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Table 2 Trial characteristics, comparison between the two study periods and publication status.

From: Publication proportions for registered breast cancer trials: before and following the introduction of the ClinicalTrials.gov results database

Trial characteristics Frequencyc Completion/terminationc p valuea Publication Statusd p valuea
  Before 1 Oct 2008 On/after 1 Oct 2008 Published Not Published
Type Interventional 297 (87 %) 158 (93 %) 139 (82 %) .002 159 (54 %) 138 (47 %) <.0001
  Observational 43(13 %) 12 (7 %) 31 (18 %)   9 (21 %) 34 (79 %)  
Phase I 47 (14 %) 28 (21 %) 19 (17 %) .917b 21 (45 %) 26 (55 %) .161b
  I/II or II 145 (43 %) 80 (59 %) 65 (60 %)   85 (59 %) 60 (41 %)  
  II/III or III 45 (13 %) 24 (18 %) 21 (19 %)   29 (64 %) 16 (36 %)  
  IV 8 (2 %) 4 (3 %) 4 (4 %)   6 (75 %) 2 (25 %)  
  Not applicable (observational studies) 43 (13 %)       
  Unknown (missing values) 52 (15 %)       
Randomization status Randomized 107 (32 %) 60 (39 %) 47 (34 %) .409 63 (59 %) 44 (41 %) .229
Non-randomized 186 (55 %) 95 (61 %) 91 (66 %)   96 (52 %) 90 (48 %)  
  Not applicable (observational studies) 43 (13 %)       
  Unknown (missing values) 4 (1 %)       
Control status Placebo only 29 (9 %) 16 (10 %) 13 (10 %) .136b 15 (52 %) 14 (48 %) .519b
  Active-control only 74 (22 %) 34 (22 %) 40 (29 %)   41 (55 %) 33 (45 %)  
  Both placebo and active-control 17 (5 %) 13 (8 %) 4 (3 %)   12 (71 %) 5 (29 %)  
  No control 172 (51 %) 92 (59 %) 80 (58 %)   90 (52 %) 82 (48 %)  
  Not applicable (observational studies) 43 (13 %)       
  Unknown (missing values) 5 (2 %)       
Blinding Open-label 255 (75 %) 128 (82 %) 127 (93 %) .006b 134 (53 %) 121 (48 %) .286b
  Single-blind 9 (3 %) 5 (3 %) 4 (3 %)   4 (44 %) 5 (56 %)  
  Double (or Triple) blind 30 (9 %) 24 (15 %) 6 (4 %)   20 (67 %) 10 (33 %)  
  Not applicable (observational studies) 43 (13 %)       
  Unknown (missing values) 3 (1 %)       
Interventional model Parallel 107 (32 %) 54 (35 %) 53 (39 %) .432b 60 (56 %) 47 (44 %) .184b
Crossover 9 (3 %) 7 (5 %) 2 (2 %)   4 (44 %) 5 (56 %)  
Factorial 4 (1 %) 2 (1 %) 2 (2 %)   4 (100 %) 0 (0 %)  
Single-group assignment 172 (51 %) 92 (59 %) 80 (58 %)   90 (52 %) 82 (48 %)  
Not applicable (observational studies) 43 (13 %)       
Unknown (missing values) 5 (2 %)       
Endpoint classification Safety only 28 (8 %) 15 (10 %) 13 (10 %) .336b 12 (43 %) 16 (57 %) .069b
Efficacy only 103 (30 %) 49 (32 %) 54 (40 %)   49 (48 %) 54 (52 %)  
  Both Safety and Efficacy 160 (47 %) 91 (59 %) 69 (51 %)   96 (60 %) 64 (40 %)  
  Not applicable (observational studies) 43 (13 %)       
  Unknown (missing values) 6 (2 %)       
Age Included adults (≥18 years, >65 years) 51 (15 %) 28 (18 %) 23 (15 %) .697b 29 (57 %) 22 (43 %) .716b
  Included adults and older adults (≥65 years) 237 (70 %) 121 (76 %) 116 (75 %)   117 (49 %) 120 (51 %)  
  Included adults and children (<18 years) 5 (2 %) 2 (1 %) 3 (2 %)   2 (40 %) 3 (60 %)  
  Included older adults (≥65 years) only 20 (6 %) 8 (5 %) 12 (8 %)   9 (45 %) 11 (55 %)  
  Included children (<18 years) only 0 (0 %) 0 (0 %) 0 (0 %)   0 (0 %) 0 (0 %)  
  Unknown (missing values) 27 (8 %)       
Gender Male only 1 (0 %) 0 (0 %) 1 (1 %) .136b 0 (0 %) 1 (100 %) .132b
  Female only 225 (66 %) 106 (62 %) 119 (70 %)   105 (47 %) 120 (53 %)  
  Both male and female 114 (34 %) 64 (38 %) 50 (29 %)   63 (55 %) 51 (45 %)  
Number of Centres Single 50 (15 %) 18 (17 %) 32 (29 %) .035 34 (68 %) 16 (32 %) 1.000
Multiple 164 (48 %) 87 (83 %) 77 (71 %)   112 (68 %) 52 (32 %)  
Unknown (missing values) 126 (37 %)       
Number of Countries Single 301 (89 %) 148 (88 %) 153 (91 %) .469 143 (48 %) 158 (53 %) .013
Multiple 36 (11 %) 20 (12 %) 16 (10 %)   25 (69 %) 11 (31 %)  
Unknown (missing values) 3 (1 %)       
Country US/Canada only 209 (62 %) 105 (63 %) 104 (62 %) .855b 100 (48 %) 109 (52 %) .013b
  International (outside USA/Canada) only 102 (30 %) 49 (29 %) 53 (31 %)   48 (47 %) 54 (53 %)  
  USA/Canada and International 26 (8 %) 14 (8 %) 12 (7 %)   20 (77 %) 6 (23 %)  
  Unknown (missing values) 3 (1 %)       
Primary sponsor Industry 91 (27 %) 45 (27 %) 46 (27 %) .609 45 (50 %) 46 (51 %) .545b
Government (US and non-US) 42 (12 %) 24 (14 %) 18 (11 %)   24 (57 %) 18 (43 %)  
Non-industry/non-government 207 (61 %) 101 (59 %) 106 (62 %)   99 (48 %) 108 (52 %)  
Registered before initiation Yes 59 (17 %) 22 (14 %) 37 (27 %) .005 35 (59 %) 24 (41 %) .171
No 241 (71 %) 139 (86 %) 102 (73 %)   119 (49 %) 122 (51 %)  
Unknown (missing dates) 40 (12 %)       
Registered within 21 days of initiation Yes 93 (27 %) 30 (19 %) 63 (30 %) .000 47 (51 %) 46 (50 %) .980
No 217 (64 %) 127 (81 %) 90 (59 %)   110 (51 %) 107 (49 %)  
Unknown (missing dates) 30 (9 %)       
Completed/terminated Completed 288 (85 %) 148 (87 %) 140 (82 %) .228 155 (54 %) 133 (46 %) <.0001
Terminated 52 (15 %) 22 (13 %) 30 (18 %)   13 (25 %) 39 (75 %)  
Registered before completion/termination? Yes 283 (84 %) 131 (78 %) 152 (90 %) .002 135 (48 %) 148 (52 %) .155
No 55 (16 %) 38 (23 %) 17 (10 %)   32 (58 %) 23 (42 %)  
Unknown (missing dates) 2 (1 %)       
Results posted in ClinicalTrials.gov? Yes 59 (17 %) 20 (12 %) 39 (23 %) .007 31 (53 %) 28 (48 %) .597
No 281 (83 %) 150 (88 %) 131 (77 %)   137 (49 %) 144 (51 %)  
Publication link available Yes 77 (23 %) 41 (24 %) 36 (21 %) .517 77 (100 %) 0 (0 %) <.0001
No 263 (77 %) 129 (76 %) 134 (79 %)   91 (35 %) 172 (51 %)  
  1. aPearson chi-square p values used unless otherwise. For cells with expected cell count less than 5, exact p values (Fisher’s exact test or Monte Carlo significance) were used
  2. bLikelihood ratio p value
  3. cPercentages by column for frequencies and study period comparisons (some percentages may not add up to 100 % due to rounding)
  4. dPercentages by row for publication comparisons