Anatomic variation and dosimetric consequences of neoadjuvant hormone therapy before radiation therapy for prostate cancer

Adam D Melancon; Andrew K Lee; Rajat Kudchadker; Lifei Zhang; Susan L Tucker; Deborah Kuban; Lei Dong

doi:10.1016/j.prro.2012.10.004

Anatomic variation and dosimetric consequences of neoadjuvant hormone therapy before radiation therapy for prostate cancer

Pract Radiat Oncol. 2013 Oct-Dec;3(4):329-36. doi: 10.1016/j.prro.2012.10.004. Epub 2012 Nov 9.

Authors

Adam D Melancon¹, Andrew K Lee², Rajat Kudchadker³, Lifei Zhang³, Susan L Tucker⁴, Deborah Kuban², Lei Dong³

Affiliations

¹ Department of Radiation Physics, The University of Texas MD Anderson Cancer Center, Houston, Texas. Electronic address: [email protected].
² Department of Radiation Oncology, The University of Texas MD Anderson Cancer Center, Houston, Texas.
³ Department of Radiation Physics, The University of Texas MD Anderson Cancer Center, Houston, Texas.
⁴ Department of Biomathematics and Computational Biology, The University of Texas MD Anderson Cancer Center, Houston, Texas.

PMID: 24674406
DOI: 10.1016/j.prro.2012.10.004

Abstract

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 cm(3) (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.