Constant Current Driver with a Step-Up Regulator IC
This will work with some modifications. First, the inductor needs to be increased to 680uH according to the datasheet, or else system may be unstable. Output cap should be rated for 100V. If you get flicker, you may need to increase size of output cap.

You need to select compensation resistor value of about 1K based on your load, min input voltage and max output voltage. Feedback cap will need to be computed according to the datasheet.  

Also, since Vf of LEDs varies from one lot to another you need to verify if 54V is typical, or max. If typical, than you need to determine max. Even with typical value, you are closing in on the maximum operating voltage of 60V for the IC, as LEDs will require minimum of 54V plus 1.23V across Rsense plus 0.5V across diode. Also keep in mind that Vf of LEDs increases with increased temp, so you may get very close to the operating limit of the IC. If you exceed it, this may result in damage to the internal switch, or flicker if the output voltage does not get high enough.

Good luck and enjoy.