Statistical analysis
The sample size calculation was implemented presuming an expected
objective cure rate of minimum 80 % for both patient groups. A minimum
sample size of 64 patients was required for each group to detect a
difference of 13% in cure rates between the two procedures, with 80%
power and false non-match rate (alpha) of 0.05. Assuming a follow-up
loss rate of 24% after four years, a total enrolment of 168 patients
was projected.
Absolute and relative frequencies were computed for categorical
variables; mean ± standard deviation for continuous variables.
Statistical significance of differences between groups of patients was
analyzed by a Fisher exact test for categorical variables and the
Mann–Whitney U test for continuous and nominal variables. Odds ratio
and its 95% confidence interval was adopted for the description of
group influence on binary endpoints occurrence. The SPSS Statistics
(IBM) software was used, and p < 0.05 was considered
statistically significant.