Table 3. Main characteristics of studies on GSTM1 and GSTT1 polymorphisms and clinical TNM stages of RCC included in the meta-analysis.

Study	GSTM1						GSTT1
	I		II		III + IV		I		II		III + IV
	Present	Null	Present	Null	Present	Null	Present	Null	Present	Null	Present	Null
Ahmad	48	22	29	31	17	49	37	33	21	39	13	53
De Martino	27	44	2	1	38	35	60	11	2	1	58	15
Sweeney	37	35	18	15	8	15	51	21	25	8	17	6
Salinas							29	30	11	9	11	25