The present invention is for an improved pencil sharpener that is slidingly disposed about a pencil. The system may include a rocker shaft having a hydraulic fluid supply circuit extending through the rocker shaft to a port on the outer surface of the rocker shaft and a solenoid valve adapted to selectively supply hydraulic fluid to the rocker shaft hydraulic fluid supply circuit. The cell has an opening size within a range of 10-100 micrometers and an aspect ratio less than or equal to 1. Additionally disclosed are methods of treating patients with tyrosine kinase inhibitors such as sunitinib based on results obtained from the disclosed methods and kits that facilitate the methods.