Hi May,
I'm not a stats-kinda-gal but will share my own experience.
I chose fractionated radiation via CK as my #1 goal (for me) was hearing preservation. Mine was fractionated over 5 days. At time of treatment, I had some hearing loss, with word recognition at 92-96%. Approx 6 mos post-CK, there was some tumor swelling going on, thus, I temp lost what you noted, approx 10-15db. Once the swelling subsided, my hearing remained the same as pre-treatment.
I am now just shy of 3 yrs post-CK.... last hearing test was last month. My hearing has remained the same as pre-CK... I had 96% word recognition with minimal hearing loss.
I know "individual results may vary" as I have heard many that had GK and CK and retained hearing levels.. and some that had CK and GK and lost hearing... I believe the end result depends on the individual.
Hope this helps.
Phyl