P019 Multi-variable models predicting specific patient-reported acute urinary symptoms after radiotherapy for prostate cancer: Ad interim results of a cohort study

Incidence of genitourinary complications following radiation therapy for localised prostate cancer

Purpose

Studies of genitourinary toxicity following radiotherapy for prostate cancer are mainly from high volume single institutions and the incidence and burden of treatment remain uncertain. Hence we determine the cumulative incidence of treatment-related genitourinary toxicity in patients with localised prostate cancer treated with primary external beam radiotherapy (EBRT) at a state population level.

Methods

We analysed data from a prospective population-based cohort, including hospital admission and cancer registry data, for men with localised prostate cancer who underwent primary EBRT without nodal irradiation between 1998 and 2019 in South Australia. The 10-year cumulative incidence of genitourinary toxicity requiring hospitalisation or procedures was determined. Clinical predictors of toxicity and the volume of admissions, non-operative, minor operative and major operative procedures were determined.

Results

All the included patients (n = 3350) had EBRT, with a median (IQR) of 74 Gy (70–78) in 37 fractions (35–39). The 10-year cumulative incidence of was 28.4% (95% CI 26.3–30.6) with a total of 2545 hospital admissions, including 1040 (41%) emergency and 1893 (74%) readmissions. The 10-year cumulative incidence of patients in this cohort requiring a urological operative procedure was 18% (95% CI 16.1–19.9), with a total of 106 (4.2%) non-operative, 1044 (41%) minor operative and 57 (2.2%) major operative urological procedures.

Conclusions

Genitourinary toxicity after radiotherapy for prostate cancer is common. Although there continue to be advancements in radiotherapy techniques, patients and physicians should be aware of the risk of late toxicity when considering EBRT.

Supplementary Information

The online version contains supplementary material available at 10.1007/s00345-022-04124-x.

Voxel-Based Analysis for Identification of Urethrovesical Subregions Predicting Urinary Toxicity After Prostate Cancer Radiation Therapy

PURPOSE

To apply a voxel-based analysis to identify urethrovesical symptom-related subregions (SRSs) associated with acute and late urinary toxicity in prostate cancer radiation therapy.

METHODS AND MATERIALS

Two hundred seventy-two patients with prostate cancer treated with intensity-modulated radiation therapy/image-guided radiation therapy were analyzed prospectively. Each patient's computed tomography imaging was spatially normalized to a common coordinate system via nonrigid registration. The obtained deformation fields were used to map the dose of each patient to the common coordinate system. A voxel-based statistical analysis was applied to generate 3-dimensional dose-volume maps for different urinary symptoms, allowing the identification of corresponding SRSs with statistically significant dose differences between patients with or without toxicity. Each SRS was propagated back to each individual's native space, and dose-volume histograms (DVHs) for the SRSs and the whole bladder were computed. Logistic and Cox regression were used to estimate the SRS's prediction capability compared with the whole bladder.

RESULTS

A local dose-effect relationship was found in the bladder and the urethra. SRSs were identified for 5 symptoms: acute incontinence in the urethra, acute retention in the bladder trigone, late retention and dysuria in the posterior part of the bladder, and late hematuria in the superior part of the bladder, with significant dose differences between patients with and without toxicity, ranging from 1.2 to 9.3 Gy. The doses to the SRSs were significantly predictive of toxicity, with maximum areas under the receiver operating characteristic curve of 0.73 for acute incontinence, 0.62 for acute retention, 0.70 for late retention, 0.81 for late dysuria, and 0.67 for late hematuria. The bladder DVH was predictive only for late retention, dysuria, and hematuria (area under the curve, 0.65-0.72).

CONCLUSIONS

The dose delivered to the urethra and the posterior and superior parts of the bladder was predictive of acute incontinence and retention and of late retention, dysuria, and hematuria. The dose to the whole bladder was moderately predictive.