Oct. 7, 2021 — For patients diagnosed with a cancer that starts in a solid organ like a lung, colon, breast, or prostate, oncologists want to identify the best treatment for each patient.
To figure that out, oncologists must answer a critical question: Has the cancer spread to other parts of the body? The process of determining where the cancer is, called staging, gives doctors a clearer sense of the cancer’s biological behavior and prognosis, and it helps define the best treatment strategy.
The most common method of staging a cancer evaluates the size and invasiveness of where the cancer started — the primary tumor — as well as whether cancer cells have spread to draining lymph nodes in the region or have traveled through the bloodstream to more distant sites in the body — advanced or metastatic disease. The contributions of the tumor, nodes, and metastases define the TNM staging system.
Our treatments for cancer tend to work either locally or systemically. Local therapies, like surgery or radiation, are effective in the specific area they are directed. Surgery that removes a tumor is effective at eliminating the risk of disease from that location, and radiation helps kill cancer cells within the “field” in which the radiation is pointed.
Systemic therapies, such as chemotherapy and immunotherapy, work throughout the entire body and can be given intravenously (IV), orally with a pill, or occasionally by injection. Immunotherapy, typically an IV treatment, helps stimulate a patient’s immune system to recognize and attack the cancer. The goal of systemic therapies is to treat the disease that’s visible on scans or a physical examination as well as any potential microscopic or invisible disease that a scan or exam cannot detect but that may grow over time.
Historically, surgery or radiation has been the cornerstone of managing early-stage cancers, and chemotherapy or other systemic therapies have been the mainstay of advanced cancer care.
Doctors typically use local therapies when the primary tumor is not too large, has not invaded surrounding tissues, and the spread to lymph nodes is limited. In fact, for early stage cancers, local therapies like surgery or radiation can be curative.
However, as the size and number of lymph nodes involved with a cancer increases, the probability that the cancer has or will spread to other areas of the body also increases. Patients with more advanced cancers typically undergo systemic therapy to cast a wider treatment net and catch not only the disease you see but also the disease you can’t.
Over time, however, we have found that systemic therapies can also improve results for many high-risk but still earlier-stage cancers, and local therapies may be helpful for specific types of metastatic cancer.
For instance, in some patients with early-stage, localized cancer, chemotherapy may be given before surgery or at the same time as radiation. Combining systemic and local therapies can improve how well the local therapy works against the visible disease we can see and often helps catch the invisible disease before it can take hold. For many cancers, chemotherapy or immunotherapy has been shown to shrink tumors before surgery or during radiation and increase the chance that patients will be cancer free years after treatment.
Local therapies like surgery or radiation may also be appropriate for patients with advanced cancer. If the cancer has metastasized to the brain, for example, a patient may benefit from surgery or radiation directed to the tumor site because many systemic cancer drugs cannot reach the brain in high enough concentrations to shrink these tumors. Similarly, when a tumor mass is causing symptoms that need to be treated immediately, such as bleeding or difficulty breathing, local therapy targeting the problem are may do the job best. In addition, patients with metastatic disease may only have one or two tumors growing at a concerning rate. This situation, called oligo-metastatic disease (oligo meaning “few”), is unusual but may call for a local treatment directed at that fast-growing tumor.
That is precision medicine — the concept of identifying the right tools for each individual — at work.
H. Jack West, MD, is an associate clinical professor and the executive director of employer services at City of Hope Comprehensive Cancer Center in Duarte, CA. West serves as web editor for JAMA Oncology, edits and writes several sections on lung cancer for UpToDate, and leads a wide range of continuing education programs and other educational programs, including hosting the podcast West Wind.