Loss of pRB in Conjunctival Squamous Cell Carcinoma: A Predictor of Poor Prognosis.

Conjunctival squamous cell carcinoma (SCC) is the most common tumor of conjunctival epithelium. It is associated with risk of permanent visual impairment and has the capability to recur, metastasize, and cause death. Deregulation of cell cycle control has been reported in a number of malignancies. The aim of the present study was to assess expression of G1/S cell cycle regulatory proteins [retinoblastoma protein (pRb)/P16(INK4a)/cyclin D1] in conjunctival SCC. Forty-four prospective cases of conjunctival SCC from a tertiary eye care referral center in northern India were included in this study. American Joint Committee on Cancer (AJCC) staging was performed and patients were followed up for 46 +/- 3.2 months. pRb loss was seen in 87% and overexpression of p16(INK4a) and cyclin D1 in 36% and 66%, respectively. Kaplan-Meier analysis revealed reduced disease-free survival in patients with pRb loss (P = 0.006). On univariate analysis, pRb loss (P = 0.02), orbital invasion (P = 0.03), and AJCC stage >= T3 (P = 0.03) emerged as significant high-risk features. On multivariate analysis pRb loss emerged as the most significant poor prognostic indicator in conjunctival SCC cases. Our findings suggest pRb loss to be a useful indicator of aggressive behavior and is recommended for identifying high-risk conjunctival SCC patients.