LACK OF CORRELATION OF P-GLYCOPROTEIN EXPRESSION WITH RESPONSE TO MICCHEMOTHERAPY IN ESOPHAGEAL CANCER

The multidrug resistance gene product P-glycoprotein (P-GP) was assess ed immunohistochemically (by antibody JSB-1) in biopsy specimens from 27 oesophageal squamous carcinomas and 10 adenocarcinomas before treat ment with mitomycin, ifosfamide and cisplatin (MIC). Tumours were asse ssed following treatment and correlation with response sought. Of the squamous carcinomas, 74% (20/27) responded to MIC but only one express ed P-GP before and after treatment. Of the adenocarcinomas, 30% (three of 10) responded. Seven of the 10 adenocarcinomas expressed P-GP befo re treatment but all 10 were P-GP positive after chemotherapy. The dif ference in prevalence and induction of P-GP between the histological t ypes was highly significant and may correlate with the greater respons e to MIC seen in squamous carcinomas compared with adenocarcinomas. P- GP cannot be used as a predictive marker of response as tumours expres s it inconsistently with response to MIC. Resistance to MIC may be due to other mechanisms.