Minnie, See the M.D. Anderson study published in Int. J. Radiation oncology Biol. Phys., Vol. 59, No. 1, pp. 43-50, 2004, entitled "Intensity-Modulated Radiation Therapy for Orophayngeal Carcinoma: Impact of Tumor Volume" By Chao, et al.

It states that only a few reports benchmarking the treatment outcome of H&N cancers (using IMRT) have been published. I believe this is the largest study reporting IMRT outcomes using 75 people with cancer of the tonsil, BOT or Soft Palate. It compares the IMRT Disease Free Survival % with 7 older studies done with conventional radiation. The results are impressive in comparison especially when comparing the combination of surgery and IMRT (Stage IV DFS of 92%). (A mix of patients getting either surgery/IMRT or just IMRT gave a Stage IV DFS of 73% and Stage III DFS of 90%.) This study showed tumor volume to be of significance. It breaks down the results in numerous ways and provides information about the IMRT target volume determination guidelines.

I haven't been able to locate any other large studies specifically about IMRT treatment outcomes.