Cancer staging in practice and research

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Published: 22 Nov 2017
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Prof James Brierley - University of Toronto, Toronto, Canada

Prof Brierly speaks with ecancer at AORTIC 2017 about the utility of cancer staging, and misconceptions in their use.

He discusses how screening, registry interrogation and tracking shifting disease progression can give accurate insights into disease burden and outcome, noting that harmonised understanding prevents any miscommunication when comparing data across regions.

For more on cancer staging, watch Dr Max Parkin discuss UICC staging here.

For more on UICC TNM staging, ecancer provides an online training module here.

I’ve given two presentations at the meeting here, the first one was about the principles and the importance of cancer stage, about how cancer stage is used by two different groups of people, really. The first is with physicians and patient interaction in helping determine the prognosis for the cancer and also the appropriate treatment for that patient. But the cancer stage is also very important in cancer control and cancer surveillance activities so that when we have data on population based incidence and report that it’s of far more value if you have stage data in conjunction with the incidence and mortality data.

Obviously if you’re trying to compare mortality or incidence across various jurisdictions you may have more cancer deaths in one area than another area but it may be because the patients are presenting late with a high stage and unless you have stage data you don’t know what the cause of that is. Similarly it’s useful to have the incidence of the cancer broken down by stage and you can use that for cancer programme planning, for instance. So if you have more stage 4 cancers you need to invest more in palliative care or expensive chemotherapy regimes whilst if you have more early stage cancer then you need to invest in surgery for the treatment of that. So it’s useful data for cancer control and cancer planning as well, so it has many uses, not just the initial use which most people think of cancer stage for with the patient-physician interaction but also on a broader population basis.

What are some of the common misconceptions?

The talk I also gave included misconceptions in staging and those are really defining different terms and how people use the wrong term. So some of them are rather, perhaps, people would consider pedantic. So people talk about the T stage and the N stage and they’re the incorrect terms. Stage is usually referred to for stage group and the proper terms are T category and N category. I talked about the difference between clinical stage and pathological stage and how certainly when you’re looking at the individual patient-physician interaction you don’t mix the two together. But for surveillance purposes if you don’t have full data you can mix them but you’ve got to identify that it’s a mixed clinical and pathological stage and for that we’ve introduced a new term, harmonised stage or H stage.

Anything else important to mention?

Stage migration is when a new investigation is introduced such as a PET scan. If you do PET scans some patients who before the PET scan were identified as stage 3 will be stage 4 and they’ll be early stage 4. So they will have a better survival than those who are identified as stage 4 without PET scan because they’ll have more advanced disease. So if you compare two populations, one with a PET scan and one without a PET scan the survival is better in those who have a PET scan because you’re moving some of the stage 3 patients who did badly because they had metastatic disease into stage  4 but they have low volume metastatic disease so they do well. So there is an improvement in survival just by introducing a new investigative tool.

Stage shift occurs if you’ve got a population of patients, say you’ve got a population where 20% of patients have metastatic disease, such as in colorectal cancer, and you introduce a screening system. You want to reduce the number of overall patients who have colorectal cancer and survival improves but that takes time to show. One of the first things you can show is a reduction in the number of patients with stage 4 cancer and that’s stage shift.

How do you make sure people over such a large area use the correct terminology?

It’s very difficult to make sure people use the right terminology. It is very important because there have been studies where people have used different staging systems and trying to compare outcome across jurisdictions and some people have used TNM fifth or sixth and seventh and others have used other staging systems and then to compare them is very difficult. So the best way is with educational activities. In the edition of the TNM book, in the introductory chapter, there are always the rules laid out but most people don’t look at those, they go straight to the breast chapter if that’s what they are interested in without reading the introduction. But to try and improve education we’ve developed a series of educational tools. One is a collaboration with ecancer, we’ve developed educational modules and there’s an introductory module that goes over the rules and the terminology. It starts off with an introduction and a pre-test and then the module itself and then a post-test. Assuming you do well and pass then you can get a certificate that you can print. So we have an introductory one, we also have other modules on specific tumour types such as lip and oral cavity, breast, prostate, colorectal cancer, lung cancer and cervix cancer. These are being updated for the current 8th edition. Some didn’t need changing, such as colorectal and breast, prostate is very minor and will be coming out soon. Lung is very complicated and takes some time; we’re waiting for the atlas to be revised and then we will update that. But they are readily available through a link on the UICC website, you have to join ecancer but they’re free otherwise.

The other thing that we’ve done is produced some educational videos; they’ve been written and they’re in the process of being made and they’ll be again freely available on the UICC website. Other resources that are available on the UICC website is there’s a helpdesk so if you’ve got any questions about staging you can fill out a questionnaire on the helpdesk and you’ll usually get a response within 48 hours. There’s also a list of frequently asked questions that go to the helpdesk with the appropriate answers for that.