PURPOSE: To characterize anatomic variation during neoadjuvant androgen deprivation (NAD) and determine a treatment planning strategy to maintain acceptable normal tissue dose while treating potential microscopic disease in the original (pre-NAD) tumor bed.
METHODS AND MATERIALS: We retrospectively examined the effects of treating the post-NAD anatomy with plans derived before and after NAD in a group of 44 patients enrolled in an institutional review board-approved protocol. An 8-field intensity modulated radiation therapy (IMRT) treatment plan was generated on anatomy both before and after NAD for the first 35 patients. The pre-NAD treatment plan was applied to the post-NAD anatomy to evaluate the effect of complete pre-NAD tumor bed treatment on normal tissue sparing, and the post-NAD treatment plan was applied to the pre-NAD anatomy to investigate whether microscopic disease might go untreated in the location of the pre-NAD tumor bed.
RESULTS: The prostate decreased in volume by an average of about 14 cm3 (24.3%) and was correlated with NAD duration (P = .002). The prostate center of volume systematically shifted in the inferior direction (mean = 1.4 mm, P = .005) and inferior shift was correlated with absolute volume reduction of the prostate (P = .044) in a multivariate model containing rectal and bladder volume change and initial prostate volume. Pre-NAD treatment planning resulted in a significant increase in the bladder volume (P < .01) but little increase in the rectal volume treated to all dose levels. Post-NAD treatment planning resulted in decreased treatment of the prostate and seminal vesicles (on the pre-NAD anatomy) at the prescribed and 95% isodose levels (prostate: P = .033 and 0.025; seminal vesicles: P < .001).
CONCLUSIONS: Anisotropic volume reduction of the prostate was found during NAD and correlated with NAD duration. Post-NAD based treatment planning can minimize excess bladder and rectal dose.
Written by:
Melancon AD, Lee AK2, Kudchadker R3, Zhang L3, Tucker SL4, Kuban D2, Dong L. Are you the author?
Department of Radiation Physics, The University of Texas MD Anderson Cancer Center, Houston, Texas; Department of Radiation Oncology, The University of Texas MD Anderson Cancer Center, Houston, Texas; Department of Biomathematics and Computational Biology, The University of Texas MD Anderson Cancer Center, Houston, Texas.
Reference: Pract Radiat Oncol. 2013 Oct-Dec;3(4):329-36.
doi: 10.1016/j.prro.2012.10.004
PubMed Abstract
PMID: 24674406
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