Prostate external beam radiotherapy combined with high-dose-rate brachytherapy: dose-volume parameters from deformably-registered plans correlate with late gastrointestinal complications

Abstract

Background: Derivation of dose-volume correlated with toxicity for multi-modal treatments can be difficult due to the perceived need for voxel-by-voxel dose accumulation. With data available for a single-institution cohort with long follow-up, an investigation was undertaken into rectal dose-volume effects for gastrointestinal toxicities after deformably-registering each phase of a combined external beam radiotherapy (EBRT)/high-dose-rate (HDR) brachytherapy prostate treatment.

A Systematic Post-QUANTEC Review of Tolerance Doses for Late Toxicity After Prostate Cancer Radiation Therapy

“…Five studies had each reported a rectal DVH threshold for Rectal bleeding defined primarily as being moderate and requiring surgery/transfusion (N=647; Tables 3, S1, S2) [35–39]. The five thresholds were located within 52–68Gy/2–12% [35–37], and within 150–180Gy/2% [38, 39] No function was explored to fit these five thresholds given lack of data in between the two clusters of DVH thresholds (Fig S1). Thresholds for other GI toxicities included intermediate rectal thresholds at 25–58Gy/4–62% for occasional Anorectal pain , occasional Defecation Urgency , Diarrhea (increase in daily stools), and Stool frequency (4–8 times/day) [35] (N=118; Table 3).…”

“…The five thresholds were located within 52–68Gy/2–12% [35–37], and within 150–180Gy/2% [38, 39] No function was explored to fit these five thresholds given lack of data in between the two clusters of DVH thresholds (Fig S1). Thresholds for other GI toxicities included intermediate rectal thresholds at 25–58Gy/4–62% for occasional Anorectal pain , occasional Defecation Urgency , Diarrhea (increase in daily stools), and Stool frequency (4–8 times/day) [35] (N=118; Table 3). For Fistula , one threshold at 93Gy/2% (N=2368) was identified [40].…”

Accumulation of rectum dose‐volume metrics for prostate external beam radiotherapy combined with brachytherapy: Evaluating deformably registered dose distribution addition using parameter‐based addition

“…However, it is common for retrospective studies, such as this one, to be constrained by resources and protocols in place at the time patients were treated. The potential influence of inter/intra‐fraction motion on rectum doses for patients in this study who received combined prostate EBRT/HDR‐BT has previously been discussed in more detail …”

What pelvic radiation disease symptoms are experienced by patients receiving external beam radiotherapy and a high-dose-rate brachytherapy boost for prostate cancer?

“…Mixed results were seen depending on questions/ symptoms for age and T-stage. Patients’ symptoms and late effects following treatment may be linked to other factors not analyzed in this study such as treatment volume, dose received to critical structures including the rectum [ 28 ], patient weight, diet, and lifestyle factors. Further research is warranted to determine whether these factors impact on incidence and severity of symptoms reported by patients.…”