How do doctors determine what stage of cancer you have? - Hyunsoo Joshua No and Trudy Wu

302,790 views ・ 2024-06-25

TED-Ed


Please double-click on the English subtitles below to play the video.

00:06
Each year, approximately 20 million people across the world
0
6794
4129
00:10
receive a cancer diagnosis.
1
10923
2086
00:13
At this overwhelming, and often scary time,
2
13092
3045
00:16
a patient usually learns their cancer’s stage,
3
16220
3003
00:19
which is typically a number, ranging from 1 to 4.
4
19223
3504
00:23
While staging is designed in part to help patients better understand
5
23019
4129
00:27
what they’re facing,
6
27148
1209
00:28
extracting this information from a simple number
7
28357
2962
00:31
can be confusing and less than straightforward.
8
31319
2961
00:34
So, what do cancer stages actually mean?
9
34572
3212
00:38
To understand stage numbers,
10
38159
2044
00:40
we first need to unpack the three variables that inform it.
11
40203
4045
00:44
Doctors utilize a system which uses the letters T, N, and M
12
44373
4964
00:49
to describe a tumor’s size,
13
49337
1918
00:51
its presence in the immune system’s lymph nodes,
14
51255
2795
00:54
and whether it has metastasized, or spread, to other organs.
15
54133
4213
00:58
Arriving at this letter staging takes thorough investigation—
16
58513
4045
01:02
physicians will consider a person’s symptoms and overall health,
17
62934
3628
01:06
and may sample, or biopsy, cancerous tissue,
18
66562
3128
01:09
order medical scans, and analyze blood tests.
19
69774
3962
01:14
The T designation is usually a number between 1 to 4,
20
74112
4087
01:18
and is, in most cases, based on tumor size.
21
78199
3587
01:21
But each type of cancer has its own T staging criteria.
22
81786
4129
01:26
Five-centimeter-wide tumors are labeled as T3 in oral cancers,
23
86290
5005
01:31
but T2 in breast cancers.
24
91295
2461
01:33
And some cancers use other staging criteria,
25
93965
3170
01:37
like esophageal cancers, which are staged based on how deeply
26
97135
4379
01:41
the tumor invades the layers of tissue.
27
101514
2336
01:44
To assign an N stage,
28
104183
2127
01:46
doctors evaluate the lymph nodes through biopsies and imaging.
29
106310
4380
01:50
Cancer cells tend to break off from the initial tumor and spread.
30
110898
4338
01:55
They often travel through the lymphatic system—
31
115361
2795
01:58
a network of vessels and nodes,
32
118156
2210
02:00
which filter waste and harbor cells that help fight infection.
33
120366
4046
02:04
Cancers that spread to larger, more distant,
34
124745
2920
02:07
or a greater number of lymph nodes typically file into higher N stages.
35
127665
5756
02:13
M staging involves a more threatening category of cancers’ spread—
36
133671
4338
02:18
when diseased cells scatter and then settle on other organs or on bones.
37
138009
6256
02:24
Historically, this stage has been a matter of just “yes” or “no,”
38
144473
3963
02:28
because once a cancer has metastasized, it’s considered to be much more lethal.
39
148436
4588
02:33
But advances in treatment have recently prompted the medical community
40
153149
3670
02:36
to rethink the M stage as a continuum.
41
156819
3003
02:40
Doctors now consider the number of organs in which the cancer has spread,
42
160198
4462
02:44
as well as the abundance and characteristics of the metastatic tumors.
43
164744
4421
02:49
All sorts of combinations of T, N, and M are possible,
44
169332
4838
02:54
and one letter doesn't always follow the other.
45
174170
2627
02:57
For example, some head and neck cancers will test positive in the lymph nodes N1
46
177089
5673
03:02
with no clear initial tumor, or T0.
47
182762
3253
03:06
So how do these three variables inform a cancer's stage number?
48
186265
4254
03:10
Each TNM combination correlates to a different overall stage,
49
190770
5380
03:16
ordered by how difficult the cancer is to treat.
50
196317
3420
03:19
This sorting is rigidly defined for each type of cancer,
51
199987
3629
03:23
based on generations of research looking at how cancers with different spreads
52
203616
4296
03:27
and characteristics tend to behave.
53
207912
2627
03:30
Importantly, what a certain overall stage means varies from cancer to cancer.
54
210831
5756
03:36
For example, a T3N1M0 combination for a breast cancer
55
216879
5798
03:42
is considered stage 3 and carries an 85% five-year survival rate.
56
222677
5630
03:48
A pancreatic cancer with this same TNM combination, however,
57
228766
4296
03:53
is sorted to stage 2, and yet is more difficult to treat
58
233062
4254
03:57
with a 15% survival rate.
59
237316
2461
04:00
The system is intricate— and ever-changing.
60
240152
2628
04:02
For instance, someone with a stage 4 throat tumor in 2017,
61
242989
4629
04:07
might be considered stage 1 just one year later.
62
247618
3504
04:11
The cancer didn’t improve; the staging system did.
63
251539
3670
04:15
Experts realized that a subset of these advanced cancers
64
255418
3879
04:19
responded to existing treatment better than others,
65
259297
3169
04:22
so their staging was downgraded.
66
262591
2503
04:25
Similar discoveries and advancements in the genetic testing of tumors
67
265344
4213
04:29
are refining staging in breast, prostate, and gynecological cancers.
68
269557
5297
04:35
Meanwhile, breakthroughs in therapies can change things seemingly overnight.
69
275104
5130
04:40
Many cancers one considered near impossible to treat
70
280484
3587
04:44
are now met with high rates of remission.
71
284071
2294
04:46
And thanks to improvements in screenings,
72
286407
2419
04:48
more and more cancers are being discovered at early stages.
73
288868
4212
04:53
So while many will deal with the reality of cancer,
74
293205
3254
04:56
either for themselves, or through the diagnosis of a loved one,
75
296459
3378
05:00
these advances offer better treatments, more targeted cures,
76
300004
4004
05:04
and greater hope for the years to come.
77
304008
2377
About this website

This site will introduce you to YouTube videos that are useful for learning English. You will see English lessons taught by top-notch teachers from around the world. Double-click on the English subtitles displayed on each video page to play the video from there. The subtitles scroll in sync with the video playback. If you have any comments or requests, please contact us using this contact form.

https://forms.gle/WvT1wiN1qDtmnspy7