We expect that patients in the test group will experience a lower number of QL-deficits at the end of the study period (Median 1 +/- 2) than patients of the control group (Median 2 +/- 2). The statistical confirmation of this expected effect requires a total sample size of N = 200 (n=100 vs. n=100, alpha = 5% [two-tailed], beta = 10%).