Journal of Thoracic Oncology:
Predictors of Outcomes after Surgical Treatment of Synchronous Primary Lung Cancers
Finley, David J. MD*; Yoshizawa, Akihiko MD†; Travis, William MD†; Zhou, Qin MA‡; Seshan, Venkatraman E. PhD‡; Bains, Manjit S. MD*; Flores, Raja M. MD*; Rizk, Nabil MD*; Rusch, Valerie W. MD*; Park, Bernard J. MD*
*Department of Surgery, Thoracic Service, †Department of Pathology, and ‡Department of Epidemiology and Biostatistics, Biostatistics Service, Memorial Sloan-Kettering Cancer Center, New York City, New York.
Disclosure: The authors declare no conflicts of interest.
Address for correspondence: Bernard J. Park, MD, Department of Surgery, Thoracic Service, Memorial Sloan-Kettering Cancer Center, 1275 York Avenue, Room C-867, New York City, NY 10021. E-mail: firstname.lastname@example.org
Introduction: Distinguishing synchronous primary lung cancers (SPLCs) from advanced disease is important because prognosis and treatments are very different and a surgical approach to SPLC may result in survival similar to solitary cancers. Determining this distinction with certainty, however, is challenging. We reviewed our experience with surgical resection of presumed SPLC to analyze outcomes and identify factors associated with prolonged survival.
Patients and Methods: A retrospective review identified patients treated for presumptive SPLC. Cases were defined using modified criteria set forth by Martini and Melamed and histologic subtyping. Survival was estimated using the Kaplan-Meier method, and factors associated with survival were evaluated using a log-rank test or Cox proportional hazards model for categorical and continuous variables, respectively.
Results: From January 1995 to July 2006, 175 patients met study criteria and underwent complete resection. Tumors were more often in different lobes of an ipsilateral chest (55 of 175, 31%) or contralateral lesions (45 of 175, 26%). More than half (104 of 175, 59%) of the patients underwent a single operation. Median follow-up was 50.3 months (4.8-164.7); median overall survival (OS) for the group was 67.4 months (46.4-80.0) with a 3-year OS of 64%. On multivariable analysis controlling for stage, only female gender was a significant predictor of better OS (p = 0.001).
Conclusions: An aggressive surgical approach to patients with apparent SPLC can result in survival that is comparable with patients with single lung cancers of similar stage. The Martini and Melamed criteria and histologic subtyping can identify appropriate patients for resection. Female gender was associated with superior OS.
The distinction of synchronous primary lung cancers (SPLC) from primary lung cancer with pulmonary metastasis is important because the prognosis and treatments are markedly different. The outcome achieved by medical treatment alone for an additional lesion of the same histology in the ipsilateral chest (T4 or M1 in the current staging system) is poor.1 Nevertheless, the diagnosis of SPLC presents a clinical dilemma because there are no rigorous clinical or histopathological criteria by which such a distinction can be made.2,3 Therefore, it is not surprising that estimates of the incidence of SPLC vary, with published rates ranging between 0.2% and 20% of all patients with non-small cell lung cancer.4,5 The most commonly used criteria to define synchronous or metachronous malignant lung disease were proposed by Martini and Melamed6 more than 30 years ago. These guidelines suggest that for lesions of similar histology, in the absence of extrathoracic metastases and lymphatic metastases in the common drainage basins, it is reasonable to treat patients for second primary disease. These criteria were based mainly on metachronous lesions, because only 18 of the patients in that study had SPLC but have proven to be durable and provide the basis for the American College of Chest Physicians lung cancer clinical practice guidelines from 2007.7 In addition, a number of recent, small case series have supported the role of resection of SPLC as defined by these criteria.1,8–10 Nakata et al.1 reported 3-year survival rates of 77.9% in 26 patients with synchronous SPLC, and a larger series has shown that the 5-year survival of patients with SPLC without lymph node metastasis exceeds 50%.11,12 Often, patients who have tumors meeting SPLC criteria are considered to have more advanced disease and are not offered surgical resection, which negatively impacts their overall survival (OS).
The goal of this study was to review our institutional experience with primary surgical resection for patients with presumed SPLC to identify factors associated with prolonged survival and to identify additional criteria, which may be useful to distinguish patients with SPLC from those with more advanced disease.
PATIENTS AND METHODS
Identification of Patients and Inclusion Criteria
Approval for the study was obtained, and the need for individual patient consent was waived by the institutional review/privacy board. An institutional review board-approved prospectively maintained database of all thoracic surgical patients undergoing lung cancer resection at a single institution was used to identify patients undergoing surgical resection of SPLC, defined as two or more cancers with the following clinical and pathologic criteria modified from Martini and Melamed6:
1. Presence of tumors with different histologies (e.g., adenocarcinoma versus squamous cell carcinoma).
2. Tumors of different histologic subtypes:(e.g., different estimated percentages of acinar versus bronchoalveolar versus papillary adenocarcinoma), regardless of nodal status.
3. Tumors of similar histology but arising from separate foci (e.g., in the case of squamous cell carcinoma, the presence of in situ carcinoma in both tumors).
4. Tumors of similar histology in the absence of metastatic disease in intervening regional or mediastinal lymph node stations and the absence of extrathoracic disease.
All patients identified had a complete chart review and were included in the study only if they met the above criteria. If there was a question of whether a patient met SPLC criteria, the case was reviewed by two surgeons (D.J.F. and B.J.P.) and two pathologists (W.T. and A.Y.), and the original surgeon was contacted, if possible. Patients previously treated for single primary lung cancers who subsequently presented with metachronous, multiple tumors were excluded from the study. Patients with bronchioalveolar carcinoma as the only histology in all lesions were not included. Patients with SPLC who subsequently developed metachronous lung cancers were included. The final pathologic stage assigned each patient was that of the most advanced staged lesion resected. A formal pathologic review was performed on all available tumors by two of the authors (A.Y. and W.T.) using the 2004 World Health Organization classification including a recently proposed modification of adenocarcinoma subtyping proposed by Motoi et al.13 Patients who did not have specimens available for review were excluded. Patients with tumors other than non-small cell carcinoma were excluded.
The treatment paradigm used for SPLC diagnosed preoperatively is shown in Figure 1. Extent of disease evaluation varied depending on the treating surgeon but typically included a computed tomography chest and upper abdomen, bone scan, and brain imaging. When available, whole body positron emission tomography became standard and replaced bone scan in the majority of cases. In cases of suspected SPLC, cervical mediastinoscopy was routinely performed to rule out nodal metastases, and more recently, endobronchial ultrasound with transbronchial needle aspiration has been used. In cases where there was a clinical suspicion for nodal disease but the endobronchial ultrasound-transbronchial needle aspiration was benign, mediastinoscopy was performed. Surgical resection was performed by means of an open or a video assisted thoracic surgery technique at the discretion of the operating surgeon. Systematic nodal dissection was performed in all the patients. Data on patient demographics, treatment, and survival were extracted from the surgical database and from the electronic medical record. All complications were graded according to the National Cancer Institute Common Terminology Criteria for Adverse Events version 3.0 (http://ctep.cancer.gov/reporting/ctc.html).
Survival was calculated from the date of first surgery to either date of death or the last follow-up date, including all in-hospital mortalities. The date of death was obtained from either the institutional medical record or Social Security Death Index. OS rate was estimated using the Kaplan-Meier method. Variables potentially affecting survival were analyzed including gender, age, smoking history, time of diagnosis (preoperatively versus intraoperatively), tumor location (same lobe, ipsilateral different lobe, or contralateral lung), histology (same versus different), and pathologic stage of the more advanced lesion. Factors significantly associated with survival were identified by using the log-rank test for categorical variables or Cox proportional hazard regression analysis for continuous variables. The Cox proportional hazard regression method was used to report hazard ratios. The stratified log-rank test was used to calculate p values for the categorical variables after controlling for stage. All analyses were performed using statistical packages Statistical Analysis Software 9.1 or R 2.3.1. All p values are two sided. A p value of less than 0.05 was considered statistically significant.
From January 1995 to July 2006, a total 428 patients were identified as having more than one lung tumor resected. One hundred seventy-five patients had metachronous disease. Sixty-eight patients were excluded because they had either a single cancer or evidence supporting stage IV disease (extrathoracic metastatic lesions). Ten patients with suspected SPLC had insufficient specimens for pathologic review. This left 175 patients meeting study criteria who underwent complete resection of SPLC and had complete clinical and pathologic data available. The median age was 69 years (range 42-87), and 62% of the patients were female. Most were former or current smokers (92%) with a median cigarette exposure of 45 pack-years (range 0-216). Only 14 patients were never smokers. Roughly half of the patients (n = 91, 52%) were diagnosed preoperatively as having SPLC, whereas 42% (73 of 175) had additional lesions discovered at the time of operation for a single lesion. Only nine patients had their lesions detected as part of a computed tomography Screening Program. Eleven patients (6%) had suspected SPLC preoperatively and were found to have additional lesions identified at exploration for a known lesion.
More than half (102 of 175, 58%) of the patients underwent a single operation, whereas 73 patients (42%) underwent two or more operations (Table 1). In all cases, complete resection was performed while maintaining optimal lung parenchymal preservation. The majority of patients (148 of 175, 84%), regardless of whether they underwent single or multiple operations, had either a single lobectomy (100 of 175, 57%) and/or sublobar resections (48 of 175, 27%). Ten patients underwent sequential bilateral lobectomies, and 13 patients required bilobectomy. Pneumonectomy was rarely performed (5 of 175, 3%). Operative morbidity was 33%, the majority of which was grade 1 or 2 (91 of 99 complications), and in-hospital mortality was 1.2%. Most patients received no additional therapy after complete resection. Twenty-five patients (14%) received adjuvant therapy with 17 undergoing chemotherapy and eight having external beam radiotherapy.
Tumor Characteristics and Stage
The median size of the largest resected tumor was 2.5 cm (range 0.5-14) (Table 2). Most patients (125 of 175, 71%) had two tumors; however, 29% (50 of 175) had more than two tumors, with one patient having a total of 11. Multiple adenocarcinomas comprised the majority (76%) of cases. There were relatively few cases of different histologies (34 of 175, 19%). After detailed histologic subtyping, only seven tumors were considered the same. None of these patients had lymph node metastasis. The most common tumor locations were in different lobes of an ipsilateral chest (55 of 175, 31%) followed by contralateral lesions (45 of 175, 26%). Overall, ipsilateral disease was slightly more common that contralateral disease (59% versus 41%). The majority of patients had node-negative, stage I disease, but 25 patients (14%) had N1 disease, and 22 patients (13%) had N2 disease.
The median follow-up was 50.3 months (4.8-164.7); the median OS for the group was 67.4 months (46.4-80.0) with a 3-year OS of 64% (Figure 2). In the cohort of patients with only two lesions (n = 125), the median survival was 54.8 months (34.8-80) with a 3-year OS of 59.5% (95% confidence interval: 50.0-67.7%; data not shown). Univariate analysis of factors associated with survival revealed that decreasing size of the largest tumor, fewer pack-years of cigarettes smoked, female gender, and T-, N-, and overall pathologic stage were associated with improved survival (Table 3). Tumor location, tumor histology, and time of diagnosis (preoperative versus intraoperative) did not seem to influence survival. There was no pattern to recurrence, regardless of the type of resection the patients underwent (data not shown). Patients with stage IA disease had a significantly better OS than patients with higher stage disease (p < 0.001) (Figure 3). Patients with stages IB, II, and III disease did not have statistically significantly different survival, although there was a trend toward worse survival. Survival was similar regardless of the location of the additional disease (Figure 4). On multivariable analysis controlling for stage, only female gender was a significant predictor of better OS (p = 0.001).
Since first described in 1924 by Beyreuther,14 SPLC were considered to be associated with a poor prognosis. Subsequent studies of SPLC (Table 4) have been difficult to interpret due to small overall numbers of cases and little information regarding tumor characteristics and stage. In addition, there are wide differences in surgical technique and no standard with respect to adjuvant treatment, all of which compound the difficulties in evaluating this data. The initial report from our institution by Martini and Melamed6 and the follow-up study by Rosengart et al.,15 which documented pathologic stage, allowed for more accurate evaluation of the outcome of patients treated for SPLC. The OS of patients with SPLC in these two studies, although slightly worse than patients with single primary lung cancer, was clearly better than for patients with stage IIIB or IV disease.6,15
In this study, we report the largest series to date of surgically treated SPLCs. We have demonstrated that with the careful use of clinical and histopathological criteria, thorough staging and appropriate surgical intervention OS rates comparable with patients with single lung cancers of similar stage can be achieved. Patients in this study with stages IA and IB SPLC who were surgically treated had a 74% and 65% 3-year OS, respectively. This is similar to patients with single lung cancers, when matched for stage16 and highlights the need to distinguish patients with SPLC from those with more advanced disease. The results presented here are consistent with other modern, albeit smaller, series of surgically treated SPLC.1,17
In attempting to identify factors associated with prolonged survival, univariate analysis revealed that decreasing tumor size, fewer pack-years of cigarettes smoked, female sex, T-, N-, and overall pathologic stage were associated with improved survival. On multivariate analysis controlling for stage, only female gender was an independent predictor of survival. This is consistent with multiple series of both single and multiple primary lung cancers.6,8,11,12,15,16,18-20 Chang et al.11 recently reported similar results, finding that nodal status was a significant prognostic factor. The OS was lower than in this report, which may be due to the selection criteria that included all patients with a second tumor at the time of resection, regardless of lymph node status or location, potentially including a significant number of patients with stage IIIB or stage IV disease.
Trousse et al.12 recently reported their data on 125 consecutive patients with SPLC over a 20-year period. In this study, patients with tumor spread to common lymphatic channels were included, raising the concern that these patients in fact had advanced disease. This concern is supported by the fact that 40% of the patients in their study had adjuvant treatment, and the reported 5-year survival was only 34%. In this study, a central pathologic review was performed, and patients who had positive nodal disease were excluded if there tumors were felt to be identical on histologic subtyping. This reduced the inclusion of patients with true stage IIIB or stage IV disease.
Nearly one half of the patients in our study had synchronous disease recognized intraoperatively, and 60% of patients had ipsilateral disease. Survival outcomes of surgical resection were similar regardless of the location of the additional primary disease (same lobe, ipsilateral, or contralateral) and were better than expected under the current staging system. This supports the changes to the T-stage descriptor proposed by the International Association for the Study of Lung Cancer.21,22 They report a median 5-year OS for patients with M1 disease (same side tumors and different lobes), which was similar to patients with T4 disease (p = 0.109). They also found that patients with T4 tumors (same lobe and multiple tumors) had similar 5-year OS to patients with T3 tumors (p = 0.6488).22 Generally, when an additional lesion is found at the time of surgery, we will proceed with the planned resection if the patient meets our modified SPLC criteria. That is, if there is no pleural disease, the intervening lymph node stations are negative on frozen section, and the new nodules do not appear to have been spread through the pleura, we will proceed with complete resection. Our data support these results and our intraoperative SPLC criteria. These data also demonstrated excellent survival results for contralateral tumors that far exceed what would be expected for M1 disease in the contralateral lung.
Adenocarcinomas often comprised various histologic subtypes (acinar, papillary, etc.),23 suggesting that these tumors have different origins. Given that most patients in this study had tumors of the same histology (81%) of which 76% were adenocarcinomas, distinguishing patients who were truly SPLC based on overall histologic type (i.e., adenocarcinoma) was not possible. Unfortunately, strict adherence to the Martini and Melamed criteria can misidentify patients as having SPLC when in fact they have metastatic disease.24 However, by defining the percentage contribution of each subtype for individual tumors allowed for the differentiation of tumors which were potentially SPLC from those that were metastatic lesions.13 The validity of this method is suggested by the improved survival of these patients, even those with lymph node metastasis, when compared with what would be expected historically of patients with stages IIIB and IV disease. In an effort to explore these findings, we recently completed a molecular analysis of suspected SPLC tumors. These results confirmed the validity of histologic subtyping in helping to identify patients with SPLC.25
There are several potential limitations of this study. First, because of the retrospective nature of this study, the results are based on a highly selected group of patients in which there are probably inherent biases. Second, as the incidence of this entity is low, it was difficult to make conclusions about certain subgroups, such as higher stage patients (II and III) or to distinguish outcomes achieved in patients with similar or different histologies. The low numbers within these subgroups may explain the fact that we did not see a statistical difference in survival between patients with stage II and stage III disease. Third, we cannot know the outcome of patients who had SPLC but were never offered surgical resection, thus not allowing us to compare patients surgically treated to those medically treated. Finally, we have not discovered additional helpful criteria in distinguishing SPLC from more advanced disease.
There have been 14 studies that propose using molecular characterization to aid in distinguishing synchronous tumors from metastatic lesions,26–39 the majority of which did not use any specific inclusion criteria to select tumors. Additionally, most used loss of heterozygosity or p53 mutational analysis, both of which are often not able to distinguish between these two distinct clinical entities. Others proposed the use of epidermal growth factor receptor and kirsten rat sarcoma mutational analysis, but these are not ubiquitous enough to be used in this patient population. Initial work by both Bhattacharjee et al.40 and Garber et al.41 suggest that it is feasible to differentiate tumors based on molecular profiling. Combining the clinical and pathologic paradigm outlined earlier with molecular profiling may help provide a more accurate diagnosis of SPLC in the future.7
This large series shows that using modified criteria originally set forth by Martini and Melamed, based on current precise histologic subtyping and rigorous mediastinal and extrathoracic staging, we can identify patients with probable SPLC who will benefit from curative resection (Figure 1). Evolving methods in molecular profiling of these lesions may further improve our ability to definitively characterize this challenging entity.
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