Clinicopathological characteristics and recurrence, according to ctDNA status
| Variable | Pretreatment ctDNA (n=159) | Postchemoradiotherapy ctDNA (n=144) | Postoperative ctDNA (n=159) | ||||||
| Positive (n=122) | Negative (n=37) | P | Positive (n=12) | Negative (n=132) | P | Positive (n=19) | Negative (n=140) | P | |
| Age, years | |||||||||
| Median | 63 | 59 | 0.69 | 61 | 62 | 0.97 | 59 | 63 | 0.97 |
| Range | 28–85 | 31–86 | 41–86 | 28–86 | 41–86 | 28–86 | |||
| Sex, n (%) | |||||||||
| Female | 40 (33) | 12 (32) | 1.00 | 4 (33) | 43 (33) | 1.00 | 6 (32) | 46 (33) | 1.00 |
| Male | 82 (67) | 25 (68) | 8 (67) | 89 (67) | 13 (68) | 94 (67) | |||
| Distance from anal verge (cm), n (%) | |||||||||
| 0–5 | 44 (36) | 13 (35) | 0.77 | 4 (33) | 48 (36) | 0.79 | 6 (32) | 51 (37) | 0.01 |
| > 5–10 | 55 (45) | 19 (51) | 5 (42) | 62 (47) | 5 (26) | 69 (49) | |||
| > 10 | 23 (19) | 5 (14) | 3 (25) | 22 (17) | 8 (42) | 20 (14) | |||
| Clinical disease stage, n (%) | |||||||||
| Stage II | 23 (19) | 12 (32) | 0.11 | 2 (17) | 29 (22) | 1.00 | 2 (11) | 33 (24) | 0.25 |
| Stage III | 99 (81) | 25 (68) | 10 (83) | 103 (78) | 17 (89) | 107 (76) | |||
| Pathological T stage, n (%) | |||||||||
| ypT0-2 | 65 (53) | 23 (62) | 0.36 | 5 (42) | 73 (55) | 0.38 | 5 (26) | 83 (59) | 0.01 |
| ypT3-4 | 57 (47) | 14 (38) | 7 (58) | 59 (45) | 14 (74) | 57 (41) | |||
| Pathological N stage, n (%) | |||||||||
| ypN0 | 91 (75) | 25 (68) | 0.40 | 6 (50) | 97 (73) | 0.10 | 10 (53) | 106 (76) | 0.05 |
| ypN1-2 | 31 (25) | 12 (32) | 6 (50) | 35 (27) | 9 (47) | 34 (24) | |||
| Pathological complete response, n (%) | |||||||||
| Yes | 24 (20) | 10 (27) | 0.36 | 1 (9) | 28 (21) | 0.46 | 2 (11) | 32 (23) | 0.37 |
| No | 98 (80) | 27 (73) | 11 (89) | 104 (79) | 17 (89) | 108 (77) | |||
| Adjuvant chemotherapy, n (%) | |||||||||
| Yes | 40 (33) | 17 (46) | 0.17 | 4 (33) | 43 (33) | 1.00 | 11 (58) | 91 (65) | 0.61 |
| No | 82 (67) | 20 (54) | 8 (67) | 89 (67) | 8 (42) | 49 (35) | |||
| Recurrence at any site, n (%) | |||||||||
| Yes | 18 (15) | 5 (14) | 1.00 | 6 (50) | 15 (11) | 0.003 | 11 (58) | 12 (9) | < 0.001 |
| No | 104 (85) | 32 (86) | 6 (50) | 117 (89) | 8 (42) | 128 (91) | |||
| Site of recurrence, n (%) | |||||||||
| Locoregional only | 3/18 (17) | 0/5 (0) | 1.00 | 0/6 (0) | 3/15 (20) | 0.53 | 1/11 (9) | 2/12 (17) | 1.00 |
| Distant±locoregional | 15/18 (83) | 5/5 (100) | 6/6 (100) | 12/15 (80) | 10/11 (91) | 10/12 (83) | |||
ctDNA, circulating tumour DNA.