Thymoma

Study objectives: Although videothoracoscopic (VTS) resection of Masaoka stage I thymoma has been reported to be a less invasive method than open thoracotomy and to achieve a comparable surgical outcome, the usefulness of this method in the treatment of stage II thymoma has not yet been prospectively evaluated. We therefore compared the VTS and open (median sternotomy) methods to see whether VTS resection could be used as successfully to treat stage II thymoma disease.

Design, setting, and patients: Patients (11 women and 11 men) with stage II thymoma were prospectively enrolled between November 1999 and September 2004. Of these, 12 patients (the VTS group) underwent tumor resection using a three-port endoscopic technique, and 10 patients (the open group) underwent tumor excision using a standard sternotomy approach. The diagnosis of all resected thymoma lesions and their stage were confirmed by histopathogic examination.

Measurements and results: Neither group experienced mortality or any major morbidity. The difference in mean age ([+ or -] SD) between the VTS and open groups (40.2 [+ or -] 16.3 years and 47.7 [+ or -] 8.5 years, p = 0.202); mean operation lime (193.3 [+ or -] 79.6 min and 207.5 [+ or -] 85.8 min, p = 0.692); mean duration of pleural drainage (4.2 [+ or -] 2.1 days and 4.6 [+ or -] 2.1 days, p = 0.702); and mean duration of postoperative hospital stay (6.8 [+ or -] 2.3 days and 8.9 [+ or -] 4.4 days, respectively; p = 0.157) were not statistically significant. However, mean intraoperative blood loss amounts were statistically different (119.2 [+ or -] 70.6 mL and 238.5 [+ or -] 110.2 mL, respectively; p = 0.006). During the mean follow-up period of 33.9 [+ or -] 19.7 months, all patients survived without sign of recurrence, and the mean survival time was not statistically significant (32.3 [+ or -] 22.0 months and 35.8 [+ or -] 17.5 months, respectively; p = 0.686).

Conclusion: Using careful and skillful technique, the VTS method is an effective treatment of stage II thymoma.

Key words: mediastinal neoplasms; minimally invasive surgery; thoracoscopy; thymoma; thymomectomy

Abbreviations: VATS = video-assisted thoracoscopic surgery; VTS = videothoracoscopy/videothorascopic

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The occurrence rate of stage II thymoma ranges from 18 to 23% in all thymoma groups. (1,2) The surgical options are medial sternotomy, thoracotomy, and video-assisted thoracoscopic surgery (VATS). The sternotomy method is the preferred standard treatment. In some situations, thoracotomy is considered for ectopic thymoma. In recent years, VATS with or without a utility thoracotomy to excise the mediastinal thymic lesions has been reported as an effective treatment. (3-9) However, there is still no prospective comparison of thoracoscopy with open methods of treating Masaoka stage II thymoma. Therefore, VATS without a utility thoracotomy (videothoracoscopy [VTS]) was compared with open resection using medial sternotomy. We wanted to determine whether this VTS approach was an effective treatment for stage II thymoma.

METHODS AND MATERIALS

Between November 1999 and September 2004, 73 cases of primary mediastinal lesions were resected with curative intent. Of these, 22 patients (11 women and 11 men) with Masaoka stage II thymoma were prospectively enrolled. Twelve of these patients underwent complete thymoma resection using a three-port endoscopic technique (VTS group). The other 10 patients underwent standard medial sternotomy to excise the thymoma (open group). Diagnoses of all resected lesions and their stage were confirmed by histopathologic examination.

All patients with suspected thymoma who were eligible for surgery were interviewed and informed about the VTS and open-surgery procedures. For the VTS method, three thoracoports were created for thoracoscopic inspection and instrument manipulation. The tumor was first dissected from the pericardial area and then upward toward the neck base. Injury to the phrenic nerve was strictly avoided. The thymic vein and other large vessels were clamped with endoclippers. Local lung invasion was wedge resected using an stapling device (Endo-GIA; US Surgical; Norwalk, CT) stapling device. If the freed mass was too large to be removed with a retrieval bag, removal would be accomplished by cutting the mass piece-by-piece in a double-layered bag. One chest tube (32F) was routinely retained after the operation. The procedure in the sternotomy group was conventional. All patients received adjuvant radiation therapy after the operation. The results were compared using the Student t test (independent samples) to determine the level of significant difference between the two groups.

RESULTS

There were no deaths or major complications in both groups and no conversion to thoracotomy in the VTS group. The mean age ([+ or -] SD) in the VTS and open groups (40.2 [+ or -] 16.3 years and 47.7 [+ or -] 8.5 years, respectively) was not statistically different (p = 0.202). Mean intraoperative blood loss amounts were significantly different in the VTS and open groups (119.2 [+ or -] 70.6 mL and 238.5 [+ or -] 110.2 mL, respectively; p = 0.006). The VTS and open groups also did not have significantly different mean operation times (193.3 [+ or -] 79.6 min and 207.5 [+ or -] 85.8 min, p = 0.692); mean duration of pleural drainage (4.2 [+ or -] 2.1 days and 4.6 [+ or -] 2.1 days, p = 0.702); and mean duration of postoperative hospital stay (6.8 [+ or -] 2.3 days and 8.9 [+ or -] 4.4 days, respectively; p = 0.157). During the mean follow-up period (33.9 [+ or -] 19.7 months; range, 5.2 to 63.5 months), all patients in both groups survived without sign of recurrence, and the mean survival time in the VTS and open groups (32.3 [+ or -] 22.0 months and 35.8 [+ or -] 17.5 months, respectively; p = 0.686) was not significantly different. Myasthenia gravis was present in six patients (50%) in the VTS group and six patients (60%) in the open group. In the VTS group, six patients had Masaoka thymoma stage IIa and six patients had stage IIb. In the open group, six patients had stage IIa and four patients had stage IIb. The difference in stage distribution between these two groups was not statistically significant (p = 0.658, one-way analysis of variance). The patient profile is summarized in Table 1.

DISCUSSION

VTS surgery with the advantages of small incision and rapid recovery offers a better-tolerated approach to treat mediastinal lesions. The objective of VTS and open surgical treatment of thymoma, with or without myasthenia gravis, is the complete removal of the tumor and all involved structures. (9,10) The resection extent is almost the same for both the VTS and transsternal approaches. (11) With the benefit of minimal invasiveness and acceptable resection extent, we consider that resection of thymoma by VTS meets both the anatomic and surgical requirements of successful treatment. The right thoracic approach is preferred, except in cases of obvious left-sided thymoma. (12)

The existence of thymoma is best detected by chest CT, with 85% sensitivity, 98.7% specificity, and 95.8% accuracy rate. (13) If the CT fails to detect great-vessel involvement or other intrathoracic metastasis, thoracoscopic resection of the entire lesion may be undertaken. Therefore, VTS resection of Masaoka stage II is not contraindicated when the entire tumor and the locally involved tissue can be removed. The careful manipulation of tumor tissue to avoid intrathoracic spreading is also important, and a two-layered retrieval bag is needed for piece-by-piece removal of a large mass.

The mean intraoperative blood loss amounts were statistically less in the VTS group, which means that the VTS approach is less invasive in treating stage II thymoma. The mean age, mean operation time, mean duration of pleural drainage, and mean duration of postoperative hospital stay were all not significantly different between these two groups. No significant decrease in the drainage time and hospital stay was found in the VTS group, but this may have been due to the small sample evaluated in this study. Operation time was similar in both groups, showing that an experienced thoracoscopist can perform the endoscopic procedure within an acceptable timeframe.

The adjuvant radiation therapy for stage II thymoma is widely advocated, but the evidence supporting it is controversial. (14) From the reports of Singhal et al (14) and Mangi et al, (15) adjuvant radiation therapy does not improve the prognosis of completely resected stage II thymoma. Therefore, the adjuvant radiation therapy used in our study is not considered to affect outcome.

CONCLUSION

This study has a limited number of cases because of its experimental intent, and follow-up duration is still not long enough. To our knowledge, this is the first prospective study on thoracoscopic resection of stage II thymoma. In careful and skillful hands, the thoracoscopic method can be performed in an effective way to treat stage II thymoma. The collection of more prospective data is needed to evaluate long-term effectiveness.

Manuscript received February 19, 2005; revision accepted March 9, 2005.

REFERENCES

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(14) Singhal S, Shrager JB, Rosenthal DI, et al. Comparison of stages I-II thymoma treated by complete resection with or without adjuvant radiation. Ann Thorac Surg 2003; 76:1635-1641; discussion 1641-1632

(15) Mangi AA, Wright CD, Allan JS, et al. Adjuvant radiation therapy for stage II thymoma. Ann Thorac Surg 2002; 74:1033-1037

Yu-Jen Cheng, MD; Eing-Long Kao, MD; and Shah-Hwa Chou, MD

* From the Division of Thoracic Surgery, Department of Surgery, Kaohsiung Medical University Hospital, Kaohsiung, Taiwan.

Correspondence to: Yu-Jen Cheng, MD, Division of Thoracic Surgery, Department of Surgery, Kaohsiung Medical University Hospital, 100 Shih-Chuan First Rd, Kaohsiung 80708, Taiwan; e-mail: yujen.cheng@msa.hinet.net

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