BACKGROUND AND PURPOSE: Prostate biopsy positivity after radiotherapy (RT) is a significant determinant of eventual biochemical failure.
We mapped pre- and post-treatment tumor locations to determine if residual disease is location-dependent.
MATERIALS AND METHODS: There were 303 patients treated on a randomized hypofractionation trial. Of these, 125 underwent prostate biopsy 2-years post-RT. Biopsy cores were mapped to a sextant template, and 86 patients with both pre-/post-treatment systematic sextant biopsies were analyzed.
RESULTS: The pretreatment distribution of positive biopsy cores was not significantly related to prostate region (base, mid, apex; p=0.723). Whereas all regions post-RT had reduced positive biopsies, the base was reduced to the greatest degree and the apex the least (p=0.045). In 38 patients who had a positive post-treatment biopsy, there was change in the rate of apical positivity before and after treatment (76 vs. 71%; p=0.774), while significant reductions were seen in the mid and base.
CONCLUSION: In our experience, persistence of prostate tumor cells after RT increases going from the base to apex. MRI was used in planning and image guidance was performed daily during treatment, so geographic miss of the apex is unlikely. Nonetheless, the pattern observed suggests that attention to apex dosimetry is a priority.
Huang KT, Stoyanova R, Walker G, Sandler K, Studenski MT, Dogan N, Al-Saleem T, Buyyounouski MK, Horwitz EM, Pollack A. Are you the author?
Department of Radiation Oncology, University of Miami Miller School of Medicine, USA; Biostatistics and Bioinformatics Core Resource, Sylvester Cancer Center, University of Miami Miller School of Medicine, USA; University of Miami Miller School of Medicine, USA; Department of Pathology, Fox Chase Cancer Center, Philadelphia, USA; Department of Radiation Oncology, Stanford University Medical Center, USA; Department of Radiation Oncology, Fox Chase Cancer Center, Philadelphia, USA.
Reference: Radiother Oncol. 2015 Apr;115(1):101-6.