A global language: cancer stages and TNM Classification

What does TNM stand for?

• T category describes the primary tumour site and size
• N category describes the regional lymph node involvement
• M category describes the presence or otherwise of distant metastatic spread

In this episode of Let's Talk Cancer, Dr Cary Adams, CEO of UICC, discusses the origin, meaning and importance of the TNM classification with Dr Mary Gospodarowicz, UICC Past-president and Co-chair of the UICC TNM project.

Cancer stages I, II, III, IV.

Many will have heard of these terms but may not know exactly what they mean or where they come from.

These terms form the basis of the international TNM (“Tumour”, “Nodes”, “Metastases”) Classification system, which describes how advanced a cancer is when it is diagnosed.

This system has proven to be groundbreaking in healthcare, as it allows doctors to explain the cancer to their patients, prescribe the appropriate treatment plan, and improve information sharing and research across populations and regions.

The Union for International Cancer Control has pioneered the TNM Classification for the past 50 years.

See podcast transcript below

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Podcast Transcript:

A global language: cancer stages and TNM Classification

Dr Cary Adams, CEO of UICC:  Hello, Welcome to Let's Talk Cancer by the Union for International Cancer Control, an organisation that unites and supports the cancer community to reduce the global cancer burden. I'm Cary Adams, the CEO of UICC, based here in Geneva, Switzerland. Stages One, Two, Three and Four. Many will have heard of these terms but may not know exactly what they mean or where they come from. They are the basis of the internationally accepted Standard for Cancer Staging, TNM - Tumour Nodes Metastasis - Classification. Doctors use this system to classify the stage at which a cancer is diagnosed, how far it has advanced in the body at the time it is detected. The Union for International Cancer Control has pioneered the TNM classification for the past fifty years. The development of a common language has been ground breaking in healthcare. Above all it is an essential tool for doctors to explain the cancer to their patients and prescribe the appropriate treatment plan. With us today to discuss the origin, meaning and importance of TNM classification is Dr Mary Gospodarowicz, UICC Past-President and co-chair of UICC's TNM project. Mary, thank you very much for being with us today. 

Dr Mary Gospodarowicz, UICC Past-President and co-chair of the TNM project: Thank you very much for having me. 

Dr Adams: Let's talk about stage one, two, three, and four. What's the difference between a one, a two, a three, or a four? 

Dr Gospodarowicz: Stage one disease is when the cancer, the tumour, is localised to the site where it's presenting. So, for example, for breast cancer the tumour is localised in the breast and it's small and it's highly curable with surgical excision. Stage two usually represents tumours that are larger and more difficult to control even without spread. Stage three is what we call locally extensive disease, so the tumour may extend beyond the breast. It may have spread to the lymph nodes that are close to the site of origin, so called regional lymph nodes. And stage four represents cancer where the tumour may have metastasised. 

Dr Adams: Very simply, what is metastatic cancer cancer? 

Dr Gospodarowicz: Cancer cells have the ability to invade the tissues and migrate to other parts of the body, so metastatic cancer just simply says that the cancer has spread from its site of origin to another part of the body. 

Dr Adams: And as you said mentioned earlier it becomes more complicated to treat a stage three and stage four cancer than stage one or two. UICC's role is quite unique isn't it, in terms of putting together a guideline which is used universally.

Dr Gospodarowicz: The UICC got involved with the TNM Classification actually longer than fifty years ago because Professor Pierre Danois from France originate the concept. The concept of cancer staging was first noted almost a hundred years ago as clinicians recognised that small tumours without spread were associated with much better prognosis. This was before treatment with drugs or any systemic therapy, the only treatment available a hundred years ago was surgery and at the beginning radiotherapy. So it was recognised that if cancer was localised to one part of the body it could be controlled for a period of time and could be sometimes occasionally cured but once it had spread all patients died, so the extent of disease became a very important determinant of prognosis. And as our toolbox of various treatments has expanded and our knowledge and ability to detect the extent of disease has expanded with the introduction of imaging and then gradual improvements in imaging, the classifications became more and more sophisticated. UICC has had commitment to continue to maintain this classification so it is relevant to clinicians and for cancer control bodies globally. 

Dr Adams: But I guess for healthcare professionals generally this is a useful language for dialogue and discussion and debate. 

Dr Gospodarowicz: The classification of cancer into the Tumour Nodes and Metastasis has been the backbone of our language to describe the extent of disease and it continues to be relevant even when we have so much more sophisticated tools to prognosticate. All the practice guidelines that exist are written according to the stage or the extent of the disease. Cancer staging is used everywhere to determine prognosis, to communicate this prognosis with patients, to determine the best possible treatment for the patient. It is indispensable.

Dr Adams: It's a massive job keeping it up to date and I know that there's a review period of every five to seven years, so in a normal review, Mary, do you see a significant number of changes or updates because of advances in our understanding of cancer? 

Dr Gospodarowicz: We try to keep the changes to a minimum because the changes in classification have a profound effect on cancer registries all over the world and it's actually quite costly to change the classification and change what's being recorded. However the classification must stay relevant to current treatment and diagnostic tools otherwise clinicians will stop using as it's not reflecting what we need to know to predict the outcome. 

Dr Adams: The last addition was in 2016, Mary. When's it going to be revised, what do you anticipate will happen? 

Dr Gospodarowicz: We are currently under discussions to produce the classifications that will come into effect in 2023 - 2024. We have some situations where the classification is difficult to interpret because of the differences that exist around the world and the availability of modern diagnostic imaging and we know that if we do more imaging we detect the spread of disease earlier and especially in prostate cancer that has become an issue worldwide because, for example, in the United Kingdom most patients at the diagnosis have MRI or magnetic resonance imaging of the prostate to confirm the extent of disease. Many patients around the world don't have access to MRI for localised prostate cancer at all. With early detection we can diagnose cancer earlier and we see what's called stage shift where more patients present with stage one and two disease than with stage three and four disease. And that stage shift is the the first indication that our programs of screening or early detections are working. There's also new molecular imaging that detects the spread of prostate cancer - PSMA pet scans - and they very often detect the spread of prostate cancer beyond the prostate, beyond the pelvis, into lymph nodes or the bones, way before this can be detected on the any other form of imaging. So we know that the use of these advanced imaging systems will move patients into the higher stage category without necessarily changing their prognosis because they've always had the extent of the disease. These changes are called stage migration, so you migrate patients to a higher stage just because you can detect more disease rather than changing the prognosis. So those two concepts that I talked about - state shift which is a good thing; with early detection, the patients are presenting with earlier disease, and the less beneficial thing, stage migration, where you basically move patients with early disease to a higher stage just because you image more - need to be understood for people to be able to interpret the meaning of stage and the disease. 

Dr Adams: I've heard about essential TNM, what is that? 

Dr Gospodarowicz: So the TNM Classification is deemed to be quite difficult for cancer registrars, new cancer registries, in developing countries where the resources may be limited, and frankly in order to determine the effectiveness of early detection and screening all you need to do is to record whether a patient has stage one, two, three, or four. Stage one and two could be put together as localised disease, stage three as locally extensive, and stage four as metastatic. And even the knowledge of having fewer patients presenting with metastatic disease is an early indication of success of early detection and screening programs. So what we proposed for new cancer registries that are just starting and I'm trying to have comprehensive set of data if we published a so called "Essential TNM" which is very simple to use and is developed for most common cancers and has been pre-tested in many countries in Africa quite successfully, so that we can start promoting the culture of recording disease everywhere. 

Dr Adams: That's a fantastic initiative. Mary, what else is there to do? 

Dr Gospodarowicz: I think what we're trying to do now is align the TNM project better with the UICC direction to improve global cancer control, having discussions on how the use of staging and prognostic factors can lead to a recording of outcomes and then can lead to better assessment of quality of intervention and looking at how the whole package deal of better diagnosis, better assessment of disease extent, better recording of disease extent, better recording of prognostic factors can help with global cancer control. Because we all talk about global cancer control from the top, from national cancer control plans, from very general decisions and interventions but we need to connect it with day to day practice of cancer diagnoses and cancer treatments so that's what we're trying to do now is to connect the work that's being done by clinicians on the ground with the work that's done by cancer control professionals so that this whole machine works better and delivers better outcomes. I should add that while TNM is very important, our work in the last couple of decades extended beyond the TNM by also raising awareness of the importance of other prognostic factors, other determinants of outcome. We know that beyond the disease, the patient is a very important determinant of outcome. Patients who are older, patients who have comorbidities, may not be able to tolerate treatment as well as younger and fit patients, and that will result in different outcomes. We also are aware that the other potential and powerful determinant of outcome is treatment and while we all know about the access to treatment and difficulties that people have accessing treatment, the other very important determinant is the quality of treatment and the quality of treatment is something that's not very well measured, but is also a very powerful determinant of outcome. So in our publications now even in the TNM book, we do put in the back what are the other factors that need to be taken into account when discussing the prognosis and the outcome of the patient and with prescribing treatment. And that work is also very important because it lets us discuss the outcomes that should be recorded and should be known other than survival in order to assess our own quality of treatment. 

Dr Adams: Thank you very much for your time, it's been fascinating. I know how important you've been to UICC over the many years but your commitment to TNM is very well respected so thank you very much indeed. 

Dr Gospodarowicz: Thank you. 

Dr Adams: Thank you for listening to this episode of Let's Talk Cancer. If you liked this podcast, please subscribe for more content from tobacco control to cancer prevention treatment and care.
 

What does TNM stand for?

• T category describes the primary tumour site and size
• N category describes the regional lymph node involvement
• M category describes the presence or otherwise of distant metastatic spread