Determinants of magnetic resonance imaging overstaging in rectal cancer T-staging

Table 1 Univariate analysis of factors affecting magnetic resonance imaging T-staging accuracy, n (%)

Variable	Cases	Understaging	χ2	P value	Overstaging	χ2	P value
Gender
Male	216	11 (5.1)	0.857	0.355	72 (33.3)	1.194	0.275
Female	133	10 (7.5)			52 (39.1)
Age (year)
< 60	123	6 (4.9)	0.436	0.509	39 (31.7)	1.212	0.271
≥ 60	226	15 (6.6)			85 (37.6)
BMI (kg/m2)
< 24	213	12 (5.6)	0.142	0.706	74 (34.7)	0.148	0.7
≥ 24	136	9 (6.6)			50 (36.8)
Distance from anal verge
≤ 5	174	7 (4.0)	4.16	0.1131	66 (37.9)	3.592	0.166
5-10 cm	138	13 (9.4)			50 (36.2)
≥ 10 cm	37	1 (2.7)			8 (21.6)
Maximum tumor diameter
< 4 cm	174	7 (4.0)	2.44	0.118	78 (44.8)	13.095	< 0.001
≥ 4 cm	175	14 (8.0)			46 (26.3)
Circumferential involvement
≤ 1/4	61	4 (6.6)	4.507	0.1951	30 (49.2)	18.69	< 0.001
> 1/4 - ≤ 1/2	149	8 (5.4)			60 (40.3)
> 1/2 - ≤ 3/4	77	2 (2.6)			25 (32.5)
> 3/4 - 1	62	7 (11.3)			9 (14.5)
Tumor location
Anterior	120	12 (10.0)	5.307	0.1351	39 (32.5)	4.096	0.255
Right	65	2 (3.1)			29 (44.6)
Posterior	99	3 (3.0)			37 (37.4)
Left	65	4 (6.2)			19 (29.2)
Neoadjuvant chemoradiotherapy
None	273	18 (6.6)	1.814	0.3781	89 (32.6)	6.34	0.04
Chemotherapy only	51	1 (2.0)			26 (51.0)
Chemoradiotherapy	25	2 (8.0)			9 (36.0)
Pathological type
Polyp carcinogenesis	59	1 (1.7)	1.516	0.2181	36 (61.0)	20.135	< 0.001
Primary carcinoma	290	20 (6.9)			88 (30.3)

¹Fisher’s exact test.

BMI: Body mass index.

Table 2 Multivariable logistic regression analysis of factors associated with magnetic resonance imaging, n (%)

Variable	Cases	Understaging	χ2	P value	Overstaging	χ2	P value
Reader experience			4.217	0.121	-	6.891	0.032
< 3 years	98	8 (8.2)			42 (42.9)
3-10 years	153	8 (8.2)			50 (32.7)
> 10 years	98	5 (5.1)			32 (32.7)
Specialty background			3.102	0.078	-	4.567	0.033
General radiologist	214	15 (7.0)			82 (38.3)
Abdominal imaging subspecialist	135	6 (4.4)			42 (31.1)
Receipt of specialized training			2.891	0.089	-	5.123	0.024
Yes	276	14 (5.1)			92 (33.3)
No	73	7 (9.6)			32 (43.8)
Reading duration (per case)			5.432	0.066	-	8.765	0.012
< 10 minutes	112	10 (8.9)			50 (44.6)
10-20 minutes	187	8 (4.3)			62 (33.2)
> 20 minutes	50	3 (6.0)			12 (24.0)
Blinded reading (without clinical information)			1.234	0.267	-	3.456	0.063
Yes	291	16 (5.5)			98 (33.7)
No	58	5 (8.6)			26 (44.8)
MDT participation			1.876	0.171	-	4.321	0.038
No (independent reading)	187	13 (7.0)			72 (38.5)
Yes	162	8 (4.9)			52 (32.1)

MDT: Multidisciplinary team.

Table 3 Multivariate analysis of factors affecting magnetic resonance imaging T-staging accuracy overstaging

Variable	Regression coefficient	OR (95%CI)	P value
Maximum tumor diameter	-0.197	0.821 (0.708-0.952)	0.009
Circumferential involvement	-0.057	0.945 (0.404-2.208)	0.105
Neoadjuvant treatment-related regression	-0.185	0.831 (0.338-2.045)	0.021
Pathological type, polypoid vs primary carcinoma	-1.546	0.213 (0.115-0.395)	< 0.001

CI: Confidence interval; OR: Odds ratio.

Table 4 Cross-tabulation: Magnetic resonance imaging T stage vs pathological T stage (n = 349)

Pathological T stage	mrTis/T1	mrT2	mrT3	mrT4	Total
pTis/ypT0	16	6	0	0	22
pT1	11	25	8	0	44
pT2	2	16	28	4	50
pT3	0	5	38	10	53
pT4	0	0	4	31	35
Total	29	52	78	46	204

Table 5 Stage-specific diagnostic performance of magnetic resonance imaging (n = 349)

Category	Sensitivity	95%CI (Wilson)	Specificity	95%CI (Wilson)
T1	25.0%	14.5%-38.7%	94.1%	91.3%-96.2%
T2	29.4%	19.2%-41.5%	92.8%	90.2%-94.9%
T3	80.6%	72.6%-86.9%	89.6%	85.6%-92.7%
T4	83.6%	74.9%-90.1%	97.3%	95.3%-98.6%