Thymectomy — removal of the thymus gland — provides clinical benefits to non-thymomatous myasthenia gravis patients for as long as five years after the procedure, according to a follow-up study.
The study, “Long-term effect of thymectomy plus prednisone versus prednisone alone in patients with non-thymomatous myasthenia gravis: 2-year extension of the MGTX randomised trial,” was published in The Lancet Neurology.
Myasthenia gravis is an autoimmune neuromuscular disease caused by autoantibodies that attack the connections between the muscles and nerves, leading to muscular weakness and fatigue.
The exact causes of the disease are unknown, but it is thought that removal of the thymus is a possible treatment.
However, no extensive studies had addressed the overall effects of thymectomy in disease progression for non-thymomatous (those without thymoma, or tumor in the thymus) patients or how long those effects would last.
The Thymectomy Trial in Non-Thymomatous Myasthenia Gravis Patients Receiving Prednisone (MGTX) (NCT00294658) studied whether removing the thymus would improve disease manifestations in these patients over three years.
The results of the trial showed that patients who had the surgery needed less prednisone and had better disease outcomes.
Nonetheless, “there was skepticism that the impact of thymectomy would persist beyond three to four years,” Gil I. Wolfe, MD, lead author of the extension study, said in a press release. “The assumption was that after that, the rates of improvement would be identical between patients who had had a thymectomy and those who had not.”
To address this point, researchers designed an extension study where they followed 68 patients, ages 19-68 at the time of enrollment, who participated in the MGTX trial for five years to evaluate the effects of thymus removal.
A total of 35 patients had undergone thymectomy and were taking prednisone; the remaining 33 were in the prednisone-only group.
Researchers found that the patients who underwent surgery reduced the doses of prednisone by a third and had up to two-thirds fewer visits to the hospital to treat disease exacerbations than patients who were only taking prednisone.
Consequently, patients who had their thymus removed had to pay considerably less for healthcare.
“Our current findings reinforce the benefit of thymectomy seen in that original study, dispelling doubts about the procedure’s benefits and how long those benefits last,” Wolfe said.
Researchers evaluated disease outcomes using the Quantitative MG Score (QMG) and found that significantly more patients who underwent surgery showed only minimal manifestations. This state is comparable to total remission.
Fourteen (42%) of 33 patients in the prednisone group had at least one adverse event by month 60, compared to 12 (34%) of 35 in the thymectomy plus prednisone group.
“Although caution is appropriate when generalizing our findings because of the small sample size of our study, they nevertheless provide further support for the benefits of thymectomy in patients with generalized non-thymomatous myasthenia gravis,” the study concluded.
“When you look at minimal manifestation rates in patients who underwent thymectomy, they are pretty much the highest reported for any population of [myasthenia gravis] patients after five to seven years of focused management,” Wolfe said. “We do hope that the new findings help reverse the apparent reluctance to do thymectomy and that the proportion of patients with [myasthenia gravis] who undergo thymectomy will increase.”
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