-day, three day imaging study, which can obviously be very impactful
in terms of missing work and, you know, radiation exposure to people around
you. Uh, so the DOTATATE PET, even if it were equivalent to an
Octreoscan in its ability to find tumors, it would still be preferred in due
to the ease of implementing a test, having it done in two hours. Uh, but it does actually have markedly better
detection sensitivity for metastatic disease compared to Octreoscan. That’s a good question. So, um, blood work can be used to determine
if there’s elevation in hormones, right? So if you have diarrhea and you haven’t
been diagnosed with neuroendocrine tumor, uh, your treating physician,
you might not have an oncologist yet, right? So your general practice
physician or maybe an endocrinologist, whomever is a GA, gastroenterologist, will be working out your
diarrhea and could, for example, secrete a serotonin level
or a chromogranin level
or a VIP level to see if that’s the cause of your diarrhea. Now, neuroendocrine tumors aren’t the only
reason you can have an elevated serotonin, right? Uh, so your urine
5HIAA may be elevated, but that does not mean you definitively
have a neuroendocrine tumor. So if you have diarrhea and you’ve
have a high serotonin level, likely your diarrhea may be caused
by the high serotonin level. That again doesn’t mean you
have neuroendocrine tumor.
And so at that time, uh, I think a Gallium 68 DOTATATE
PET is a reasonable option. Now, I will say in patients who
have biochemical evidence
of neuroendocrine tumor, but negative CTs and MR, the chance of catching a tumor on Gallium
68 DOTATATE PET is something like 10%, so it’s very unlikely. But in
our appropriate use criteria, we’ve recommended DOTATATE
PET in that setting, not because we think it’s a good test, but because it’s the best test and will
hopefully put an end to looking for neuroendocrine tumor as the cause. So a lot of patients will routinely
and for years try to find this unknown neuroendocrine tumor that’s
causing their elevated hormones, and I think a Gallium 68 somatostatin
receptor PET can hopefully put an end to that search.

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