Table 3. Subgroup Analysis of Studies Examining the Association Between Chemotherapy Duration and Overall Survival Among Patients With Stage II and III Colon Cancer.

Variable	Estimates, No.a	Hazard Ratio (95% CI)	95% Prediction Interval	I2 Statistic, %	P Value of Ratio
Treatment Variables
Chemotherapy regimen
Included patients treated with combination therapy	11	0.62 (0.45-0.85)	0.28-1.36	64.0	.53
Patients treated with monotherapy only	12	0.55 (0.46-0.66)	0.31-0.97	80.2
Middle period of diagnosis
2001 Onward	15	0.53 (0.40-0.70)	0.23-1.20	70.7	.21
Before 2001	8	0.64 (0.56-0.72)	0.48-0.84	55.3
Patient Characteristics
Age, median, y
≥65	11	0.57 (0.49-0.67)	0.42-0.88	29.0	.15
<65	8	0.69 (0.57-0.83)	0.48-0.99	47.9
% Female
≥50	4	0.62 (0.54-0.71)	0.54-0.71	0	.82
<50	14	0.63 (0.53-0.76)	0.39-1.02	59.1
Tumor Characteristics
% Colon cancer
100	15	0.53 (0.44-0.65)	0.30-0.95	71.3	.10
<100	8	0.67 (0.55-0.80)	0.45-0.99	58.3
% Stage III
100	10	0.68 (0.58-0.79)	0.49-0.94	44.9	.01
<100	12	0.46 (0.36-0.59)	0.24-0.89	75.2
Study Characteristics
Countryb
Asian	8	0.50 (0.36-0.70)	0.23-1.12	87.8	.27
Non-Asian	15	0.62 (0.53-0.72)	0.42-0.91	48.5
Median follow-up, y
≥5	8	0.72 (0.61-0.84)	0.55-0.94	27.7	.14
<5	7	0.58 (0.46-0.73)	0.36-0.92	50.5
ROBINS-I overall risk of biasc
Moderate	10	0.55 (0.43-0.72)	0.26-1.15	85.5	.66
Serious	12	0.59 (0.49-0.71)	0.40-0.87	42.1

Abbreviation: ROBINS-I, Risk of Bias in Nonrandomized Studies of Interventions.

^aThere were a total of 23 estimates from 19 studies. Some estimates do not sum to 23 because some studies did not report the patient characteristic of interest and, as a result, were excluded from the analysis (see Table 1).

^bAsian countries include Japan, Malaysia, South Korea, and Taiwan. Non-Asian countries include Australia, Canada, France, Germany, Greece, Israel, the Netherlands, and the United States.

^cConducted within observational studies only (excluded 1 randomized trial examining disease-free survival).