The thymus is often removed during surgery (Picture: Getty)
The removal of a small organ thought to be ‘useless’ in adults could in fact lead to higher chances of cancer and death, according to a new study.
Located in front of the heart behind the sternum, or breastbone, the thymus produces white blood cells that help protect the body from infections in children. However, during puberty it shrinks, with much of the tissue replaced by fat.
As a result, it is often removed during surgical procedures, including cardiothoracic operations, where it can get in the surgeon’s way.
But a study from Harvard suggests the thymus continues to play an important role in immune health in adults, and those without the organ were almost three times more likely to die from a variety of causes, with a twofold higher risk of developing cancer.
‘The magnitude of risk was something we would have never expected,’ said Harvard’s Professor David Scadden, who led the study in collaboration with researchers at Massachusetts General Hospital.
Speaking to the Harvard Gazette, he added: ‘The primary reason why the thymus has an impact on overall health seems to be as a way to protect against the development of cancer.’
The thymus has long been thought to be redundant in adults (Picture: Getty)
The team analysed data from 1,146 adult patients who had undergone a thymectomy – removal of the thymus – alongside demographically-matched control patients who had undergone similar operations but did not have the organ removed.
In all patients followed for more than five years, the rate of death in the thymectomy group was higher than in the general US population, at 9% compared to 5.2%. Death due to cancer was 2.3% in the thymectomy group, compared to 1.5% in the general population.
A subgroup of patients had their T-cell lymphocytes measured – the type of white blood cells produced by the thymus. Researchers found those without a thymus produced fewer T-cells, and showed higher levels of pro-inflammatory cytokines, which are associated with autoimmune disorders and cancer.
An increased risk of autoimmune disease was also noted when patients with preoperative infection, cancer, or autoimmune disease were excluded from the analysis.
‘The magnitude of death and cancer in patients who had undergone thymectomy was the biggest surprise for me,’ said first author Dr Kameron Kooshesh, speaking to the Harvard Gazette.
The team, from left, Kameron Kooshesh, David Sykes, David Scadden, and Karin Gustafsson (Picture: Kris Snibbe/Harvard)
‘The more we dug, the more we found. The results suggested to us that the lack of a thymus appears to perturb basic aspects of immune function.’
The study, published in The New England Journal of Medicine (NEJM), highlights only an association between the removal of the thymus and increased risk of cancer and death, not cause and effect.
However, writing in the NEJM, Dr Naomi Taylor, who was not involved in the study, said: ‘The pioneering research by Kooshesh et al. raises critical questions about the role of the aging thymus in human health.
‘It will be important to perform additional studies involving more ethnically diverse groups of patients who have undergone thymectomy and have been treated for indications that more closely match the conditions in the control group.
‘Overall, this study has important repercussions for the care of patients undergoing cardiothoracic surgery and strongly argues against total thymectomy if it can be avoided.’
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It may also help prevent cancer.