The effect of concurrent androgen deprivation and 3D conformal radiotherapy on prostate volume and clinical organ doses during treatment for prostate cancer

Abstract

ABSTRACT. In this study, we investigated the shrinking effect of concurrent threedimensional conformal radiotherapy (3D-CRT) and androgen deprivation (AD) on prostate volume, and its possible impact on the dose received by the rectum and bladder during the course of 3D-CRT. The difference between the prostatic volumes determined on pre-treatment planning CT (PL-CT) and post-treatment CT (PT-CT) following a 3D-CRT course was assessed in 52 patients with localised prostate carcinoma. The changes in mean prostate volume when compared with PL-CT and PT-CT-based measurements were assessed. The pre-and post-treatment mean prostate volumes for the whole study population were 49.7 cm 3 and 41.0 cm 3 (p50.02), respectively. The study cohort was divided into two groups depending on the duration of neoadjuvant androgen deprivation (NAD): 23 patients (44.7%) were designated as ''short NAD'' (#3 months; SNAD) and the remaining 29 (55.3%) as ''long NAD'' (.3 months; LNAD). Patients on SNAD experienced a significantly greater reduction in prostate volume compared with those on LNAD (14.1% vs 5.1%; p50.03). A significant increase in rectum V 40-60 values in PT-CT compared with PL-CT was demonstrated. LNAD patients had significantly higher rectal V 50-70 values at PT-CT compared with the SNAD group. There was a significant decline in V 30 -V 75 bladder values in PT-CT compared with PL-CT in the SNAD group. In conclusion, a higher prostate volume reduction during 3D-CRT was demonstrated when RT planning was performed within 3 months of NAD. However, this reduction and daily organ motion may lead to an unpredictable increase in rectal doses. Neoadjuvant androgen deprivation (NAD) before RT has been demonstrated to shrink the prostate volume effectively [11,12], and thus has became a widely accepted and essential part of locally advanced prostate cancer management. On average, the prostate gland shrinks about 20-50% of its initial volume within 3 months of NAD [11][12][13][14][15] and, although the rate slows down, this shrinking effect continues beyond this period [16][17][18][19] The cytoreduction in the prostate provided by NAD may lower the complication rates observed at higher RT doses by reducing the target volumes, depending on the reduced doses received by normal tissues [15,20].A relatively long treatment interval (7-8 weeks) is usually mandated for three-dimensional conformal radiotherapy (3D-CRT) of prostate carcinoma, and the shrinkage of the prostate gland continues during this period. In this setting, it is reasonable to assume, theoretically, that there is a possibility of a larger than planned volume of surrounding critical organs that may shift into the intermediate or high-dose regions during the RT course, which may unpredictably increase the dose received by the rectum and bladder [11,12,21]. Based on the above assumption, we planned to evaluate prostate shrinkage during 3D-CRT in relation to NAD duration, and to investigate the possible impact of this volume reduction on the dose received by the rectum and blad...

Simultaneous integrated boost to intraprostatic lesions using different energy levels of intensity-modulated radiotherapy and volumetric-arc therapy

“…19 MRI scans were acquired with the same conditions as CT. Because of the negative effects of androgen deprivation on the metabolism of prostate cancer cells, MRS examinations were performed in the absence of or before hormone therapy. 20 The MRI scans used for image fusion and treatment planning were acquired on a 1.5 T Siemens Avanto® MRI System (Siemens Healthcare, Erlangen, Germany).…”

“…The planning target volume for 78 Gy (PTV78) was defined as CTV with a margin of 5 mm posterior and 8 mm in other directions. 19,23 The delineation of IPL was done together with a radiologist (Figure 1). The PTV for 86 Gy (PTV86) was created using a three-dimensional, isotropic, 4-mm margin around the IPL.…”

MRI-Guided Radiation Therapy for Prostate Cancer: The Next Frontier in Ultrahypofractionation

“…Rectal filling, bladder movement, and any other OAR volume changes are associated with prostate motion and shape [ 17 , 24 , 25 ]. ADT delivery is also known to alter prostate volume and molecular characteristics [ 26 , 27 ]. Changes in volume may also occur from radiation treatment itself over time, with increase in prostate size in the short term and a decrease in size in the long term.…”

Correlation of Clinical Risk Factors with Diffusion-Weighted Magnetic Resonance Images in Prostate Cancer Patients Treated with Definitive Radiotherapy

“…Treatment strategies include watchful waiting, radical prostatectomy, or radiotherapy (RT) with or without hormonotherapy, depending on disease stage and risk factors. [1][2][3] The challenge of managing localized prostate cancer is to distinguish patients who may benefit from radical treatment from patients who do not need any intervention. Furthermore, in patients treated with RT, treatment strategies depend on clinical parameters and, notably, risk groups.…”