In the Tanach (Melachim II:20), we read that Hezekiah, King of Judah, became ill and that Isaiah came to visit him. Isaiah told him that he was soon to die—but the king became greatly upset, prayed to God, did repentance and was granted another 15 years. The Bible is replete with people aware of their prognoses as was Hezekiah—Yaakov knew he was to die and gave out blessings to his children; Moshe knew and wrote the book of Devarim.
After learning a diagnosis of cancer, it is a frequent question and often necessary to impart such information to a patient—even if unasked—because treatment decisions often depend on it. Obviously, one cannot know the prognosis with great precision or accuracy. At best, oncologists can estimate the probability of survival based on the prior experience of patients who have had the same type of tumor with similar characteristics. Multiple factors may go into such estimates, but the one that predominates is staging. Staging is almost always undertaken very soon after a cancer diagnosis is made for the purpose of prognostication, but also to determine the extent of disease, a major factor in planning treatment.
Each cancer has its own staging system, since each cancer varies in what makes its outcomes better or worse. In my description here, I focus on the solid tumors; hematologic malignancies also have staging systems, but they consider different clinical parameters.
The commonly used system for staging solid tumors is the TNM system, reflecting three categories—Tumor, Nodes, Metastasis. Each solid tumor has its own specific TNM system—you can Google to see the table for any specific cancer.
The “T” category describes how advanced the primary or original tumor is and therefore how much that may affect outcomes. For example, for breast tumors, size is the main determinant of risk. Thus, a T1 breast cancer is 0-2cm (centimeters) in size, while a T2 tumor is 2-5cm and a T3 tumor is >5cm. To be a T4 tumor, a breast cancer has to do something bad, like ulcerate through the skin, penetrate the chest muscle or have a condition known as inflammatory carcinoma, which is high-risk. These size categories are for convenience for risk estimation, but logic would tell you, and it would be right, that even within categories, size is a continuous variable; a 2.1cm tumor is better than a 4.9cm tumor even if they’re both T2.
The T stages for lung cancer are also reliant on tumor size. For colorectal and gastric cancer, the risk from the primary tumor is dependent on how far the tumor has penetrated through the bowel wall.
For the “N” classification, each organ has lymph nodes adjacent to it to which waste products and toxins are excreted, a sort of sewage/garbage system. Thus, these localized lymph nodes are often the first site of spread. The term metastasis is often used to describe this, but it is not as ominous as metastasis to distant organs—local lymph nodes with tumor can usually be resected along with the tumor during surgery, and thus offer the potential for cure, though the fact that spread has gone even that far does worsen the prognosis, usually to some intermediate level. The number of lymph nodes that are found to have tumor within them at surgery is a measure of risk. To utilize breast cancer again as our example, if the local lymph nodes are all negative for tumor, that is N0; N1 is involvement of 1-3 lymph nodes; N2 is 4-9 lymph nodes; N3 is 10 or more or involvement of the supraclavicular nodes. As with tumor size, the lymph node status is really a continuous variable—thus, even within the N2 category, for example, 4 is better than 9.
Finally, we reach the M category, the subject of our last article, metastasis. This is a dichotomous category—you either have it or you don’t; M0 or M1.
The reader will perceive that this is all rather complex, with four T categories, four N categories, and two M categories (for breast cancer, our example), resulting in 4 x 4 x 2 = 32 permutations of TNM. There are tables that offer the probability of recurrence or survival for each of these combinations, but it is a cumbersome number of details to keep track of. So to simplify the process, these TNM categories have been combined into four stages, where stage I has the lowest risk, stage IV has the highest risk, and II and III are intermediate.
To provide the probability of recurrence or mortality to a patient, one needs only to determine where he/she falls in each of these categories—information that the pathologist will usually provide on the pathology report, or that can be gleaned from radiology. In the past, I would then go to tables in books or online to find the corresponding risks, but nowadays there are easily available, well-validated algorithms online in which you can simply fill in the appropriate information, hit the “calculate” button, and get an answer. These algorithms will also take into account other prognostic details beyond stage—age, sex, etc—and so give a more individualized prognosis.
We will discuss more cheerful topics in the next installment of Thoughts on Cancer.
Alfred I. Neugut, MD, PhD, is a medical oncologist and cancer epidemiologist at Columbia University Irving Medical Center/New York Presbyterian and Mailman School of Public Health in New York.
This article is for educational purposes only and is not intended to be a substitute for professional medical advice, diagnosis or treatment, and does not constitute medical or other professional advice. Always seek the advice of your qualified health provider with any questions you may have regarding a medical condition or treatment.
