Spatial rectal dose/volume metrics predict patient-reported gastro-intestinal symptoms after radiotherapy for prostate cancer

Acta Oncol. 2017 Nov;56(11):1507-1513. doi: 10.1080/0284186X.2017.1370130. Epub 2017 Sep 8.


Background: Gastro-intestinal (GI) toxicity after radiotherapy (RT) for prostate cancer reduces patient's quality of life. In this study, we explored associations between spatial rectal dose/volume metrics and patient-reported GI symptoms after RT for localized prostate cancer, and compared these with those of dose-surface/volume histogram (DSH/DVH) metrics.

Material and methods: Dose distributions and six GI symptoms (defecation urgency/emptying difficulties/fecal leakage, ≥Grade 2, median follow-up: 3.6 y) were extracted for 200 patients treated with image-guided RT in 2005-2007. Three hundred and nine metrics assessed from 2D rectal dose maps or DSHs/DVHs were subject to 50-times iterated five-fold cross-validated univariate and multivariate logistic regression analysis (UVA, MVA). Performance of the most frequently selected MVA models was evaluated by the area under the receiving-operating characteristics curve (AUC).

Results: The AUC increased for dose-map compared to DSH/DVH-based models (mean SD: 0.64 ± 0.03 vs. 0.61 ± 0.01), and significant relations were found for six versus four symptoms. Defecation urgency and faecal leakage were explained by high doses at the central/upper and central areas, respectively; while emptying difficulties were explained by longitudinal extensions of intermediate doses.

Conclusions: Predictability of patient-reported GI toxicity increased using spatial metrics compared to DSH/DVH metrics. Novel associations were particularly identified for emptying difficulties using both approaches in which intermediate doses were emphasized.

MeSH terms

  • Defecation*
  • Dose-Response Relationship, Radiation
  • Fecal Incontinence / diagnosis*
  • Fecal Incontinence / etiology
  • Gastrointestinal Diseases / diagnosis*
  • Gastrointestinal Diseases / etiology
  • Humans
  • Male
  • Prostatic Neoplasms / radiotherapy*
  • Radiation Injuries / diagnosis*
  • Radiation Injuries / etiology
  • Radiotherapy, Conformal / adverse effects*
  • Rectum / pathology*
  • Rectum / radiation effects