In vivo imaging method for cancer

A method for the identification and/or monitoring of cancer in a subject wherein said cancer is characterised by abnormal expression of peripheral benzodiazepine receptors (PBR) and with the proviso that said cancer is not colon cancer, prostate cancer, breast cancer or colorectal carcinoma, wherein said method comprises the following steps:

• (a) administering to said subject an in vivo imaging agent of Formula I:
• wherein:
• R1 is C1-3 alkyl or C1-3 fluoroalkyl;
• R2 is hydrogen, hydroxy, halo, cyano, C1-3 alkyl, C1-3 alkoxy, C1-3 fluoroalkyl, or C1-3 fluoroalkoxy;
• R3 and R4 are independently C1-3 alkyl, C7-10 aralkyl, or R3 and R4, together with the nitrogen to which they are attached, form a nitrogen-containing C4-6 aliphatic ring optionally comprising 1 further heteroatom selected from nitrogen, oxygen and sulfur;
• Y1 is O, S, SO, SO2 or CH2;
• and,
• Y2 is CH2, CH2—CH2, CH(CH3)—CH2 or CH2—CH2—CH2;
• and wherein said in vivo imaging agent of Formula I comprises an atom which is a radioisotope suitable for in vivo imaging;
• (b) allowing said administered in vivo imaging agent of step (a) to bind to PBR expressed in said subject;
• (c) detecting signals emitted by the radioisotope comprised in said bound in vivo imaging agent of step (b) using a suitable in vivo imaging procedure;
• (d) generating an image representative of the distribution and/or extent of said signals detected in step (c);
• (e) determining the distribution and/or extent of PBR expression in said subject wherein said expression is directly correlated with the distribution and/or extent of said signals as represented in said image generated in step (d);
• and,
• (f) using the distribution and extent of PBR expression as determined in step (e) in the identification and/or monitoring of said cancer.