How common are new cancers in cancer survivors?
A surprisingly high number of incident cancer cases involve people who have already survived a previous cancer, US researchers have found.
Their study, published in JAMA Oncology, looked at around 750,000 people diagnosed with a new cancer from 2009 to 2013. It found that a quarter of patients over the age of 65 had already survived at least once cancer, while 11% of younger patients had a prior cancer history.
Prevalence of a prior cancer ranged from 3.5% to 37%, depending on the type of incident cancer diagnosed and the age of the patient.
In younger patients, prior cancer was most prevalent in those diagnosed with leukaemia (25%), bowel cancer (18%), cancers of the female reproductive organs (15%) and lung cancer (14.6%).
In those over the age of 65, more than a third of melanoma patients had a prior history of cancer. This was also the case for patients with incident leukaemia and cancers of the bone and joints. Most prior cancer among the older age group occurred in a different site.
Over 30% of older people diagnosed with cancers attributable to human papilloma virus or tobacco use had a prior cancer.
The high rate of prior cancer in leukaemia patients might reflect the leukaemogenic effects of earlier cancer treatments, the study authors from the University of Texas said.
They noted that prior cancer has important implications for cancer care delivery.
“Patients may have competing priorities concerning treatment decisions: a new diagnosis may interrupt management, treatment adherence, or outcomes related to a prior cancer. Differences in the prevalence of prior cancer by incidence cancer type also highlight underlying or shared risk factors that may be amenable to targeted surveillance,” they wrote.
In a linked editorial, clinical oncologist Dr Nancy Davidson argued that the findings “should spur us to revisit our long-accepted policies of excluding many otherwise well patients with a history of previous early-stage invasive cancer from participation in cancer treatment trials”.
She said these common restrictions greatly limit the participation of older patients, the very population where cancer is most commonly diagnosed and where we are most in need of strong evidence to guide treatment.
“As the population of cancer survivors continues to grow, understanding the nature and impact of a prior cancer is critical to improving clinical trial accrual, generalisability of results from trials and observational studies, disease outcomes and patient experience,” the study authors concluded.
You can access the study here.