Almost one in 12 patients diagnosed with primary cancer will go on to develop secondary cancer, new research suggests.
The study of more than two million people found that more than half of those who were diagnosed with a secondary cancer died from the disease.
Secondary cancer occurs when cancer cells break away from the primary cancer and settle and grow in another part of the body.
Researchers said those most at risk of developing secondary tumours need to be monitored more closely post-disease, as it could “significantly improve” survival rates among cancer patients.
Researchers analysed data from more than two million cancer patients, aged 18 and over, who were diagnosed with a primary malignancy from the 10 most common cancer sites: prostate, breast, lung, colon, rectum, bladder, uterus, kidney, melanoma, and non-Hodgkin lymphoma.
Of the two million patients identified, 8% went on to develop a secondary tumour elsewhere, often in the lungs.
Among patients who developed a second cancer, 13% died of their primary cancer, while 55% died of their second tumour.
Dr Karim Chamie, the study’s lead author and an assistant professor of urology at the David Geffen School of Medicine at UCLA, said that doctors should rethink how they handle follow-up care.
“As clinicians, we can become so focused on surveilling our patients to see if a primary cancer recurs that we sometimes may not be aware that patients can be at risk of developing a second, unrelated cancer,” he explained.
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The study, published in the journal Cancer, found that people diagnosed with bladder cancer had the highest risk of developing a second malignancy - 34% of bladder cancer patients who were followed for up to 20 years developed a second cancer, and of those, 25% developed lung cancer.
Chamie said it puts forward a strong case for making an annual CT scan compulsory for bladder cancer survivors - particular those who smoke.
“We could make a significant improvement in cancer survivorship, for instance, if we monitored bladder cancer patients annually for second, unrelated lung cancers,” he said.
In addition to bladder cancer, patients with non-Hodgkin lymphoma were also at higher risk of developing second cancers including lung, prostate and breast cancers.