Period Numbers of treatmentcourse Incident level Lv.1 Lv.2 Lv.3* Lv.4** Lv.5** Lv.6** May 2009-April 2010 566 0 0 22 (4%) 56 (10%) 33 (6%) 132 (23%) May 2010-April 2011 585 0 0 14 (2%) 19 (3%) 7 (1%) 58 (10%) May 2011-April 2012 638 0 0 7 (1%) 21 (3%) 5 (1%) 25 (4%) May 2012-April 2013 561 0 0 6 (1%) 13 (2%) 4 (1%) 12 (2%) Total 2350 0 0 49 (2%) 109 (5%) 50 (2%) 227 (10%)

Table 2: Incident distribution for each classification and incident rate (%) regarding the number of treatment courses during each period shown in parentheses. Lv., level. *Significant incident rate reduction in the third and fourth years, compared with that in the first year (p<0.01). **Significant incident rate reduction in the second, third, and fourth years, compared with that in the first year (p<0.001).