Randomized clinical trial on preoperative radiotherapy 25 Gy in rectal cancer--treatment results at 5-year follow-up.

"Conflicts of interest None."

"Mann–Whitney U and χ 2 tests were used where appropriate to compare the distribution of individual variables between groups. Survival data were analyzed according to the Kaplan–Meier method and included postoperative mortality; the log-rank test was used to detect differences between groups. p < 0.050 was considered statistically significant. Statistical analyses were performed using the Statistica version 9.0 (Stat Soft Inc.) software package. The local and systemic recurrence rate for preoperative radiotherapy and early surgery was estimated at approximately 14% at 5 years, whereas the local and systemic recurrence rate for delayed surgery was estimated as 2%. Sample Power release 2.0 (SPSS Inc.) was used to calculate the population required to achieve a test power of 80%. Sample size needed for each arm was established as 80 patients (two-sided test, α = 0.05). The actual recruitment in the study was slightly lower (77 patients in both arms), so the actual power is lower than 80%. The study was registered at ClinicalTrials.gov, identifier NCT01444495."