Abstract
OBJECTIVES
About one-third of patients with thymoma have myasthenia gravis (MG). It remains controversial whether MG affects the prognosis of patients with thymoma. The aim of this study was to evaluate the effect of MG on the prognosis of patients with thymoma in a multicentre database.
METHODS
Patients with thymoma who underwent thymectomy were identified from 2 prospectively collected databases in 2 medical centres from 2010 to 2018. Kaplan–Meier curves and the log-rank test were used to assess overall survival and recurrence-free survival, and a Cox proportional hazards model was used to determine significant contributors to survival. Propensity score matching was performed to eliminate selection bias.
RESULTS
A total of 514 patients with thymoma were included in this study, of whom 320 patients were MG-free and 194 had MG. Patients with MG were younger (median age 50 vs 54 years, P = 0.001) and had smaller tumours (4.4 ± 2.0 vs 4.9 ± 2.3 cm, P = 0.020). Pathological analysis showed that type B tumours especially B2−B3 (B2 + B3 + mix B tumours, 55.2%) are more common in patients with MG, while type AB (37.2%) was the most common in patients without MG. A larger proportion of Masaoka III–IV stage tumour (25.7% vs 11.0%, P < 0.001) was seen in patients with thymoma and MG. Multivariable Cox regression analysis demonstrated that MG (hazard ratio [HR] = 3.729, 95% confidence interval [CI]: 1.398–9.947, P = 0.009), incomplete resection (HR = 5.441, 95% CI: 1.500–19.731, P = 0.010) and Masaoka stage III + IV (HR = 3.390, 95% CI: 1.196–9.612, P = 0.022) were negative prognostic factors of overall survival. Meanwhile, MG (HR =3.489, 95% CI: 1.403–8.680, P = 0.007) and Masaoka stage III + IV (HR = 6.582, 95% CI: 2.575–16.828, P < 0.001) were negative prognostic factors of recurrence-free survival. Propensity-matched analysis compared 148 patient pairs. K-M survival analysis demonstrated that MG was associated with worse overall survival and recurrence-free survival in propensity score-matched patients (log-rank, P = 0.034 and 0.017, respectively).
CONCLUSIONS
Thymoma patients with MG have smaller tumours and a higher percentage of late-stage tumours, which are mainly of WHO B types, especially B2−B3 types. In addition, MG is significantly associated with worse overall survival and recurrence-free survival in thymoma.
Keywords: Thymoma, Myasthenia gravis, Prognosis, Propensity score matching
INTRODUCTION
About one-third of thymoma cases are accompanied by myasthenia gravis (MG) [1–3]. The presence of MG complicates treatment in patients with thymoma. It remains controversial whether MG affects the prognosis of thymoma patients. Some experts suggested MG could increase perioperative mortality due to postoperative myasthenia crisis [4, 5], while others considered that earlier detection of thymomas due to MG might lead to a favourable prognosis [6, 7]. The purpose of this study was to further evaluate the effect of MG on the prognosis of thymoma patients by using data from 2 medical centres in China.
PATIENTS AND METHODS
Patients with thymoma who underwent surgical treatment were identified from 2 prospectively collected databases at Beijing Hospital and Peking University People’s Hospital from January 2010 to December 2018. This study was approved by the Institutional Ethics Review Board of Beijing Hospital and Peking University People’s Hospital (2018PHB046-01, 2018.05.15). Informed consent was waived because no additional treatment was planned (retrospective study).
Patients diagnosed with thymic carcinoma or recurrent thymoma were excluded. Clinical and pathological data were collected, including perioperative data, World Health Organization (WHO) classes and modified Masaoka stages. The diagnosis of MG was confirmed by clinical presentation, neostigmine assay and electrodiagnostic tests, including repeated nerve stimulation with low and high frequencies and simple-fibre electromyography. Detection of autoantibodies, such as anti-acetylcholine receptor (AChR-Ab) and anti-MuSK antibodies, was recommended. MG clinical severity was graded by the Osserman classification system.
All operations were performed by unilateral video-assisted thoracoscopic surgery (VATS) or sternotomy. Patients with MG underwent extended thymectomy, including removal of the tumour, the thymic gland, the anterior mediastinal fat tissue between both phrenic nerves and the fat tissue from both pericardiophrenic angles. Patients without MG underwent thymectomy, including removal of the tumour, the thymic gland and the anterior mediastinal fat tissue between both phrenic nerves. Extended resection to surrounding organs was performed when they were invaded by tumours, e.g. the lung, the pericardium and the superior vena cava.
All patients with MG resumed their preoperative medications as soon as possible postoperatively to control MG symptoms. In addition, they were recommended to continue outpatient or inpatient treatment in the Neurology Department after discharge. Postoperative radiotherapy was suggested to patients with Masaoka stage II–IV or incompletely resected tumours (R1/R2 resection). Postoperative chemotherapy was suggested to patients with Masaoka stage IV or R2 resected tumours.
Follow-up information was collected via telephone or outpatient records, including tumour recurrence and survival status, MG medications and postintervention MG status. The primary endpoint was overall survival (OS) and the secondary endpoint was recurrence-free survival (RFS). The length of OS was defined as the interval between the date of surgical resection and death from any cause. Survivors were censored at the date of last follow-up. Time to recurrence (RFS) was defined as the interval between the date of surgical resection and first recurrence or last follow-up. The postoperative effect of MG was examined by a skilled neurologist according to Myasthenia Gravis Foundation of America criteria defining the postintervention status [8].
Statistical analysis
Patients were categorized into 2 cohorts, including individuals with MG and those without. Continuous variables were compared by Student’s t-test and categorical variables were compared by Pearson’s chi-square test. Survival curves by MG status were generated by the Kaplan–Meier method, and the log-rank test was applied for comparison.
Univariable Cox proportional hazard models were used to determine the statistical significance of associations of clinical variables with OS. The multivariable Cox model was used to examine whether MG was independently associated with survival. The proportional hazard assumption was evaluated by the graphic method based on Cox cumulative hazard function.
Propensity score matching (PSM) was performed for patients by MG status using 6 variables, including age, gender, tumour diameter, resection condition, WHO classification and Masaoka stage. Patients were matched 1:1 using nearest neighbour matching with a calliper distance of 0.2. Standardized mean differences were used to evaluate the balances of matched covariates in this study and <10% of differences was considered to be matched adequately. In matched groups, paired t-test was performed to assess continuous variables, and categorical variables were analysed by the McNemar’s test. Two-sided P < 0.05 was considered statistically significant.
Statistical analyses were performed with Statistical Package for Social Sciences, version 22.0 (IBM SPSS Statistics, Chicago, IL, USA). STATA version 14.0 (Stata Corporation, College Station, TX, USA) was used for PSM.
RESULTS
Patient characteristics
A total of 514 patients with thymoma (261 men and 253 women) were included in this study. Median patient age was 52 years (range, 12–83 years). The mean diameter of tumours was 4.7 ± 2.2 cm. Totally, 194 cases (37.7%) were accompanied by MG and 320 patients (62.3%) had no MG. Male–female ratios in both groups were comparable (162/158 vs 99/95, P = 0.93). Patients with MG were younger (median age, 50 vs 54 years; P = 0.001) and had smaller tumours (4.4 ± 2.0 vs 4.9 ± 2.3 cm, P = 0.020). The demographic characteristics of both groups are listed in Table 1. According to the Osserman classification system, there were 56 (28.9%) type I, 52 (26.8%) type IIa, 67 (34.5%) type IIb, 14 (7.2%) type III and 5 (2.6%) type IV cases with MG. Among individuals with MG, 157 patients were treated preoperatively with pyridostigmine bromide (median, 240 mg/day [range: 90–480 mg/day]), 5 cases received pyridostigmine bromide and tacrolimus, 5 were administered intravenous immunoglobulin and the remaining 27 received no medication due to mild symptoms.
Table 1:
Clinical data in thymoma patients with and without myasthenia gravis
| Variable | Patients with MG | Patients without MG | T or x2 value | P-value |
|---|---|---|---|---|
| N | 194 | 320 | ||
| Age (years, median with range) | 50 (15–83) | 54 (12–82) | −3.418 | 0.001 |
| Gender (male/female) | 99/95 | 162/158 | 0.008 | 0.93 |
| Tumour diameter (cm) | 4.4 ± 2.0 | 4.9 ± 2.3 | −2.332 | 0.020 |
| VATS/sternotomy | 137/57 | 288/32 | 31.689 | <0.001 |
| Operation time (min) | 136.6 ± 46.5 | 124.9 ± 57.4 | 2.399 | 0.017 |
| Blood loss (ml) | 129.3 ± 287.4 | 112.1 ± 376.9 | 0.544 | 0.51 |
| Postoperative drainage(days) | 3.3 ± 1.6 | 2.7 ± 1.8 | 3.462 | 0.001 |
| Length of postoperative stay (days) | 8.3 ± 7.4 | 5.5 ± 4.8 | 5.159 | <0.001 |
| Masaoka stage (n, %) | 27.796 | <0.001 | ||
| I | 58 (29.9%) | 156 (48.8%) | ||
| II | 86 (44.4%) | 129 (40.4%) | ||
| III | 35 (18.0%) | 21 (6.6%) | ||
| IV | 15 (7.7%) | 14 (4.4%) | ||
| WHO classification (n, %) | 58.727 | <0.001 | ||
| A | 1 (0.5%) | 42 (13.1%) | ||
| AB | 42 (21.6%) | 119 (37.2%) | ||
| B1 | 43 (22.2%) | 59 (18.4%) | ||
| B2 | 69 (35.6%) | 67 (20.9%) | ||
| B3 | 13 (6.7%) | 14 (4.4%) | ||
| Mixed B types | 25 (12.9%) | 13 (4.1%) | ||
| MNT | 1 (0.5%) | 4 (1.3%) | ||
| U | 0 (0.0%) | 2 (0.6%) | ||
| Resection status (n, %) | 1.861 | 0.17 | ||
| R0 | 184 (94.8%) | 311 (97.2%) | ||
| R1/R2 | 10 (5.2%) | 9 (2.8%) | ||
| Complications (n, %) | 14 (7.2%) | 17 (5.3%) | 0.936 | 0.33 |
| Bleeding | 2 (14.3%) | 2 (11.8%) | ||
| Deep vein thrombosis | 4 (28.6%) | 0 (0.0%) | ||
| Cardiac events | 6 (42.9%) | 4 (23.5%) | ||
| Diaphragmatic paralysis | 1 (7.1%) | 5 (29.4%) | ||
| Pneumonia | 1 (7.1%) | 2 (11.8%) | ||
| Incision infection | 0 (0.0%) | 2 (11.8%) | ||
| Chylothorax | 0 (0.0%) | 1 (5.9%) | ||
| Acute lower limb arterial embolism | 0 (0.0%) | 1 (5.9%) | ||
| Other autoimmune disorders | 22 (11.3%) | 20 (6.25) | 4.171 | 0.041 |
MG: myasthenia gravis; MNT: micronodular thymoma with lymphoid stroma; U: unknown; VATS: video-assisted thoracoscopic surgery.
Perioperative and pathological data
VATS thymectomy was performed in 425 (82.7%) patients, including 2 cases that were converted to thoracotomy due to great vessel invasion. Sternotomy was performed in 89 (17.3%) patients. One patient with MG died of ventilator-associated pneumonia at the second month after VATS thymectomy. Perioperative results, WHO classes and modified Masaoka stages are listed in Table 1.
Compared with patients with MG, a larger percentage of cases without MG received VATS thymectomy (90% vs 70.6%, P < 0.001). Patients without MG had shorter operation time (124.9 ± 57.4 vs 136.6 ± 46.5 min, P = 0.017), shorter drainage duration (2.7 ± 1.8 vs 3.3 ± 1.6 day, P = 0.001) and shorter postoperative hospital stay (5.5 ± 4.8 vs 8.3 ± 7.4 day, P < 0.001). Pathological analysis showed that type B tumours especially B2−B3 (B2 + B3 + mix B tumours, 55.2%) are more common in patients with MG, while type AB (37.2%) was the most common in patients without MG. Patients with MG had a larger proportion of Masaoka III–IV stage tumours (25.7% vs 11.0%, P < 0.001) (Table 1).
Postoperative treatment and follow-up results
A total of 153 patients received postoperative adjuvant therapy, including 138 administered radiotherapy, 10 administered chemotherapy and 5 administered concurrent radiotherapy and chemotherapy. The 138 patients who underwent radiotherapy included 75 (54.3%) Masaoka stage II, 49 (35.5%) Masaoka stage III and 14 (10.1%) Masaoka stage IV cases. One patient of stage III was R2-resection, 7 patients of stage IVA were R1-resection and 1 patient of stage IVA was R2-resection. Totally 437 patients (85.0%) were successfully followed up. The median follow-up period was 46 months (range, 2–116 months).
In this study, 5-year and 8-year OS rates were 93.9% and 86.5%, respectively, for all thymoma patients; 5-year and 8-year RFS rates were 91.9% and 86.5%, respectively. There were 28 deaths, including 6 due to thymoma recurrence, 8 due to MG, 5 due to infection, 2 due to other tumours, 1 due to pure red cell aplasia, 1 due to cardiac infarction, 1 due to cerebral infarction, 1 due to traumatism and 3 of unknown cause.
Twenty patients with MG (10.3%) experienced postoperative myasthenic crisis (POMC) within the first month after surgery. Totally, 162 patients (83.5%) were successfully evaluated for postintervention status of MG, including 55 patients (34.0%) with complete stable remission, 3 (1.85%) with pharmacologic remission, 37 (22.8%) with minimal manifestations, 42 (25.9%) with improved condition, 9 (5.5%) with unchanged condition, 4 (2.5%) with worse condition, 4 (2.5%) with exacerbation and 8 (4.9%) who died of MG. The overall effective rate (including complete stable remission, pharmacologic remission, minimal manifestations and improved condition) was 84.5% (137/162).
Prognostic factors in thymoma
In univariable analysis of OS, MG (P = 0.018), tumour diameter (P = 0.018), incomplete resection (P < 0.001), sternotomy (P < 0.001), Masaoka stage III + IV (P < 0.001) and postoperative therapy (P = 0.049) were associated with worse OS. In multivariable analysis, MG (hazard ratio [HR] = 3.729, 95% CI: 1.398–9.947, P = 0.009), incomplete resection (HR = 5.441, 95% CI: 1.500–19.731, P = 0.010) and Masaoka stage III + IV (HR = 3.390, 95% CI: 1.196–9.612, P = 0.022) were independent factors determining worse OS (Table 2).
Table 2:
Univarible and multivariable cox analyses of overall survival in thymoma patients
| Univariable analysis |
Multivariable analysis |
|||||
|---|---|---|---|---|---|---|
| HR | 95% CI | P-value | HR | 95% CI | P-value | |
| Age | 1.020 | 0.990–1.050 | 0.19 | 1.031 | 0.998–1.064 | 0.060 |
| Sex (male versus female) | 0.786 | 0.367–1.683 | 0.54 | 1.424 | 0.622–3.258 | 0.40 |
|
MG status (with versus without) |
2.502 | 1.167–5.367 | 0.018 | 3.729 | 1.398–9.947 | 0.009 |
| Tumour diameter | 1.205 | 1.033–1.405 | 0.018 | 1.18 | 0.960–1.451 | 0.12 |
| Incomplete resection | 11.836 | 4.148–33.776 | <0.001 | 5.441 | 1.500–19.731 | 0.010 |
|
Surgical procedure (VATS versus sternotomy) |
0.256 | 0.121–0.541 | <0.001 | 0.462 | 0.171–1.249 | 0.13 |
|
Masaoka stage (III + IV versus I + II) |
5.801 | 2.746–12.255 | <0.001 | 3.39 | 1.196–9.612 | 0.022 |
| WHO type (B types versus A + AB + MNT) | 1.292 | 0.595–2.804 | 0.52 | 0.531 | 0.200–1.411 | 0.20 |
| Postoperative therapy (Y versus N) | 2.138 | 1.002–4.562 | 0.049 | 0.857 | 0.300–2.444 | 0.77 |
HR: hazard ratio; MG: myasthenia gravis; VATS: video-assisted thoracoscopic surgery.
In univariable analysis of RFS, MG (P < 0.001), tumour diameter (P = 0.001), incomplete resection (P < 0.001), sternotomy (P < 0.001), Masaoka stage III+IV (P < 0.001), B type (P = 0.033) and postoperative therapy (P < 0.001) were associated with worse RFS. In multivariable analysis, independent factors associated with worse RFS included MG (HR = 3.489, 95% CI: 1.403–8.680, P = 0.007) and Masaoka stage III + IV (HR = 6.582, 95% CI: 2.575–16.828, P < 0.001) (Table 3).
Table 3:
Univariable and multivariable cox analyses of recurrence-free survival in thymoma patients
| Univariable analysis |
Multivariable analysis |
|||||
|---|---|---|---|---|---|---|
| HR | 95% CI | P-value | HR | 95% CI | P-value | |
| Age | 0.983 | 0.958–1.008 | 0.18 | 0.990 | 0.963–1.018 | 0.49 |
| Sex (male versus female) | 1.247 | 0.629–2.473 | 0.53 | 1.601 | 0.764–3.353 | 0.21 |
| MG status (with versus without) | 3.819 | 1.848–7.891 | <0.001 | 3.489 | 1.403–8.680 | 0.007 |
| Tumour diameter | 1.258 | 1.099–1.441 | 0.001 | 1.183 | 0.982–1.426 | 0.077 |
| Incomplete resection | 8.589 | 3.454–21.360 | <0.001 | 2.254 | 0.808–6.291 | 0.12 |
| Surgical procedure (VATS versus sternotomy) | 0.242 | 0.122–0.484 | <0.001 | 0.558 | 0.233–1.339 | 0.19 |
| Masaoka stage (III + IV versus I + II) | 10.893 | 5.361–22.132 | <0.001 | 6.582 | 2.575–16.828 | <0.001 |
| WHO type (B types versus A + AB + MNT) | 2.372 | 1.073–5.245 | 0.033 | 0.849 | 0.341–-2.113 | 0.73 |
| Postoperative Therapy (Y versus N) | 3.678 | 1.822–7.425 | <0.001 | 0.936 | 0.380–2.305 | 0.89 |
HR: hazard ratio; MG: myasthenia gravis; VATS: video-assisted thoracoscopic surgery.
Propensity score matching results
Propensity-matched analysis compared 148 patient pairs. After matching, there were no significant differences in all clinical variables between patients with MG and those without (Table 4). K-M survival analysis demonstrated that MG was significantly associated with worse OS (P = 0.015, 0.034) and RFS (P = 0.001, 0.017) before and after PSM (Figs 1A and B and 2A and B).
Table 4:
Comparison between thymoma patients with and without myasthenia gravis after propensity score matching
| Variable | Patients with MG | Patients without MG | P-value |
|---|---|---|---|
| N | 148 | 148 | |
| Age (years) | 51.0 ± 12.8 | 50.7 ± 13.2 | 0.86 |
| Gender (male/female) | 68/80 | 67/81 | 0.91 |
| Tumour diameter (cm) | 4.3 ± 2.0 | 4.7 ± 2.1 | 0.12 |
| Masaoka stage (n, %) | 0.93 | ||
| I | 51 (34.5) | 56 (37.8) | |
| II | 72 (48.6) | 69 (46.6) | |
| III | 16 (10.8) | 14 (9.5) | |
| IV | 9 (6.1) | 9 (6.1) | |
| WHO classification (n, %) | 0.92 | ||
| A + MNT | 2 (1.4) | 3 (2.0) | |
| AB | 39 (26.4) | 44 (29.7) | |
| B1 | 37 (25.0) | 38 (25.7) | |
| B2 | 49 (33.1) | 42 (28.4) | |
| B3 | 10 (6.8) | 12 (8.1) | |
| Mixed B types | 11 (7.4) | 9 (6.1 | |
| Resection status (n, %) | 1.00 | ||
| R0 | 144 (97.3) | 143 (96.6) | |
| R1/R2 | 4 (2.7) | 5 (3.4) | |
MG: myasthenia gravis; WHO: World Health Organization.
Figure 1:
(A) Overall survival of patients with myasthenia gravis (MG) and without MG before propensity score matching. Patients with MG had worse overall survival compared with those without MG (log-rank, P = 0.015). (B) Recurrence-free survival of patients with MG and without MG before propensity score matching. Patients with MG had worse recurrence-free survival compared with those without MG (log-rank, P = 0.001). MG: myasthenia gravis.
Figure 2:
(A) Overall survival of patients with myasthenia gravis (MG) and without MG after propensity score matching. Patients with MG had worse overall survival compared with those without MG (log-rank, P = 0.034). (B) Recurrence-free survival of patients with MG and without MG after propensity score matching. Patients with MG had worse recurrence-free survival compared with those without MG (log-rank, P = 0.017). MG: myasthenia gravis.
DISCUSSION
About one-third of patients with thymoma have MG, which is an autoimmune disease with a neuromuscular junction disorder characterized by fluctuating weakness of the skeletal muscles. Previous reports pointed out that MG is highly correlated with B-type thymoma and slightly associated with A–AB tumours [1, 2, 9]. The current results also showed that WHO B2 and B1 were the most common types correlating with MG, and AB was the most common type in patients without MG. According to the WHO classification [10], B-type thymomas consist of plump epithelioid neoplastic cells with a component of T lymphocytes at different stages of maturation, while A-type thymomas show less lymphocytes. The pathogenesis of MG may involve the epithelial function, which induces autoreactive T-lymphocyte development in B-type thymoma. MG symptoms may lead to an earlier diagnosis of thymomas, and studies demonstrated that MG is correlated with early Masaoka-Koga stages [1, 11, 12]. In this study, tumour diameter was smaller in patients with MG compared with the non-MG cases. However, thymoma cases with MG had a larger proportion of advanced stage tumours than those without MG in this study. The biological behaviours and pathogenesis of thymomas with and without MG are quite different and need further investigation.
There is no clear conclusion regarding the mechanism by which MG affects the prognosis of thymoma patients. Related studies available are few, with small sample sizes, and involved different demographic characteristics. The presence of MG complicates treatment, especially in patients with severe MG symptoms. Glucocorticoids and immunosuppressants may be essential for controlling symptoms, which can increase the risk of perioperative complications, including infections, deep venous thrombosis and so on. Meanwhile, postoperative myasthenic crisis may increase perioperative mortality [4, 13]. In this study, MG was the first cause of death in thymoma cases with MG (8/15), while tumour recurrence was the main death cause in thymoma without MG. Therefore, it was proposed that MG is a negative prognostic factor in thymoma [4, 5]. However, others argued that MG is a positive prognostic factor, because its symptoms might lead to an earlier diagnosis of thymoma [6, 7], which is beneficial to complete tumour resection. Meanwhile, in other studies comparing patients of the same Masaoka stage between the 2 groups, MG seemed to have little effects on prognosis in thymoma [14, 15].
To eliminate selection bias, we enrolled a large-scale sample and used PSM to obtain new paired patients with similar baseline characteristics between the 2 groups. Survival analysis was performed for the matched patients, and thymoma patients with MG had significantly poorer OS and RFS than those without MG, corroborating the above multivariable Cox regression analysis. Therefore, we concluded that MG was an independent negative prognostic factor in thymoma patients.
Thymoma and MG interact with each other. The prognosis of thymoma patients with MG is based on such interaction, and it is difficult to completely separate their individual effects. Previous findings pointed out that thymoma recurrence may lead to the aggravation of MG symptoms and could be early diagnosed [16], but MG aggravation may in turn influence tumour treatment. In another report, we revealed a favourable outcome of postoperative effect of MG in thymoma patients with MG [17]. In the latter study, the 5-year postoperative effect of MG of achieving complete stable remission was 44.1%, and the effective rate was 84.5%. However, MG patients with thymoma have been reported to achieve a worse MG outcome than those with thymus hyperplasia [18, 19]. The postoperative status of MG could influence patients’ tolerance to radiotherapy and chemotherapy. In this study, 2 patients with MG could not complete the full course of radiotherapy because of aggravated MG symptoms. Therefore, we considered that thymoma and MG mutually influence their treatment effects, which may explain the worse prognosis of thymoma patients with MG compared with counterparts without MG.
Compared with previous studies, this was the first research using PSM to evaluate how MG affects the prognosis of thymoma patients, with a relatively larger sample size. Several limitations should also be emphasized. First, this was a retrospective study, and selection bias was unavoidable. Secondly, the follow-up period was relatively short and thymoma patients always have a long-term survival. Thus, a longer follow-up period is required in further researches. Third, tests of autoantibodies were lacking for most patients in this study. Subclinical MG may be underestimated.
CONCLUSIONS
Thymoma patients with MG have smaller tumours and a higher percentage of late-stage tumours, which are mainly WHO B types, especially B2–B3 types. In addition, MG is significantly associated with worse OS and RFS in thymoma.
Conflict of interest: none declared.
ABBREVIATIONS
- HR
Hazard ratio
- MG
Myasthenia gravis
- OS
Overall survival
- PSM
Propensity score matching
- RFS
Recurrence-free survival
- VATS
Video-assisted thoracoscopic surgery
Author contributions
Wenxin Tian: Data curation, Investigation, Methodology, Writing—original draft. Xiao Li: Conceptualization, Data curation, Investigation, Methodology, Writing—original draft. Yaoguang Sun: Formal analysis, Supervision, Validation. Jun Wang: Conceptualization, Project administration, Supervision. Guanchao Jiang: Methodology, Supervision, Validation, Writing—review & editing. Hongfeng Tong: Conceptualization, Project administration, Validation.
Reviewer information
Interactive CardioVascular and Thoracic Surgery thanks Alper Toker and the other anonymous reviewers for their contribution to the peer review process of this article.
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