A nonparametric test to compare survival distributions with covariate adjustment

Nonparametric combination tests for comparing two survival curves with informative and non-informative censoring

This paper looks at permutation methods used to deal with hypothesis testing within the survival analysis framework. In the literature, several attempts have been made to deal with the comparison of survival curves and, depending on the survival and hazard functions of two groups, they can be more or less efficient in detecting differences. Furthermore, in some situations, censoring can be informative in that it depends on treatment effect. Our proposal is based on the nonparametric combination approach and has proven to be very effective under different configurations of survival and hazard functions. It allows the practitioner to test jointly on primary and censoring events and, by using multiple testing methods, to assess the significance of the treatment effect separately on the survival and the censoring process.

A prospective study of tumor suppressor gene methylation as a prognostic biomarker in surgically resected stage I to IIIA non-small-cell lung cancers

INTRODUCTION

While retrospective analyses support an association between early tumor recurrence and tumor suppressor gene promoter methylation in early-stage non-small-cell lung cancers (NSCLCs), few studies have investigated this question prospectively.

METHODS

Primary tumor tissue from patients with resected pathologic stage I to IIIA NSCLCs was collected at the time of surgery and analyzed for promoter methylation via methylation-specific reverse transcriptase polymerase chain reaction (MethyLight). The primary objective was to determine an association between promoter methylation of 10 individual tumor suppressor genes (CDKN2A, CDH13, RASSF1, APC, MGMT, GSTP1, DAPK1, WIF1, SOCS3, and ADAMTS8) and recurrence-free survival (RFS), with the secondary objectives of determining association with overall survival (OS), and relation to clinical or pathologic features.

RESULTS

A total of 107 patients had sufficient tumor tissue for successful promoter methylation analysis. Majority of patients were former/current smokers (88%) with lung adenocarcinoma (78%) and pathologic stage I disease (62%). Median follow-up was 4 years. When controlled for pathologic stage, promoter methylation of the individual genes CDKN2A, CDH13, RASSF1, APC, MGMT, GSTP1, DAPK1, WIF1, and ADAMTS8 was not associated with RFS. Promoter methylation of the same genes was not associated with OS except for DAPK1 which was associated with improved OS (p = 0.03). The total number of genes with methylated promoters did not correlate with RFS (p = 0.89) or OS (p = 0.55).

CONCLUSION

Contrary to data established by previous retrospective series, tumor suppressor gene promoter methylation (CDKN2A, CDH13, RASSF1, APC, MGMT, GSTP1, DAPK1, WIF1, and ADAMTS8) was not prognostic for early tumor recurrence in this prospective study of resected NSCLCs.

Distinct clinical course of EGFR-mutant resected lung cancers: results of testing of 1118 surgical specimens and effects of adjuvant gefitinib and erlotinib

BACKGROUND

EGFR and KRAS mutations are mutually exclusive and predict outcomes with epidermal growth factor receptor (EGFR) tyrosine kinase inhibitor (TKI) treatment in patients with stage IV lung cancers. The clinical significance of these mutations in patients with resected stage I-III lung cancers is unclear.

METHODS

At our institution, resection specimens from patients with stage I-III lung adenocarcinomas are tested for the presence of EGFR or KRAS mutations during routine pathology analysis such that the results are available before consideration of adjuvant therapy. In a cohort of 1118 patients tested over 8 years, overall survival was analyzed using multivariate analysis to control for potential confounders, including age, sex, stage, and smoking history. The impact of adjuvant erlotinib or gefitinib was examined in an independent data set of patients exclusively with EGFR mutation, in which date of recurrence was recorded.

RESULTS

In the overall population, we identified 227 KRAS (25%) and 222 EGFR (20%) mutations. Patients with EGFR-mutant lung cancers had a lower risk of death compared with those without EGFR mutations, overall survival (OS) HR 0.51 (95% confidence interval [CI]: 0.34-0.76, p < 0.001). Patients with KRAS-mutant lung cancers had similar outcomes compared with individuals with KRAS wild-type tumors, OS HR 1.17 (95% CI: 0.87-1.57, p = 0.30). A separate data set includes only patients with EGFR-mutant lung cancers identified over 10 years (n = 286). In patients with resected lung cancers and EGFR mutation, treatment with adjuvant erlotinib or gefitinib was associated with a lower risk of recurrence or death, disease-free survival HR 0.43 (95% CI: 0.26-0.72, p = 0.001), and a trend toward improved OS.

CONCLUSIONS

Patients with resected stage I-III lung cancers and EGFR mutation have a lower risk of death compared with patients without EGFR mutation. This may be because of treatment with EGFR TKIs. Patients with, and without KRAS mutation have similar OS. These data support reflex testing of resected lung adenocarcinomas for EGFR mutation to provide prognostic information and identify patients for enrollment on prospective clinical trials of adjuvant EGFR TKIs.

A nuclear grading system is a strong predictor of survival in epitheloid diffuse malignant pleural mesothelioma

Epithelioid mesothelioma is the most prevalent subtype of diffuse malignant pleural mesothelioma in which only staging is prognostic for survival. In this study of epithelioid diffuse malignant pleural mesothelioma, we investigate the prognostic utility of nuclear features. The slides of 232 epithelioid diffuse malignant pleural mesothelioma patients (14 stage I, 54 stage II, 130 stage III, and 34 stage IV) from a single institution were reviewed for the following seven nuclear features: nuclear atypia, nuclear/cytoplasmic ratio, chromatin pattern, intranuclear inclusions, prominence of nucleoli, mitotic count, and atypical mitoses. MIB-1 immunohistochemistry was performed using tissue microarray, and MIB-1 labeling index was recorded as the percentage of positive tumor cells. Median overall survival of all patients was 16 months and correlated with nuclear atypia (P<0.001), chromatin pattern (P=0.031), prominence of nucleoli (P<0.001), mitotic count (P<0.001), and atypical mitoses (P<0.001) by univariate analysis. Multivariate analysis revealed nuclear atypia (P=0.012) and mitotic count (P<0.001) as independent prognostic factors, and these two factors were utilized to create a three-tier nuclear grade score. The resulting nuclear grade stratified patients into three distinct prognostic groups: grade I (n=107, median overall survival=28 months), grade II (n=91, 14 months), and grade III (n=34, 5 months). Not only was nuclear grade an independent predictor of overall survival (P<0.001), but it was also a stronger discriminator of survival than all currently available factors. Furthermore, nuclear grade was associated with time to recurrence (P=0.004) in patients who underwent complete surgical resection (n=159). MIB-1 labeling index correlated with mitotic count (P<0.001) and nuclear atypia (P=0.037) and stratified overall survival (P<0.001) and time to recurrence (P=0.048), confirming the prognostic value of the nuclear grade. Nuclear grading in epithelioid mesothelioma provides a simple, practical, and cost-effective prognostic tool that better stratifies clinical outcome and time to recurrence than currently available clinicopathologic factors.

Pleomorphic epithelioid diffuse malignant pleural mesothelioma: a clinicopathological review and conceptual proposal to reclassify as biphasic or sarcomatoid mesothelioma

INTRODUCTION

In patients with epithelioid diffuse malignant pleural mesothelioma (DMPM), clinical stage is the current primary prognostic factor. We sought to investigate whether histologic subtyping can prognostically stratify patients with epithelioid DMPM.

METHODS

Hematoxylin and eosin-stained slides of 232 patients with epithelioid DMPM (14 stage I, 54 stage II, 130 stage III, and 34 stage IV) from a single institution were reviewed. We classified the tumors into five subtypes, according to the predominant histological pattern: trabecular, tubulopapillary, micropapillary, solid, and pleomorphic (≥10% of tumor).

RESULTS

Median overall survival (OS) of all patients with epithelioid DMPM was 16.2 months. Patients with pleomorphic subtype (n = 34) had the worst median OS (8.1 months), followed by solid (n = 89, 13.7 months), micropapillary (n = 20, 15.8 months), tubulopapillary (n = 51, 17.9 months), and trabecular (n = 38, 24.9 months). The pleomorphic subtype was associated with lymphatic and vascular invasion (p < 0.001). The micropapillary subtype was associated with lymphatic invasion (p < 0.001). In univariate analyses, pleomorphic subtype was significantly associated with poor OS (p = 0.003). The pleomorphic subtype showed no significant difference on OS compared with biphasic and sarcomatoid DMPM. In a multivariate analysis, the pleomorphic subtype was an independent predictor of poor OS (p = 0.031). In patients who underwent R1 resection, pleomorphic subtype had the shortest median time to recurrence (13.7 months).

CONCLUSION

Our finding that the pleomorphic subtype is a predictor of aggressive behavior in epithelioid DMPM with no survival difference from biphasic or sarcomatoid DMPM suggests that it may be best regarded as a sarcomatoid pattern rather than a subtype of epithelioid DMPM.