New study: Blood test can detect colon cancer
With March being colon cancer awareness month, it’s a good time to look at some startling numbers on the disease here in the United States. Once considered only a medical concern for middle-age or older adults, colon cancer cases are on the rise in younger adults. In fact, data shows a rise in colon cancer diagnoses in the U.S. over the past 30 years in adults in their 20s, 30s and 40s. Deaths are on the rise, too, with a recent study finding colorectal cancer is now the leading cause of cancer-related deaths in men and second in women under age 50.
For those patients already diagnosed with advanced colon cancer (stage 3), one of the big decisions after surgery is whether to follow up with chemotherapy or other treatment. A new study shows an easy blood test may be able to help in that decision. Data published in The Journal of Clinical Oncology shows a blood test called ctDNA (circulating tumor DNA) with the brand name Guardant Reveal helped to accurately identify patients at high risk of returning cancer. The study found patients with detectable cancer DNA in their blood after surgery were significantly more likely to have cancer return and had higher morbidity rates even if traditional follow-up suggested their risk was lower.
“The technology of detecting tumor DNA in the blood is a very exciting development allowing another data point for a more precise assessment of prognosis and risk of recurrence,” says Dr. James McCormick, a colon rectal Surgeon and Chairperson of the Colon and Rectal Cancer Program at Allegheny Health Network Cancer Institute. “This may allow us to better tailor treatments for the individual patient.”
AHN has been using the test, and McCormick says the next step is to use it to better identify which patients would benefit from certain types of therapy and who can avoid it.
An interesting point of the study is that the DNA is being detected without requiring information about the DNA makeup of the primary cancerous tumor.
“Some ctDNA testing protocols require information about the primary tumor DNA for it to be detected in the blood – This is a so-called tumor-informed assay,” McCormick explains. “This means we need to have sufficient tumor DNA from the primary tumor, often requiring more extensive biopsy or even surgery. By passing this requirement, we may be able to use this test on patients who may be wishing to avoid surgery.”
Surgery to remove the tumor and at-risk lymph nodes is the primary treatment for most colon cancers. If lymph nodes are affected, this is stage 3 with chemotherapy usually prescribed to fight recurrence. If lymph nodes are clear, that means stage 2 and usually no chemotherapy.
“If we can predict the actual risk of recurrence of an individual with colorectal more accurately, we can better select which patients will benefit from chemotherapy and in which patients it can safely be avoided,” says McCormick. “This is one of the goals we hope to achieve by detecting tumor DNA in the blood. So, a person with stage 2 who would normally not receive chemo would be given chemo if the blood test were positive. Conversely, a patient with stage 3 disease may be spared chemotherapy if their ctDNA blood test shows them to be low risk for recurrence. This would be a major shift from current practice of treatment being given based upon stage.”
AHN is currently using the blood test as an option for watching for recurrence and is enrolling patients in clinical trials to test it. AHN is also offering it to patients who may be highly motivated to avoid certain treatments or who seek more aggressive surveillance programs.
About one-third of all patients diagnosed with colorectal cancer are stage 3 and are more likely to be having symptoms. When cancer is detected in patients with no symptoms on a screening exam, the stage tends to be lower with better cure rates. That is one of the reasons screenings are so important starting at age 45 for average-risk patients (even younger for those with a family history or other risk factors). Colon polyps, the precursors to colorectal cancer, can be removed during a screening colonoscopy to stop the cancer from ever forming.
“When there is regional or distant spread, curing the disease is more difficult and often requires treatment with chemotherapy. So, early detection of colon cancer is critical,” stresses McCormick. “But, remember, colorectal cancer can affect anyone at any age and is affecting younger patients more frequently than ever. In fact, those born in the 1990s are two times more likely to develop colon cancer and four times more likely to develop rectal cancer compared to prior generations – these are people not even of screening age.”
The key to early detection for everyone of any age is to never ignore symptoms, which can include change in bowel habits, bleeding, abdominal discomfort or bloating, loss of appetite, unexplained weight loss, weakness or fatigue. Talk to your doctor right away and insist on a colonoscopy.