New Aspects of the Clinicopathology and Genetic Profile of Metachronous Multiple Lung Cancers

Multiple primary lung cancer: Updates and perspectives

Management of multiple primary lung cancer (MPLC) remains challenging, partly due to its increasing incidence, especially with the significant rise in cases of multiple lung nodules caused by low-dose computed tomography screening. Moreover, the indefinite pathogenesis, diagnostic criteria, and treatment selection add to the complexity. In recent years, there have been continuous efforts to dissect the molecular characteristics of MPLC and explore new diagnostic approaches as well as treatment modalities, which will be reviewed here, with a focus on newly emerging evidence and future perspectives, hope to provide new insights into the management of MPLC and serve as inspiration for future research related to MPLC.

Towards the molecular era of discriminating multiple lung cancers

In the era of histopathology-based diagnosis, the discrimination between multiple lung cancers (MLCs) poses significant uncertainties and has thus become a clinical dilemma. However, recent significant advances and increased application of molecular technologies in clonal relatedness assessment have led to more precision in distinguishing between multiple primary lung cancers (MPLCs) and intrapulmonary metastasis (IPMs). This review summarizes recent advances in the molecular identification of MLCs and compares various methods based on somatic mutations, chromosome alterations, microRNAs, and tumor microenvironment markers. The paper also discusses current challenges at the forefront of genomics-based discrimination, including the selection of detection technology, application of next-generation sequencing, and intratumoral heterogeneity (ITH). In summary, this paper highlights an entrance into the primary stage of molecule-based diagnostics.

EGFR mutation status in non-small cell lung cancer receiving PD-1/PD-L1 inhibitors and its correlation with PD-L1 expression: a meta-analysis

Meta-analysis was performed on the Web of Science, PubMed, Embase, and Cochrane databases to evaluate the effect of epidermal growth factor receptor (EGFR) mutation status on programmed cell death protein 1/programmed death ligand 1 (PD-1/PD-L1) immune checkpoint inhibitors, and the association between EGFR mutation status and PD-L1 expression in non-small cell lung cancer (NSCLC) patients. Pooled effect (hazard ratio/odds ratio, HR/OR) with 95% confidence interval (CI) was calculated, and the source of heterogeneity was explored by subgroup analysis and meta-regression using Stata/SE 15.0. Meta-analysis of the association between EGFR mutation status and overall survival (OS) in NSCLC with immunotherapy was calculated from four randomized controlled trials. We found that immune checkpoint inhibitors significantly prolonged OS over docetaxel overall (HR 0.71, 95% CI 0.64-0.79) and in the EGFR wild type (HR = 0.67, 95% CI = 0.60-0.75), but not in the EGFR mutant subgroup (HR = 1.11, 95% CI = 0.80-1.52). Meta-analysis of the association between EGFR mutation status and PD-L1 expression in NSCLC included 32 studies. The pooled OR and 95% CI were 0.60 (0.46-0.80), calculated by random effects model. No source of heterogeneity was found in subgroup analysis. Sensitivity analysis was carried out with a fixed model, and the influence of a single study on the pooled results showed no significant change with robust meta-analysis methods. Harbord's weighted linear regression test (P = 0.956) and Peters regression test (P = 0.489) indicated no significant publication bias. The limited benefit of single-agent PD-1/PD-L1 inhibitors in the second-line or later setting for EGFR-mutated NSCLC may be partly due to the lower expression of PD-L1.

The Role of Whole Exome Sequencing in Distinguishing Primary and Secondary Lung Cancers

Non-small cell lung cancer (NSCLC) that presents with multiple lung tumors (MLTs) poses a challenge to accurate staging and prognosis. MLTs that arise as clonally related secondary metastases from a common primary are higher stage and often require adjuvant chemotherapy or may in fact be incurable stage IV lesions. Conversely, MLTs that represent distinct primaries have a better prognosis and may be overtreated if inappropriately classified as related secondaries. Historically, pathologic and radiographic criteria were used to distinguish between primary and secondary MLTs; however, the advent of genomic profiling has demonstrated limitations to these historic classification systems. In this review, we discuss the use of molecular profiling to distinguish between primary and secondary lung cancers, with a focus on the insights gleaned from whole exome sequencing (WES) analyses. While WES is not yet feasible in routine clinical practice, WES studies have helped elucidate the clonal relationship between primary and secondary lung cancers and provide important context for the application of targeted sequencing panel-based analyses.

Morphological and genetic heterogeneity of synchronous multifocal lung adenocarcinoma in a Chinese cohort

Background

Synchronous multifocal lung cancer (SMLC) is diagnosed with increasing frequency in clinical practice globally. Due to innate variation in clinical management and outcome, it is vital to properly distinguish between synchronous multifocal primary lung cancer (SMPLC) and intrapulmonary metastasis (IM). The pathologic features and principal classification criteria of multifocal lung cancer remain unclear. Our objective was to evaluate the diagnostic value of histological morphologic features and driver gene mutations in SMLC classification.

Methods

We collected a unique cohort of Chinese patients with SMLC, and fully explored the morphologic, immunohistochemical, and molecular features of the disease. Twenty-one SMLC patients with a total of 50 tumours were included in our study. The pathological features that were presented by these patients were analysed, including the tumours location, tumours size, pathological types, predominant pattern of adenocarcinoma, and immunohistochemical staining. We conducted molecular testing of nine driver oncogenes that are associated with lung cancer, namely, EGER, KRAS, BRAF, NRAS, ALK, ROS1, RET, HER2, and PIK3CA.

Results

According to the Martini-Melamed classification and refined standard, 8 and 17 patients, respectively, were considered to have SMPLCs. Gene mutations were identified in 18 tumours (36%). Twelve patients had different gene mutations.

Conclusions

We demonstrate that conventional morphological assessment is not sufficient to clearly establish the clonal relationship of SMPLCs. Instead, the evaluation of histological subtypes, including nonmucinous adherent components, is required. Multiplex genotypic analysis may also prove to be a useful additional tool.

An Observational Study of Acquired EGFR T790M-Dependent Resistance to EGFR-TKI Treatment in Lung Adenocarcinoma Patients in Taiwan

In Taiwan, epidermal growth factor receptor (EGFR) tyrosine kinase inhibitors (EGFR-TKIs), gefitinib, erlotinib, and afatinib are served as first-line therapy for non-small lung cell cancer (NSCLC) patients with EGFR sensitizing mutations. However, the majority of patients who initially respond to EGFR-TKIs, progress through acquiring EGFR T790M mutations (T790M), which is the most common resistant mechanism. Patients with T790M gain the opportunity of subsequent treatment with third-generation EGFR-TKI, osimertinib. This study aimed to evaluate the association between prior EGFR-TKI therapy and incidence of acquired T790M resistance in lung adenocarcinoma patients who have progressed on first/second-generation EGFR-TKI therapy. This retrospective study included lung adenocarcinoma patients who had a radiographically-confirmed progressive disease under EGFR-TKI treatment and had re-biopsy samples for T790M testing from seven medical centers in Taiwan from June 2013 to December 2018. Patients harboring de novo T790M or using more than one EGFR-TKI were excluded. Of the 407 patients enrolled, the overall T790M acquisition rate was 52.8%. The patients treated with gefitinib, erlotinib or afatinib had a statistically significant difference in the T790M rates (59.9, 45.5, and 52.7%, respectively; p = 0.037) after disease progression. Patients with common baseline EGFR mutations (Del-19 and L858R) (p = 0.005) and longer treatment duration with EGFR-TKIs (p < 0.001) had higher chances of T790M acquisition. Multivariate logistic regression analysis further showed that patients with common baseline EGFR mutations, gefitinib (compared to erlotinib) administration, and longer treatment duration with EGFR-TKIs had higher T790M incidence. There was no significant difference in the incidence of acquired T790M between different re-biopsy tissue samples or complications. In conclusion, this study showed that patients who progressed from gefitinib treatment, bearing common EGFR mutations, and with longer EGFR-TKI treatment duration had increased incidence of T790M acquisition and, therefore, were suitable for subsequent osimertinib treatment.

The differences of immunologic and TP53 mutant phenotypes between synchronous and metachronous head and neck cancer and esophageal cancer

OBJECTIVE

To determine the tumor genomic, immunologic expression, and risk factors of treatment outcomes for patients with double head and neck squamous cell carcinoma (HNSCC) and esophageal squamous cell carcinoma (ESCC).

METHODS

We reviewed patients with double HNSCC and ESCC between 1995 and 2014. The TP53 genomic mutation, CD8+ tumor infiltrating lymphocytes (TIL) and tumor programmed cell death ligand 1 (PD-L1) expression of paired HNSCC and ESCC were analyzed.

RESULTS

A total of 116 patients (57 metachronous and 59 synchronous) were included. There were 88 (75.86%) patients with HNSCC and 80 (68.97%) with ESCC harboured TP53 disruptive mutation. Nearly 106 (91.38%) patients had different clonality of TP53 mutation in paired HNSCC and ESCC. The immunologic expression of synchronous and metachronous patients was significantly different. Compared to the metachronous patients, the synchronous patients had significantly higher HNSCC CD8+ TIL (p = 0.03), ESCC CD8+ TIL (p < 0.001), HNSCC PD-L1+ tumor proportion score (TPS, p = 0.04), and ESCC PD-L1+ TPS (p = 0.04). Furthermore, among the synchronous patients, the immunologic expression between HNSCC and ESCC was significantly correlated. The CD8+ TIL and PD-L1 TPS had strongly (r = 0.63, p < 0.0001) and moderately (r = 0.42, p = 0.001) positive correlations, respectively. Finally, advanced stage (III/IV) HNSCC was a significant factor for disease-free (p = 0.03) and overall survival (p = 0.005).

CONCLUSION

In patients with double HNSCC and ESCC, nearly all HNSCC and ESCC were of multicentric origin. For the synchronous patients, there was more adaptive immune resistance in HNSCC and ESCC. The immunologic expression between paired HNSCC and ESCC was also significantly correlated.

Unexpected encounters: high prevalence of synchronous primary lung cancers in a tertiary academic center

Background

Accurate staging of lung cancer is paramount for directing treatment. After an internal audit suggested a higher than expected rate of synchronous multiple primary lung cancers (SMPLC), we have sought to evaluate the prevalence of SMPLC at our single, large academic center.

Methods

From January 2019 to September 2019, patients with non-small cell lung cancer who underwent surgical resection were retrospectively reviewed. Clinical characteristics, pre- and post-op imaging, 30-day morbidity and mortality, as well as pathological findings were reviewed. SMPLCs were defined using modified Martini criteria.

Results

Among 83 patients who underwent surgical resection for primary lung cancer with the intention of cure, 17 (20.5%) had pathologically confirmed SMPLC’s, 53 (64%) were single primary lung cancers, and 13 (16%) had metastatic lesions from primary lung cancer or extra-thoracic cancers. Mean length of stay was 2 days with no mortalities. Of the SMPLC group, 9 (53%) had previous extra-thoracic neoplasms, compared with 8 (15%) in the single primary group. Four (24%) had a history of resected lung cancers more than 2 years previously, and were participating in lung cancer surveillance programs.

Conclusions

The rate of SMPLC at our institution appears to be considerably higher than traditionally reported. Failure to recognize the high incidence of synchronous primary lung cancers exposes patients to the risks of under treatment and poor outcomes.

Metachronous primary lung adenocarcinomas harboring distinct KRAS mutations

To distinguish whether multiple lung nodules represent multiple primary lung cancers (MPLC) or intrapulmonary metastases (IPM) is crucial for staging and subsequent therapy. We herein present the first report of a patient with two simultaneously resected metachronous lung adenocarcinomas in the right upper lobe, each with a distinct driver mutation in the KRAS gene identified by targeted next generation sequencing (NGS). The nodules appeared chronologically metachronous, with a 3.7 year interval. Histopathology showed two histologically identical adenocarcinomas, without lymph node metastases. It was hard to decide whether they should be classified as either MPLC or IPM based only on the clinicopathological criteria. Sequencing further revealed distinct KRAS mutation in each tumor, with one tumor harboring the KRAS‐G12C mutation, and the other tumor harboring the KRAS‐Q61H mutation. Incorporation of the molecular data cleared the confusion with regard to staging and spared this patient from adjuvant therapy. This case highlights that molecular profiling allows for better differentiation between MPLC and IPM than histopathology alone.

Key points

To the best of our knowledge, this is the first case of multiple primary lung cancers harboring distinct KRAS mutations.

The case highlights the importance of incorporating molecular profiling using NGS along with the clinicopathological criteria in classifying multiple lung tumors.

A Rare Case Of Synchronous Multiple Primary Lung Cancer: Squamous Cell Cancer And Small Cell Lung Cancer

The incidence of synchronous multiple primary malignancies has been reported to be low. We report a rare case of synchronous lung squamous cell cancer and small cell lung cancer in an 82-year-old male patient. There is a lack of standard diagnostic criteria for multiple primary lung cancer. Two tumors with similar morphology are difficult to draw conclusions about the same lineage or different lineages. If the patient's physical condition permits, multiple tumors should be sampled and tested. Besides, imaging features are helpful for identification. It is advisable to diagnose synchronous multiple primary malignancies in an early stage, which contributes to a favorable outcome.

Clonality analysis of pulmonary tumors by genome-wide copy number profiling

Multiple tumors in patients are frequently diagnosed, either synchronous or metachronous. The distinction between a second primary and a metastasis is important for treatment. Chromosomal DNA copy number aberrations (CNA) patterns are highly unique to specific tumors. The aim of this study was to assess genome-wide CNA-patterns as method to identify clonally related tumors in a prospective cohort of patients with synchronous or metachronous tumors, with at least one intrapulmonary tumor. In total, 139 tumor pairs from 90 patients were examined: 35 synchronous and 104 metachronous pairs. Results of CNA were compared to histological type, clinicopathological methods (Martini-Melamed-classification (MM) and ACCP-2013-criteria), and, if available, EGFR- and KRAS-mutation analysis. CNA-results were clonal in 74 pairs (53%), non-clonal in 33 pairs (24%), and inconclusive in 32 pairs (23%). Histological similarity was found in 130 pairs (94%). Concordance between histology and conclusive CNA-results was 69% (74 of 107 pairs: 72 clonal and two non-clonal). In 31 of 103 pairs with similar histology, genetics revealed non-clonality. In two out of four pairs with non-matching histology, genetics revealed clonality. The subgroups of synchronous and metachronous pairs showed similar outcome for the comparison of histological versus CNA-results. MM-classification and ACCP-2013-criteria, applicable on 34 pairs, and CNA-results were concordant in 50% and 62% respectively. Concordance between mutation matching and conclusive CNA-results was 89% (8 of 9 pairs: six clonal and two non-clonal). Interestingly, in one patient both tumors had the same KRAS mutation, but the CNA result was non-clonal. In conclusion, although some concordance between histological comparison and CNA profiling is present, arguments exist to prefer extensive molecular testing to determine whether a second tumor is a metastasis or a second primary.

Using Genomics to Differentiate Multiple Primaries From Metastatic Lung Cancer

INTRODUCTION

Genomic technologies present a promising mechanism of resolving the clinical dilemma of distinguishing independent primary tumors from intrapulmonary metastases in NSCLC. We evaluated the utility of discordant mapping somatic junctions from chromosomal rearrangements in diagnosing metastatic disease compared to the current standard histologic review.

MATERIAL AND METHODS

Mate-pair sequencing was performed on DNA extracted from 76 distinct tumors from 37 cases of multiple lung cancers. Discordant mapping junctions and chromosomal copy levels were assessed for each tumor. Blood-derived DNA was available on 22 of these cases for germline assessments. A lung cancer next-generation sequencing panel was additionally performed on tumor pairs from 17 patients.

RESULTS

Whereas mate-pair sequencing was able to classify lineage in all tumor pairs, histologic review appeared to misclassify lineage in 9 of 33 (27%) same-histology tumor pair comparisons. Based on disagreement between the reviewing pathologists, histopathologic lineage was classified as indeterminate in seven cases. In two cases where pathologists agreed on a metastatic call, no shared junctions were found suggesting independent primaries. Although germline junctions passing algorithmic filters were common, on average less than three were present and all had predictable structures of small focal rearrangements or transposons. Evaluation of shared chromosomal copy changes and driver mutations through a lung cancer next-generation sequencing panel, while informative, were nondefinitive in calling lineage in all cases.

CONCLUSIONS

The highly unique nature and prevalence of chromosomal rearrangement in lung cancers provide a useful and definitive technique for calling lineage in multifocal lung cancer.

Association between PD-L1 expression and driver gene status in non-small-cell lung cancer: a meta-analysis

OBJECTIVE

To assess the association between PD-L1 expression and driver gene mutations in patients with non-small-cell lung cancer (NSCLC).

METHOD

We performed a meta-analysis of 26 studies (7541 patients) which were published from 2015 to 2017. Pooled odds ratios (ORs) with 95% confidence intervals (CI) were calculated to describe the correlation. Subgroup analysis was performed based on population characteristics, types of PD-L1 antibodies and quality of individual studies.

RESULTS

A lower frequency of PD-L1 positivity was observed in NSCLCs harboring EGFR mutation (OR: 0.64, 95% CI, 0.45-0.91, p = 0.014). A negative correlation was also found at 1% (OR: 0.35, 95% CI, 0.22-0.55, p = 0.000) and 50% (OR: 0.33, 95% CI, 0.14-0.81, p = 0.015) cutoff for PD-L1 positive, elderly age group (OR: 0.56, 95% CI, 0.35-0.89, p = 0.013), female dominant group (OR: 0.55, 95% CI, 0.29-0.94, p = 0.030) and smoker dominant group (OR: 0.52, 95% CI, 0.29-0.96, p = 0.035). No significant differences in PD-L1 expression were observed among patients with different ALK, BRAF, HER2, PIK3CA status and MET expression level. Higher level of PD-L1 was found in tumors with KRAS mutation (OR: 1.45, 95% CI, 1.18-1.80, p = 0.001). PD-L1 expression level was not significantly different between triple (EGFR/ALK/KRAS) wild type NSCLCs and those with EGFR/ALK/KRAS mutation.

CONCLUSIONS

PD-L1 expression in EGFR mutated NSCLCs were lower than those in EGFR wild type NSCLCs, while tumors with KRAS mutation showed higher levels of PD-L1.

[Research Progress in Diagnosis and Management Strategies of Multiple Primary Lung Cancer]

原发肺癌（multiple primary lung cancer, MPLC）的发病率呈逐年上升趋势，但关于MPLC的发病机制、诊断、鉴别诊断和临床处理策略仍存在诸多争议。本综述将对目前关于MPLC的发病机制、诊断标准、鉴别诊断和处理策略方面的研究进展做一个回顾，旨在为该病的诊疗提供理论基础。

Local Therapy for Limited Metastatic Non-Small Cell Lung Cancer: What Are the Options and Is There a Benefit?

Distant metastasis is common in non-small cell lung cancer (NSCLC) and typically associated with poor prognosis. Aggressive local therapy including surgery and/or radiation for limited metastatic disease from colorectal cancer and sarcoma is associated with survival benefit and has become part of the standard of care. In this article, we review the literature and ongoing studies concerning surgery, radiation, and radiofrequency ablation for oligometastatic NSCLC.

Translational research in thoracic surgery-the National Taiwan University Hospital experience

Thoracic surgeons should be more aware of the latest information about histopathological, genetic and epigenetic alterations that may influence treatment policy and patient outcome in the biomolecular era. Translational research studies often produce a promising diagnostic tool or new treatment that can be used clinically. The results of these translational studies may even change the practical guidelines and current staging system in thoracic malignancies. The following article summarizes the experiences of translational research in esophageal cancer and non-small cell lung cancer (NSCLC) at National Taiwan University Hospital in Taiwan.

Toxicity and Pharmacokinetic Studies of Aerosolized Clinical Grade Azacitidine

BACKGROUND

Azacitidine as an effective epigenetic therapeutic agent has not been used as an aerosol form to treat lung cancer patients. We aerosolized clinical grade azacitidine (Aza), optimized the formulation, and studied its pharmacokinetics and toxicity in mice.

METHODS

Extrusion-precipitation method and DNA methyltransferase inhibition rate were used to measure the aerodynamic size and aerosolized Aza activity. In the single dose pharmacokinetic study, Aza concentrations in peripheral blood and lungs were measured by LC-MS method. In the multiple-dose toxicity studies, histo-pathological evaluation was used to determine the organ and bone marrow toxicities.

RESULTS

In pharmacokinetic study, aerosolized Aza was found to deposit mainly into the lung with very little drug detected in the circulation. In contrast, intravenously injected (IV) Aza resulted in a high Aza concentration in the peripheral blood, with trace amounts of drug in the lung, and it was associated with significant myelosuppression. No significant myelosuppression, pulmonary toxicity, hepatotoxicity, or nephrotoxicity were observed at a daily dose of 2.5 mg/m(2) for 7 days. Reversible lung inflammation was found in mice treated with 7.5 mg/m(2) aerosolized Aza at 3 but not 6 weeks after treatment.

CONCLUSIONS

Aerosol Aza aerodynamic size favors deposition of the drug to the human lower airways. The aerosol process do not compromise the drug activity. Aerosolized Aza has higher lung deposition and much less systemic toxicity than IV drug. The safe starting dose for clinical phase I trials should be 2.5 mg/m(2) for 5 to 7 days.

Pulmonary Metastases from NSCLC and MPLC (Multiple Primary Lung Cancers): Management and Outcome in a Single Centre Experience

BACKGROUND

This is an institutional review of surgical management of second pulmonary tumours in patients with history of Non-small Cell Lung Cancer (NSCLC) resection according to The American College of Chest Physicians' (ACCP) revision to the Martini and Melamed's criteria for the classification of multiple primary lung cancers (MPLC).

METHODS

All patients who underwent iterative pulmonary resections for pulmonary metastasis (Group A) or MPLC (Group B) between 2006 and 2012 were reviewed and their survivals compared accordingly. The main criteria of insertion in Group B were different histology and the same histology with disease-free interval ≤ 4 years; we excluded loco-regional recurrence in nodes and/or on bronchial stump.

RESULTS

Group A: Twenty patients; Disease free time (DFT) after first operation was 15.2 months (range 2-44). One, two and three years overall survival after second resection was 74%, 29%, 14% respectively. Group B: Thirty-six patients. One, two and three years overall survival was 94%, 81%, and 69% respectively. No statistical differences on outcome were found between the two groups in spite of the apparent worse survival rate for Group A (p=.197).

CONCLUSIONS

A further resection for additional nodules, whether designated as intrapulmonary metastases or second primary NSCLC, can be an appropriate curative strategy in selected patients with unimpaired respiratory function and no evidence of distant metastatic disease. The site, the extent of the second resection, the histology and even the stage are unlikely to be related to survival.

PD-L1 is highly expressed in lung lymphoepithelioma-like carcinoma: A potential rationale for immunotherapy

OBJECTIVES

Programmed cell death-ligand 1 (PD-L1) and driver mutations are found in non-small cell lung cancers (NSCLCs) and may be suitable targets for specific therapies, but their roles in lymphoepithelioma-like carcinoma (LELC) of the lung are unclear.

MATERIALS AND METHODS

Sixty-six patients with pulmonary LELCs were investigated. Paraffin-embedded tumor sections were stained with PD-L1 antibody. Tumors with moderate-to-strong membrane staining in ≥5% of tumor cells were positive for PD-L1 overexpression. The presence of driver mutations in the genes for epidermal growth factor receptor (EGFR), KRAS, and BRAF were examined by direct sequencing. Anaplastic lymphoma kinase (ALK) and ROS1 levels were determined by immunohistochemistry. Correlations of PD-L1 expression and driver mutations with clinicopathologic parameters were analyzed.

RESULTS

The overall frequency of PD-L1 overexpression and EGFR mutation was 75.8% and 12.1%, respectively. No KRAS, BRAF, ALK or ROS1 aberrations could be detected. PD-L1 expression was not associated with driver mutations. Multivariate analysis revealed that smoking and advanced stage were independent risk factors for poor overall survival, whereas PD-L1 positivity was not significantly associated with patient outcome.

CONCLUSION

There are high PD-L1 expression and infrequent driver mutations in LELCs compared with conventional NSCLCs. The high expression of PD-L1 in EBV and inflammation associated LELC may provide a rationale for immunotherapy in this subtype of lung cancer.

Prognosis of synchronous and metachronous multiple primary lung cancers: systematic review and meta-analysis

BACKGROUND

With the development of imaging technology, an increasing number of multiple primary lung cancers (MPLC) are diagnosed in recent years. However, there is still ambiguity in the stage classification rules for patients with MPLC. Our purpose was to access the prognosis of synchronous and metachronous MPLC.

METHODS

A systematic literature search was performed on four databases (EBSCO, Pubmed, OVID and Springer) to obtain relevant articles. We used published hazard ratios (HRs) of overall survival (OS) if available or estimates from the published survival data.

RESULTS

There were 1796 patients with MPLC in 22 relevant studies, who were eligible for analysis. We found that the OS of patients with synchronous MPLC was inferior to the one of metachronous MPLC patients when starting from the diagnosis of the first metachronous tumor (HR 3.36, 95% CI 2.39-4.74; p<0.001). However, there was no difference when starting from the diagnosis of the second metachronous tumor (HR 1.19, 95% CI 0.86-1.66; p=0.29). From further analysis we found the OS of patients with MPLC was superior to that of patients with intrapulmonary metastasis (HR 2.66, 95% CI 1.30-5.44; p=0.007). Besides, we found no difference in OS between synchronous (HR 1.39, 95% CI 0.98-1.96; p=0.06) and metachronous (HR 1.05, 95% CI 0.75-1.47; p=0.77) patients, in spite of the histology. In terms of unilateral and bilateral MPLC patients, the OS had no difference either (HR 1.30, 95% CI 1.00-1.69; p=0.05).

CONCLUSION

We found that MPLC had better OS than the lung cancer patients with intrapulmonary metastasis. And despite the tumor-free interval, the OS for metachronous MPLC was as good as that for synchronous MPLC. Furthermore, there was no difference of OS in different subgroups, including histology and position.