Dosimetric effects of edema in permanent prostate seed implants: a rigorous solution

Chen, Zhe; Yue, Ning J.; Wang, Xiaohong; Roberts, Kenneth B.; Peschel, Richard E.; Nath, Ravinder

doi:10.1016/s0360-3016(00)00549-6

Cited by 43 publications

(39 citation statements)

References 14 publications

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“…The prostate edema caused a volume increase to 49 ± 13 cm 3 (p < 0.001), range 28-75 cm 3 , on day 1, resulting in an average increase of 32%, range 0-130%. On day 30, prostate volume dropped to 40 ± 9 cm 3 , range 24-59 cm 3 , not completely reaching the initial size (p = 0.011).…”

Section: Resultsmentioning

confidence: 99%

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Changes of Dose Delivery Distribution within the First Month after Permanent Interstitial Brachytherapy for Prostate Cancer

et al. 2006

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With a decreasing edema of the prostate, an increasing dose both to the prostate and the anterior rectal wall resulted--the postimplant interval is essential for the dosimetry report. Due to a larger edema, a higher prescription dose might be needed for optimal cancer control in smaller prostates. Compared to day 1, the dose to the surrounding tissues increased on day 30, particularly at the posterior and inferior prostate borders.

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Section: Resultsmentioning

confidence: 99%

“…Most reports focused on the dose delivered to the prostate [3,4,22,25]. Waterman & Dicker additionally described the effect on the urethral [21] and rectal dose [20].…”

Section: Introductionmentioning

confidence: 99%

Changes of Dose Delivery Distribution within the First Month after Permanent Interstitial Brachytherapy for Prostate Cancer

et al. 2006

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“…With implant induced prostatic edema, the prostate volume and source locations become function of time and thus instantaneous dose rate at point 'P' will not be a simple exponential function of time but is given by the following relation 45 which accounts for an edema -induced dose reduction at time 't'…”

Section: Effective Treatment Time T Effmentioning

confidence: 99%

“…18,19 Many investigators have modeled resolution of post-implant edema. 5,11,45,50 Mathematically, the volume of prostate at time 't' with edema resolution can be expressed by…”

Section: Effective Treatment Time T Effmentioning

confidence: 99%

Changes in radiobiological parameters in ¹³¹Cs permanent prostate implants

et al. 2013

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In prostate permanent implants using 131 Cs seeds, the prostatic edema developed during the implantation procedure, increases the separation between the seeds. This leads to a decrease in the prostate coverage and thus causes an edema induced dose reduction, which results in an increase in tumour cell surviving fraction (SF) with a corresponding decrease in tumour control probability (TCP). To investigate the impact of edema on the SF and the TCP, the expression of the SF of the linear quadratic (LQ) model was extended to account for the effects of edema using the exponential nature of edema resolution and the dose delivered to the edematous prostate. The SF and the TCP for edematous prostate implants were calculated for 31 patients who underwent real time 131 Cs permanent seed implantation. The dose delivered to the edematous prostate was calculated to compute the SF and the TCP for these patients for edema half lives (EHL) ranging from 4 days to 34 days and for edema of magnitudes (M 0 ) varying from 5 to 60% of the actual prostate volume.A reduction in the dose delivered to the edematous prostate was found with the increase of EHL and edema magnitude which results in an increase of the SF, and corresponding decrease in the TCP. The dose reductions in 131 Cs implants varied from 1.1% (for EHL ¼ 4 days and M 0 ¼ 5%) to 32.3% (for EHL ¼ 34 days and M 0 ¼ 60%). These are higher than the dose reduction in 125 I implants, which vary from 0.3% (for EHL ¼ 4 days and M 0 ¼ 5%) to 17.5% (for EHL ¼ 34 days and M 0 ¼ 60%). As edema half life increased from 4 days to 34 days and edema magnitude increased from 5 to 60% the SF increased by 4.57 log, and the TCP decreased by 0.80. Compensation of edema induced increase in the SF and decrease in the TCP in 131 Cs seed implants should be carefully done by redefining seed positions with the guidance of post-needle plans. The presented model in this study can be used to estimate the SF or the TCP for pre plan or real time permanent prostate implants using day 0 post-implant CT images.

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“…(11) as (13) Many different treatment options, ranging from a second implant to EBRT, can theoretically be used to compensate a calculated BED reduction. Because a second implant could pose many technical challenges, such as the need to avoid overlapping of newly implanted seeds with the old ones and the need to consider the prostate edema induced by the second implant, we chose the intensity-modulated external beam radiotherapy (IMRT) delivered consecutively on a daily basis to illustrate the magnitude of required additional irradiations.…”

Section: Additional Irradiations Needed For Compensation Of Edema-mentioning

confidence: 99%

On the Need to Compensate for Edema-Induced Dose Reductions in Preplanned 131Cs Prostate Brachytherapy

Chen

Deng

Roberts

et al. 2008

International Journal of Radiation Oncology*Biology*Physics

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Purpose-Surgical-trauma-induced edema and its protracted resolution can lead to significant dose reduction in pre-planned 131 Cs prostate brachytherapy. The purpose of this work was to examine whether these dose reductions should be actively compensated and to estimate the magnitude of additional irradiations needed for dose compensation.Methods and Materials-Quantitative edema resolution characteristics observed by Waterman et. el. were used to examine the physical and radiobiological effects of prostate edema in preplanned 131 Cs implants. The need for dose compensation was assessed based on the dose-responses observed in 125 I and 103 Pd prostate implants. Biologically effective dose calculated with full consideration of edema evolution was used to estimate the additional irradiations needed for dose compensation.Results-Edema-induced dose reduction in pre-planned 131 Cs implants could easily exceed 10% prescription dose for implants with moderate or large edemas. These dose reductions could lead to more than 10% reduction in biochemical recurrence-free survival for individual patients if the effect of edema was ignored. For a prescribed dose of 120 Gy, the number of 2-Gy external-beam fractions needed to compensate a 5%, 10%, 15%, 20%, or 25% edema-induced dose reduction could be 1, 4, 6, 7, or 9, respectively, for prostate cancers with a median potential doubling time of 42 days. The required additional irradiation increases for tumors that are fast growing and/or are less efficient in sub-lethal damage repair.Conclusions-Compensation of edema-induced dose reductions in pre-planned 131 Cs prostate brachytherapy should be actively considered for those implants with moderate or large edemas.

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Dosimetric effects of edema in permanent prostate seed implants: a rigorous solution

Cited by 43 publications

References 14 publications

Changes of Dose Delivery Distribution within the First Month after Permanent Interstitial Brachytherapy for Prostate Cancer

Changes of Dose Delivery Distribution within the First Month after Permanent Interstitial Brachytherapy for Prostate Cancer

Changes in radiobiological parameters in ¹³¹Cs permanent prostate implants

On the Need to Compensate for Edema-Induced Dose Reductions in Preplanned 131Cs Prostate Brachytherapy

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Dosimetric effects of edema in permanent prostate seed implants: a rigorous solution

Cited by 43 publications

References 14 publications

Changes of Dose Delivery Distribution within the First Month after Permanent Interstitial Brachytherapy for Prostate Cancer

Changes of Dose Delivery Distribution within the First Month after Permanent Interstitial Brachytherapy for Prostate Cancer

Changes in radiobiological parameters in 131Cs permanent prostate implants

On the Need to Compensate for Edema-Induced Dose Reductions in Preplanned 131Cs Prostate Brachytherapy

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Changes in radiobiological parameters in ¹³¹Cs permanent prostate implants