Is thymectomy in non-thymomatous myasthenia gravis of any benefit?

Abstract

A best evidence topic in thoracic surgery was written according to a structured protocol. The question addressed was if thymectomy in non-thymomatous myasthenia gravis was of any benefit? Overall, 137 papers were found using the reported search, of which 16 represented the best evidence to answer the clinical question. The authors, journal, date and country of publication, patient group studied, study type, relevant outcomes and results of these papers are tabulated. The outcome variables were similar in all of the papers, including complete stable remission (CSR), pharmacological remission, age at presentation, gender, duration of symptoms, preoperative classification (Oosterhius, Osserman or myasthenia gravis Foundation of America (MGFA)), thymic pathology, preoperative medications (steroids, immunosuppressants), mortality and morbidity. We conclude that evidence-based reviews have shown that relative rates of thymectomy patients compared with non-thymectomy patients attaining outcome indicate that the former group of patients is more likely to achieve medication-free remission, become asymptomatic and clinically improve (54%, P < 0.01), particularly patients with severe and generalized symptoms (P = 0.007). Patients with generalized myasthenia gravis showed 11% stronger association with favourable outcomes after thymectomy. Some studies show early remission rates (RRs), as early as 6 months post-thymectomy, of 44%. Overall, the reported remission rate for non-thymomatous myasthenia gravis is between 38 and 72% up to 10 years of follow-up. Among these patients, those with thymic hyperplasia show the best complete stable remission rates (42%, P < 0.04) in the majority of studies. Age showed variability across the studies and the cut-off was also different among them. Overall age < 45 years showed a higher probability of achieving complete stable remission during follow-up (81% benefit rate (BR), P < 0.02). Pharmacological improvement is reported between 6 and 42%. However, the certainty of these benefits has not been established due to factors such as the confounding differences between myasthenia gravis patients receiving and not receiving thymectomy, the non-randomized nature of class II studies and the lack of Class I evidence to support its use. There is currently a randomized trial ongoing looking at thymectomy by sternotomy vs controls and the results are eagerly awaited.

Diffusion-weighted magnetic resonance imaging of thymoma: ability of the Apparent Diffusion Coefficient in predicting the World Health Organization (WHO) classification and the Masaoka-Koga staging system and its prognostic significance on disease-free survival

“…Thymomas are benign or low-grade malignant tumours of the thymic epithelium and represent up to half of all neoplasms of the anterior mediastinum [1][2][3][4][5][6]. The histological classification proposed by the World Health Organization (WHO) and the Masaoka-Koga staging system, based on surgical findings, is currently used for treatment planning and significantly correlate with prognosis [1][2][3][4][5][6][7][8].…”

“…The histological classification proposed by the World Health Organization (WHO) and the Masaoka-Koga staging system, based on surgical findings, is currently used for treatment planning and significantly correlate with prognosis [1][2][3][4][5][6][7][8].…”

“…Indeed, in nonthymomatous MG, the clinical efficacy of thymectomy has been questioned because the evidence supporting its use is not clear and has largely been based on single-institution retrospective, observational studies. 3 Currently, although no uniformly accepted guidelines are available, thymectomy is believed to be suitable for patients with generalized MG under 50 years with antiAChR antibodies and TLH, as an option to increase the probability of clinical improvement or complete stable remission. 16 Contrariwise, effectiveness of extended thymectomy is still under discussion in patients with generalized MG and atrophic thymus or histological NT because the results of different studies are controversial, and stable remission rates up to 10 years of follow-up are significantly higher in TLH compared to NT or atrophic thymus in the majority of studies.…”

“…16 Contrariwise, effectiveness of extended thymectomy is still under discussion in patients with generalized MG and atrophic thymus or histological NT because the results of different studies are controversial, and stable remission rates up to 10 years of follow-up are significantly higher in TLH compared to NT or atrophic thymus in the majority of studies. 3,4 To date, no study characterized the NT with DW imaging nor evaluated the ability of DW-MRI in differentiating TLH from NT. In the present study, the mean ADC of TLH was significantly lower than that of NT, although overlapped values were found.…”

Thymectomy in Myasthenia Gravis

“…Findings from non-randomized studies showed that thymectomy has contributed to MG remission and recovery [14,21], although before the MGTX study, usefulness of thymectomy was found to be controversial in the treatment of AChR antibody-associated MG in absence of thymoma.…”