Oncology Viewpoint
The AJCC Cancer Staging Manual 8th edition is 997 pages, not counting the index. The internet is littered with articles about how we're doing things wrong, from peeling bananas to parking our cars. But with the complications of the AJCC cancer staging system, there's a good chance you are actually staging wrong. In this article, I'll review common errors in staging using the AJCC system and point out ambiguities where no one knows if they're staging right.
The most common error I see is when providers improperly change a patient's stage group at recurrence. "He's now stage IV," is an inappropriate way to describe a patient treated for early-stage lung cancer who later develops a brain metastasis. The correct description for such a patient's cancer could be, "distant metastatic recurrence of stage IIA disease."
According to the 8th edition, patients should have their TNM category reevaluated in various "windows," including at diagnosis, after surgery, post-therapy, at recurrence or at autopsy (autopsy staging is only done in cancers incidentally found during this procedure). However, stage group, the 0-IV designation, should only be assigned at diagnosis or after surgery, not at recurrence.1 The survival graphs and other prognostic information included in the staging manual are for patients staged at diagnosis, not for those with recurrence after treatment, and these groups may have different prognoses. For example, in colorectal cancer, patients with isolated recurrence in the liver may have a better prognosis than patients who present with similar liver metastases.
Confusingly, the manual does not give guidance on what to do if the clinical and pathological stage groups differ, other than to say if patients receive neoadjuvant therapy and have a complete response, they may be categorized ypT0 ypN0 cM0, but no pathological stage group can be assigned (so they only have their clinical stage). This raises the question of which stage to choose for patients with a partial response to neoadjuvant therapy. Should a patient with cN1 disease who has ypN0 disease after neoadjuvant therapy be downstaged? I believe that most practitioners would stick with the original clinical stage, but the manual leaves this issue unresolved.
Another common staging mistake providers make is inappropriate metastasis staging. MX is not a valid category at any stage of workup, even in patients who have not had imaging, and patients should be recorded as having M0 disease unless they have evidence of metastases. Patients may be staged pM1 if there is pathologic evidence of metastasis, but there is no defined pM0 category, so patients without evidence of metastasis can only be staged cM0. Additionally, once patients have been staged either cM1 or pM1 the M category cannot change, even if the evidence for metastases resolves on subsequent studies.
Finally, providers sometimes fail to use the T0 designation appropriately. The T0 category exists for many cancer sites, including head and neck cancers, GI cancers, and lung and breast cancer. Once a patient has completed workup, they should be assigned T0, not TX, if there is no evidence of primary malignancy. The T0 designation seems particularly underutilized in recurrent prostate cancer. Biochemical recurrence, for example, is properly categorized rcT0 rcN0 cM0.
In addition to errors that providers make, there are also oversights in the AJCC system that sometimes make it impossible to stage patients accurately. Esophageal staging, for example, requires endoscopic ultrasound or surgery for assessment of T-category. What staging should be assigned for patients who cannot be staged with EUS, or that started treatment without a prior EUS? In the manual's General Staging Rules it states, "If uncertainty exists regarding how to assign a category, subcategory, or stage group, the lower of the two possible categories, subcategories or groups is assigned..." (emphasis original). Esophageal cancer has six distinct T-category classifications. Cases without an EUS may be most correctly staged "TX-Tumor cannot be assessed," which sidesteps the question of T-category, but leaves stage group unresolved. The manual does not provide a stage group for TX patients, and T-category could be used to assign patients to stage group I through IVA. Should all of these patients really be given stage group I?
Apart from ambiguities in the staging manual, another underlying reason many patients are mis-staged comes from the complexity of the staging system. With each new edition, new TNM categories are added, and few seem to be taken away. Tellingly, the handbook version was phased out after the 7th edition. If the goal of staging is clear communication, then categories have to be simple enough that they are remembered by a broad range of providers.
With all these challenges in mind, it's no wonder staging is sometimes done wrong. Hopefully, this article will help you do staging right.
What Are Your Thoughts on Staging?
Share your challenges on staging, as well as any advice you can share with your colleagues. Send your thoughts to the editor at mailto:[email protected].
CHRIS WATSON, MD, is a board-certified radiation oncologist practicing in Indianapolis.
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