Intensive follow-up vs conventional follow-up for patients with non-metastatic colorectal cancer treated with curative intent: A meta-analysis

Table 3 Subgroup analyses for investigated outcomes

Outcomes	Factors	Subgroups	No. of studies	HR or RR and 95%CI	P value	I2(%)	P value for I2	Interaction P value	RHR or RRR with 95%CI
Overall survival	Sample size	≥ 500	4	0.96 (0.84-1.10)	0.579	0.0	0.581	0.135	1.19 (0.95-1.48)
		< 500	12	0.81 (0.68-0.97)	0.019	0.0	0.693
	Mean age (yr)	≥ 65.0	9	0.94 (0.78-1.14)	0.538	0.0	0.563	0.584	1.07 (0.84-1.35)
		< 65.0	6	0.88 (0.77-1.02)	0.082	7.7	0.367
	Male (%)	≥ 60.0	5	0.97 (0.81-1.16)	0.758	0.0	0.503	0.339	1.11 (0.89-1.39)
		< 60.0	11	0.87 (0.76-0.99)	0.035	0.0	0.620
	Tumor location (C/R)	≥ 70.0	8	0.93 (0.78-1.11)	0.429	0.0	0.742	0.584	1.07 (0.84-1.36)
		< 70.0	7	0.87 (0.74-1.02)	0.082	16.9	0.301
	Follow-up (yr)	≥ 5.0	8	0.84 (0.72-0.97)	0.017	0.0	0.635	0.163	0.86 (0.69-1.06)
		< 5.0	8	0.98 (0.84-1.15)	0.837	0.0	0.658
Cancer-specific survival	Sample size	≥ 500	4	0.99 (0.83-1.17)	0.866	0.0	0.804	0.837	1.04 (0.70-1.54)
		< 500	6	0.95 (0.67-1.36)	0.782	49.4	0.079
	Mean age (yr)	≥ 65.0	5	1.12 (0.80-1.57)	0.515	29.3	0.226	0.281	1.23 (0.84-1.79)
		< 65.0	5	0.91 (0.77-1.08)	0.276	0.0	0.510
	Male (%)	≥ 60.0	3	1.05 (0.77-1.43)	0.750	0.0	0.603	0.645	1.09 (0.75-1.60)
		< 60.0	7	0.96 (0.77-1.20)	0.732	37.6	0.142
	Tumor location (C/R)	≥ 70.0	4	1.23 (0.84-1.81)	0.281	23.9	0.268	0.155	1.35 (0.89-2.05)
		< 70.0	6	0.91 (0.78-1.07)	0.254	0.0	0.560
	Follow-up (yr)	≥ 5.0	5	0.89 (0.72-1.10)	0.288	0.0	0.464	0.245	0.82 (0.58-1.15)
		< 5.0	5	1.09 (0.83-1.42)	0.552	35.9	0.182
Relapse-free survival	Sample size	≥ 500	4	1.18 (1.02-1.36)	0.025	18.8	0.296	0.063	1.24 (0.99-1.56)
		< 500	11	0.95 (0.80-1.14)	0.589	0.0	0.583
	Mean age (yr)	≥ 65.0	9	1.10 (0.89-1.36)	0.388	23.5	0.234	0.885	1.02 (0.79-1.31)
		< 65.0	6	1.08 (0.95-1.23)	0.220	3.6	0.394
	Male (%)	≥ 60.0	4	1.14 (0.87-1.50)	0.340	51.1	0.105	0.633	1.08 (0.80-1.45)
		< 60.0	11	1.06 (0.94-1.20)	0.364	0.0	0.569
	Tumor location (C/R)	≥ 70.0	6	1.15 (0.94-1.40)	0.171	9.5	0.355	0.778	1.04 (0.81-1.32)
		< 70.0	7	1.11 (0.96-1.28)	0.159	6.2	0.380
	Follow-up (yr)	≥ 5.0	8	1.01 (0.86-1.18)	0.917	0.0	0.597	0.265	0.87 (0.68-1.11)
		< 5.0	7	1.16 (0.96-1.39)	0.120	27.9	0.215
Salvage surgery	Sample size	≥ 500	3	2.12 (1.05-4.29)	0.036	71.7	0.029	0.990	1.00 (0.48-2.11)
		< 500	11	2.11 (1.67-2.66)	< 0.001	0.0	0.567
	Mean age (yr)	≥ 65.0	8	1.95 (1.42-2.69)	< 0.001	0.0	0.910	0.675	0.89 (0.50-1.56)
		< 65.0	6	2.20 (1.38-3.50)	0.001	65.8	0.012
	Male (%)	≥ 60.0	4	1.64 (1.06-2.53)	0.026	38.1	0.183	0.256	0.75 (0.45-1.23)
		< 60.0	9	2.19 (1.72-2.80)	< 0.001	0.0	0.726
	Tumor location (C/R)	≥ 70.0	6	1.44 (1.08-1.91)	0.013	0.0	0.759	0.022	0.54 (0.31-0.92)
		< 70.0	6	2.69 (1.71-4.24)	< 0.001	24.0	0.254
	Follow-up (yr)	≥ 5.0	7	1.69 (1.15-2.48)	0.007	28.2	0.213	0.189	0.73 (0.46-1.16)
		< 5.0	7	2.30 (1.79-2.97)	< 0.001	0.0	0.591
Recurrence	Sample size	≥ 500	4	1.38 (1.00-1.89)	0.048	82.1	0.001	0.075	1.37 (0.97-1.93)
		< 500	11	1.01 (0.89-1.15)	0.891	0.0	0.585
	Mean age (yr)	≥ 65.0	8	1.23 (0.87-1.73)	0.238	75.4	< 0.001	0.645	1.09 (0.76-1.56)
		< 65.0	6	1.13 (1.01-1.26)	0.027	0.0	0.808
	Male (%)	≥ 60.0	3	1.54 (0.71-3.30)	0.273	89.7	< 0.001	0.357	1.44 (0.66-3.12)
		< 60.0	11	1.07 (0.97-1.18)	0.185	0.0	0.618
	Tumor location (C/R)	≥ 70.0	6	1.13 (0.96-1.32)	0.130	0.0	0.461	0.583	0.92 (0.68-1.24)
		< 70.0	8	1.23 (0.95-1.59)	0.116	64.3	0.006
	Follow-up (yr)	≥ 5.0	8	1.09 (0.95-1.25)	0.223	0.0	0.715	0.317	0.85 (0.62-1.17)
		< 5.0	7	1.28 (0.97-1.71)	0.085	76.3	< 0.001
Interval recurrence	Sample size	≥ 500	3	0.74 (0.45-1.20)	0.221	74.8	0.019	0.060	1.76 (0.98-3.18)
		< 500	4	0.42 (0.30-0.58)	< 0.001	0.0	0.557
	Mean age (yr)	≥ 65.0	3	0.45 (0.34-0.60)	< 0.001	0.0	0.423	0.173	0.65 (0.35-1.21)
		< 65.0	4	0.69 (0.40-1.19)	0.182	62.0	0.048
	Male (%)	≥ 60.0	2	0.77 (0.32-1.85)	0.558	86.9	0.006	0.424	1.48 (0.57-3.87)
		< 60.0	4	0.52 (0.35-0.77)	0.001	47.6	0.126
	Tumor location (C/R)	≥ 70.0	2	1.12 (0.75-1.67)	0.586	0.0	0.435	0.007	1.96 (1.21-3.20)
		< 70.0	4	0.57 (0.43-0.75)	< 0.001	0.0	0.412
	Follow-up (yr)	≥ 5.0	4	0.76 (0.47-1.23)	0.265	57.1	0.072	0.044	1.77 (1.02-3.07)
		< 5.0	3	0.43 (0.33-0.57)	< 0.001	0.0	0.795

CI: Confidence interval; HR: Hazard ratio; RR: Risk ratio; RHR: Ratio of hazard ratio; RRR: Ratio of risk ratio; C/R: Colon/rectal ratio.