Table 1. Characteristics of trials included in the final meta-analysis (n = 14).
| No. | Source (project name) | Journal | Country | Design (type of prevention) | Participants (average age, yr; Women, %) | Duration of supplemen-tation, yr (follow-up period, yr) | Intervention vs. control | No. of bladder cancer patients/No. of participants | |
|---|---|---|---|---|---|---|---|---|---|
| Intervention | Control | ||||||||
| 1 | 1977 Byar et al. | Urology | USA | OLRCT (Secondary) | 118 patients with stage Ⅰ bladder cancer (NA) | 2 (2.0) | 25 mg of pyridoxine (vitamin B6) vs. placebo per day | 15/32 | 29/48 |
| 2 | 1994 Lamm et al. | J Urol | USA | RDBPCT (Secondary) | 65 bladder cancer (67; 17) | 3.8 (3.8) | RDA plus | 14/35 | 24/30 |
| 40,000 IU of vitamin A + 100 mg of vitamin B6 + 2,000 mg of vitamin C + 400 IU of vitamin E + 90 mg of zinc vs. RDA multivitamin per day | |||||||||
| 3 | 1994 ATBC | N Engl J Med | Finland | RDBPCT (Primary) | 29,133 male smokers 50 to 69 years of age (57; 0) | 1.5 (1.5) | 50 mg of vitamin E + 20 mg of beta carotene vs. placebo per day | Vit E 79/14,560 | Vit E 76/14,573 |
| Beta carotene 81/14,564 | Beta carotene 74/14,569 | ||||||||
| 4 | 1996 CARET | J Natl Cancer Inst | USA | RDBPCT (Primary) | 18,314 men and women at high risk of developing lung cancer (58; 44) | 4 (4.0) | 30 mg of beta-carotene + 25,000 IU of vitamin A vs. placebo per day | 42/9,420 | 36/8,894 |
| 5 | 1999 WHS | J Natl Cancer Inst | USA | RDBPCT (Primary) | 39,876 healthy women (55; 100) | 2.1 (4.1) | 50 mg of beta-carotene vs. placebo on alternate day | 5/19,939 | 6/19,937 |
| 6 | 2000 Decensi et al. | Cancer Epidemiol Biomarkers Prev | Italy | RDBPCT (Secondary) | 99 subjects with resected superficial bladder cancer (63; 19) | 2 (3.0) | 200 mg of fenretinide (vitamin A) per day vs. no treatment | 22/49 | 29/50 |
| 7 | 2000 PHS | Cancer Causes Control | USA | RDBPCT (Primary) | 22,071 US male physicians (40–84; 0) | 13(13.0) | 50 mg of beta-carotene vs. placebo on alternate day | 62/11,036 | 41/11,035 |
| 8 | 2002 NPC | Cancer Epidemiol Biomarkers Prev | USA | RDBPCT (Primary) | 1,250 nonmelanoma skin cancer patients (63; 25) | 13 (13.0) | 200 µg of selenium vs. placebo per day | 10/621 | 8/629 |
| 9 | 2003 IHNCSG | Oncol Rep | Italy | OLRCT (Primary) | 214 patients with a radically treated stage Ⅰ–Ⅱ squamous head and neck tumor (61; 18) | 3 (5.0) | 75 mg of beta-carotene daily for 3-month cycles within 1-month intercycle intervals vs. no treatment | 1/104 | 0/110 |
| 10 | 2005 Bairati et al. | J Clin Oncol | Canada | RDBPCT (Primary) | 540 patients with stage Ⅰ or Ⅱ head and neck cancer (63; 21) | 3 (4.3) | 400 IU of α-tocopherol (vitamin E) + 30 mg of beta-carotene vs. placebo per day | 2/273 | 0/267 |
| 11 | 2008 Sabichi et al. | Clin Cancer Res | USA | RDBPCT (Secondary) | 137 patients with non-muscle-invasive bladder TCC (67; 18) | 1 (1.3) | 200 mg of fenretinide (vitamin A) vs. placebo per day | 22/70 | 22/67 |
| 12 | 2010 Nepple et al. | J Urol | USA | RDBPCT (Secondary) | 670 patients with nonmuscle invasive bladder cancer (68; 24) | 3.1 (4.0) | 36,000 IU of vitamin A + 25 mg of vitamin B6 + 2,000 mg of vitamin C + 1,600 IU of vitamin D + 400 IU of vitamin E + 1.6 mg of folate + 30.4 mg of zinc vs. RDA vitamin per day | 118/334 | 113/336 |
| 13 | 2012 SELECT | J Urol | USA, Canada, Puerto Rico | RDBPCT (Primary) | 34,888 men (62; 0) | 6 (7.1) | 200 µg of selenium + 400 IU of vitamin E vs. placebo per day | 171/26,192 | 53/8,696 |
| 14 | 2012 Mazdak et al. | Int J Prev Med | Iran | OLRCT (Secondary) | 46 patients with a single, low-grade, superficial bladder cancer (60; 11) | 2 (2.0) | 400 IU of vitamin E per day vs. no treatment | 4/21 | 9/25 |
NA = not applicable, ATBC = the Alpha-tocopherol Beta-carotene Cancer Prevention Study, CARET = the Beta-Carotene and Retinol Efficacy Trial, IHNCSG = the Italian Head and Neck Chemoprevention Study Group, NPC = Nutritional Prevention of Cancer, PHS = the Physicians' Health Study, RDA = recommended daily allowance, SELECT = Selenium and Vitamin E Cancer Prevention Trials, WHS = the Women's Health Study.