The overall goals of RP1 are to use advanced techniques of IMRT to improve local control and to reduce the morbidity associated with the radiotherapy of carcinomas of the prostate and nasopharynx. Having demonstrated in prostate cancer a safe escalation of dose to 86.4 Gy, the first aim of RP1a is to address the important question of whether androgen deprivation will obviate the need for higher doses or whether androgen deprivation is unnecessary when higher dose levels can be administered. A randomized Phase III trial will be conducted, comparing the outcomes of 86.4 Gy IMRT alone with the combination of adjuvant androgen deprivation and 75.6 Gy IMRT, in either unfavorable risk or intermediate risk patients with Gleason scores of 8-10. We hypothesize that 86.4 Gy will improve local control and decrease the rate of distant metastasises to the same extent as 75.6 Gy and androgen deprivation therapy and that the quality of life of patients treated with radiotherapy alone will be superior to that of those receiving adjuvant androgen deprivation.
The second aim i s to conduct a Phase I dose-escalation study in stages II-IVB nasopharynx carcinoma using the 'dose painting' capability of IMRT to deliver a simultaneous, fieldwithin-a-field boost to regions of gross disease. Thirty fractions of 2.34 Gy to 70.2 Gy, and then 2.5 Gy to 75 Gy, will be tested. Much improvement is needed in the local outcome for advanced nasopharynx cancer, and preliminary results from our pilot study indicate that local tumor control may be improved with IMRT. We will ultimately test whether an improvement in local control by IMRT may result in a survival benefit. RP1b will investigate the influence of dose distributions, target and normal organ volumes irradiated, and anatomic location on outcome. Data from the dose-escalation and Phase III prostate trials will be used to assess the influence of volumes of rectal wall at the various doses on late rectal bleeding. We will study the dependence of biopsy outcome on risk group and dose distributions, and use data from high-dose patients to test the hypothesis that the inhomogeneities in their PTV/rectum overlap do not prevent improvement in outcome. Data from the lung studies in RP2 will be used to assess the influence of volume and location of irradiated lung on pneumonitis and provide limits for the safe treatment of NSCLC. Our initial study in nasopharynx aims to provide limits on the target inhomogeneity that will prevent significant loss of local control. These limits will determine the maximum degree of cochlea sparing for each patient. The study results will also generate the dose response of cochlea hearing loss and provide a rational basis for the minimization of both local failure and hearing loss.
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