Additional benefits have been seen in patients with myasthenia gravis who undergo thymectomy, according to results from an extension phase of the landmark MGTX trial.

The previously reported primary outcomes of the study showed that thymectomy plus prednisone was superior to prednisone alone in primary outcomes at three years.

Newly published results in Neurology from a two year extension to the trial show that thymectomy increases the likelihood of patients achieving sustained minimal manifestation status (MMS)  with complete withdrawal of prednisone, compared to prednisone alone.

The findings comes from a post-hoc analysis of the two year extension phase of international multi-centre study in which 60 patients with acetylcholine receptor antibody positive MG were randomised to thymectomy plus prednisone and  51 prednisone alone.

All patients received oral prednisone titrated up to 100mg on alternate-days until they achieved MMS, which prompted a standardised prednisone taper as long as MMS was maintained.

At five years, MG patients in the thymectomy plus prednisone group achieved sustained MMS with complete withdrawal of prednisone more frequently (64% vs 38%). Patients in the thymectomy group also achieved sustained MMS earlier (median time 30 months vs no median time achieved, P<0.001), with both outcomes indicating that disease relapses during prednisone tapers were less frequent after thymus removal.

Steroid sparing immunosuppressive agents had to be used more frequently to achieve sustained MMS with complete prednisone withdrawal in the prednisone alone group (35%) than in the thymectomy plus prednisone group (5%).

Losing MMS was noted in 30% of thymectomy plus prednisone and 35% of prednisone alone group. However, among patients who lost MMS while off prednisone, all but three regained MMS after re-introducing low doses of prednisone, “supporting a strategy of slowly tapering prednisone completely off in patients with sustained MMS”.

The analysis also showed that prednisone associated adverse symptoms were more frequent in the prednisone alone group, and distress level increased with higher doses of prednisone.

The study authors – including Dr John King of the Department of Neurology, Royal Melbourne Hospital – concluded that the findings provided further evidence to support early consideration of thymectomy as an option for patients with MG.

“These results further demonstrate the superiority of thymectomy plus prednisone compared to prednisone alone in disease control, while lowering prednisone and other immunosuppressive agent requirements,” they said.