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Eur J Cardiothorac Surg 2007;31:109-113. doi:10.1016/j.ejcts.2006.10.022
Copyright © 2007, European Association for Cardio-Thoracic Surgery. Published by Elsevier B.V. All rights reserved
a Thoracic Surgery Department, University of Eastern Piedmont A. Avogadro, Novara, Italy
b Thoracic Surgery Department, University of Torino, Italy
c Pathology Department, University of Torino, Italy
Received 24 August 2006; received in revised form 27 September 2006; accepted 3 October 2006.
* Corresponding author. Address: Thoracic Surgery Department, University of Eastern Piedmont, Maggiore della Carità General Hospital, Novara, Via Frasconi 14, 28100 Novara, Italy. Tel.: +39 0321 3733076; fax: +39 0321 3733578. (Email: ottaviorena{at}libero.it).
| Abstract |
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Key Words: Thymoma Surgery Radiotherapy Survival
| 1. Introduction |
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Whereas surgery alone is considered curative for stage I thymoma, and results in 5-year and 10-year overall survival rates of over 100% and 100%, respectively [3], current therapeutic indication for stage II thymoma are still controversial. Controversies are dependent from the concept that a transcapsular invasion could not be completely managed by surgical removal. During the past decades, following this consideration, adjuvant radiation therapy was advocated in hope to reduce the incidence of local relapse. The criteria for administering adjuvant radiation to patients with stage II thymoma remain controversial too. Current indications range from postoperative radiation for all thymoma patients [5,6], to postoperative radiation for only patients with large tumours (>5 cm in great diameter) or with radiographic evidence of invasiveness [7]. Because of the absence of a large consensus, in the current practice radiation therapy is recommended for the majority of stage II thymoma patients. It may be that patients in whom radiotherapy is not indicated will receive it, subjecting them to the morbidity related to this therapeutic modality. The aim of this study was to investigate whether or not the utilisation of adjuvant radiation therapy confers an advantage by reducing the frequency of local relapse or by influencing the long-term survival in patients undergoing operation for stage II thymoma.
| 2. Material and methods |
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2.1 Patient population and evaluation methods
Between January 1988 and December 2000, 197 patients underwent thymoma resection at the University of Torino and of Eastern Piedmont. Hospital and office medical records were reviewed to extract information including demographic and clinical characteristics (age, gender), clinical presentation (myasthenia gravis, other autoimmune related diseases, local symptoms and incidental findings), preoperative studies (CT-scan or MRI of the chest), surgical approach (median sternotomy, thoracotomy, transcervical thymectomy), postoperative course and complication, pathologic report. Patients follow-up was obtained by review of hospital and office records, telephone interviews with patients or physicians.
2.2 Clinical and pathologic revision
Operative notes were reviewed to determine if there was or not an intraoperative suspicion of local invasion, gross tumour extension and adhesion to adjacent structures and completeness of surgical resection. Pathology charts were obtained for each patient. Slides of 58 consecutive patients believed to be affected by stage II thymoma were available and reviewed by a single pathologist (DN). There was a complete agreement between the pathological records and the revision on margin status, histological subtype and degree of transcapsular or adjacent structures invasion. Thymomas were retrospectively classified into the five WHO histological classification subtype [8]. Surgical notes and pathology were reviewed by a single surgeon (GM) and pathologist (DN), and patients were than staged using the modified Masaoka classification system [4].
2.3 Adjuvant radiation therapy
The decision to refer patients for adjuvant radiation therapy was based on the surgeon's subjective assessment of the risk of recurrence considering the great diameter of the neoplasm (>4 cm), previous open biopsies, close resection margins (stripping of the phrenic nerve). Treatment regimens for patients undergoing radiotherapy (RT) were reviewed for total doses, fractionation and short- and long-term complication.
2.4 Follow-up
Complete follow-up was obtained for 56 patients and 2 were lost at long-term follow-up (1 submitted to surgery alone and 1 to surgery and RT). Patients were followed-up with computed tomographic scan every 6 months until death or lost at follow-up. Survival was calculated from the date of operation. Treatment-related deaths (operative or postoperative, or radiation related) were considered as death from thymoma. Time to relapse (disease-free survival), time until death from thymoma (disease-specific survival) and time until death from other causes (overall survival) were registered for all patients. Disease-specific survival was censored if patients died from non-thymoma-related causes. In this series of patients, the mean follow-up was 91 months and ranged from 9 to 171. Patients at risk at 5- and 10-year were 43 and 16, respectively.
2.5 Statistical analyses
Variables such as histological subtype, Masaoka stage, treatment and morbidity were analysed with respect to relapse and survival. The Student's t-test (no categorical data) and the Fisher's exact test (categorical data) were used to compare the mean value of the variables of the groups studied as appropriate. A p-value less than 0.05 was considered significant. The KaplanMeier method was used to estimate the time to relapse or death. Log-rank test was used to compare survival between groups.
| 3. Results |
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Thirty-two patients received only surgical complete resection of their disease. Twenty-six patients were submitted to postoperative radiation therapy. Of the 25 stage IIA and 33 stage IIB patients, similar number received surgery with and without RT (11/2544% and 15/3345.4%, respectively). Histological subtypes of radiated and non-radiated patients are illustrated in Table 2 .
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The median follow-up time after surgery or surgery and RT was 91 months (range 9170); one patients of each group was lost at follow up. Three patients out of 26 (11.5%) submitted to postoperative RT had treatment-related complications: two radiation pneumonia requiring steroids and one pericarditis with good recovery after conservative treatment. Four patients died of other causes: no one had signs of thymoma recurrence at time of death. Disease-free survival rate at 5- and 10-year were 94% and 87%, respectively. Among 31 patients treated with surgery alone, 2 (6.45%) had tumour recurrence. These patients, affected by stage IIA AB thymoma and stage IIB B1 thymoma manifested a mediastinal recurrence and drop metastases to the diaphragm and parietal pleura after 8.4 and 4.3 years, respectively. Both were submitted to surgical resection of their disease and subsequent chemotherapy; the first is alive and disease free after 2.5 years and the second died for unrelated causes 3.4 years after the re-operation. Among 25 patients treated with surgery and RT, 3 (12%) suffered from tumour relapse. One patient affected by stage IIA B1 thymoma had mediastinal relapse 6.8 years after surgery: he was submitted to re-operation and adjuvant chemotherapy; he is still alive with not operable recurrent disease 4.5 years after the second step therapy. Two patients affected by stage IIB AB and B2 thymoma experienced pleural recurrence after 4.7 and 1.7 years: both were submitted to re-operation and adjuvant chemotherapy, the first died for other causes after 4.2 years and the second died of tumour relapse after 3.6 years.
In particular, all pleural recurrences occurred in stage IIB thymoma with pleural adhesions (1/8, 12.5% not radiated and 2/11, 18.2% radiated patients, respectively). There was no statistical difference (p = 0.432, log-rank test) between the KaplanMeier disease-free survival curves of patients submitted to surgery alone and to surgery and RT (Fig. 1 ).
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| 4. Discussion |
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During the past decades, some authors have advocated postoperative radiation therapy [1719], whereas few studies have argued against it [7,20]. Curran et al. [18] reported about 19 patients undergoing complete resection for stage II thymoma. One patient received postoperative RT without long-term recurrence. Six patients out of 18 submitted to surgery only experienced recurrence: the authors stated that resection without RT is not acceptable. Statistical analysis was not feasible because of the presence of only one patient in the harm of surgery and RT. Nakahara et al. [6] in 1988 reported 29% (2 of 7) recurrence rate for patients with stage II thymoma submitted to surgery only, whereas 8% (2 of 25) patients have disease relapse after surgery and RT. Ogawa et al. [19] presented 61 Masaoka stage II patients undergoing postoperative mediastinal RT. Six thymomas recurred despite RT (two mediastinal and four pleural). They concluded that mediastinal RT probably prevents local recurrence, but cannot avoid pleural relapse. Blumberg et al. [7] reported about 30 patients submitted to surgery and RT (n = 17) or to surgery alone (n = 13): the recurrence and survival rates were similar for the two groups.
In some cases, the association of RT to surgery for the treatment of stage II thymomas seems to negatively affect long-term survival. Quintanilla-Martinez et al. [21] in 1994 presented 32 stage II patients submitted to surgery. Seven of them received postoperative RT. Recurrence rates were 28% and 8% for patients undergoing surgery and RT and surgery alone, respectively (difference was not significant). In a previous study with a different focus, one of the authors referred about the lower recurrent rate in a cohort of patients submitted to surgery compared with patients submitted to surgery and RT (the difference was significant p = 0.02): the effect of postoperative RT seemed potentially harmful [20]. The great part of the mentioned literature does not perform disease-free or disease-specific survival analysis for stage II thymoma, but demonstrated only the absence of impact on survival in all thymoma patients.
More recently, two papers focused on the value of postoperative RT in stage II completely resected thymomas. Mangi et al. [22] updated their 27-year experience and presented 49 completely resected stage II patients. Thirty-five patients were submitted to surgery alone, whereas 14 patients underwent surgery and RT. The addition of adjuvant RT did not affect long-term disease control. Disease-specific survival for stage II thymoma patients was 100% with and without RT (p = 0.87).
Singhal et al. [23] reported about two groups of patients with stage II thymomas submitted to radical surgery (n = 20) and to radical surgery and RT (n = 20). Recurrence rate was 5% in the group of surgery and RT and null in the group of surgery alone; no differences in long-term disease-free survival were recorded (p = 0.72).
Our experience adds to those recent reports suggesting that complete resection alone seems to be a sufficient management for stage II thymoma. Appropriateness of adjuvant therapy with reference to the histological type of the tumour was not easily investigated because of the restricted number of cases for each subtype of thymoma. Stage IIA disease manifested mediastinal whereas stage IIB thymoma manifested primarily pleural recurrence. This fact agree with previous reports that stated the most common failure of thymoma treatment is pleural recurrences and it is well known that mediastinal radiation does not prevent pleural recurrences. Conversely, the great part of patients with recurrent thymoma during an accurate follow-up may benefit of second surgery and adjuvant chemotherapy with good control of their disease for a relative long period. In the future, it should be more indicative to consider adjuvant chemotherapy in stage IIB thymoma, particularly regard to those histological subtypes demonstrated to be more aggressive.
Concluding, thymoma is confirmed to be a tumour with an indolent natural history and low recurrence rate even if locally invasive as in stage II of Masaoka classification. Mediastinal irradiation does not seem to affect local control in stage IIA and cannot prevent pleural recurrences, which are the more frequent relapsing mode of stage IIB resected thymoma. When recurrent during an accurate follow-up, because of its moderately aggressive behaviour, thymoma frequently can benefit of second step surgery and adjuvant therapies with good long-term response.
| Appendix A |
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Dr A. End (Vienna, Austria): Just to clarify, was this a single or a multi-institutional study?
Dr Rena: This was a two-institutional study.
Dr M. Dusmet (London, United Kingdom): I have just two quick comments. First of all, Id like to invite you to please, please, please stop presenting this paper to surgeons. Were convinced. Present your paper to the oncologists so that we can convince our oncology colleagues to stop irradiating these patients, because I find it impossible to convince our radiation oncologists that, at best, they are doing no harm to these patients, and I think that youve demonstrated that even that is probably not the case. So please try to convince our radiation oncologists instead of surgeons, because they are the ones that need convincing, not us. And perhaps, Paul, you could use your influence with the EORTC to set up a randomised trial so that we can finally have the kind of evidence that oncologists cannot refuse so that we can finally stop irradiating completely resected thymoma patients.
Dr M. Zielinski (Zakopane, Poland): Did you find any correlation between the recurrence and the histological type of thymoma according to WHO or the MullerHermelink classification?
Dr Rena: The question is absolutely important, but there are five subtypes distributed in a small series and it's not very easy to study a correlation between histological subtypes and the recurrences. The only thing I can say is that we have recurrences in type AB, B1 and B2.
Dr P. Van Schil (Antwerp, Belgium): Would you comment on the type of incision used. Was it the same in all patients with thymoma and could it influence the results?
Dr Rena: We used total median sternotomy in 50 patients and 8 cervicotomy and upper partial sternotomy. In these 8 cases, upper partial sternotomy was used because the thymoma was very small on the preoperative CT scan of the chest.
Dr Van Schil: Was your rate of recurrence influenced by the type of incision?
Dr Rena: We have not investigated whether there is a pattern, but, if I remember, only one patient had recurrence in this population, so about 12%.
Dr T. Stoke (Szeged, Hungary): I think the two groups are not comparable. You indicated adjuvant radiotherapy if the tumour was greater than 5 cm and the resection margins were very close. I think the radicality of operation is not similar in the two groups.
Dr Rena: Radiation therapy was administered on the basis of a subjective assessment of risk of recurrence. Yes, this is not a prospective randomised trial. The only message that I would give is that thymoma is a tumour with an intermediate behaviour, and so probably sometimes with strict follow-up, detection of early recurrence may benefit for surgery of second or third steps.
| Footnotes |
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\#9734;\#9734; The study was performed within the Research Fellowship Program Dottorato di Ricerca in Tecnologie e Terapie Avanzate in Chirurgia, appointed by Tor Vergata University, Rome, Italy.
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