Wow. I checked on Amazon & there a so many different stengths. How to know which one would be best?

SSC T1N1, Moderate discection of left tongue 9/9/10, removed lymph nodes, no chemo or radiation. 2 clear PET scans then cancer returned T3 (high 2) 3/2011. Lymph node byopsy clear. 6 weeks radation June 6-July 20. Weekly Carboplatin.