The thymus is necessary for normal immune system development. However, with age, this organ shrinks and loses its activity. Partly because of this, it is less clear how important it is for the health of an adult. American researchers have now looked at the health outcomes of adults who underwent a thymectomy – a procedure that is routinely performed in many operations in that area in the US. The researchers looked at the risk of death, infection, cancer and autoimmune diseases.
The Americans obtained data from a registry of patients who had undergone thymectomy at Massachusetts General Hospital in the period January 1993-February 2020. Patients who underwent cardiac surgery without thymectomy in the period 2000-2019 served as a control group. The researchers excluded patients who died within 90 days after this operation or who underwent cardiac surgery (again) within five years.
The researchers matched 1146 thymectomy patients with control patients for gender, ethnicity, age group and the prevalence of preoperative infections, cancers and autoimmune diseases. About half of the thymectomies were performed without malignancy or other thymic disease.
Five years after surgery, those who no longer had a thymus had a higher proportion of death than those who still had the thymus (8.1 vs. 2.8%; relative risk (RR): 2.9; 95%- CI: 1.7-4.8). These patients also developed cancer more often (7.4 vs. 3.7%; RR: 2.0; 95% CI: 1.3-3.2). After excluding patients with preoperative infections, cancer or autoimmune diseases, these differences persisted. In addition, the researchers found a difference in the risk of new autoimmune diseases (12.3 vs. 7.9%; RR: 1.5; 95% CI: 1.02-2.2). Furthermore, in a small subgroup analysis of 22 people from the thymectomy group and 19 from the control group (mean follow-up: 14.2 years), the former produced significantly fewer CD4+ and CD8+ lymphocytes than the control patients.
Striking results, says Ad Verhagen, professor of lung surgery at Radboudumc. ‘Although the somewhat curious design of the study is susceptible to confounding. The pathology of half of the patients who underwent a free thymectomy is largely ignored. That means we don’t really know how comparable the groups are.’
The American researchers conclude that the thymus remains functional in adulthood and is important for maintaining good health. The thymus should therefore be left alone as much as possible. Verhagen: ‘It is also not customary in the Netherlands to perform a thymectomy in passing during cardiac surgery. Usually the thymus can be easily split in the midline.’
2023-09-07 04:00:00
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