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

Prostatic Urethral Length on MRI Potentially Predicts Late Genitourinary Toxicity After Prostate Cancer Radiation

RATIONALE AND OBJECTIVES

The purpose of our study was to evaluate pretreatment prostate quantitative magnetic resonance imaging (MRI) measurements and clinical characteristics in predicting genitourinary (GU) toxicity after radiotherapy (RT) for prostate cancer.

MATERIALS AND METHODS

In this single-institution retrospective cohort study, we evaluated patients with prostate adenocarcinoma who underwent MRI within 6 months before completing definitive RT and follow-up information in our GU toxicity database from June 2016 to February 2023. MRI measurements included quantitative urethra, prostate, and bladder measurements. GU toxicity was physician-scored using the Common Terminology Criteria for Adverse Events (CTCAE v4.0) with acute toxicity defined as ≤180 days and late defined as >180 days. Multivariable logistic regression model was constructed for grade ≥2 acute toxicity and Cox proportional hazards regression for late toxicity, adjusted for clinical factors and RT method.

RESULTS

A total of 361 men (median age 68 years, interquartile range [IQR] 62-73) were included; 14.4% (50/347) men experienced grade ≥2 acute toxicity. Brachytherapy (odds ratio [OR]: 2.9, 95% confidence interval [CI]: 1.5-5.8), P < 0.01) was associated with increased odds of acute GU toxicity, and longer MUL (OR: 0.41 [95%CI: 0.18-0.92], P = 0.03) with decreased odds. Median follow-up for late toxicity was 15.0 months (IQR: 9.0-28.0) with approximately 88.7% and 72.0% patients free of toxicity at 1 and 3 years, respectively. Only longer prostatic urethral length (hazard ratio [HR]: 1.6, 95%CI: 1.2-2.1, P < 0.01) was associated with increased risk of late GU toxicity, notably urinary frequency/urgency symptoms (HR: 1.7 [95%CI: 1.3-2.3], P < 0.01).

CONCLUSION

Longer prostatic urethral length measured on prostate MRI is independently associated with higher risk of developing late grade ≥2 GU toxicity after radiation therapy for prostate cancer. This pretreatment metric may be potentially valuable in risk-stratification models for quality of life following prostate RT.

Quality of Life Longitudinal Evaluation in Prostate Cancer Patients from Radiotherapy Start to 5 Years after IMRT-IGRT

PURPOSE

The purpose of this study is to study the evolution of quality of life (QoL) in the first 5 years following Intensity-modulated radiation therapy (IMRT) for prostate cancer (PCa) and to determine possible associations with clinical/treatment data.

MATERIAL AND METHODS

Patients were enrolled in a prospective multicentre observational trial in 2010-2014 and treated with conventional (74-80 Gy, 1.8-2 Gy/fr) or moderately hypofractionated IMRT (65-75.2 Gy, 2.2-2.7 Gy/fr). QoL was evaluated by means of EORTC QLQ-C30 at baseline, at radiation therapy (RT) end, and every 6 months up to 5 years after IMRT end. Fourteen QoL dimensions were investigated separately. The longitudinal evaluation of QoL was analysed by means of Analysis of variances (ANOVA) for multiple measures.

RESULTS

A total of 391 patients with complete sets of questionnaires across 5 years were available. The longitudinal analysis showed a trend toward the significant worsening of QoL at RT end for global health, physical and role functioning, fatigue, appetite loss, diarrhoea, and pain. QoL worsening was recovered within 6 months from RT end, with the only exception being physical functioning. Based on ANOVA, the most impaired time point was RT end. QoL dimension analysis at this time indicated that acute Grade ≥ 2 gastrointestinal (GI) toxicity significantly impacted global health, physical and role functioning, fatigue, appetite loss, diarrhoea, and pain. Acute Grade ≥ 2 genitourinary (GU) toxicity resulted in lower role functioning and higher pain. Prophylactic lymph-nodal irradiation (WPRT) resulted in significantly lower QoL for global health, fatigue, appetite loss, and diarrhoea; lower pain with the use of neoadjuvant/concomitant hormonal therapy; and lower fatigue with the use of an anti-androgen.

CONCLUSIONS

In this prospective, longitudinal, observational study, high radiation IMRT doses delivered for PCa led to a temporary worsening of QoL, which tended to be completely resolved at six months. Such transient worsening was mostly associated with acute GI/GU toxicity, WPRT, and higher prescription doses.

Rectum and Bladder Toxicity in Postoperative Prostate Bed Irradiation: Dose-Volume Parameters Analysis

Although prostate cancer treatment is increasingly effective, its toxicities pose a major concern. The aim of our study was to assess the rate of adverse events (AEs) and the prognostic value of dose-volume histogram (DVH) parameters for the occurrence of treatment toxicity in patients treated with post-prostatectomy prostate bed radiotherapy (RT). The AEs were scored according to the CTCAE v.5.0. The rectum and bladder were contoured according to the RTOG Guidelines. The DVH parameters were assessed using data exported from the ECLIPSE treatment-planning system. Genitourinary (GU) and gastrointestinal (GI) toxicity were analysed using consecutive dose thresholds for the percentage of an organ at risk (OAR) receiving a given dose and the QUANTEC dose constraints. A total of 213 patients were included in the final analysis. Acute grade 2 or higher (≥G2) GU AEs occurred in 18.7% and late in 21.3% of patients. Acute ≥G2 GI toxicity occurred in 11.7% and late ≥G2 in 11.2% of the patients. Five patients experienced grade 4 AEs. The most common adverse effects were diarrhoea, proctitis, cystitis, and dysuria. The most significant predictors of acute ≥G2 GI toxicity were rectum V47 and V46 (p < 0.001 and p < 0.001) and rectum wall V46 (p = 0.001), whereas the most significant predictors of late ≥G2 GI AEs were rectum wall V47 and V48 (p = 0.019 and p = 0.021). None of the bladder or bladder wall parameters was significantly associated with the risk of acute toxicity. The minimum doses to bladder wall (p = 0.004) and bladder (p = 0.005) were the most significant predictors of late ≥G2 GU toxicity. Postoperative radiotherapy is associated with a clinically relevant risk of AEs, which is associated with DVH parameters, and remains even in patients who fulfil commonly accepted dose constraints. Considering the lack of survival benefit of postoperative adjuvant RT, our results support delaying treatment through an early salvage approach to avoid or defer toxicity.

Dependence of the AUC of NTCP models on the observational dose-range highlights cautions in comparison of discriminative performance

BACKGROUND

Normal tissue complication probability (NTCP) models are probabilistic models that describe the risk of radio-induced toxicity in tissues or organs. In the field of radiotherapy, the area under the ROC curve (AUC) is widely used to estimate the performance in risk prediction of NTCP models.

METHODS

In this work, we derived an analytical expression of the AUC for the logistic NTCP model in the case of both symmetrical and asymmetrical dose (to the normal tissue) windows around D50. Using numerical simulations, we studied the behavior of the AUC in general clinical settings, enforcing non-logistic NTCP models (Lyman-Kutcher-Burman and LogEUD) and including risk factors beyond the dose. We validated our findings using real-world radiotherapy data sets of prostate cancer patients.

RESULTS

Our analytical expression of the AUC made explicit the dependence on both the steepness of the logistic curve (β) and the dose window width (w), showing that an increase of w pushes AUC towards higher values. Increasing values of the AUC with increasing values of w were consistently observed across simulated data sets with diverse clinical settings from published studies and real clinical data sets.

CONCLUSION

Our results reveal that the AUC of NTCP models inherits intrinsic characteristics from the clinical setting of the data set on which the models are developed, and warn against the use of the AUC to compare the performance of models constructed upon data from trials in which substantially different dose ranges were administered or accounting for different risk factors beyond the dose.

Associations of Clinical and Dosimetric Parameters with Urinary Toxicities after Prostate Brachytherapy: A Long-Term Single-Institution Experience

To examine the association of clinical, treatment, and dose parameters with late urinary toxicity after low-dose-rate brachytherapy (LDR-BT) for prostate cancer, we retrospectively studied patients with prostate cancer who underwent LDR-BT from January 2007 through December 2016. Urinary toxicity was assessed using the International Prostate Symptom Score (IPSS) and Overactive Bladder (OAB) Symptom Score (OABSS). Severe and moderate lower urinary tract symptoms (LUTS) were defined as IPSS ≥ 20 and ≥ 8, respectively; OAB was defined as a nocturnal frequency of ≥ 2 and a total OABSS of ≥ 3. In total, 203 patients (median age: 66 years) were included, with a mean follow-up of 8.4 years after treatment. The IPSS and OABSS worsened after 3 months of treatment; these scores improved to pretreatment levels after 18-36 months in most patients. Patients with a higher baseline IPSS and OABSS had a higher frequency of moderate and severe LUTS and OAB at 24 and 60 months, respectively. LUTS and OAB at 24 and 60 months were not correlated with the dosimetric factors of LDR-BT. Although the rate of long-term urinary toxicities assessed using IPSS and OABSS was low, the baseline scores were related to long-term function. Refining patient selection may further reduce long-term urinary toxicity.

High weekly integral dose and larger fraction size increase risk of fatigue and worsening of functional outcomes following radiotherapy for localized prostate cancer

Introduction

We hypothesized that increasing the pelvic integral dose (ID) and a higher dose per fraction correlate with worsening fatigue and functional outcomes in localized prostate cancer (PCa) patients treated with external beam radiotherapy (EBRT).

Methods

The study design was a retrospective analysis of two prospective observational cohorts, REQUITE (development, n=543) and DUE-01 (validation, n=228). Data were available for comorbidities, medication, androgen deprivation therapy, previous surgeries, smoking, age, and body mass index. The ID was calculated as the product of the mean body dose and body volume. The weekly ID accounted for differences in fractionation. The worsening (end of radiotherapy versus baseline) of European Organisation for Research and Treatment of Cancer EORTC) Quality of Life Questionnaire (QLQ)-C30 scores in physical/role/social functioning and fatigue symptom scales were evaluated, and two outcome measures were defined as worsening in ≥2 (WS2) or ≥3 (WS3) scales, respectively. The weekly ID and clinical risk factors were tested in multivariable logistic regression analysis.

Results

In REQUITE, WS2 was seen in 28% and WS3 in 16% of patients. The median weekly ID was 13.1 L·Gy/week [interquartile (IQ) range 10.2-19.3]. The weekly ID, diabetes, the use of intensity-modulated radiotherapy, and the dose per fraction were significantly associated with WS2 [AUC (area under the receiver operating characteristics curve) =0.59; 95% CI 0.55-0.63] and WS3 (AUC=0.60; 95% CI 0.55-0.64). The prevalence of WS2 (15.3%) and WS3 (6.1%) was lower in DUE-01, but the median weekly ID was higher (15.8 L·Gy/week; IQ range 13.2-19.3). The model for WS2 was validated with reduced discrimination (AUC=0.52 95% CI 0.47-0.61), The AUC for WS3 was 0.58.

Conclusion

Increasing the weekly ID and the dose per fraction lead to the worsening of fatigue and functional outcomes in patients with localized PCa treated with EBRT.

Predicting post-radiation genitourinary hospital admissions in patients with localised prostate cancer

PURPOSE

The risk of treatment-related toxicity is important for patients with localised prostate cancer to consider when deciding between treatment options. We developed a model to predict hospitalisation for radiation-induced genitourinary toxicity based on patient characteristics.

METHODS

The prospective South Australian Prostate Cancer Clinical Outcomes registry was used to identify men with localised prostate cancer who underwent curative intent external beam radiotherapy (EBRT) between 1998 and 2019. Multivariable Cox proportional regression was performed. Model discrimination, calibration, internal validation and utility were assessed using C-statistics and area under ROC, calibration plots, bootstrapping, and decision curve analysis, respectively.

RESULTS

There were 3,243 patients treated with EBRT included, of which 644 (20%) patients had a treated-related admission. In multivariable analysis, diabetes (HR 1.35, 95% CI 1.13-1.60, p < 0.001), smoking (HR 1.78, 95% CI 1.40-2.12, p < 0.001), and bladder outlet obstruction (BOO) without transurethral resection of prostate (TURP) (HR 7.49, 95% CI 6.18-9.08 p < 0.001) followed by BOO with TURP (HR 4.96, 95% CI 4.10-5.99 p < 0.001) were strong independent predictors of hospitalisation (censor-adjusted c-statistic = 0.80). The model was well-calibrated (AUC = 0.76). The global proportional hazards were met. In internal validation through bootstrapping, the model was reasonably discriminate at five (AUC 0.75) years after radiotherapy.

CONCLUSIONS

This is the first study to develop a predictive model for genitourinary toxicity requiring hospitalisation amongst men with prostate cancer treated with EBRT. Patients with localised prostate cancer and concurrent BOO may benefit from TURP before EBRT.

Pre-clinical Research on Bladder Toxicity After Radiotherapy for Pelvic Cancers: State-of-the Art and Challenges

Despite the dramatic advancements in pelvic radiotherapy, urinary toxicity remains a significant side-effect. The assessment of clinico-dosimetric predictors of radiation cystitis (RC) based on clinical data has improved substantially over the last decade; however, a thorough understanding of the physiopathogenetic mechanisms underlying the onset of RC, with its variegated acute and late urinary symptoms, is still largely lacking, and data from pre-clinical research is still limited. The aim of this review is to provide an overview of the main open issues and, ideally, to help investigators in orienting future research. First, anatomy and physiology of bladder, as well as the current knowledge of dose and dose-volume effects in humans, are briefly summarized. Subsequently, pre-clinical radiobiology aspects of RC are discussed. The findings suggest that pre-clinical research on RC in animal models is a lively field of research with growing interest in the development of new radioprotective agents. The availability of new high precision micro-irradiators and the rapid advances in small animal imaging might lead to big improvement into this field. In particular, studies focusing on the definition of dose and fractionation are warranted, especially considering the growing interest in hypo-fractionation and ablative therapies for prostate cancer treatment. Moreover, improvement in radiotherapy plans optimization by selectively reducing radiation dose to more radiosensitive substructures close to the bladder would be of paramount importance. Finally, thanks to new pre-clinical imaging platforms, reliable and reproducible methods to assess the severity of RC in animal models are expected to be developed.

Automated Radiotherapy Planning for Patient-Specific Exploration of the Trade-Off Between Tumor Dose Coverage and Predicted Radiation-Induced Toxicity-A Proof of Principle Study for Prostate Cancer

Background: Currently, radiation-oncologists generally evaluate a single treatment plan for each patient that is possibly adapted by the planner prior to final approval. There is no systematic exploration of patient-specific trade-offs between planning aims, using a set of treatment plans with a-priori defined (slightly) different balances. To this purpose, we developed an automated workflow and explored its use for prostate cancer. Materials and Methods: For each of the 50 study patients, seven plans were generated, including the so-called clinical plan, with currently clinically desired ≥99% dose coverage for the low-dose planning target volume (PTVLow). The six other plans were generated with different, reduced levels of PTVLow coverage, aiming at reductions in rectum dose and consequently in predicted grade≥2 late gastro-intestinal (GI) normal tissue complication probabilities (NTCPs), while keeping other dosimetric differences small. The applied NTCP model included diabetes as a non-dosimetric predictor. All plans were generated with a clinically applied, in-house developed algorithm for automated multi-criterial plan generation. Results: With diabetes, the average NTCP reduced from 24.9 ± 4.5% for ≥99% PTVLow coverage to 17.3 ± 2.6% for 90%, approaching the NTCP (15.4 ± 3.0%) without diabetes and full PTVLow coverage. Apart from intended differences in PTVLow coverage and rectum dose, other differences between the clinical plan and the six alternatives were indeed minor. Obtained NTCP reductions were highly patient-specific (ranging from 14.4 to 0.1%), depending on patient anatomy. Even for patients with equal NTCPs in the clinical plan, large differences were found in NTCP reductions. Conclusions: A clinically feasible workflow has been proposed for systematic exploration of patient-specific trade-offs between various treatment aims. For each patient, automated planning is used to generate a limited set of treatment plans with well-defined variations in the balances between the aims. For prostate cancer, trade-offs between PTVLow coverage and predicted GI NTCP were explored. With relatively small coverage reductions, significant NTCP reductions could be obtained, strongly depending on patient anatomy. Coverage reductions could also make up for enhanced NTCPs related to diabetes as co-morbidity, again dependent on the patient. The proposed system can play an important role in further personalization of patient care.

Patterns in ano-rectal dose maps and the risk of late toxicity after prostate IMRT

Purpose: The aim of this work was to determine how the spatial pattern of dose in the ano-rectal wall is related to late gastro-intestinal toxicity for prostate cancer patients treated with mainly IMRT.Patients and methods: Patients from the DUE-01 multicentre study with patient-reported (prospective) follow-up and available dosimetric data were included. Conventionally fractionated patients received 74-80 Gy and hypofractionated patients received 65-75.2 Gy. A large majority of the patients were treated with intensity-modulated radiotherapy (IMRT). Dose-surface maps (DSMs) for the anal canal and rectum as a single structure, and for the anal canal and the rectum separately, were co-registered rigidly in two dimensions and, for the patients with and without toxicity, respectively, the mean value of the dose in each pixel was calculated. A pixel-wise t-test was used to highlight the anatomical areas where there was a significant difference between the 'mean dose maps' of each group. Univariate models were also fitted to a range of spatial parameters. The endpoints considered were a mean grade ≥1 late fecal incontinence and a maximum grade ≥2 late rectal bleeding.Results: Twenty-six out of 213 patients had fecal incontinence, while 21/225 patients had rectal bleeding. Incontinence was associated with a higher dose in the caudal region of the anal canal; the most relevant spatial parameter was the lateral extent of the low and medium isodoses (5-49 Gy in EQD2). Bleeding was associated with high isodoses reaching the posterior rectal wall. The spatial dose parameters with the highest AUC value (.69) were the lateral extent of the 60-70 Gy isodoses.Conclusions: To avoid fecal incontinence it is important to limit the portion of the anal canal irradiated. Our analysis confirms that rectal bleeding is a function of similar spatial dose parameters for patients treated with IMRT, compared to previous studies on patients treated with three-dimensional conformal radiotherapy.

Multi-centre technical evaluation of the radiation-induced lymphocyte apoptosis assay as a predictive test for radiotherapy toxicity

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The RILA assay is the leading candidate biomarker for radiotherapy toxicity.

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We describe work to standardise its use across multiple centres.

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Patient factors including smoking and arthritis were found to affect RILA score.

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RILA predicts acute breast pain but not other acute end-points.

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This work establishes the basis for implementing the assay clinically.

Predicting which patients will develop adverse reactions to radiotherapy is important for personalised treatment. Prediction will require an algorithm or nomogram combining clinical and biological data. The radiation-induced lymphocyte apoptosis (RILA) assay is the leading candidate as a biological predictor of radiotherapy toxicity. In this study we tested the potential of the assay for standardisation and use in multiple testing laboratories.

The assay was standardised and reproducibility determined using samples from healthy volunteers assayed concurrently in three laboratories in Leicester (UK), Mannheim (Germany) and Montpellier (France). RILA assays were performed on samples taken prior to radiotherapy from 1319 cancer patients enrolled in the REQUITE project at multiple centres. The patients were being treated for breast (n = 753), prostate (n = 506) or lung (n = 60) cancer.

Inter-laboratory comparisons identified several factors affecting results: storage time, incubation periods and type of foetal calf serum. Following standardisation, there was no significant difference in results between the centres. Significant differences were seen in RILA scores between cancer types (prostate > breast > lung), by smoking status (non-smokers > smokers) and co-morbidity with rheumatoid arthritis (arthritics > non-arthritics).

An analysis of acute radiotherapy toxicity showed as expected that RILA assay does not predict most end-points, but unexpectedly did predict acute breast pain. This result may elucidate the mechanism by which the RILA assay predicts late radiotherapy toxicity.

The work shows clinical trials involving multiple laboratory measurement of the RILA assay are feasible and the need to account for tumour type and other variables when applying to predictive models.

Volumetric image-guided conformal radiotherapy for localized prostate cancer: Analysis of dosimetric and clinical factors affecting acute and late toxicity

Aim

To identify factors influencing toxicity in patients affected by localized prostate cancer treated with conformal image-guided radiotherapy.

Background

Image guidance in combination with conformal techniques is the standard of care in localized prostate cancer, but factors affecting toxicity are still under investigation.

Materials and methods

294 patients were analyzed. Median age at diagnosis was 71 year. 76 Gy (38 × 2 Gy) were delivered to the target volume. We used the χ² test to analyse associations between toxicity and dosimetric and clinical parameters. Multivariate analysis was performed using binary logistic regression. Kaplan-Meier method was used for survival analysis.

Results

Median follow-up was 62.9 months. Acute grade ≥2 gastro-intestinal toxicity (GI) was 12.1%. Acute genito-urinary (GU) toxicity of grade ≥2 was 33.9%. Actuarial 4 and 5 years late grade ≥2 GI was 3% and 4%, respectively. Four and 5-year late grade ≥2 GU toxicity was 6% and 10%. At multivariate analysis for acute toxicity rectal V₇₀ was correlated with GI toxicity (p = 0.01, HR 2.73 CI 1.19-6.26), and smoking habit with GU toxicity (p < 0.01, HR 2.50 CI 1.51-4.14). For late toxicity, rectal V₇₀ was correlated with gastro-intestinal toxicity (p = 0.04, HR 4.76 CI 1.07-21.13), and pre-radiotherapy urinary symptoms with genito-urinary toxicity (p = 0.01, HR 2.84 CI 1.29-6.22).

Discussion

Conformal image-guided radiotherapy shows low rates of toxicity. Smoking should be avoided during radiotherapy. Besides the evaluation of high doses received by the organs at risk, individual factors, such as co-morbidities and lifestyle choices, have an impact on normal-tissue complication risk.

Fitting NTCP models to bladder doses and acute urinary symptoms during post-prostatectomy radiotherapy

BACKGROUND

To estimate the radiobiological parameters of three popular normal tissue complication probability (NTCP) models, which describe the dose-response relations of bladder regarding different acute urinary symptoms during post-prostatectomy radiotherapy (RT). To evaluate the goodness-of-fit and the correlation of those models with those symptoms.

METHODS

Ninety-three consecutive patients treated from 2010 to 2015 with post-prostatectomy image-guided intensity modulated radiotherapy (IMRT) were included in this study. Patient-reported urinary symptoms were collected pre-RT and weekly during treatment using the validated Prostate Cancer Symptom Indices (PCSI). The assessed symptoms were flow, dysuria, urgency, incontinence, frequency and nocturia using a Likert scale of 1 to 4 or 5. For this analysis, an increase by ≥2 levels in a symptom at any time during treatment compared to baseline was considered clinically significant. The dose volume histograms of the bladder were calculated. The Lyman-Kutcher-Burman (LKB), Relative Seriality (RS) and Logit NTCP models were used to fit the clinical data. The fitting of the different models was assessed through the area under the receiver operating characteristic curve (AUC), Akaike information criterion (AIC) and Odds Ratio methods.

RESULTS

For the symptoms of urinary urgency, leakage, frequency and nocturia, the derived LKB model parameters were: 1) D50 = 64.2Gy, m = 0.50, n = 1.0; 2) D50 = 95.0Gy, m = 0.45, n = 0.50; 3) D50 = 83.1Gy, m = 0.56, n = 1.00; and 4) D50 = 85.4Gy, m = 0.60, n = 1.00, respectively. The AUC values for those symptoms were 0.66, 0.58, 0.64 and 0.64, respectively. The differences in AIC between the different models were less than 2 and ranged within 0.1 and 1.3.

CONCLUSIONS

Different dose metrics were correlated with the symptoms of urgency, incontinence, frequency and nocturia. The symptoms of urinary flow and dysuria were poorly associated with dose. The values of the parameters of three NTCP models were determined for bladder regarding four acute urinary symptoms. All the models could fit the clinical data equally well. The NTCP predictions of urgency showed the best correlation with the patient reported outcomes.

Understanding Urinary Toxicity after Radiotherapy for Prostate Cancer: First Steps Forward

One of the most relevant achievements of Professor Gianni Bonadonna was the implementation of the methodology of controlled clinical trials in medical oncology. It is valid for all cancer types, oncological disciplines and clinical endpoints, both survival and toxicity. This narrative review reports on the status of the current knowledge of the radiation-induced urinary syndrome after external-beam radiotherapy for prostate cancer. In recent years, the syndrome has been the object of large-scale prospective observational trials specifically devoted to investigating the association of patient and treatment features with acute/late urinary toxicity. The first results of these trials allow initial attempts at predictive modeling, which can serve as a basis for the optimization of patient selection and treatment planning.

Associations between volume changes and spatial dose metrics for the urinary bladder during local versus pelvic irradiation for prostate cancer

BACKGROUND

Inter-fractional variation in urinary bladder volumes during the course of radiotherapy (RT) for prostate cancer causes deviations between planned and delivered doses. This study compared planned versus daily cone-beam CT (CBCT)-based spatial bladder dose distributions, for prostate cancer patients receiving local prostate treatment (local treatment) versus prostate including pelvic lymph node irradiation (pelvic treatment).

MATERIAL AND METHODS

Twenty-seven patients (N = 15 local treatment; N = 12 pelvic treatment) were treated using daily image-guided RT (1.8 Gy@43-45 fx), adhering to a full bladder/empty rectum protocol. For each patient, 9-10 CBCTs were registered to the planning CT, using the clinically applied translations. The urinary bladder was manually segmented on each CBCT, 3 mm inner shells were generated, and semi and quadrant sectors were created using axial/coronal cuts. Planned and delivered DVH metrics were compared across patients and between the two groups of treatment (t-test, p < .05; Holm-Bonferroni correction). Associations between bladder volume variations and the dose-volume histograms (DVH) of the bladder and its sectors were evaluated (Spearman's rank correlation coefficient, r_s).

RESULTS

Bladder volumes varied considerably during RT (coefficient of variation: 16-58%). The population-averaged planned and delivered DVH metrics were not significantly different at any dose level. Larger treatment bladder volumes resulted in increased absolute volume of the posterior/inferior bladder sector receiving intermediate-high doses, in both groups. The superior bladder sector received less dose with larger bladder volumes for local treatments (r_s ± SD: -0.47 ± 0.32), but larger doses for pelvic treatments (r_s ± SD: 0.74 ± 0.24).

CONCLUSIONS

Substantial bladder volume changes during the treatment course occurred even though patients were treated under a full bladder/daily image-guided protocol. Larger bladder volumes resulted in less bladder wall spared at the posterior-inferior sector, regardless the treatment received. Contrary, larger bladder volumes meant larger delivered doses to the superior bladder sector for pelvic RT but smaller doses for local treatments.

Adverse Health Outcomes Associated with Postdiagnosis Smoking in Prostate Cancer Patients: A Literature Review

This literature review presents what is currently known about the association between postdiagnosis smoking and adverse health outcomes in prostate cancer. A literature search was conducted using Ovid Embase and Ovid MEDLINE. Information from 36 studies was summarized. There is strong evidence across the included studies of higher overall mortality and biochemical recurrence in current smokers diagnosed with prostate cancer. In addition, enhanced adverse effects following surgery, radiation, and hormone therapy have also been identified in current smokers of this population.

Acute Urinary Morbidity Following Stereotactic Body Radiation Therapy for Prostate Cancer with Prophylactic Alpha-Adrenergic Antagonist and Urethral Dose Reduction

BACKGROUND

Stereotactic body radiation therapy (SBRT) delivers high doses of radiation to the prostate while minimizing radiation to the adjacent critical organs. Large fraction sizes may increase urinary morbidity due to unavoidable treatment of the prostatic urethra. This study reports rates of acute urinary morbidity following SBRT for localized prostate cancer with prophylactic alpha-adrenergic antagonist utilization and urethral dose reduction (UDR).

METHODS

From April 2013 to September 2014, 102 patients with clinically localized prostate cancer were treated with robotic SBRT to a total dose of 35-36.25 Gy in five fractions. UDR was employed to limit the maximum point dose of the prostatic urethra to 40 Gy. Prophylactic alpha-adrenergic antagonists were initiated 5 days prior to SBRT and continued until resolution of urinary symptoms. Quality of life (QoL) was assessed before and after treatment using the American Urological Association Symptom Score (AUA) and the Expanded Prostate Cancer Index Composite-26 (EPIC-26). Clinical significance was assessed using a minimally important difference (MID) of one half SD change from baseline.

RESULTS

One hundred two patients underwent definitive prostate SBRT with UDR and were followed for 3 months. No patient experienced acute urinary retention requiring catheterization. A mean baseline AUA symptom score of 9.06 significantly increased to 11.83 1-week post-SBRT (p = 0.0024) and 11.84 1-month post-SBRT (p = 0.0023) but returned to baseline by 3 months. A mean baseline EPIC-26 irritative/obstructive score of 87.7 decreased to 74.1 1-week post-SBRT (p < 0.0001) and 77.8 1-month post-SBRT (p < 0.0001) but returned to baseline at 3 months. EPIC-26 irritative/obstructive score changes were clinically significant, exceeding the MID of 6.0. At baseline, 8.9% of men described their urinary function as a moderate to big problem, and that proportion increased to 37.6% 1 week following completion of SBRT before returning to baseline by 3 months.

CONCLUSION

Stereotactic body radiation therapy for localized prostate cancer with utilization of prophylactic alpha-adrenergic antagonist and UDR was well tolerated as determined by acute urinary function and bother, and symptoms were comparable to those observed following conventionally fractionated external beam radiation therapy (EBRT). Longer follow-up is required to assess long-term toxicity and efficacy following SBRT with UDR.

Predicting toxicity in radiotherapy for prostate cancer

This comprehensive review addresses most organs at risk involved in planning optimization for prostate cancer. It can be considered an update of a previous educational review that was published in 2009 (Fiorino et al., 2009). The literature was reviewed based on PubMed and MEDLINE database searches (from January 2009 up to September 2015), including papers in press; for each section/subsection, key title words were used and possibly combined with other more general key-words (such as radiotherapy, dose-volume effects, NTCP, DVH, and predictive model). Publications generally dealing with toxicity without any association with dose-volume effects or correlations with clinical risk factors were disregarded, being outside the aim of the review. A focus was on external beam radiotherapy, including post-prostatectomy, with conventional fractionation or moderate hypofractionation (<4Gy/fraction); extreme hypofractionation is the topic of another paper in this special issue. Gastrointestinal and urinary toxicity are the most investigated endpoints, with quantitative data published in the last 5years suggesting both a dose-response relationship and the existence of a number of clinical/patient related risk factors acting as dose-response modifiers. Some results on erectile dysfunction, bowel toxicity and hematological toxicity are also presented.