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Proton Therapy Delivery and Its Clinical Application in Select Solid Tumor Malignancies
Published on: February 6, 2019
The relative importance of hormonal therapy and biological effective dose in optimizing prostate brachytherapy
Richard G Stock1, Michael Buckstein, Jerry T Liu
1Department of Radiation Oncology, Mount Sinai School of Medicine, New York, NY 10029, USA. richard.stock@mountsinai.org
Objectives:
To compare the relative importance of radiation dose escalation vs androgen deprivation therapy (ADT) in the definitive treatment of prostate adenocarcinoma.
Patients And Methods:
In total, 2427 patients with prostate adenocarcinoma were treated with definitive brachytherapy or brachytherapy with external beam radiation with or without ADT. Over the 20-year period of the present study (median follow-up of 78 months), patients were treated with a range of doses that were converted to the biological effective dose (BED) and/or ADT as the treatment paradigms were optimized. Using univariate and multivariate analysis, the relative impact on the biochemical control and post-treatment prostate biopsy results of BED vs ADT was determined.
Results:
The 10-year freedom from biochemical failure (FBF) was significantly affected by BED group: ≤150 Gy2 (64%), >150-200 Gy2 (88%), >200-220 Gy2 (89%) and >220 Gy2 (89.5%) (P < 0.001). When stratified into dose groups, ADT improved FPF on multivariate analysis for the BED group (<150 Gy2 , hazard ratio = 0.55; >150-200 Gy2 , hazard ratio = 0.39) but not for the higher BED groups. Among patients receiving ADT, a significant difference in 10-year FBF was seen when stratifying BED into groups ≤150 Gy2 (78%) vs >150 Gy2 (87%) (P = 0.01). On logistic regression, ADT had a significant impact on obtaining a negative biopsy (hazard ratio = 0.21) with BED <200 Gy2 , although there was no difference with BED >200 Gy2 .
Conclusions:
When treated with brachytherapy with or without EBT, ADT improves FBF only in the setting of lower doses. The benefit of ADT may be primarily as an enhancer of local control, explaining why high radiation doses can compensate for its absence.
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