0:01

We're going to move on now to, uh, we talked about

0:03

anatomy, we talked about technique, now we're

0:05

going to jump into actually looking at the cases.

0:09

As I mentioned right at the onset, you have a template.

0:12

It's important you follow the template,

0:13

you answer the questions on the template.

0:15

What I'm going to try and do with these cases

0:18

is sort of run over some of the key points

0:20

that you need to keep in mind when you're

0:22

filling in specific questions on the template.

0:25

Talk about a few of the adverse prognostic

0:29

indicators that you need to be aware of.

0:32

And again, they're all mentioned in the

0:33

template, but you just need to reemphasize

0:36

some of these adverse prognostic factors.

0:39

And then, you know, each of these cases

0:41

have a specific point in terms of making

0:44

sure that you, you, you pay attention to.

0:47

And so here is, um, a relatively young

0:50

patient who comes in with rectal bleeding.

0:53

Like I said before, I sit down to read, I need to

0:55

make sure that this patient has, without any doubt,

0:58

biopsy-proven rectal cancer, which the patient does.

1:01

And so now we have been asked to stay because

1:04

based on what we see on MR, the patients

1:06

essentially get put into two buckets.

1:09

The first bucket is those patients that can go directly

1:12

to surgery, and then the second bucket is where they

1:15

typically get neoadjuvant chemoradiation to shrink

1:19

the cancer and then bring the patient to therapy now.

1:23

The neoadjuvant chemoradiation

1:25

treatment paradigm is changing.

1:27

There are, you know, various components in

1:30

terms of short course or long course radiation

1:33

in terms of giving the amount of chemotherapy.

1:36

And we don't need to dwell on that.

1:38

Suffice it to say is there are certain key elements on

1:41

imaging that will put the patient into the bucket of

1:45

getting neoadjuvant chemoradiation prior to surgery.

1:48

And so, as I said, the first

1:50

sequence you look at is the sagittal.

1:52

That gives you a good sense of whether

1:54

the relevant anatomy has been covered.

1:56

And it also gives you a good

1:58

sense of where the tumor is.

1:59

So the first thing we're going to try and do is,

2:02

as you can see, here is a midline sort of image,

2:05

and you can see the tumor is right in here.

2:08

And the question is, where is the tumor?

2:11

And as I said, the rectum is a part of

2:15

the GI tract, which spans 15 centimeters.

2:18

And for the sake of convenience, we divide

2:20

the 15 centimeters into the lower five, the

2:23

middle five, and the upper five centimeters.

2:26

And so if the tumor is in the lower five centimeters,

2:28

it's low rectal cancer; if the tumor is in the mid,

2:31

mid five, it's mid rectal cancer; and if the tumor

2:34

is in the upper five, it's upper rectal cancer.

2:38

Uh, the way you want to do that is you kind

2:40

of measure the distance from the anal verge.

2:43

So that's what we're going to try and do here.

2:48

So here you can see it's about roughly

2:50

about 10 centimeters from the anal verge,

2:54

and that puts the tumor in the upper

2:56

rectum, upper to mid rectum, if you will.

2:59

And so that's where the cancer is.

3:01

So you give them the distance from the

3:03

anal verge, then that kind of gives

3:05

them an idea of where the tumor lies.

3:07

The next thing you want to do is after you do that

3:10

is you give them the actual length of the tumor.

3:13

And so what we're going to try and do is sort

3:16

of measure the tumor to the best of our ability.

3:19

And this tumor measures roughly about 4.3 cm.

3:21

76 00:03:23,070 --> 00:03:24,940 And that's the next measurement that you do.

3:24

Now comes the most important part, is

3:26

to look at the staging of the tumor.

3:30

So we start with the T staging.

3:31

And if you have a tumor that is confined

3:34

to the submucosa, that's T1 cancer.

3:37

If the tumor goes to the muscularis but does not go beyond

3:41

the muscularis into the adjacent fat, that's T2 tumor.

3:45

And then T3 tumor is when the tumor goes through

3:47

the wall into the adjacent mesorectal fat.

3:50

And T4 tumor is when it goes through the fat,

3:53

invades adjacent organs like the prostate in

3:56

this instance, or the pelvic sidewall musculature,

3:59

or the levator muscle.

4:01

Now, a couple of points to emphasize

4:04

is we on MR are not able to distinguish

4:07

reliably between T1 and T2 tumors.

4:10

And one should not make an attempt because

4:13

if you try and do that, you may make errors.

4:16

And sometimes the surgeons will try and force

4:18

you to do that because, you know, T1 tumors

4:21

can be managed with an endoanal excision,

4:24

whereas T2 tumors require mesorectal excision.

4:28

So, that's, again, we don't, we, we can

4:33

do a good job with MR, so we, we shouldn't

4:35

be even trying to make the distinction.

4:38

The key is, on MR, is what they're looking

4:41

mainly is to see if there is tumor extension

4:43

beyond the, so here is the muscular layer, the

4:46

dark signal. Is it going beyond the muscularis?

4:49

Is it clearly sort of involving the muscle, uh,

4:52

because you lose the dark layer posteriorly here.

4:55

But the question is, am I extending

4:56

beyond that or is it T3 cancer?

4:59

Because once you have T3 cancer, that then puts

5:03

the patient in the treatment paradigm of getting

5:05

neoadjuvant chemoradiation prior to surgery.

5:08

So, as I alluded to earlier, it can be a

5:10

challenge in terms of looking at, uh, true

5:13

axial images and providing the information, and

5:16

you need to make sure you look at the oblique

5:18

axial images to see what's going on.

5:21

When I typically look at this on my PACS monitor, I

5:25

usually have all the planes of the T2 on a single

5:27

monitor, so it's four on one, where I have the

5:30

sagittal, the coronal, the true axial, and the

5:32

oblique axial, and I'm cross-correlating as I go

5:35

along to get a good sense of what the tumor is doing.

5:39

So here is the oblique axial image, and

5:41

you can see that I'm showing you the

5:43

outline of the tumor in this instance.

5:46

And as we scroll through, you can see that

5:49

there clearly are nubbin-like projections

5:52

right here, which are extending into the

5:54

mesorectal fat as well as right here.

5:57

And so, seeing that, you can say with a, you

6:01

know, high level of certainty that the tumor

6:03

not only is involving the wall of the rectum,

6:05

but it extends beyond the mesorectal fat.

6:09

fat.

6:09

So this is mesorectal fat extension.

6:11

So this is a T3 tumor.

6:14

When you have a T3 tumor, what you need

6:16

to tell them is how much of an extent beyond

6:20

the muscularis is the tumor going into the

6:23

fat, because it has been shown that T3 tumors

6:27

that extend beyond five millimeters into the

6:28

mesorectal fat typically have a cancer-specific

6:33

five-year mortality of approximately 50%.

6:37

Whereas if it is less than five millimeters,

6:39

the five-year survival exceeds 85%.

6:45

And so what you want to do is, if you look

6:48

at the template, it kind of tells you to distinguish

6:51

if you have a T3 tumor, you have to tell them, is it

6:54

T3A, which is extension of less than one millimeter?

6:58

Is it T3B, which is one to five millimeters, or is

7:02

it T3C, which is greater than five to 15 millimeters,

7:07

and T3D, which is more than 15 millimeters.

7:10

So that is the level I'm looking at, and as you can

7:13

see as I cross-correlate the area where we found the

7:15

slight nubbin that is projecting anteriorly, that is

7:20

right in this location, and it gives, it's sort of

7:22

easier to measure it on sagittal than it is on the

7:25

oblique, and so we'll go ahead and measure that,

7:28

and that is about, you know, I would say 5 millimeters.

7:32

And so this would be a T3B if, in case it's,

7:36

I'm over-measuring it, if it's around five

7:37

millimeters, that's what it would be around.

7:40

And so, as I mentioned earlier, it's essentially the

7:43

five millimeters is the important sort of landmark.

7:46

If it is less than five, the prognosis is better

7:48

versus greater than five, the prognosis is worse.

7:51

So then you may ask me, well, if it's five

7:53

millimeters, why don't we just have a T3

7:55

that is less than five and more than five?

7:57

Why do we have A, B, C, and D?

7:59

Where A is less than 1, B is 1 to 5, C

8:02

is 5 to 15, and D is greater than 15.

8:05

The reason for that is at some institutions,

8:08

and mainly in Europe, if it is less than

8:12

5 millimeters, they want to know if it is less than

8:14

1 or greater than 1, because if it is less than 1, 178 00:08:17,909 --> 00:08:20,999 they treat it as a T2 disease and actually go

8:20

and do a mesorectal excision and have favorable

8:24

outcomes, whereas if it is more than that, then they

8:27

think about doing neoadjuvant chemo-radiation.

8:29

So it's sort of mainly a treatment

8:31

based issue in terms of staging the T3.

8:34

But the important point to keep in

8:36

mind is from a prognostication purpose, it

8:39

is five millimeters is the cutoff

8:42

in terms of looking at five-year survival.

8:44

But when you're actually dictating it and

8:46

are using the template, you will see it as

8:48

A, B, C, and D in terms of looking at T3.

8:52

So that's sort of the most important point.

8:54

193 00:08:55,200 --> 00:08:57,620 And then obviously, if it extends beyond

8:57

15 millimeters, you try and see if there

8:59

is involvement of the mesorectal fascia.

9:01

You try and see if there's involvement of the,

9:04

of the peritoneal reflection, none of which are present,

9:07

obviously, because this is only about 4 millimeters

9:09

or 4 and a half millimeters extension beyond.

9:12

You look for any lymph nodes and we'll

9:14

be talking about when you call nodes

9:16

positive, which is not the case here.

9:18

And where do you look for the lymph nodes?

9:21

And then the last thing you obviously look for is, uh,

9:24

to see if there is any synchronous or any additional

9:27

lesion, which you don't see in this instance.

9:29

So, uh, so those are some of

9:31

the key points to keep in mind.

9:33

Uh, in this case, this is a, uh, T3, uh, uh,

9:37

B-lesion, uh, where there is extension beyond the wall.

9:41

And the extension is, uh, uh, less than five.

9:44

Hence, it is T3B.

9:45

There are no suspicious nodes.

9:47

There is also, I'm looking closely on the oblique axial.

9:50

On the sagittal.

9:51

I can see the normal flow voids in the vessels.

9:54

So there is no clear involvement of

9:56

the perirectal venous plexus, which is

9:58

again an important point to keep in mind.