Table 3. Criteria for MRI Diagnosis of Complete Tumor Response.

MR Method	Criterion	Number of Articles*
T2	Visible tumor signal is absent.
	- Normalization of wall in tumor bed; no detectable mass, nodular intermediate signal, or wall thickening (with individual layers of wall identified again)	4
	- mrTRG1†: linear/crescentic thin scar in mucosa/submucosa or apparent normalization of wall in tumor bed	5
	- Regular, hypointense scar in inner layer without bulging or breach by intermediate signal and homogeneous intermediate signal in underlying layer of wall in tumor bed	1
	- Normalization of wall or hypointense wall (with thickening) without intermediate signal in tumor bed	5
	- mrTRG1–2†: mrTRG1 or dense fibrosis with no obvious residual tumor	4
	Visible tumor signal may be present in small amount.
	- mrTRG1–3†: mrTRG1–2 or > 50% fibrosis or mucin and visible residual intermediate tumor signal	1
	- Residual intermediate tumor signal in ≤ 25% of tumor bed	1
	Obscure	3
DWI	No hyperintense signal on high b-value (≥ 800 sec/mm2) DWI in tumor bed	8
	Hyperintense signal in ≤ 25% in tumor bed	1
	Obscure	2
Combined T2 and DWI‡	When both T2 and DWI are negative for residual tumor	1
	When both T2 and DWI are negative for residual tumor, with DWI being decisive if T2 findings are equivocal	2
	T2 findings as primary results, with DWI to override T2 when T2 findings are equivocal or DWI to increase reader confidence if T2 and DWI findings are consistent	1
	Obscure	4

^*One article may present more than one criterion, ^†mrTRG is magnetic resonance tumor regression grade system proposed by MERCURY study group (24). Descriptions for mrTRG categories are according to most recent relevant papers (9,24,29), ^‡Rules to combine T2 and DWI results.