Late Toxicities of Prostate Radiotherapy: Can We Further SMARTen Up the Therapeutic Index?

Associations of dose to the urethra and long-term patient-reported outcomes after radiotherapy with EBRT and HDR brachytherapy boost for prostate cancer

Purpose

Implications of radiation dose exposure to the urethra on urinary morbidity after prostate radiotherapy are poorly understood, especially by long-term patient-reported outcomes (PRO). Therefore, our primary objective was to investigate associations of urethral dose and long-term patient-reported urinary morbidity after external beam radiotherapy and high-dose rate brachytherapy boost for prostate cancer.

Materials and methods

We conducted a pre-registered (https://doi.org/10.17605/OSF.IO/A6DC3) cross-sectional study at a tertiary academic center including a consecutive sample of patients being at least two years after treatment. Primary outcome measurements included urinary domains of the EPIC-26 questionnaire. Their associations with predefined urethral dose levels were assessed by univariable analyses (Pearson's correlation) and by predefined multivariable analyses (multiple regression). Sample size calculation was based on a predefined multivariable model. A p-value < 0.05 was considered statistically significant.

Results

Among 277 screened patients, 113 patients were alive, eligible, consented, and provided PRO. The median time passed since radiotherapy was 4 years. Per univariable analysis, a higher near maximum point dose of the urethra (DU0.1cc) was associated with worse urinary incontinence (r = -0.32; CI = -0.48 - -0.13; p < 0.001) and worse overall urinary function (r = -0.21; CI = -0.38 - -0.03; p = 0.02) of the respective EPIC-26 domains. Per predefined multivariable analysis, DU0.1cc and urinary incontinence remained significantly associated (B = -0.005; CI = -0.008 - -0.002; p = 0.003). These associations were only present, when very high DU0.1 cc above 137 Gy were kept in the analysis.

Conclusions

Very high urethral near point doses appear to be associated with worse long-term patient-reported urinary morbidity after radiotherapy for prostate cancer. Urethral dose should be considered in practice and future trials to potentially minimize long-term urinary morbidity.

Trial registration

The study protocol was pre-registered prior to patient accrual on the Open Science Framework (https://doi.org/10.17605/OSF.IO/A6DC3).

Incidence and Management of Radiation Cystitis After Pelvic Radiotherapy for Prostate Cancer: Analysis From a National Database

OBJECTIVE

To determine the incidence of radiation cystitis on prostate cancer (PCa) patients undergoing pelvic radiotherapy (RT), evaluating the most used management strategies, and identifying potential risk factors associated with the development of this condition.

METHODS

A retrospective analysis was conducted using the PearlDiver Mariner database, containing patient records compiled between 2011 and 2022. International Classification of Diseases (ICD) and Current Procedural Terminology (CPT) codes were employed to identify population and outcomes. We evaluated patients who underwent RT for PCa and subsequently developed radiation cystitis. Primary objective was to determine the overall incidence of radiation cystitis. Furthermore, we investigated its associated risk factors and management.

RESULTS

A total of 274,865 PCa patients underwent RT during the study period. Of these, 48,713 (17.7%) experienced hematuria following RT, while 7721 (2.8%) were diagnosed with radiation cystitis. After the diagnosis, 2307 patients (29.9%) received diagnostic or therapeutic endoscopic interventions. Only 59 patients (0.76%) underwent endovascular embolization, while 151 patients (1.95%) required cystectomy. Hyperbaric oxygen therapy, administered to 1287 patients (16.67%), was the only treatment that displayed a significant upward trend. Multivariate logistic regression identified obesity (OR 1.29; 95% CI 1.23-1.35), smoking (OR 1.27; 95% CI 1.22-1.33), and diabetes (OR 1.32; 95% CI 1.26-1.39), as significant risk factors for radiation cystitis (all P-values <.001).

CONCLUSION

Radiation cystitis represents a rare complication after pelvic RT with significant clinical impact. Its incidence has remained stable throughout the study period. The identified risk factors corroborate the pathophysiology of radiation cystitis. Hyperbaric oxygen therapy was the only treatment to show an upward trend during the study period.

Randomized Trial of Concomitant Hypofractionated Intensity Modulated Radiation Therapy Boost Versus Conventionally Fractionated Intensity Modulated Radiation Therapy Boost for Localized High-Risk Prostate Cancer (pHART2-RCT)

PURPOSE

The aim of this work is to report on the results of a phase 2 randomized trial of moderately hypofractionated (MH) versus conventionally fractionated (CF) radiation therapy to the prostate with elective nodal irradiation.

METHODS AND MATERIALS

This was a single-center, prospective, phase 2 randomized study. Patients with high-risk disease (cT3, prostate-specific antigen level >20 ng/mL, or Gleason score 8-10) were eligible. Patients were randomized to either MH using a simultaneous integrated boost (68 Gy in 25 fractions to prostate; 48 Gy to pelvis) or CF (46 Gy in 23 fractions with a sequential boost to the prostate of 32 Gy in 16 fractions), with long-term androgen deprivation therapy. The primary endpoint was grade ≥2 acute gastrointestinal (GI) and genitourinary (GU) toxicity (Common Terminology Criteria for Adverse Events version 3.0). Secondary endpoints included late GI and GU toxicity, quality of life, and oncologic outcomes.

RESULTS

One-hundred eighty patients were enrolled; 90 were randomized to and received MH and 90 to CF. The median follow-up was 67.4 months. Seventy-five patients (41.7%) experienced a grade ≥2 acute GI and/or GU toxicity, including 34 (37.8%) in the MH and 41 (45.6%) in the CF arms, respectively (P = .29). Late grade ≥2 GI (P = .07) and GU (P = .25) toxicity was not significantly different between arms; however, late grade ≥3 GI toxicity was worse in the MH group (P = .01). There were no statistically significant quality-of-life differences between the 2 treatments. There were no statistically significant differences observed in cumulative incidence of biochemical failure (P = .71) or distant metastasis (P = .31) and overall survival (P = .46).

CONCLUSIONS

MH to the prostate and pelvis with androgen deprivation therapy for men with high-risk localized prostate cancer was not significantly different than CF with regard to acute toxicity, quality of life, and oncologic efficacy. However, late grade ≥3 GI toxicity was more common in the MH arm.