Background:

The necessity and optimal duration of post-thymectomy immunoregulatory medication (IM) in myasthenia gravis (MG) remain unclear.

Objectives:

This study aimed to evaluate whether IM is required after thymectomy in MG patients and to determine the appropriate duration of IM in patients without postoperative deterioration by comparing long-term clinical outcomes.

Design:

This triple-center, retrospective study included 1248 MG patients who underwent thymectomy. Among these patients, we compared outcomes between 483 patients without post-thymectomy IM and 765 patients receiving IM.

Methods:

Efficacy outcomes included post-thymectomy deterioration and minimal manifestation status (MMS) at 1 year. Safety outcomes, tumor growth, and serious complications were assessed between groups. Subgroup analyses were performed in mild cases (Myasthenia Gravis Foundation of America clinical classification (MGFA) ⩽2a at discharge), patients receiving IM for >1 year, and patients receiving IM for >2 years. Propensity score matching (PSM) was conducted for validation.

Results:

Relative to 438 MG patients underwent thymectomy with no-IM therapy, 756 thymectomized MG patients receiving concomitant IM showed significantly superior outcomes, including lower deterioration (hazard ratio (HR) = 0.44, adjusted p < 0.001), lower deteriorated MGFA class (adjusted coefficient = 0.94, p < 0.001), and higher odds of achieving MMS at 1 year (odds ratio = 2.06, adjusted p < 0.001). No significant differences were observed in tumor development (3 years: p = 0.78; 5 years: p = 0.27) or serious complications (p = 0.53). Similar trends were observed across subgroups. Among patients without postoperative deterioration, IM longer than 1 year reduced deterioration risk compared with ⩽1 year (HR = 0.67 (0.50–0.91), p = 0.01), whereas extending IM beyond 2 years offered no additional benefit (p = 0.137). PSM analysis confirmed these findings.

Conclusion:

Our real-world analysis of 1248 MG patients suggests that thymectomy alone is not sufficient to achieve satisfactory outcomes. Post-thymectomy IM is recommended for at least 1 year, while extending treatment beyond 2 years appears to offer no further advantage in patients without deterioration.

Plain language summary

A multiple center real-world study looking at whether and for how long patients with myasthenia gravis need to continue immuno regulatory medications after thymectomy surgery to prevent symptoms from returning

Why was this study done? For patients with myasthenia gravis (MG)—a chronic condition that causes muscle weakness—undergoing surgery to remove the thymus gland (a procedure called thymectomy) is a common and effective treatment. However, a major question remains for doctors and patients after the operation: Is it necessary to continue using immunoregulatory medications, and if so, for how long? There is a critical balance to be struck. Stopping these medications too early could risk the disease symptoms returning. On the other hand, using them for longer than needed exposes patients to potential side effects, such as a higher risk of infections, without a clear benefit. Currently, there is no strong consensus on the best approach. Therefore, this study was conducted to obtain evidence for this important treatment decision for patients and their doctors.

What did the researchers do? To answer this question, we conducted a tri-center study that looked back at the medical records of 1,248 MG patients who had a thymectomy. We specifically compared the long-term health outcomes of 483 patients who did not receive any immunoregulatory medication after surgery to 765 patients who did. We examined key outcomes, including whether the MG symptoms came back (deterioration), the patients’ clinical status one year after surgery, and important safety issues like the risk of developing tumors or other serious complications. To make sure our comparisons were fair, we used adequate statistical methods to account for differences between the patient groups, ensuring the results were robust and reliable.

What did the researchers find? Patients who took immunoregulatory medications after thymectomy had significantly better outcomes compared to those who did not. Their risk of the disease returning was less than half. They were also twice as likely to achieve a state of minimal or no symptoms one year after the operation. Reassuringly, we found no evidence that taking these medications increased the risk of tumors or other serious complications over the study period. Furthermore, for patients who showed no signs of the disease returning after surgery, we found that continuing the medication for more than one year was significantly better at preventing future deterioration than stopping within the first year. However, a key finding was that extending the medication beyond two years did not provide enough benefit in preventing recurrence compared to stopping at the two-year mark.

What do these findings mean? This study provides evidence that for MG patients, a thymectomy should not be considered a standalone cure. Continuing immunoregulatory medications for at least one year after surgery is crucial to effectively prevent the disease from returning. Importantly, the findings also suggest that for the many patients who remain symptom-free after surgery, continuing these medications for longer than two years may be unnecessary, allowing them to try reducing treatment and avoid potential long-term side effects. This evidence helps doctors and patients create more personalized, safer treatment plans.