Thymus surgery leads to drug-free remission for MG patients
Study in China finds thymectomy 'positive predictor' of sustained remission
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- Thymectomy significantly increases drug-free remission in myasthenia gravis (MG) patients.
- Benefits are strongest for early-onset MG, ocular MG, and those with an enlarged thymus.
- Patients with a normal thymus or thymoma showed less or no benefit from thymectomy.
Thymectomy, or the surgical removal of the thymus gland, may help people with myasthenia gravis (MG) achieve and maintain disease remission without the need for other treatments, according to a study in China.
Thymectomy was significantly associated with a threefold higher chance of achieving that outcome, called maintained complete sustained remission (mCSR), relative to standard treatments. People with early-onset MG (EOMG), in which the disease occurs before age 50; ocular MG, which affects eye-related muscles; or thymus enlargement saw the strongest benefits.
“This study, through a longitudinal follow-up of patients with a median disease duration of 10 years, found that for MG patients, thymectomy is a positive predictor for reaching mCSR, which means patients with thymectomy might successfully discontinue MG-related treatment and remain symptom-free,” the researchers wrote.
The study, “Thymectomy promotes maintained complete stable remission in myasthenia gravis,” was published in the Journal of Neuroimmunology.
Analysis reveals long-term efficacy
MG is caused when the immune system mistakenly attacks proteins involved in nerve-muscle communication. These attacks are most commonly driven by self-reactive antibodies that target a protein called acetylcholine receptor (AChR).
MG associated with anti-AChR antibodies is thought to be closely linked to abnormalities in the thymus, a gland of the immune system. These abnormalities, including an enlarged thymus, are observed in more than 80% of these patients, with thymus tumors (thymomas) found in up to 30%.
Thymectomy is a well-established treatment for MG, especially for AChR-related MG. It can help to ease MG symptoms and reduce the need for immunosuppressive medications. However, “there remains a paucity of robust long-term follow-up data to conclusively establish the sustained efficacy of thymectomy in MG patients,” the researchers wrote.
The team conducted a retrospective analysis to assess the role of thymectomy in helping AChR-related MG patients achieve mCSR, which was defined as the complete absence of symptoms for at least one year without any MG-related treatment.
The single-center study involved 421 people living with AChR-related MG for at least five years. Most participants were women, their median age at disease onset was about 40, and they had had the disease for about 10 years.
Overall, 164 (39%) underwent thymectomy, usually within three years of disease onset. The remaining participants (61%) had conservative treatment, meaning they did not undergo surgery. A significantly greater proportion of patients in the thymectomy group had generalized MG, which also affects muscles outside the eyes (56.1% vs. 38.9%).
mCSR rates were about three times higher in the thymectomy group than in the conservative treatment group (12.2% vs. 4.3%), resulting in a significantly higher cumulative mCSR rate.
Subgroup statistical analysis demonstrated that thymectomy was significantly associated with a higher chance of mCSR in people with EOMG (by more than 4.5 times), those with ocular MG (by threefold), and female patients (by more than 2.5 times).
After adjusting statistical analyses for age, sex, and MG type, thymectomy remained an independent predictor of mCSR. Moreover, mCSR rates increased with longer intervals between disease onset and surgery, rising from 10.8% in participants who underwent thymectomy within one year of MG onset to 18.8% in those who had surgery more than three years after diagnosis.
Most participants in the thymectomy group had thymoma (63.4%), while 30% had thymus enlargement. Those with thymoma were significantly older at disease onset and had a shorter disease duration before thymectomy than those with other thymus issues.
The mCSR rate was higher in people with thymus enlargement compared with those with thymoma (24.5% vs. 7.7%).
“Notably, no patients with normal thymus achieved mCSR after thymectomy, a finding that deserves our attention,” the researchers wrote. “This phenomenon may indicate that the disease exacerbation in this special group may be less thymus-dependent, and the clinical features and [underlying mechanisms] of such patients should be further studied.”
Statistical analyses adjusted for age, sex, MG type, and disease duration showed that thymoma was significantly associated with a 66% lower probability of reaching mCSR.
“Findings from this long-duration MG [group] suggested that thymectomy was beneficial for achieving mCSR in patients with MG, including ocular and [non-thymoma] subgroups,” the researchers wrote. “Both [thymus enlargement] and EOMG represent subgroups associated with favorable postoperative prognosis following thymectomy.”
Still, the team noted that multicenter studies involving a larger number of patients are needed to confirm these findings.
Helen Langhorne
Oddly enough, my paternal grandmother was diagnosed with MG. So was my older brother and I was too. Yet it’s not genetic.