Predicting tumor response after preoperative chemoradiation using clinical parameters in rectal cancer

Table 1 Patient demographics and tumor characteristics in the test and validation sets n (%)

Characteristics	Test set	Validation set
Total number of patients	249 (100)	15 (100)
Median age (yr, ranges)	55, 24-81	56, 33-74
Sex
Male	177 (71.1)	11 (73.3)
Female	72 (28.9)	4 (26.7)
Low margin from anal verge (cm)
≤ 5	187 (75.1)	12 (80)
> 5	62 (24.9)	3 (20)
Histological type
Adenocarcinoma	238 (95.6)	14 (93.3)
Mucinous	9 (3.6)	1 (6.7)
Signet ring cell	2 (0.8)	0 (0)
Surgery
Abdominal-perineal resection	37 (14.9)	0 (0)
Low anterior resection	208 (83.5)	14 (93.3)
Hartmann’s operation	4 (1.6)	1 (6.7)
Chemotherapy regimen1
FL group	200 (80.6)	9 (60)
Capecitabine group	48 (19.4)	6 (40)
Median interval to surgery (d, ranges)	55, 26-120	54, 41-78

¹Missing data: n = 1, test set; FL: 5-fluorouracil and leucovorin.

Table 2 Univariate analysis to identify predictors of tumor and complete regression

Variable	Tumor regression grade		P value
	0-3	4
Sex			0.940
Male	127	50
Female	52	20
Age (yr)			0.926
≤ 56	96	38
> 56	83	32
Low margin from AV (cm)			0.641
≤ 5	133	54
> 5	46	16
Pre-CRT size (cm)			0.001
≤ 4	73	44
> 4	102	23
cT classification			0.054
cT2, 3	146	64
cT4	33	6
cN classification			0.073
cN -	37	22
cN +	142	48
Pre-CRT involved bowel circumference			0.365
Encircling	65	21
One direction	114	49
Pre-CRT movability			< 0.001
Movable	13	20
Tethered/fixed	166	50
Pre-CRT CEA (ng/mL)1			0.021
≤ 5	97	52
> 5	48	11
ycT classification			< 0.001
ycT 1,2	42	38
ycT 3,4	137	32
ycN classification			< 0.001
ycN -	57	44
ycN +	122	26
Post-CRT size (cm)			< 0.001
≤ 3	115	64
> 3	64	6
Post-CRT morphology			0.004
Benign-like shape	154	69
Malignancy-like shape	25	1
Cell type			0.141
High grade	161	67
Low grade	18	3
Gross Change			< 0.001
Yes	129	67
No	50	3
Post-CRT SUV2			< 0.001
≤ 5	63	29
> 5	86	5

Low grade: Poorly differentiated or mucinous; High grade: Well or moderately differentiated;

¹Missing data: n = 41;

²Missing data: n = 66. AV: Anal verge; CRT: Chemoradiation therapy; CEA: Carcinoembryonic antigen; SUV: Standard uptake value.

Table 3 Multivariate analysis to identify predictors of tumor and complete regression

	Tumor regression grade (0-3 vs 4)
	OR	95% CI	P value
Pre-CRT size	1.265	0.622-2.569	0.516
Pre-CRT movability	2.780	1.141-6.777	0.024
Post-CRT size	3.473	1.235-9.767	0.018
Post-CRT morphology	11.100	1.389-88.673	0.023
Gross Change	5.847	1.519-19.814	0.009
ycT classification	2.073	0.968-4.440	0.061
ycN classification	1.887	0.917-3.883	0.085

CRT: Chemoradiation therapy; OR: Odd ratio; CI: Confidence interval.

Table 4 Scoring model

	No. of points
Parameters	0	1
Pre-CRT movability	Tethered/fixed	Movable
Pre-CRT CEA (ng/mL)	> 5	≤ 5
Post-CRT morphology	Malignancy-like shape	Benign-like shape
Post-CRT SUV	> 5	≤ 5
Post-CRT size (cm)	> 3	≤ 3
Gross change	No	Yes

CRT: Chemoradiation therapy; CEA: Carcinoembryonic antigen; SUV: Standard uptake value .

Table 5 Predicting score accuracy

Measure of accuracy	Cut off value, 4.5
	n	%
Sensitivity	20/31	64.5
Specificity	96/120	80
Positive predictive value	30/44	45.5
Negative predictive value	96/107	89.7