1. Clinicopathological data
Table 1 shows a comparison of the general clinicopathological data of the PC group (268 patients) and the NPC group (1295 patients). Compared with the NPC group, the PC group had older patients, a longer operation time and more blood loss during the operation (p<0.05). However, there was no significant difference in pathological staging between the two groups (p>0.05).
Table 1. Clinicopathological characteristics of postoperative complications(PC) group and non- complications(NPC) group. Note: ASA: American Society of Anesthesiologists
Variables
|
PC group
(n=268)
|
NPC group
(n=1295)
|
P values
|
Gender n (%)
|
|
|
.188
|
Male
|
210(78.4%)
|
962(74.3%)
|
|
Female
|
58(21.6%)
|
333(25.7%)
|
|
Age(mean±SD, years)
|
63.14±9.79
|
60.25±10.72
|
.000
|
ASA
|
|
|
.077
|
<3
|
253(94.4%)
|
1252(96.7%)
|
|
≥3
|
15(5.6%)
|
43(3.3%)
|
|
Tumor diameter
|
|
|
.139
|
<50
|
113(42.2%)
|
611(47.2%)
|
|
≥50
|
155(57.8%)
|
684(52.8%)
|
|
Tumor location
|
|
|
.951
|
Upper
|
71(26.5%)
|
333(25.7%)
|
|
Middle
|
58(21.6%)
|
279(21.5%)
|
|
Lower
|
99(36.9%)
|
501 (38.7%)
|
|
Mix
|
40(14.9%)
|
182(14.1%)
|
|
BMI(mean±SD,kg/m2)
|
22.57±3.15
|
22.17±5.63
|
.272
|
Blood lost median(rang) ML
|
135.76±266.35
|
84.89±120.27
|
.000
|
Surgical time median(rang) min
|
201.76±68.49
|
186.39±57.41
|
.000
|
Type of surgery
|
|
|
.090
|
Total
|
169(63.1%)
|
767((59.2%)
|
|
Distal
|
94(35.1%)
|
518(40.0%)
|
|
Proximal
|
5(1.9%)
|
10(0.8%)
|
|
Vessel/ Lymphatic infiltration
|
|
|
.241
|
Present
|
103(38.4%)
|
449(34.7%)
|
|
Absent
|
165(61.6%)
|
846(65.3%)
|
|
Nerve infiltration
|
|
|
.020
|
Present
|
98(36.6%)
|
378(29.2%)
|
|
Absent
|
170(63.4%)
|
917(70.8%)
|
|
pT stage
|
|
|
.164
|
1
|
1(0.4%)
|
32(2.5%)
|
|
2
|
21(7.8%)
|
113(8.7%)
|
|
3
|
123(45.9%)
|
585(45.2%)
|
|
4
|
123(45.9%)
|
565(43.6%)
|
|
pN stage
|
|
|
.925
|
N0
|
41(15.3%)
|
195(15.1%)
|
|
N1
|
227(84.7%)
|
1100(84.9%)
|
|
pTNM stage
|
|
|
.669
|
Ⅱ
|
85(31.7%)
|
431(35.1%)
|
|
Ⅲ
|
183(68.3%)
|
864(66.7%)
|
|
Adjuvant chemotherapy
|
|
|
.022
|
Yes
|
196(73.1%)
|
1031(79.6%)
|
|
No
|
72(21.4%)
|
264(20.4%)
|
|
Type of adjuvant chemotherapy
|
|
|
0.073
|
Platinum
|
110(56.1%)
|
497(48.2%)
|
|
Capecitabine
|
48(24.5%)
|
334(32.4%)
|
|
Paclitaxel
|
13(6.6%)
|
49(4.8%)
|
|
Others
|
25(12.8%)
|
151(14.6%)
|
|
2. Surgical morbidity and mortality
The details of the complications in all patients are shown in eTable.1 (Supplement material eTable.1). Pulmonary infection was the most frequent morbidity (89 cases, 6.78%), followed by Intra-abdominal infection (60 cases, 3.83%) and anastomotic leakage (34 cases, 2.17%). Wound complications are the rarest (16 cases, 1.08%). Complications of grade II were found in 206 cases (13.18%), grade III in 34 cases (2.18%) , while those of grade IV or V occurred in 28 cases (1.8%). Surgical mortality was never observed.
3. Survival analysis
As shown in Fig. 2, the 5-year OS rate of the PC group was significantly lower than that of the NPC group (55.2% vs 63.3%, p=0.016); the 5-year RFS rate of the PC group was lower than that of the NPC group, but the difference was not statistically significant (53.7% vs 58.8%, p=0.14). A univariate analysis of the entire population, PC group and NPC group showed that age, tumor size, tumor location, vascular lymphatic infiltration, nerve infiltration, and adjuvant chemotherapy were closely related to OS and RFS at 5 years after surgery (all p <0.05, Supplement material eTable 5, eTable 7). Multivariate analysis showed that age, tumor size, tumor location, vascular lymphatic invasion, nerve invasion, and postoperative adjuvant chemotherapy were independent prognostic factors for 5-year OS and RFS in the entire population and NPC group (all p<0.05), and tumor size [OS: HR=2.062 (1.362-3.122), p <0.000; RFS: HR=1.968 (1.319-2.936), p <0.000], nerve infiltration [OS: HR=2.236 (1.575-3.176), p <0.000; RFS: HR=1.193 (1.312-2.791), p=0.001] and adjuvant chemotherapy [OS: HR=0.498 (0.316-0.783), p=0.003; RFS: HR=0.485 (0320-0.737), p =0.001] were identified as independent prognostic factors of OS and RFS in patients with PCs at 5 years after the operation (Supplement material eTable 6, eTable 8).
4. Recurrence patterns
Fig. 1A shows that there were 124 (46.3%) and 533 (41.2%)recurrences in the PC group and NPC group, respectively. In the PC group, 11 patients had local recurrence (4.1%), 40 had peritoneal metastasis (13.8%), and 87 had distant metastasis (32.5%); in the NPC group, 70 patients (5.4%) had local recurrence, 160 (12.4%) had peritoneal metastasis, and 380 (29.3%) had distant metastasis; The median times to recurrence in the two groups were 17.6 months and 15.8 months. in the PC group, the median time to local recurrence was 55 months, that to peritoneal metastasis was 24 months, and that to distant metastasis was 14.7 months; in the NPC group, the median time to local recurrence was 50 months, that to peritoneal metastasis was 17.7 months, and that to distant metastasis was 16.6 months; There was no significant difference in the location of recurrence or time to recurrence between the two groups (p>0.05) (Supplement material eTable 2). According to the stratified analysis, there was no significant difference in the location of recurrence or time to recurrence between stage II and stage III patients (p>0.05) (Fig. 1B, Fig. 1C; Supplement material eTable 3, eTable 4).
5. The effect of adjuvant chemotherapy (AC)
According to whether adjuvant chemotherapy (AC) was received, a stratified analysis of the PC group and NPC group showed that AC significantly improved the 5-year OS and RFS rates of patients with and without PCs (both p<0.05). In addition, the 5-year OS and RFS rates of patients in the PC group who received AC were significantly higher than those of patients without adjuvant chemotherapy(NAC) group (both p<0.05), and there was no significant difference in the 5-year OS and RFS rates between the PC group and NPC group when they were given AC. (both p >0.05) (Fig. 3A, Fig. 3B).
Further stratified analysis based on pathological staging showed that in stage II patients with PCs (Fig. 3C, Fig. 3D), AC did not significantly improve 5-year OS or RFS (both p>0.05). In stage III patients (Fig. 3E, Fig. 3F), the 5-year OS and RFS rates of the PC group who received AC were significantly higher than NAC group (both p<0.05).
6. The effect of the time interval (TI) from radical operation to initiation of adjuvant chemotherapy
eFig. 2A(Supplement material eFig. 2A) shows the distribution of the TI. The median TI of patients with PCs was 36 days. The 5-year OS and RFS rates of patients in the TI≥6weeks group and TI< 6 weeks group were significantly better than those of patients in the NAC group (both p<0.05) (Fig. 3G, Fig. 3H).
The stratified analysis of pathological stage showed that the median TI of stage II and stage III patients with PCs were 35 days and 36 days, respectively (Supplement material eFig. 2B, eFig. 2C). Among the stage II patients, only the 5-year OS (p=0.038) and RFS (p=0.005) rates of patients with PCs in the TI<6 weeks group were significantly higher than NAC group, while a TI≥6 weeks did not significantly improve the 5-year OS and RFS rates of stage II PC group (Fig. 3I, Fig. 3J). Among stage III patients, the 5-year OS and RFS rates of those with PCs in a TI≥6 weeks group and a TI<6 weeks group were significantly higher than NAC group (both p<0.05) (Fig. 3K, Fig. 3L).