Doctors and patients have long wondered: when can someone with colon cancer be considered truly cured?
A large new study may finally provide a clear answer.
According to research led by IRCCS Ospedale Policlinico San Martino in Italy, along with the Mayo Clinic and other international cancer centers, the risk of colon cancer returning drops to less than 0.5% by six years after surgery.
This gives a practical point in time when many patients can safely consider themselves cured.
Colon cancer recurrence has often been difficult to define clearly. Previous studies sometimes counted deaths or new cancers in other parts of the body as “recurrences,” even though these events don’t always mean the original cancer has come back. That made it hard to know when a patient was truly in the clear.
Earlier research showed that the risk of colon cancer coming back was about 1.5% at five years and 0.5% at eight years after treatment. These numbers suggested that most recurrences happen in the first few years, and very few happen later.
In this new study, published in JAMA Oncology, researchers looked closely at data from 35,213 patients who had stage II or stage III colon cancer.
These patients took part in 15 major clinical trials between 1996 and 2015. All of them had surgery to remove the cancer, followed by chemotherapy. Each trial followed patients for at least six years, and in some cases, much longer.
The data showed that the risk of the cancer coming back was highest in the first year after treatment—about 6.4% between 6 and 12 months. After that, the risk went down every six months. By year 6.5, the chance of cancer coming back dropped below 0.5%, and it stayed that low through year 10.
The study also found that counting deaths and new cancers as recurrences made the numbers look worse than they really were, especially in older patients. For example, older people are more likely to die from other causes, which can make the risk of recurrence seem higher if those deaths are included in the statistics.
Interestingly, women had a lower risk of recurrence compared to men when deaths were taken into account. And age played a role too—patients over 40 had higher rates of events than younger patients, though this was partly due to the increased likelihood of death from other causes in older age groups.
Out of all the people in the study, about 27% did experience a recurrence, either in the original area or in other parts of the body. That’s a significant number, but most recurrences happened in the early years after treatment.
The researchers believe that reaching six years after colon cancer surgery with no signs of the disease is a good milestone to define a cure. This could help patients and doctors plan better follow-up care, reduce unnecessary long-term testing, and offer peace of mind to people who have fought colon cancer and won.
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The study is published in JAMA Oncology.
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