Purpose <p>To evaluate whether principal component analysis (PCA) of rectal and bladder dose–volume histograms (DVHs) identifies dose regions associated with late toxicity after prostate stereotactic body radiotherapy (SBRT).</p> Methods/patients <p>This retrospective single-institution study included 106 patients with linked clinical and dosimetric data after prostate SBRT to 36.25&#xa0;Gy in five fractions. PCA was applied separately to whole-organ and wall-based rectal and bladder DVHs. Associations with late grade ≥ 2 gastrointestinal (GI) and genitourinary (GU) toxicity at 12&#xa0;months were explored using Spearman correlation, ROC analysis and deliberately limited logistic regression. Toxicity was extracted retrospectively from institutional follow-up records scored according to CTCAE v5.0.</p> Results <p>Among 84 patients with 12-month follow-up in the DVH-linked dosimetric cohort, grade ≥ 2 toxicity was uncommon, with 3 GI events (3.6%) and 2 GU events (2.4%). Intermediate-dose rectal metrics showed the strongest exploratory signal for late GI toxicity, particularly rectal V18.1&#xa0;Gy (AUC 0.868, 95% CI 0.740–0.997) and V29 Gy (AUC 0.827). These estimates are based on very few events and should not be interpreted as validated predictive performance or as evidence of a new planning threshold. No bladder or bladder-wall metric showed clinically meaningful discrimination for GU toxicity.</p> Conclusions <p>Intermediate whole-rectum dose was associated with late GI toxicity in this low-event SBRT cohort, but the findings are exploratory and require validation. No isolated dosimetric predictor of late GU toxicity was identified.</p>

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Intermediate rectal dose is associated with late toxicity after prostate SBRT: a dose–volume histogram principal component analysis

  • Amadeo J. Wals Zurita,
  • Ana Illescas Vacas,
  • Héctor Miras del Río,
  • María Rubio Jiménez,
  • Paula Vicente Ruíz,
  • Jonathan Saavedra Bejarano,
  • Antonio Ureña,
  • Mónica Ortiz Seidel,
  • Francisco Carrasco Peña

摘要

Purpose

To evaluate whether principal component analysis (PCA) of rectal and bladder dose–volume histograms (DVHs) identifies dose regions associated with late toxicity after prostate stereotactic body radiotherapy (SBRT).

Methods/patients

This retrospective single-institution study included 106 patients with linked clinical and dosimetric data after prostate SBRT to 36.25 Gy in five fractions. PCA was applied separately to whole-organ and wall-based rectal and bladder DVHs. Associations with late grade ≥ 2 gastrointestinal (GI) and genitourinary (GU) toxicity at 12 months were explored using Spearman correlation, ROC analysis and deliberately limited logistic regression. Toxicity was extracted retrospectively from institutional follow-up records scored according to CTCAE v5.0.

Results

Among 84 patients with 12-month follow-up in the DVH-linked dosimetric cohort, grade ≥ 2 toxicity was uncommon, with 3 GI events (3.6%) and 2 GU events (2.4%). Intermediate-dose rectal metrics showed the strongest exploratory signal for late GI toxicity, particularly rectal V18.1 Gy (AUC 0.868, 95% CI 0.740–0.997) and V29 Gy (AUC 0.827). These estimates are based on very few events and should not be interpreted as validated predictive performance or as evidence of a new planning threshold. No bladder or bladder-wall metric showed clinically meaningful discrimination for GU toxicity.

Conclusions

Intermediate whole-rectum dose was associated with late GI toxicity in this low-event SBRT cohort, but the findings are exploratory and require validation. No isolated dosimetric predictor of late GU toxicity was identified.