Decreased tumor cell proliferation as an indicator of the effect of preoperative radiotherapy of rectal cancer

Background: Rectal cancer is a common malignancy, with significant local re currence and death rates, Preoperative radiotherapy and refined surgical te chnique can improve local control rates and disease-free survival. Purpose: To investigate the relationship between the tumor growth fraction in rectal cancer measured with Ki-67 and the outcome, with and without shor t-term preoperative radiotherapy. Method: Ki-67 (MIB-1) immunohistochemistry was used to measure tumor cell p roliferation in the preoperative biopsy and the surgical specimen. Materials: Specimens from 152 patients from the Southeast Swedish Health Ca re region were included in the Swedish rectal cancer trial 1987-1990, Results: Tumors with low proliferation treated with preoperative radiothera py had a significantly reduced recurrence rate. The influence on death from rectal cancer was shown only in the univariate analysis. Preoperative radi otherapy of tumors with high proliferation did not significantly improve lo cal control and disease-free survival, The interaction between Ki-67 status and the benefit of radiotherapy was significant for the reduced recurrence rate (p = 0.03), with a trend toward improved disease-free survival (p = 0 .08). In the surgery-alone group, Ki-67 staining did not significantly corr elate with local recurrence or survival rates. Conclusion: Many Ki-67 stained tumor cells in the preoperative biopsy predi cts an increased treatment failure rate after preoperative radiotherapy of rectal cancer. (C) 2001 Elsevier Science Inc.