Lack of correlation of P-glycoprotein expression with response to MIC chemotherapy in oesophageal cancer.

gene. Oesophageal cancer is the most common cancer among South African black men,2 with more than 96% being squamous cell carcinomas. As the disease is often diagnosed late, prognosis is usually poor even with the availability of all known treatments (median survival ranges from 2.5-6 months).' Brachytherapy alone is one of the recent methods that has been introduced in the palliation of advanced disease. Studies from the department of radiation oncology of our institution have shown that median survival improved to seven months following brachytherapy. The majority of the treated patients are dysphagia-free with death often due to disseminated malignancy (Sur et al, unpublished data). Since 1994, it has been our policy to treat oesophageal cancers diagnosed early (albeit few) with preoperative brachytherapy followed by total oesophagectomy. Interesting radiation changes have been demonstrated in the oesophageal wall, the centre of the tumour, and lymph nodes.4 Using immunohistochemistry we measured P-gp expression in the tumour cells and adjacent stratified squamous mucosa in the pre-radiation biopsies of early oesophageal squamous cell cancers and in the post-brachytherapy resection specimens from eight patients. Monoclonal antibody to P-gp (clone JSB-1, Novocastra Laboratories, Newcastle upon Tyne, UK) was used in the modified sandwich technique on formalin fixed, paraffin wax embedded sections. P-gp was not expressed in either preor post-brachytherapy tissue specimens (after brachytherapy of 20 Gy) in any of the eight cases. These findings, together with those of Darnton et al,' indicate that P-gp expression is of no value in predicting the responsiveness of the tumour to chemotherapy or radiotherapy in squamous cell cancers. It is therefore likely that there may be alternative factors associated with drug resistance in squamous cell carcinoma. The MDR1 gene does, however, have some value in predicting the response