Correlation between aggregated molecular cancer subtypes and selected clinical features
Acute Myeloid Leukemia (Primary blood derived cancer - Peripheral blood)
17 October 2014  |  analyses__2014_10_17
Maintainer Information
Citation Information
Maintained by TCGA GDAC Team (Broad Institute/MD Anderson Cancer Center/Harvard Medical School)
Cite as Broad Institute TCGA Genome Data Analysis Center (2014): Correlation between aggregated molecular cancer subtypes and selected clinical features. Broad Institute of MIT and Harvard. doi:10.7908/C1D21WGW
Overview
Introduction

This pipeline computes the correlation between cancer subtypes identified by different molecular patterns and selected clinical features.

Summary

Testing the association between subtypes identified by 6 different clustering approaches and 5 clinical features across 200 patients, 5 significant findings detected with P value < 0.05 and Q value < 0.25.

  • 3 subtypes identified in current cancer cohort by 'Copy Number Ratio CNMF subtypes'. These subtypes correlate to 'Time to Death'.

  • 5 subtypes identified in current cancer cohort by 'METHLYATION CNMF'. These subtypes correlate to 'Time to Death' and 'AGE'.

  • CNMF clustering analysis on sequencing-based mRNA expression data identified 3 subtypes that do not correlate to any clinical features.

  • Consensus hierarchical clustering analysis on sequencing-based mRNA expression data identified 6 subtypes that correlate to 'Time to Death' and 'AGE'.

  • 4 subtypes identified in current cancer cohort by 'MIRSEQ CNMF'. These subtypes do not correlate to any clinical features.

  • 3 subtypes identified in current cancer cohort by 'MIRSEQ CHIERARCHICAL'. These subtypes do not correlate to any clinical features.

Results
Overview of the results

Table 1.  Get Full Table Overview of the association between subtypes identified by 6 different clustering approaches and 5 clinical features. Shown in the table are P values (Q values). Thresholded by P value < 0.05 and Q value < 0.25, 5 significant findings detected.

Clinical
Features
Time
to
Death
AGE GENDER RACE ETHNICITY
Statistical Tests logrank test Kruskal-Wallis (anova) Fisher's exact test Fisher's exact test Fisher's exact test
Copy Number Ratio CNMF subtypes 0.00346
(0.0899)
0.0454
(1.00)
0.075
(1.00)
1
(1.00)
0.258
(1.00)
METHLYATION CNMF 9.57e-05
(0.00268)
2.57e-09
(7.72e-08)
0.32
(1.00)
0.677
(1.00)
1
(1.00)
RNAseq CNMF subtypes 0.502
(1.00)
0.24
(1.00)
0.101
(1.00)
0.0366
(0.877)
0.583
(1.00)
RNAseq cHierClus subtypes 0.000903
(0.0244)
3.26e-05
(0.000947)
0.414
(1.00)
0.146
(1.00)
0.0819
(1.00)
MIRSEQ CNMF 0.0943
(1.00)
0.0105
(0.262)
0.923
(1.00)
0.858
(1.00)
1
(1.00)
MIRSEQ CHIERARCHICAL 0.194
(1.00)
0.457
(1.00)
0.391
(1.00)
0.956
(1.00)
1
(1.00)
Clustering Approach #1: 'Copy Number Ratio CNMF subtypes'

Table S1.  Description of clustering approach #1: 'Copy Number Ratio CNMF subtypes'

Cluster Labels 1 2 3 4
Number of samples 148 14 27 2
'Copy Number Ratio CNMF subtypes' versus 'Time to Death'

P value = 0.00346 (logrank test), Q value = 0.09

Table S2.  Clustering Approach #1: 'Copy Number Ratio CNMF subtypes' versus Clinical Feature #1: 'Time to Death'

nPatients nDeath Duration Range (Median), Month
ALL 166 105 0.9 - 94.1 (12.0)
subtype1 131 77 0.9 - 94.1 (13.9)
subtype2 11 8 0.9 - 42.0 (10.0)
subtype3 24 20 1.0 - 73.0 (9.5)

Figure S1.  Get High-res Image Clustering Approach #1: 'Copy Number Ratio CNMF subtypes' versus Clinical Feature #1: 'Time to Death'

'Copy Number Ratio CNMF subtypes' versus 'AGE'

P value = 0.0454 (Kruskal-Wallis (anova)), Q value = 1

Table S3.  Clustering Approach #1: 'Copy Number Ratio CNMF subtypes' versus Clinical Feature #2: 'AGE'

nPatients Mean (Std.Dev)
ALL 189 55.1 (16.1)
subtype1 148 53.7 (16.0)
subtype2 14 62.4 (13.1)
subtype3 27 58.7 (16.6)

Figure S2.  Get High-res Image Clustering Approach #1: 'Copy Number Ratio CNMF subtypes' versus Clinical Feature #2: 'AGE'

'Copy Number Ratio CNMF subtypes' versus 'GENDER'

P value = 0.075 (Fisher's exact test), Q value = 1

Table S4.  Clustering Approach #1: 'Copy Number Ratio CNMF subtypes' versus Clinical Feature #3: 'GENDER'

nPatients FEMALE MALE
ALL 86 103
subtype1 73 75
subtype2 6 8
subtype3 7 20

Figure S3.  Get High-res Image Clustering Approach #1: 'Copy Number Ratio CNMF subtypes' versus Clinical Feature #3: 'GENDER'

'Copy Number Ratio CNMF subtypes' versus 'RACE'

P value = 1 (Fisher's exact test), Q value = 1

Table S5.  Clustering Approach #1: 'Copy Number Ratio CNMF subtypes' versus Clinical Feature #4: 'RACE'

nPatients ASIAN BLACK OR AFRICAN AMERICAN WHITE
ALL 2 14 171
subtype1 2 11 133
subtype2 0 1 13
subtype3 0 2 25

Figure S4.  Get High-res Image Clustering Approach #1: 'Copy Number Ratio CNMF subtypes' versus Clinical Feature #4: 'RACE'

'Copy Number Ratio CNMF subtypes' versus 'ETHNICITY'

P value = 0.258 (Fisher's exact test), Q value = 1

Table S6.  Clustering Approach #1: 'Copy Number Ratio CNMF subtypes' versus Clinical Feature #5: 'ETHNICITY'

nPatients HISPANIC OR LATINO NOT HISPANIC OR LATINO
ALL 3 183
subtype1 2 143
subtype2 1 13
subtype3 0 27

Figure S5.  Get High-res Image Clustering Approach #1: 'Copy Number Ratio CNMF subtypes' versus Clinical Feature #5: 'ETHNICITY'

Clustering Approach #2: 'METHLYATION CNMF'

Table S7.  Description of clustering approach #2: 'METHLYATION CNMF'

Cluster Labels 1 2 3 4 5
Number of samples 48 45 65 14 22
'METHLYATION CNMF' versus 'Time to Death'

P value = 9.57e-05 (logrank test), Q value = 0.0027

Table S8.  Clustering Approach #2: 'METHLYATION CNMF' versus Clinical Feature #1: 'Time to Death'

nPatients nDeath Duration Range (Median), Month
ALL 169 106 0.9 - 94.1 (12.0)
subtype1 42 30 1.0 - 69.0 (8.1)
subtype2 42 13 0.9 - 94.1 (21.6)
subtype3 55 43 0.9 - 56.1 (12.0)
subtype4 13 7 1.0 - 42.0 (13.0)
subtype5 17 13 4.0 - 73.0 (12.0)

Figure S6.  Get High-res Image Clustering Approach #2: 'METHLYATION CNMF' versus Clinical Feature #1: 'Time to Death'

'METHLYATION CNMF' versus 'AGE'

P value = 2.57e-09 (Kruskal-Wallis (anova)), Q value = 7.7e-08

Table S9.  Clustering Approach #2: 'METHLYATION CNMF' versus Clinical Feature #2: 'AGE'

nPatients Mean (Std.Dev)
ALL 194 55.1 (16.0)
subtype1 48 55.9 (14.1)
subtype2 45 45.6 (15.5)
subtype3 65 63.1 (12.9)
subtype4 14 63.5 (11.2)
subtype5 22 43.9 (16.0)

Figure S7.  Get High-res Image Clustering Approach #2: 'METHLYATION CNMF' versus Clinical Feature #2: 'AGE'

'METHLYATION CNMF' versus 'GENDER'

P value = 0.32 (Fisher's exact test), Q value = 1

Table S10.  Clustering Approach #2: 'METHLYATION CNMF' versus Clinical Feature #3: 'GENDER'

nPatients FEMALE MALE
ALL 89 105
subtype1 24 24
subtype2 24 21
subtype3 26 39
subtype4 8 6
subtype5 7 15

Figure S8.  Get High-res Image Clustering Approach #2: 'METHLYATION CNMF' versus Clinical Feature #3: 'GENDER'

'METHLYATION CNMF' versus 'RACE'

P value = 0.677 (Fisher's exact test), Q value = 1

Table S11.  Clustering Approach #2: 'METHLYATION CNMF' versus Clinical Feature #4: 'RACE'

nPatients ASIAN BLACK OR AFRICAN AMERICAN WHITE
ALL 2 13 177
subtype1 1 2 45
subtype2 1 2 41
subtype3 0 6 59
subtype4 0 2 12
subtype5 0 1 20

Figure S9.  Get High-res Image Clustering Approach #2: 'METHLYATION CNMF' versus Clinical Feature #4: 'RACE'

'METHLYATION CNMF' versus 'ETHNICITY'

P value = 1 (Fisher's exact test), Q value = 1

Table S12.  Clustering Approach #2: 'METHLYATION CNMF' versus Clinical Feature #5: 'ETHNICITY'

nPatients HISPANIC OR LATINO NOT HISPANIC OR LATINO
ALL 1 190
subtype1 0 48
subtype2 0 44
subtype3 1 63
subtype4 0 14
subtype5 0 21

Figure S10.  Get High-res Image Clustering Approach #2: 'METHLYATION CNMF' versus Clinical Feature #5: 'ETHNICITY'

Clustering Approach #3: 'RNAseq CNMF subtypes'

Table S13.  Description of clustering approach #3: 'RNAseq CNMF subtypes'

Cluster Labels 1 2 3
Number of samples 74 54 45
'RNAseq CNMF subtypes' versus 'Time to Death'

P value = 0.502 (logrank test), Q value = 1

Table S14.  Clustering Approach #3: 'RNAseq CNMF subtypes' versus Clinical Feature #1: 'Time to Death'

nPatients nDeath Duration Range (Median), Month
ALL 151 94 0.9 - 94.1 (12.0)
subtype1 65 39 1.0 - 94.1 (16.1)
subtype2 48 31 0.9 - 75.1 (10.5)
subtype3 38 24 0.9 - 62.0 (12.0)

Figure S11.  Get High-res Image Clustering Approach #3: 'RNAseq CNMF subtypes' versus Clinical Feature #1: 'Time to Death'

'RNAseq CNMF subtypes' versus 'AGE'

P value = 0.24 (Kruskal-Wallis (anova)), Q value = 1

Table S15.  Clustering Approach #3: 'RNAseq CNMF subtypes' versus Clinical Feature #2: 'AGE'

nPatients Mean (Std.Dev)
ALL 173 55.3 (16.1)
subtype1 74 54.4 (17.3)
subtype2 54 58.4 (13.9)
subtype3 45 52.9 (16.4)

Figure S12.  Get High-res Image Clustering Approach #3: 'RNAseq CNMF subtypes' versus Clinical Feature #2: 'AGE'

'RNAseq CNMF subtypes' versus 'GENDER'

P value = 0.101 (Fisher's exact test), Q value = 1

Table S16.  Clustering Approach #3: 'RNAseq CNMF subtypes' versus Clinical Feature #3: 'GENDER'

nPatients FEMALE MALE
ALL 80 93
subtype1 31 43
subtype2 22 32
subtype3 27 18

Figure S13.  Get High-res Image Clustering Approach #3: 'RNAseq CNMF subtypes' versus Clinical Feature #3: 'GENDER'

'RNAseq CNMF subtypes' versus 'RACE'

P value = 0.0366 (Fisher's exact test), Q value = 0.88

Table S17.  Clustering Approach #3: 'RNAseq CNMF subtypes' versus Clinical Feature #4: 'RACE'

nPatients ASIAN BLACK OR AFRICAN AMERICAN WHITE
ALL 2 13 156
subtype1 1 3 68
subtype2 1 2 51
subtype3 0 8 37

Figure S14.  Get High-res Image Clustering Approach #3: 'RNAseq CNMF subtypes' versus Clinical Feature #4: 'RACE'

'RNAseq CNMF subtypes' versus 'ETHNICITY'

P value = 0.583 (Fisher's exact test), Q value = 1

Table S18.  Clustering Approach #3: 'RNAseq CNMF subtypes' versus Clinical Feature #5: 'ETHNICITY'

nPatients HISPANIC OR LATINO NOT HISPANIC OR LATINO
ALL 1 169
subtype1 0 71
subtype2 1 53
subtype3 0 45

Figure S15.  Get High-res Image Clustering Approach #3: 'RNAseq CNMF subtypes' versus Clinical Feature #5: 'ETHNICITY'

Clustering Approach #4: 'RNAseq cHierClus subtypes'

Table S19.  Description of clustering approach #4: 'RNAseq cHierClus subtypes'

Cluster Labels 1 2 3 4 5 6
Number of samples 16 14 15 58 26 44
'RNAseq cHierClus subtypes' versus 'Time to Death'

P value = 0.000903 (logrank test), Q value = 0.024

Table S20.  Clustering Approach #4: 'RNAseq cHierClus subtypes' versus Clinical Feature #1: 'Time to Death'

nPatients nDeath Duration Range (Median), Month
ALL 151 94 0.9 - 94.1 (12.0)
subtype1 15 4 0.9 - 62.0 (46.1)
subtype2 14 5 0.9 - 75.1 (20.0)
subtype3 13 6 6.0 - 94.1 (19.0)
subtype4 50 38 1.0 - 73.0 (11.5)
subtype5 23 13 1.0 - 62.0 (10.0)
subtype6 36 28 1.0 - 69.0 (9.5)

Figure S16.  Get High-res Image Clustering Approach #4: 'RNAseq cHierClus subtypes' versus Clinical Feature #1: 'Time to Death'

'RNAseq cHierClus subtypes' versus 'AGE'

P value = 3.26e-05 (Kruskal-Wallis (anova)), Q value = 0.00095

Table S21.  Clustering Approach #4: 'RNAseq cHierClus subtypes' versus Clinical Feature #2: 'AGE'

nPatients Mean (Std.Dev)
ALL 173 55.3 (16.1)
subtype1 16 47.8 (14.9)
subtype2 14 57.7 (14.6)
subtype3 15 36.6 (13.9)
subtype4 58 59.8 (15.5)
subtype5 26 53.3 (16.7)
subtype6 44 58.7 (13.0)

Figure S17.  Get High-res Image Clustering Approach #4: 'RNAseq cHierClus subtypes' versus Clinical Feature #2: 'AGE'

'RNAseq cHierClus subtypes' versus 'GENDER'

P value = 0.414 (Fisher's exact test), Q value = 1

Table S22.  Clustering Approach #4: 'RNAseq cHierClus subtypes' versus Clinical Feature #3: 'GENDER'

nPatients FEMALE MALE
ALL 80 93
subtype1 9 7
subtype2 6 8
subtype3 6 9
subtype4 22 36
subtype5 16 10
subtype6 21 23

Figure S18.  Get High-res Image Clustering Approach #4: 'RNAseq cHierClus subtypes' versus Clinical Feature #3: 'GENDER'

'RNAseq cHierClus subtypes' versus 'RACE'

P value = 0.146 (Fisher's exact test), Q value = 1

Table S23.  Clustering Approach #4: 'RNAseq cHierClus subtypes' versus Clinical Feature #4: 'RACE'

nPatients ASIAN BLACK OR AFRICAN AMERICAN WHITE
ALL 2 13 156
subtype1 0 2 13
subtype2 0 0 14
subtype3 0 0 15
subtype4 1 3 53
subtype5 0 6 20
subtype6 1 2 41

Figure S19.  Get High-res Image Clustering Approach #4: 'RNAseq cHierClus subtypes' versus Clinical Feature #4: 'RACE'

'RNAseq cHierClus subtypes' versus 'ETHNICITY'

P value = 0.0819 (Fisher's exact test), Q value = 1

Table S24.  Clustering Approach #4: 'RNAseq cHierClus subtypes' versus Clinical Feature #5: 'ETHNICITY'

nPatients HISPANIC OR LATINO NOT HISPANIC OR LATINO
ALL 1 169
subtype1 0 15
subtype2 1 13
subtype3 0 15
subtype4 0 56
subtype5 0 26
subtype6 0 44

Figure S20.  Get High-res Image Clustering Approach #4: 'RNAseq cHierClus subtypes' versus Clinical Feature #5: 'ETHNICITY'

Clustering Approach #5: 'MIRSEQ CNMF'

Table S25.  Description of clustering approach #5: 'MIRSEQ CNMF'

Cluster Labels 1 2 3 4
Number of samples 60 38 43 47
'MIRSEQ CNMF' versus 'Time to Death'

P value = 0.0943 (logrank test), Q value = 1

Table S26.  Clustering Approach #5: 'MIRSEQ CNMF' versus Clinical Feature #1: 'Time to Death'

nPatients nDeath Duration Range (Median), Month
ALL 164 102 0.9 - 94.1 (12.0)
subtype1 53 38 1.0 - 69.0 (9.0)
subtype2 34 18 0.9 - 62.0 (14.5)
subtype3 35 23 1.0 - 94.1 (12.0)
subtype4 42 23 0.9 - 73.0 (15.5)

Figure S21.  Get High-res Image Clustering Approach #5: 'MIRSEQ CNMF' versus Clinical Feature #1: 'Time to Death'

'MIRSEQ CNMF' versus 'AGE'

P value = 0.0105 (Kruskal-Wallis (anova)), Q value = 0.26

Table S27.  Clustering Approach #5: 'MIRSEQ CNMF' versus Clinical Feature #2: 'AGE'

nPatients Mean (Std.Dev)
ALL 188 54.9 (16.2)
subtype1 60 57.4 (14.3)
subtype2 38 56.6 (14.9)
subtype3 43 57.4 (18.0)
subtype4 47 48.0 (16.2)

Figure S22.  Get High-res Image Clustering Approach #5: 'MIRSEQ CNMF' versus Clinical Feature #2: 'AGE'

'MIRSEQ CNMF' versus 'GENDER'

P value = 0.923 (Fisher's exact test), Q value = 1

Table S28.  Clustering Approach #5: 'MIRSEQ CNMF' versus Clinical Feature #3: 'GENDER'

nPatients FEMALE MALE
ALL 87 101
subtype1 26 34
subtype2 17 21
subtype3 21 22
subtype4 23 24

Figure S23.  Get High-res Image Clustering Approach #5: 'MIRSEQ CNMF' versus Clinical Feature #3: 'GENDER'

'MIRSEQ CNMF' versus 'RACE'

P value = 0.858 (Fisher's exact test), Q value = 1

Table S29.  Clustering Approach #5: 'MIRSEQ CNMF' versus Clinical Feature #4: 'RACE'

nPatients ASIAN BLACK OR AFRICAN AMERICAN WHITE
ALL 2 13 171
subtype1 1 4 55
subtype2 0 2 36
subtype3 0 2 40
subtype4 1 5 40

Figure S24.  Get High-res Image Clustering Approach #5: 'MIRSEQ CNMF' versus Clinical Feature #4: 'RACE'

'MIRSEQ CNMF' versus 'ETHNICITY'

P value = 1 (Fisher's exact test), Q value = 1

Table S30.  Clustering Approach #5: 'MIRSEQ CNMF' versus Clinical Feature #5: 'ETHNICITY'

nPatients HISPANIC OR LATINO NOT HISPANIC OR LATINO
ALL 1 184
subtype1 1 59
subtype2 0 38
subtype3 0 41
subtype4 0 46

Figure S25.  Get High-res Image Clustering Approach #5: 'MIRSEQ CNMF' versus Clinical Feature #5: 'ETHNICITY'

Clustering Approach #6: 'MIRSEQ CHIERARCHICAL'

Table S31.  Description of clustering approach #6: 'MIRSEQ CHIERARCHICAL'

Cluster Labels 1 2 3
Number of samples 70 35 83
'MIRSEQ CHIERARCHICAL' versus 'Time to Death'

P value = 0.194 (logrank test), Q value = 1

Table S32.  Clustering Approach #6: 'MIRSEQ CHIERARCHICAL' versus Clinical Feature #1: 'Time to Death'

nPatients nDeath Duration Range (Median), Month
ALL 164 102 0.9 - 94.1 (12.0)
subtype1 62 42 1.0 - 69.0 (9.5)
subtype2 30 16 0.9 - 62.0 (18.0)
subtype3 72 44 0.9 - 94.1 (13.5)

Figure S26.  Get High-res Image Clustering Approach #6: 'MIRSEQ CHIERARCHICAL' versus Clinical Feature #1: 'Time to Death'

'MIRSEQ CHIERARCHICAL' versus 'AGE'

P value = 0.457 (Kruskal-Wallis (anova)), Q value = 1

Table S33.  Clustering Approach #6: 'MIRSEQ CHIERARCHICAL' versus Clinical Feature #2: 'AGE'

nPatients Mean (Std.Dev)
ALL 188 54.9 (16.2)
subtype1 70 55.8 (14.8)
subtype2 35 57.3 (15.2)
subtype3 83 53.1 (17.6)

Figure S27.  Get High-res Image Clustering Approach #6: 'MIRSEQ CHIERARCHICAL' versus Clinical Feature #2: 'AGE'

'MIRSEQ CHIERARCHICAL' versus 'GENDER'

P value = 0.391 (Fisher's exact test), Q value = 1

Table S34.  Clustering Approach #6: 'MIRSEQ CHIERARCHICAL' versus Clinical Feature #3: 'GENDER'

nPatients FEMALE MALE
ALL 87 101
subtype1 36 34
subtype2 13 22
subtype3 38 45

Figure S28.  Get High-res Image Clustering Approach #6: 'MIRSEQ CHIERARCHICAL' versus Clinical Feature #3: 'GENDER'

'MIRSEQ CHIERARCHICAL' versus 'RACE'

P value = 0.956 (Fisher's exact test), Q value = 1

Table S35.  Clustering Approach #6: 'MIRSEQ CHIERARCHICAL' versus Clinical Feature #4: 'RACE'

nPatients ASIAN BLACK OR AFRICAN AMERICAN WHITE
ALL 2 13 171
subtype1 1 6 63
subtype2 0 2 33
subtype3 1 5 75

Figure S29.  Get High-res Image Clustering Approach #6: 'MIRSEQ CHIERARCHICAL' versus Clinical Feature #4: 'RACE'

'MIRSEQ CHIERARCHICAL' versus 'ETHNICITY'

P value = 1 (Fisher's exact test), Q value = 1

Table S36.  Clustering Approach #6: 'MIRSEQ CHIERARCHICAL' versus Clinical Feature #5: 'ETHNICITY'

nPatients HISPANIC OR LATINO NOT HISPANIC OR LATINO
ALL 1 184
subtype1 0 70
subtype2 0 35
subtype3 1 79

Figure S30.  Get High-res Image Clustering Approach #6: 'MIRSEQ CHIERARCHICAL' versus Clinical Feature #5: 'ETHNICITY'

Methods & Data
Input
  • Cluster data file = LAML-TB.mergedcluster.txt

  • Clinical data file = LAML-TB.merged_data.txt

  • Number of patients = 200

  • Number of clustering approaches = 6

  • Number of selected clinical features = 5

  • Exclude small clusters that include fewer than K patients, K = 3

Clustering approaches
CNMF clustering

consensus non-negative matrix factorization clustering approach (Brunet et al. 2004)

Consensus hierarchical clustering

Resampling-based clustering method (Monti et al. 2003)

Survival analysis

For survival clinical features, the Kaplan-Meier survival curves of tumors with and without gene mutations were plotted and the statistical significance P values were estimated by logrank test (Bland and Altman 2004) using the 'survdiff' function in R

Fisher's exact test

For binary clinical features, two-tailed Fisher's exact tests (Fisher 1922) were used to estimate the P values using the 'fisher.test' function in R

Q value calculation

For multiple hypothesis correction, Q value is the False Discovery Rate (FDR) analogue of the P value (Benjamini and Hochberg 1995), defined as the minimum FDR at which the test may be called significant. We used the 'Benjamini and Hochberg' method of 'p.adjust' function in R to convert P values into Q values.

Download Results

In addition to the links below, the full results of the analysis summarized in this report can also be downloaded programmatically using firehose_get, or interactively from either the Broad GDAC website or TCGA Data Coordination Center Portal.

References
[1] Brunet et al., Metagenes and molecular pattern discovery using matrix factorization, PNAS 101(12):4164-9 (2004)
[3] Bland and Altman, Statistics notes: The logrank test, BMJ 328(7447):1073 (2004)
[4] Fisher, R.A., On the interpretation of chi-square from contingency tables, and the calculation of P, Journal of the Royal Statistical Society 85(1):87-94 (1922)
[5] Benjamini and Hochberg, Controlling the false discovery rate: a practical and powerful approach to multiple testing, Journal of the Royal Statistical Society Series B 59:289-300 (1995)