Retinoblastoma gene abnormalities in early laryngeal cancer

The retinoblastoma gene (Rb) is postulated to be important in carcinoma of the larynx. Its cellular protein (pRb) is involved in regulation of the cell cycle and may be influential in the cells response to irradiation injury. From the University of Liverpool Head and Neck Database we identified 35 patients with a T2 N0 laryngeal squamous carcinoma whom received primary irradiation and had a minimum of 5 years follow up. Laser capture microdissection was performed on paired normal and tumour biopsy material to analyse for loss of heterozygosity (LOH) and microsatellite instability (MI) of the Rb gene and immunohistochemistry (IHC) was carried out to detect pRb expression. Of 35 tumours, 13 were normal, 12 had MI and 5 had LOH of the Rb gene. Abnormalities at the Rb locus did not correlate with loss of pRb expression. There was also no significant difference between the distribution of normal and abnormal gene sequences and whether or not the primary laryngeal tumour recurred after radiotherapy. Rb gene abnormalities occurred in one third of T2 N0 laryngeal carcinomas. These were not in isolation predictive of cure by radiotherapy.