Table 1.
Characteristics of the 225 randomly assigned subjects according to treatment group*
| Characteristic | Placebo (n = 74) | 13-cis-RA + AT (n = 77) | 9-cis-RA (n = 74) | P value† |
|---|---|---|---|---|
| Sex, No. (%) | .65 | |||
| Male | 45 (60.8) | 42 (54.6) | 40 (54.1) | |
| Female | 29 (39.2) | 35 (45.5 | 34 (45.9) | |
| Race, No. (%) | .82 | |||
| White | 65 (87.8) | 67 (87.0) | 69 (93.2) | |
| African American | 6 (8.1) | 6 (7.8) | 4 (5.4) | |
| Hispanic | 3 (4.1) | 3 (3.9) | 1 (1.4) | |
| Asian | 0 (0.0) | 1 (1.3) | 0 (0.0) | |
| Smoking-related cancer‡, No. (%) | .40 | |||
| No | 64 (86.5) | 69 (89.6) | 69 (93.2) | |
| Yes | 10 (13.5) | 8 (10.4) | 5 (6.8) | |
| Age, y | .24 | |||
| Mean ± SD | 58.4 ± 9.1 | 56.8 ± 10.0 | 56.0 ± 10.0 | |
| Median (range) | 58.9 (34.9–75.6) | 56.5 (34.0–78.2) | 55.1 (35.9–78.1) | |
| No. of years of smoking | .07 | |||
| Mean ± SD | 30.2 ± 9.9 | 26.6 ± 8.4 | 26.7 ± 9.4 | |
| Median (range) | 30 (15–50) | 25 (11–49) | 25 (10–50) | |
| No. of packs smoked per day | .56 | |||
| Mean ± SD | 1.8 ± 0.7 | 1.8 ± 0.8 | 1.9 ± 0.8 | |
| Median (range) | 1.8 (1–4) | 1.5 (0.8–4) | 2 (0.8–4) | |
| No. of pack-years | .28 | |||
| Mean ± SD | 53.9 ± 31.1 | 46.1 ± 23.7 | 50.1 ± 28.8 | |
| Median (range) | 44 (20–152) | 39 (20–136) | 40 (20–136) | |
| No. of smoking quit-years§ | .79 | |||
| Mean ± SD | 10.2 ± 8.1 | 10.9 ± 9.4 | 11.2 ± 8.9 | |
| Median (range) | 9.7 (1.0–35.2) | 8.2 (1.0–46.0) | 8.4 (1.0–48.1) |
RA = retinoic acid; AT = α-tocopherol; SD = standard deviation.
The Kruskal–Wallis test was performed to test the equal median of continuous variables among the three treatment groups. The chi-square test (for sex and smoking-related cancer) or Fisher’s exact test (for race) was performed to test the association between two categorical variables. All statistical tests were two-sided.
All smoking-related cancers were lung cancers, except for two head-and-neck cancers and one bladder cancer in the 13-cis-RA and AT group and one head-and-neck cancer in the 9-cis-RA group.
No. of smoking quit-years was calculated from data from 218 participants whose smoking status was confirmed by serum cotinine level. Seven participants (three in the placebo group, one in the 13-cis-RA group, and three in the 9-cis-RA group) with serum cotinine levels of more than 20 ng/mL at baseline were considered to be active smokers and so were excluded from this calculation.