Prognostic value of apoptosis-regulating protein expression in anal squamous cell carcinoma

This study evaluated the prognostic value of pro and antiapoptotic protein expression, as well as that of spontaneous apoptosis, in anal carcinoma patients treated by radiotherapy (RT) with or without chemotherapy.

Ninety-eight patients with available pretreatment biopsy specimens were studied. Patients had been treated with split-course RT: 30-40 Gy fractionated external beam, followed by a 20-22-Gy boost using interstitial or external RT. Fifty-one patients also received concomitant mitomycin-C and 5-fluorouracil. Median follow-up for surviving patients was 124 months. Tissue sections were examined immunohistochemically for expression of proapoptotic proteins (Bax, p53), antiapoptotic proteins (Bcl-2, Mcl-1), and spontaneous apoptosis (M30). Except for M30, staining of less than 5% of tumor cells was considered negative. Protein expression was correlated with local tumor control (LC) and disease-free survival (DFS) outcomes. The Kaplan-Meier method was used for the monovariate analysis and the Cox proportional hazard models for the multivariate analysis.

For LC, beside advanced T- and N-categories and longer overall treatment time (OTT), lack of Bcl-2 expression was associated with poorer 5-year outcome (62 versus 84%, P = 0.009). For DFS, advanced T- and N-categories, longer OTT, and the lack of Bcl-2 expression correlated significantly with lower rates. In the multivariate analysis, N-category (P = 0.0026), OTT (P = 0.04), Bcl-2 (P = 0.0015), and M30 (P = 0.035) expressions were significant factors for LC. For DFS, age (P = 0.049) an N-category (P < 0.0001), as well as expression of Bcl-2 (P = 0.001), p53 (P = 0.003), and M30 (P = 0.03), were found to be independent significant variables. Patients with Bcl-2(+)/p53(-) tumors had a significantly higher 5-year LC compared with patients whose tumors were Bcl-2(-)/p53(+) (93 versus 53%, P = 0.004).

Bcl-2 and particularly the combination of p53 and Bcl-2 expression may prove to be useful predictors of tumor response to RT or radiochemotherapy in anal carcinomas. Patients having tumors that are Bcl-2(-) and p53(+) may require intensified radiochemotherapy or adoption of an alternative therapeutic approach.