Impact of neoadjuvant relugolix on patient-reported sexual function and bother

Introduction

Sexual function following local treatment for prostate cancer is an important quality of life concern. Relugolix is a novel oral GnRH receptor antagonist used in combination with radiation therapy in the treatment of unfavorable prostate cancer. It has been shown to achieve rapid and profound testosterone suppression. As a result, these very low testosterone levels may impact both sexual functioning and perceptions. This prospective study sought to assess neoadjuvant relugolix-induced sexual dysfunction prior to stereotactic body radiation therapy (SBRT).

Methods

Between March 2021 and September 2023, 87 patients with localized prostate cancer were treated with neoadjuvant relugolix followed by SBRT per an institutional protocol. Sexual function and bother were assessed via the sexual domain of the validated Expanded Prostate Index Composite (EPIC-26) survey. Responses were collected for each patient at pre-treatment baseline and after several months of relugolix. A Utilization of Sexual Medications/Devices questionnaire was administered at the same time points to assess erectile aid usage.

Results

The median age was 72 years and 43% of patients were non-white. The median baseline Sexual Health Inventory for Men (SHIM) score was 13 and 41.7% of patients utilized sexual aids prior to relugolix. Patients initiated relugolix at a median of 4.5 months (2-14 months) prior to SBRT. 95% and 87% of patients achieved effective castration (≤ 50 ng/dL) and profound castration (< 20 ng/dl) at SBRT initiation, respectively. Ability to have an erection, ability to reach orgasm, quality of erections, frequency of erections, and overall sexual function significantly declined following relugolix. There was a non- significant increase in sexual bother.

Discussion

In concordance with known side effects of androgen deprivation therapy (ADT), neoadjuvant relugolix was associated with a significant decline in self-reported sexual function. However, patients indicated only a minimal and non-significant increase in bother. Future investigations should compare outcomes while on relugolix directly to GnRH agonist-induced sexual dysfunction.

Prognostic utility of biopsy-based PTEN and ERG status on biochemical progression and overall survival after SBRT for localized prostate cancer

Introduction/background

Phosphatase and tensin homolog (PTEN) genomic deletions and transmembrane protease, serine 2/v-ets avian erthyroblastosis virus E26 oncogene homolog (ERG) rearrangements are two of the most common genetic abnormalities associated with prostate cancer. Prior studies have demonstrated these alterations portend worse clinical outcomes. Our objective is to evaluate the impact of biopsy-determined PTEN losses and TMPRSS2-ERG fusion on biochemical progression-free survival (bPFS) and overall survival (OS) in patients who receive SBRT for localized prostate cancer.

Methods/materials

Patients received SBRT for localized prostate cancer on a prospective quality-of-life (QoL) and cancer outcomes study. For each patient, the single biopsy core with the highest grade/volume of cancer was evaluated for PTEN and ERG abnormalities. Differences in baseline patient and disease characteristics between groups were analyzed using ANOVA for age and χ2 for categorical groupings. bPFS and OS were calculated using the Kaplan Meier (KM) method with Log-Rank test comparison between groups. Predictors of bPFS and OS were identified using the Cox proportional hazards method. For all analyses, p <0.05 was considered statistically significant.

Results

Ninety-nine consecutive patients were included in the analysis with a median follow-up of 72 months. A statistically significant improvement in bPFS (p = 0.018) was observed for wild type ERG patients with an estimated 5-year bPFS of 94.1% vs. 72.4%. Regarding PTEN mutational status, significant improvements in were observed in both bPFS (p = 0.006) and OS (p < 0.001), with estimated 5-year bPFS rates of 91.0% vs. 67.9% and 5-year OS rates of 96.4% vs. 79.4%. When including both ERG and PTEN mutational status in the analysis, there were statistically significant differences in both bPFS (p = 0.011) and OS (p < 0.001). The estimated 5-year bPFS rates were 100%, 76.6%, 72.9%, and 63.8% for patients with ERG+/PTEN+, ERG-/PTEN+, ERG+/PTEN-, and ERG-/PTEN- phenotypes respectively. The estimated 5-year OS rates were 93.9%, 100%, 80.0%, and 78.7% for patients with ERG+/PTEN+, ERG-/PTEN+, ERG+/PTEN-, and ERG-/PTEN- phenotypes respectively.

Conclusion

ERG rearrangements and PTEN deletions detected on biopsy samples are associated with poorer oncologic outcomes in prostate cancer patients treated with SBRT and merit further study in a dedicated prospective trial.

Early biochemical outcomes following neoadjuvant/adjuvant relugolix with stereotactic body radiation therapy for intermediate to high risk prostate cancer

Introduction

Injectable GnRH receptor agonists have been shown to improve cancer control when combined with radiotherapy. Prostate SBRT offers an abbreviated treatment course with comparable efficacy to conventionally fractionated radiotherapy. Relugolix is a new oral GnRH receptor antagonist which achieves rapid, sustained testosterone suppression. This prospective study sought to evaluate early testosterone suppression and PSA response following relugolix and SBRT for intermediate to high prostate cancer.

Methods

Relugolix was initiated at least 2 months prior to SBRT. Interventions to improve adherence were not utilized. PSA and total testosterone levels were obtained prior to and 1-4 months post SBRT. Profound castration was defined as serum testosterone ≤ 20 ng/dL. Early PSA nadir was defined as the lowest PSA value within 4 months of completion of SBRT. Per prior trials, we examined the percentage of patients who achieved PSA level of ≤ 0.5 ng/mL and ≤ 0.2 ng/mL during the first 4 months post SBRT.

Results

Between July 2021 and January 2023, 52 men were treated at Georgetown with relugolix (4-6 months) and SBRT (36.25-40 Gy in 5 fractions) per an institutional protocol (IRB 12-1775). Median age was 71 years. 26.9% of patients were African American and 28.8% were obese (BMI ≥30 kg/m2). The median pretreatment PSA was 9.1 ng/ml. 67% of patients were ≥ Grade Group 3. 44 patients were intermediate- and 8 were high-risk. Patients initiated relugolix at a median of 3.6 months prior to SBRT with a median duration of 6.2 total months. 92.3% of patients achieved profound castration during relugolix treatment. Poor drug adherence was observed in 2 patients. A third patient chose to discontinue relugolix due to side effects. By post-SBRT month 4, 87.2% and 74.4% of patients achieved PSA levels ≤ 0.5 ng/ml and ≤ 0.2 ng/ml, respectively.

Discussion

Relugolix combined with SBRT allows for high rates of profound castration with low early PSA nadirs. We observed a 96% testosterone suppresion rate without the utilization of scheduled cues/reminders. This finding supports the notion that patients with localized prostate cancer can consistently and successfully follow an oral ADT protocol without daily reminders. Given relugolix's potential benefits over injectable GnRH receptor agonists, its usage may be preferred in specific patient populations (fear of needles, prior cardiovascular events). Future studies should focus on boundaries to adherence in specific underserved populations.

Bothersome Hot Flashes Following Neoadjuvant Androgen Deprivation Therapy and Stereotactic Body Radiotherapy for Localized Prostate Cancer

PURPOSE/OBJECTIVE(S)

Androgen deprivation therapy (ADT) may improve cancer control in unfavorable localized prostate cancer treated with stereotactic body radiotherapy (SBRT). ADT is known to cause hormonally related symptoms that resolve with testosterone recovery. Hot flashes are particularly burdensome. This study sought to evaluate the timeline of hot flashes following short-course ADT and SBRT as well as its relationship with testosterone recovery.

MATERIALS/METHODS

Institutional IRB approval was obtained for this retrospective review of prospectively collected data (IRB#: 2009-510). ADT was initiated three months prior to the start of SBRT. Hot flashes were self-reported via question 13a a healthcare software prior to ADT initiation, the first day of robotic SBRT, and at each follow-up (1, 3, 6, 9, 12, 18, 24 and 36 months). The responses were grouped into three relevant categories (no problem, very small-small problem and moderate-big problem). Scores were transformed to a 0-100 scale with higher scores reflecting less bother. Testosterone levels were measured at each follow-up.

RESULTS

From 2007 to 2010, 122 localized prostate cancer patients (9 low-, 64 intermediate-, and 49 high-risk according to the D'Amico classification) at a median age of 72 years (range 54.5-88.3) were treated with short course ADT (3-6 months) and SBRT (35-36.25 Gy) at Georgetown University Hospital. Thirty-two percent were black and 27% were obese. 77% of patient received three months of ADT. At baseline, 2% of men experienced hot flashes that were a "moderate to big problem" and that proportion peaked at the start of SBRT (45%) before returning to baseline 9 months post-SBRT with a cumulative incidence of 52.4%. The median baseline healthcare software hot flash score of 94 declined to 50 at the start of SBRT but this returned to baseline by six months post SBRT. These changes were both statistically and clinically significant (MID = 9.5083). Testosterone recovery (> 230 ng/dL) occurred in approximately 70% of patients by 12 months post SBRT. Resolution of hot flashes correlated with testosterone recovery.

CONCLUSION

Bothersome hot flashes occur in greater than 50% of men treated with neoadjuvant ADT. Resolution of hot flashes occurs in the majority of patients within one year after treatment. Reassurance of the temporary nature of hot flashes may assist in reducing patient anxiety. Measuring testosterone levels at follow-up visits may allow for anticipatory counseling that may limit the associated bother.

Bothersome Gynecomastia Following Neoadjuvant GnRH Agonists and Stereotactic Body Radiotherapy for Localized Prostate Cancer

PURPOSE/OBJECTIVE(S)

Androgen deprivation therapy (ADT) is increasingly utilized in combination with stereotactic body radiotherapy (SBRT) for unfavorable prostate cancer. ADT such as gonadotropin releasing hormone (GnRH) agonists are known to cause hormonal-related side effects such as gynecomastia. The incidence of bothersome breast tenderness and/or enlargement following short course GnRH agonists and SBRT is unknown. This study sought to evaluate the timeline of gynecomastia as well as its relationship with testosterone recovery.

MATERIALS/METHODS

Gynecomastia was self-reported via question 13b of a healthcare software prior to ADT initiation, the first day of robotic SBRT, and at each follow-up (1, 3, 6, 9, 12, 18, 24 and 36 months). The responses were grouped into three relevant categories (no problem, very small-small problem, and moderate-big problem). Scores were transformed to a 0-100 scale with higher scores reflecting less bother. Testosterone levels were measured at each follow-up.

RESULTS

From 2007 to 2010, 122 localized prostate cancer patients (9 low-, 64 intermediate-, and 49 high-risk according to the D'Amico classification) at a median age of 72 years (range 54.5-88.3) were treated with short course ADT (3-6 months) and SBRT (35-36.25 Gy) at Georgetown University Hospital. Of the participants, 48% percent were non-white and 48% were overweight. 77% of patients received three months of ADT. At baseline, 2% of men experienced gynecomastia that was a "moderate to big problem" and that proportion peaked at 3 and 12 months post-SBRT (7%) before returning to less than baseline (0%) 24 months post-SBRT with a cumulative incidence of 14.75%. The median baseline healthcare software hot flash score of 98 declined to 90 at 3 months post-SBRT but this returned to baseline by 24 months post SBRT. These changes were both statistically and clinically significant (MID = 6.5). Testosterone recovery (> 230 ng/dL) occurred in approximately 70% of patients by 12 months post SBRT. The development and resolution of gynecomastia fluctuated at various timepoints and did not directly correlate with testosterone recovery.

CONCLUSION

Bothersome gynecomastia occurs in less than 15% of men treated with neoadjuvant ADT. Resolution of gynecomastia occurs in most patients within two years after treatment. Reassurance of the temporary nature of gynecomastia may assist in reducing patient anxiety. Institutional IRB (IRB#: 2009-510) approval was obtained for retrospective review of prospectively collected data.

Marginless 5-Fraction Robotic Radiosurgery for Unfavorable Nonfunctioning Pituitary Macroadenoma: 5-year Outcomes from a Single Institution Protocol

PURPOSE/OBJECTIVE(S)

Nonfunctioning macroadenoma is a commonly diagnosed pituitary tumor. Resection is the favored treatment, with radiosurgery often utilized for residual or progressing disease. Long-term outcomes are established for single-session radiosurgery, but mature outcomes are lacking for multisession radiosurgery. We report our institution's 5-year efficacy and safety results for unfavorable nonfunctioning pituitary macroadenoma patients treated with marginless 5-fraction robotic radiosurgery.

MATERIALS/METHODS

Between 2010-2020, patients who completed marginless 5-fraction radiosurgery for the treatment of unfavorable nonfunctioning pituitary macroadenomas were included. A tumor was considered unfavorable if the gross tumor volume (GTV) was larger than 5 cc or if it closely approached a critical structure (optic apparatus, brainstem or pituitary gland). Local control was calculated using the Kaplan-Meier Method.

RESULTS

Twenty predominately female patients (60%), age from 21-77 (median: 53 years) were included in this study. All underwent primary resection. Indications for radiosurgery included unresectable recurrence (85%) and residual disease progression (70%). Median tumor volume was 3.4 cm3 (range: 0.3-20.8 cm3) and 40% of the tumors were suprasellar. A mean dose of 28.8 Gy (range: 25 Gy-30 Gy), was delivered to a median isodose line of 80% (range: 75%-89%). The median optic chiasm maximum point dose was 21.8 Gy (range: 12.0-25.9 Gy). Toxicity was minimal with 12 patients (40%) developing acute short-lived headaches and 1 patient (5%) developing a brief ipsilateral 6th nerve palsy. There was no radiation induced optic or pituitary dysfunction identified in this cohort. At a median follow up of 5 years local control was 95%. There was 1 in-field failure pathologically confirmed following surgery for pituitary tumor hemorrhage and 2 radiographically confirmed out-of-field failures in patients with large tumors (>20 cc).

CONCLUSION

The treatment of unfavorable nonfunctioning pituitary macroadenoma with marginless 5-fraction robotic radiosurgery provides excellent local control to date, with minimal toxicity. However, tumors with GTV's greater than 20 cc may require conventionally fractionated treatment with a margin to optimize local control.

Low Incidence of Late Lymphopenia Following Stereotactic Body Radiotherapy for Localized Prostate Cancer

PURPOSE/OBJECTIVE(S)

Stereotactic body radiotherapy (SBRT) is increasing in use for the treatment of localized prostate cancer. The utilization of highly conformal photon therapy such as SBRT may increase the whole-body integral dose. Lymphocytes are very radiation sensitive. This dose increase could lead to unintended consequences such as lymphopenia. Prior studies have shown that lymphopenia following radiation therapy may negatively impact long-term outcomes. This study sought to evaluate the incidence and timeline of chronic lymphopenia following prostate SBRT.

MATERIALS/METHODS

Institutional IRB (IRB#: 2012-1175) approval was obtained. The absolute lymphocyte count was measured 1-2 hours prior to robotic SBRT (35-36.25 Gy in 5 fractions) and at each follow-up (3, 6, 12, 18 and 24 months). Lymphopenia was graded using the CTCAEv.4: Grade 1 (1.0-0.8 k/μl), Grade 2 (0.8-0.5 k/μl), Grade 3 (0.5-0.2 k/μl) and Grade 4 (<0.2 k/μl). Late lymphopenia was defined as lymphopenia occurring 3 or more months post-SBRT.

RESULTS

From 2019 to 2022, 198 localized prostate cancer patients (23 low-, 148 intermediate-, and 27 high-risk according to the D'Amico classification) at a median age of 73.5 years were treated with SBRT (35-36.25 Gy) at Georgetown University Hospital on a prospective clinical trial. Baseline lymphopenia was uncommon: Grade 1 (3.5%), Grade 2 (1.5%) and Grade 3 (0%). The baseline ALC of 1.9 k/μl decreased to 1.5 k/μl at 3 months post-SBRT and then remained stable for the remainder of the two-year follow-up. Overall, 14.6% of men experienced lymphopenia in the two years following SBRT: Grade 1 (7.6%), Grade 2 (6.6%) and Grade 3 (0.5%). No patient experienced Grade 4 lymphopenia.

CONCLUSION

Prostate SBRT leads to a low rate of late lymphopenia with the vast majority of toxicities being low grade. The peak incidence occurred at 3 months post-SBRT. Resolution of lymphopenia occurs in most patients within two years after SBRT. Future studies should explore the possible impact on quality of life and cancer control outcomes.

Dosimetric predictors of acute bowel toxicity after Stereotactic Body Radiotherapy (SBRT) in the definitive treatment of localized prostate cancer

INTRODUCTION

SBRT is an increasingly popular treatment for localized prostate cancer, though considerable variation in technical approach is common and optimal dose constraints are uncertain. In this study, we sought to identify dosimetric and patient-related predictors of acute rectal toxicity.

METHODS

Patients included in this study were treated with prostate SBRT on a prospective institutional protocol. Physician-graded toxicity and patient-reported outcomes were captured at one week, one month, and three months following SBRT. DVH data were extracted and converted into relative volume differential DVHs for NTCP modeling. Patient- and disease-related covariates along with NTCP model predictions were independently tested for significant association with physician-graded toxicity or a decline in bowel-related QoL. A multivariate model was constructed using forward selection, and significant parameter cutoff values were obtained with Fischer's exact test to group patients by risk of developing physician-graded toxicity or detriments in patient-reported QoL.

RESULTS

One hundred and three patients treated for localized prostate cancer with SBRT were included in our analysis. 52% of patients experienced a clinically significant decline in bowel-related QOL within 1 week of completion of treatment, while only 27.5% of patients developed grade 2+ physician-graded rectal toxicity. Sequential feature selection multivariate logistic regression identified rectal V22.5 Gy (p = 0.001) and D19% (p = 0.001) as independent predictors of clinically significant toxicity, while rectal V20Gy (p = 0.004) and D25.3% (p = 0.007) were independently correlated with physician-graded toxicity. Global multivariate step-wise logistic regression identified only D19% (p = 0.001) and V20Gy (p = 0.004) as independent predictors of acute bowel bother or physician-graded rectal toxicity respectively.

CONCLUSIONS

Moderate doses to large rectal volumes, D19% and V20Gy, were associated with an increased incidence of a clinically significant decrease in patient-reported bowel QOL and physician-scored grade 2+ rectal toxicity, respectively. These dosimetric parameters may help practitioners mitigate acute toxicity in patients treated with prostate SBRT.

Association of baseline self-reported fatigue with overall survival after stereotactic body radiation therapy for localized prostate cancer

Introduction

Stereotactic Body Radiation Therapy (SBRT) has emerged as a definitive therapy for localized prostate cancer (PCa). However, more data is needed to predict patient prognosis to help guide which patients will benefit most from treatment. The FACIT-Fatigue (FACIT-F) is a well validated, widely used survey for assessing fatigue. However, the role of fatigue in predicting PCa survival has yet to be studied. Herein, we investigate the role of FACIT-F as a baseline predictor for overall survival (OS) in patients undergoing SBRT for localized PCa.

Methods

A retrospective review was conducted of 1358 patients who received SBRT monotherapy between January 2008 to April 2021 at an academic, tertiary referral center. FACIT-F scores (range 0 to 52) were summed for patients who answered all 13-items on the survey. FACIT-F total scores of ≥35 represented severe fatigue. Patients receiving androgen deprivation therapy were excluded. Differences in fatigue groups were evaluated using chi-squared tests. OS rates were determined using the Kaplan-Meier method and predictors of OS were evaluated using Cox proportional hazard method.

Results

Baseline full FACIT-F scores and survival data was available for 891 patients. 5-year OS was 87.6% and 95.2%, respectively, for the severely fatigued and non-fatigued groups. Chi-squared analysis of fatigue groups showed no significant difference in the following categories: D'Amico risk group, age, ethnicity, grade group, T-stage, or PSA density. Severe fatigue was associated with a significant decrease in OS (hazard ratio 2.76; 95%CI 1.55 - 4.89). The Cox proportional hazard model revealed that age and FACIT-F were both statistically significant (p <0.05).

Conclusion

Baseline FACIT-F scores are significantly associated with OS. Higher FACIT-F scores, representing less fatigued patients, are associated with an overall survival benefit. These results indicate that the FACIT-F survey could serve as an additional metric for clinicians in determining prognostic factors for patients undergoing SBRT.

Leptin modulated microRNA-628-5p targets Jagged-1 and inhibits prostate cancer hallmarks

MicroRNAs (miRNAs) are single-stranded non-coding RNA molecules that play a regulatory role in gene expression and cancer cell signaling. We previously identified miR-628-5p (miR-628) as a potential biomarker in serum samples from men with prostate cancer (PCa) (Srivastava et al. in Tumour Biol 35:4867–4873, 10.1007/s13277-014-1638-1, 2014). This study examined the detailed cellular phenotypes and pathways regulated by miR-628 in PCa cells. Since obesity is a significant risk factor for PCa, and there is a correlation between levels of the obesity-associated hormone leptin and PCa development, here we investigated the functional relationship between leptin and miR-628 regulation in PCa. We demonstrated that exposure to leptin downregulated the expression of miR-628 and increased cell proliferation/migration in PCa cells. We next studied the effects on cancer-related phenotypes in PCa cells after altering miR-628 expression levels. Enforced expression of miR-628 in PCa cells inhibited cell proliferation, reduced PCa cell survival/migration/invasion/spheroid formation, and decreased markers of cell stemness. Mechanistically, miR-628 binds with the JAG1-3′UTR and inhibits the expression of Jagged-1 (JAG1). JAG1 inhibition by miR-628 downregulated Notch signaling, decreased the expression of Snail/Slug, and modulated epithelial-mesenchymal transition and invasiveness in PC3 cells. Furthermore, expression of miR-628 in PCa cells increased sensitivity towards the drugs enzalutamide and docetaxel by induction of cell apoptosis. Collectively our data suggest that miR-628 is a key regulator of PCa carcinogenesis and is modulated by leptin, offering a novel therapeutic opportunity to inhibit the growth of advanced PCa.

Abstract 5822: Leptin modulated microRNA-628-5p targets Jagged1 and inhibits prostate cancer hallmarks

Prostate cancer (PCa) is the most commonly diagnosed non-cutaneous cancer and the second leading cause of cancer deaths in men. Obesity is a major risk factor for prostate cancer. Leptin is an obesity hormone that controls body weight by regulating energy intake and expenditure, and clinical studies have demonstrated a correlation between blood leptin levels and PCa development. MicroRNAs (miRs) are master regulators of cancer cell signaling, including in advanced PCa. We previously identified miR-628-5p as a potential biomarker in PCa patients that was downregulated in serum samples of men with PCa (Tumor Biol., 2014, 35: 4867). In this study, we investigated the link between the obesity hormone leptin and the functional role of miR-628-5p in PCa cell lines. We demonstrate that leptin downregulates the expression of miR-628-5p and increases cell proliferation and migration in PCa cells. Enforced expression of miR-628-5p inhibited cell proliferation in PCa cells. Further, miR-628-5p reduced PCa cell survival/migration/invasion/spheroids formation and cell stemness. Mechanistically, miR-628-5p binds with JAG1-3’UTR and inhibits the expression of Jagged-1 (JAG1). JAG1 inhibition by miR-628-5p also downregulated Notch signaling, decreased the expression of snail/slug, and modulated epithelial-mesenchymal transition and invasiveness in PC3 cells. Furthermore, miR-628-5p increased sensitivity towards enzalutamide and docetaxel by inducing cell apoptosis. Collectively our data suggested that miR-628-5p is a key regulator of PCa carcinogenesis modulated by adipokine leptin and offers a novel therapeutic opportunity to inhibit the growth of advanced PCa.

Citation Format: Leslimar Rios Colon, Juliet Chijioke, Suryakant Niture, Zainab Afzal, Qi Qi, Anvesha Srivastava, Malathi Ramalinga, Habib Kedir, Patrice Cagle, Elena Arthur, Gagan Deep, Simeng Suy, Sean Collins, Deepak Kumar. Leptin modulated microRNA-628-5p targets Jagged1 and inhibits prostate cancer hallmarks [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 5822.

Ejaculatory Function Following Stereotactic Body Radiation Therapy for Prostate Cancer

BACKGROUND

Ejaculatory dysfunction is an important male quality of life issue which has not yet been studied in the setting of prostate stereotactic body radiation therapy (SBRT).

AIM

The purpose of this study is to evaluate ejaculatory function following SBRT for prostate cancer.

METHODS

Two hundred and thirty-one patients on a prospective quality of life study with baseline ejaculatory capacity treated with prostate SBRT from 2013 to 2019 were included in this analysis. Ejaculation was assessed via the Ejaculation Scale (ES-8) from the Male Sexual Health Questionnaire. Patients completed the questionnaire at 1, 3, 6, 9, 12, 18, and 24 months post-SBRT. Elderly patients (Age > 70) and those who received hormonal therapy were excluded from analysis. Patients were treated to 35-36.25 Gy in 5 fractions delivered with the CyberKnife Radiosurgical System (Accuray).

OUTCOMES

Ejaculatory function was assessed by ES-8 scores (range 4-40) with lower values representing increased interference or annoyance.

RESULTS

Median age at the time of treatment was 65 years. Median follow up was 24 months (IQR 19-24.5 months). 64.5% of patients had ED at baseline (SHIM < 22). The 2-year anejaculation rate was 15%. Mean composite ES-8 scores showed a decline in the first month following treatment then stabilized: 30.4 (start of treatment); 26.5 (1 month); 27.6 (3 month); 27.0 (6 month); 26.2 (9 month); 25.4 (12 month); 25.0 (18 month) and 25.4 (24 month). White race, higher pre-treatment SHIM (≥22), and higher ES-8 (≥31) at treatment start were significantly associated with a decreased probability of a clinically significant decline. Patient-reported ejaculate volume was significantly reduced at all time points post-SBRT. Ejaculatory discomfort peaked at 1 month and 9 months post-SBRT. Prior to treatment, 8.0% of men reported that they were very to extremely bothered by their ejaculatory dysfunction. The number of patients reporting this concern increased to 14.4% at one year and dropped to 11% at 24-months post-SBRT.

CLINICAL TRANSLATION

Patients undergoing prostate SBRT may experience meaningful changes in ejaculatory function and should be counseled on the trajectory of these side effects.

STRENGTHS & LIMITATIONS

This was a retrospective analysis of a prospectively maintained database. Subjective questionnaire responses captured limited aspects of ejaculatory function in this cohort.

CONCLUSION

The high incidence of moderate to extreme bother in ejaculatory function before and after SBRT suggests a need for novel approaches to improving ejaculation. Sholklapper T, Creswell M, Cantalino J, et al. Ejaculatory Function Following Stereotactic Body Radiation Therapy for Prostate Cancer. J Sex Med 2022;19:771-780.

Rationale for Utilization of Hydrogel Rectal Spacers in Dose Escalated SBRT for the Treatment of Unfavorable Risk Prostate Cancer

In this review we outline the current evidence for the use of hydrogel rectal spacers in the treatment paradigm for prostate cancer with external beam radiation therapy. We review their development, summarize clinical evidence, risk of adverse events, best practices for placement, treatment planning considerations and finally we outline a framework and rationale for the utilization of rectal spacers when treating unfavorable risk prostate cancer with dose escalated Stereotactic Body Radiation Therapy (SBRT).

Patient-Reported Financial Burden Following Stereotactic Body Radiation Therapy for Localized Prostate Cancer

Introduction and Objectives

In patients with localized prostate cancer, 5-fraction, stereotactic body radiation therapy (SBRT) has been found to offer comparable oncologic outcomes and potential for improved treatment compliance compared to conventional, 40-plus fraction radiation therapy (RT). Recent studies of oncologic patient experiences have highlighted both the impact of therapy-associated financial toxicity (FT) on treatment adherence and health-related quality of life (HRQOL).

Methods

A cross-sectional assessment of FT after SBRT was performed using the 12-item COST questionnaire. The total questionnaire score (range 0–44) was used to evaluate the FT grade (0–3), with a higher COST value representing lower grade. The patient zip code was used to approximate the distance from the index hospital. Univariate and multivariate analyses of the average COST score (0–4) are performed.

Results

The response rate was 57.5% (332 of 575 consented patients) with 90.7%, 8.2%, and 1.1% experiencing grade 0, 1, and 2 FT, respectively, with no grade 3. Unemployment or disability, non-white race, low income, and concurrent hormonal therapy were associated with a statistically significant worse FT (lower COST value) on univariate and multivariate analyses (p < 0.05). Education level and insurance status significant were evaluated on univariate analysis only. There was a non-statistically significant difference in age, marital status, time since treatment, and distance from the index hospital.

Conclusions

SBRT was associated with low FT. However, statistically significant socioeconomic disparities in FT remain despite ultra-hypofractionated treatment.

Treatment Interruptions During Stereotactic Body Radiotherapy for Prostate Cancer

Background

During the course of radiation treatment for prostate cancer, patients may have unintentional interruptions in their treatment course due to a wide variety of factors. Stereotactic body radiation therapy (SBRT) decreases the number of treatments compared to conventionally fractionated radiation; hence, it has the potential to decrease treatment delays and non-completion. This study sought to determine the incidence of treatment delay and characterize the etiology and length in a large cohort of men treated with SBRT for their prostate cancer.

Methods

One thousand three hundred and thirty-six patients treated with SBRT from 2008 to 2021 at the Georgetown University Hospital for prostate cancer were included in this retrospective study. A treatment delay was defined as a patient requiring longer than 14 days to complete 5 fractions of SBRT. Non-completion was defined as patients treated with less than 5 fractions. In the patients who experienced delays, chart review was performed to characterize the length and etiology of each delay. Multivariate analysis was performed via binary logistic regression modeling on PSPP.

Results

All individuals in the cohort eventually completed the planned 5-fraction regimen. Thirty-three patients experienced a treatment delay. Median length of time to complete treatment was 11 days (range 5–155 days). In patients who experienced a delay, nearly half (45.5%) experienced only a one-day delay. The most common reason for a delay was a technical issue (48.5%), including the machine maintenance, fiducial misalignment, or inadequate pretreatment bowel preparation. Other reasons included unplanned breaks due to acute side effects (21.2%), logistical issues (18.2%), non-treatment related health issues (9.1%), and inclement weather (3.0%). There were no significant sociodemographic, oncologic, or treatment variables that predicted treatment interruption on multivariate analysis.

Conclusions

The incidence of treatment interruptions in patients undergoing SBRT for their prostate cancer was low. Most treatment delays were short.

Lobar Gross Endobronchial Disease Predicts for Overall Survival and Grade 5 Pulmonary Toxicity in Medically Inoperable Early Stage Non-Small Cell Lung Cancer Patients Treated With Stereotactic Body Radiation Therapy

Purpose

Stereotactic body radiation therapy (SBRT) is considered standard of care for medically inoperable early stage non-small cell lung cancer (ES-NSCLC). Central tumor location is a known risk factor for severe SBRT related toxicity. Bronchoscopy allows for visualization of the central airways prior to treatment. Five fraction SBRT approaches have been advocated to mitigate treatment induced toxicity. In this report, we examine the mature clinical outcomes of a diverse cohort of ES-NSCLC patients with both peripheral and central tumors treated with a conservative 5 fraction SBRT approach and evaluate the role of lobar gross endobronchial disease (LGED) in predicting overall survival and treatment-related death.

Methods

Medically inoperable biopsy-proven, lymph node-negative ES-NSCLC patients were treated with SBRT. Bronchoscopy was completed prior to treatment in all centrally located cases. The Kaplan-Meier method was used to estimate overall survival (OS), local control (LC), regional control (RC), distant metastasis free survival (DMFS) and disease-free survival (DFS). Overall survival was stratified based on clinical stage, histology, tumor location and LGED. Toxicities were scored according to the National Cancer Institute Common Terminology Criteria for Adverse Events, Version 5.0.

Results

From December 2010 to December 2015, 50 consecutive patients were treated uniformly with a 50 Gy in 5 fraction SBRT approach (tumor BED₁₀ ≥ 100 Gy) and followed for a minimum of 5 years or until death. At a median follow up of 42 months for all patients, 3-year OS was 50%. Three-year OS did not statistically differ between stage I and stage II disease (51% vs. 47%; p=0.86), adenocarcinoma and squamous cell carcinoma (50% vs. 45%; p=0.68), or peripheral and central tumors (56% vs. 45%; p=0.46). Five central tumors were found to have LGED, and 3-year OS for this cohort was quite poor at 20%. Cox regression analysis identified LGED as a predictor of OS while controlling for age, stage and location (OR:4.536, p-value=0.038). Despite the relatively low dose delivered, treatment likely contributed to the death of 4 patients with central tumors. Lobar gross endobronchial disease was an independent predictor for grade 5 pulmonary toxicity (n=4, p=0.007). Specifically, 3 of the 5 patients with LGED developed fatal radiation-induced bronchial stricture. Three-year LC, RC, DMFS and DFS results for the group were similar to contemporary studies at 90%, 90%, 82% and 65%.

Conclusions

Central location of ES-NSCLC is a well-established predictor for severe SBRT-related toxicity. Here we identify LGED as a significant predictor of poor overall survival and grade 5 pulmonary toxicity. The relatively high rates of severe treatment-related toxicity seen in patients with central ES-NSCLC may be due in part to LGED. Underlying LGED may cause irreparable damage to the lobar airway, unmitigated by SBRT treatment thus increasing the risk of severe treatment-related toxicity. These findings should be verified in larger data sets. Future prospective central ES-NSCLC clinical trials should require staging bronchoscopy to identify LGED and further assess its clinical significance.

Bothersome Hematospermia Following Stereotactic Body Radiation Therapy for Prostate Cancer

Background

Hematospermia following prostate radiation therapy is a benign and often self-limiting side effect. However, it may be bothersome to some men and their partners with a negative impact on sexual quality of life (QOL). This study sought to evaluate the incidence, duration, and resolution of hematospermia in patients following stereotactic body radiation therapy (SBRT) for prostate cancer.

Methods

227 patients treated with SBRT from 2013 to 2019 at Georgetown University Hospital for localized prostate carcinoma with a minimum follow up of two years were included in this retrospective review of data that was prospectively collected. Patients who were greater than 70 years old and/or received hormonal therapy were excluded. Hematospermia was defined as bright red blood in the ejaculate. Time points for data collection included initial consultation, pre-treatment, 1-, 3-, 6-, 9-, 12-, 18-, 24-month. All patients were treated with the CyberKnife Radiosurgical System (Accuray). Data on hematospermia including duration, resolution and recurrence was collected. Utilization of 5-alpha reductase inhibitors was documented at each visit.

Results

227 patients (45 low-, 177 intermediate-, and 5 high-risk according to the D’Amico classification) at a median age of 65 years (range 47-70) received SBRT for their localized prostate cancer. The 2-year cumulative incidence of hematospermia was 5.6%(14 patients). For these patients, all but one patient (93%) saw resolution of their hematospermia by two years post-SBRT. The median time for hematospermia was 9 months post-treatment. Of the 14 patients who reported hematospermia, 70% were managed with 5-alpha reductase inhibitors. Hematospermia was transient in most patients with 70% of the men reporting resolution by the next follow-up visit.

Conclusion

The incidence of bothersome hematospermia following SBRT was low. Hematospermia, as noted by other studies, often self-resolves. 5-alpha reductase inhibitors may lead to quicker resolution of bothersome hematospermia.

Refining the definition of biochemical failure in the era of stereotactic body radiation therapy for prostate cancer: The Phoenix definition and beyond

BACKGROUND AND PURPOSE

The Phoenix definition for biochemical failure (BCF) after radiotherapy uses nadir PSA (nPSA) + 2 ng/mL to classify a BCF and was derived from conventionally fractionated radiotherapy, which produces significantly higher nPSAs than stereotactic body radiotherapy (SBRT). We investigated whether an alternative nPSA-based threshold could be used to define post-SBRT BCFs.

MATERIALS AND METHODS

PSA kinetics data on 2038 patients from 9 institutions were retrospectively analyzed for low- and intermediate-risk PCa patients treated with SBRT without ADT. We evaluated the performance of various nPSA-based definitions. We also investigated the relationship of relative PSA decline (rPSA, PSA_18month/PSA_6month) and timing of reaching nPSA + 2 with BCF.

RESULTS

Median follow-up was 71.9 months. BCF occurred in 6.9% of patients. Median nPSA was 0.16 ng/mL. False positivity of nPSA + 2 was 30.2%, compared to 40.9%, 57.8%, and 71.0% for nPSA + 1.5, nPSA + 1.0, and nPSA + 0.5, respectively. Among patients with BCF, the median lead time gained from an earlier nPSA + threshold definition over the Phoenix definition was minimal. Patients with BCF had significantly lower rates of early PSA decline (mean rPSA 1.19 vs. 0.39, p < 0.0001) and were significantly more likely to reach nPSA + 2 ≥ 18 months (83.3% vs. 21.1%, p < 0.0001). The proposed criterion (rPSA ≥ 2.6 or nPSA + 2 ≥ 18 months) had a sensitivity and specificity of 92.4% and 81.5%, respectively, for predicting BCF in patients meeting the Phoenix definition and decreased its false positivity to 6.4%.

CONCLUSION

The Phoenix definition remains an excellent definition for BCF post-SBRT. Its high false positivity can be mitigated by applying additional criteria (rPSA ≥ 2.6 or time to nPSA + 2 ≥ 18 months).

Bleeding Risk Following Stereotactic Body Radiation Therapy for Localized Prostate Cancer in Men on Baseline Anticoagulant or Antiplatelet Therapy

Purpose

Patients on anticoagulant/antiplatelet medications are at a high risk of bleeding following external beam radiation therapy for localized prostate cancer. SBRT may reduce the bleeding risk by decreasing the volume of bladder/rectum receiving high doses. This retrospective study sought to evaluate the rates of hematuria and hematochezia following SBRT in these patients.

Methods

Localized prostate cancer patients treated with SBRT from 2007 to 2017 on at least one anticoagulant/antiplatelet at baseline were included. The minimum follow-up was 3 years with a median follow-up of 72 months. Patients who had a rectal spacer placed prior to SBRT were excluded. Radiotherapy was delivered in 5 fractions to a dose of 35 Gy or 36.25 Gy utilizing the CyberKnife system. Hematuria and hematochezia were prospectively assessed before and after treatment using the Expanded Prostate Cancer Index Composite (EPIC-26). Toxicities were scored using the CTCAE v4. Cystoscopy and colonoscopy findings were retrospectively reviewed.

Results

Forty-four men with a median age of 72 years with a history of taking at least one anticoagulant and/or antiplatelet medication received SBRT. Warfarin (46%), clopidogrel (34%) and rivaroxaban (9%) were the most common medications. Overall, 18.2% experienced hematuria with a median time of 10.5 months post-SBRT. Altogether, 38.6% experienced hematochezia with a median time of 6 months post-SBRT. ≥ Grade 2 hematuria and hematochezia occurred in 4.6% and 2.5%, respectively. One patient required bladder neck fulguration and one patient underwent rectal cauterization for multiple non-confluent telangiectasia. There were no grade 4 or 5 toxicities. Cystoscopy revealed bladder cancer (40%) and benign prostatic bleeding (40%) as the most common hematuria etiology. Colonoscopy demonstrated hemorrhoids (54.5%) and radiation proctitis (9.1%) as the main causes of hematochezia. There was no significant change from the mean baseline EPIC-26 hematuria and hematochezia scores at any point during follow up.

Conclusion

In patients with baseline anticoagulant usage, moderate dose prostate SBRT was well tolerated without rectal spacing. High grade bleeding toxicities were uncommon and resolved with time. Baseline anticoagulation usage should not be considered a contraindication to prostate SBRT.

Toxicity After Stereotactic Body Radiation Therapy for Prostate Cancer in Patients With Inflammatory Bowel Disease: A Multi-institutional Matched Case-Control Series

Purpose

To evaluate the safety of stereotactic body radiation therapy (SBRT) for prostate cancer in men with inflammatory bowel disease (IBD).

Methods and Materials

We queried a consortium database for patients with IBD receiving SBRT for prostate cancer between 2006 and 2012. Identified patients were matched with patients without a history of IBD in a 3:1 fashion based on dose, fractionation, use of androgen deprivation therapy, and age distribution. Logistic regression was used to evaluate the association between having IBD and experiencing acute and late gastrointestinal (GI) and genitourinary (GU) toxicities as scored on the Common Terminology Criteria for Adverse Events scale. Time to late toxicity was evaluated using proportional hazard Cox models. Our study was limited by absence of data on prostate size, baseline International Prostate Symptom Score, and rectal dose-volume histogram parameters.

Results

Thirty-nine patients with flare-free IBD at time of treatment (median follow-up 83.9 months) and 117 matched controls (median follow-up 88.7 months) were identified. A diagnosis of IBD was associated with increased odds of developing any late grade GI toxicity (odds ratio [OR] 6.11, P <.001) and GU toxicity (odds ratio 6.14, P < .001), but not odds of developing late grade ≥2 GI (P = .08) or GU toxicity (P = .069). Acute GI and GU toxicity, both overall and for grade ≥2 toxicities, were more frequent in men with IBD (P < .05). Time to late GI and GU toxicity of any grade was significantly shorter in patients with IBD (P < .001). Time to late grade ≥2 GU, but not grade ≥2 GI toxicity, was also shorter in patients with IBD (P = .044 for GU and P = .144 for GI).

Conclusions

Patients with IBD who received SBRT for PCa had a higher likelihood of developing acute GI and GU toxicity, in addition to experiencing lower grade late toxicities that occurred earlier. However, patients with IBD did not have a higher likelihood for late grade ≥2 GI or GU toxicity after SBRT compared with the control cohort. Interpretation of this data are limited by the small sample size. Thus, men with IBD in remission should be properly counseled about these risks when considering SBRT.

Abstract PO-060: Blood based metabolomic biomarker assay to predict radiation late effects in prostate cancer patients

Introduction and Objective: Radiation therapy (RT) is an effective modality as a primary treatment of cancers, or as an adjuvant to surgery or chemotherapy. However, about 10 % of treated patients experience radiation treatment related late effects that adversely affect quality of life. Availability of a blood test that can be used to predict or monitor adverse symptoms would help stratify sensitive sub-populations of patients receiving radiation therapy. We have developed a kit based assay for the measurement of a small molecule based biomarker panel that is predictive of radiation treatment related toxicities in prostate cancer patients. Methods: We performed multiple reaction monitoring based targeted metabolomic/lipidomic analyses using baseline (samples obtained before radiation therapy) from the plasma of a cohort of 100 prostate cancer patients. Pre-processed data along with clinical annotations were used for the analyses. An optimized classifier algorithm was developed, using baseline plasma samples collected prior to the initiation of radiation therapy. We compared groups of sub-sets of patients who developed adverse symptoms to those who did not (control group), over the course of a two-year follow-up interval. Feature selection for building classifiers was performed using LASSO Logistic regression to avoid over-fitting of the model through iterative selection, and cross validation of candidate markers, in compliance with FDA biomarker development guidelines. Results: We have used a combination of metabolomics and clinical data for developing a kit based assay for identification of prostate cancer patients Metabolite signatures predictive of adverse responses to radiation therapy were developed in the patient cohort treated with stereotactic body radiation therapy (SBRT) for prostate cancer. We were able to develop high accuracy, predictive algorithms for recurrence, urinary symptoms and rectal proctitis episodes in this cohort. A plasma metabolite index was developed for the evaluation of susceptibility to adverse outcomes of radiation therapy. Furthermore, a visualization software was developed to integrate clinical and biomarker data for easier clinical translation. Conclusions: We developed candidate predictive biomarker panels that can be used for identifying patients who are at increased risk for developing adverse symptoms following radiation therapy. Following analytical validation, this kit based assay is a candidate for a clinical validation study to determine clinical utility.

Citation Format: Amrita K. Cheema, Scott Grindrod, Yaoxiang Li, Shivani Bansal, Simeng Suy, Sean Collins, Anatoly Dritschilo. Blood based metabolomic biomarker assay to predict radiation late effects in prostate cancer patients [abstract]. In: Proceedings of the AACR Virtual Special Conference on Radiation Science and Medicine; 2021 Mar 2-3. Philadelphia (PA): AACR; Clin Cancer Res 2021;27(8_Suppl):Abstract nr PO-060.

Ten-Year Single Institutional Analysis of Geographic and Demographic Characteristics of Patients Treated With Stereotactic Body Radiation Therapy for Localized Prostate Cancer

Objectives

Stereotactic Body Radiation Therapy (SBRT) offers definitive treatment for localized prostate cancer with comparable efficacy and toxicity to conventionally fractionated radiotherapy. Decreasing the number of treatment visits from over 40 to five may ease treatment burden and increase accessibility for logistically challenged patients. Travel distance is one factor that affects a patient’s access to treatment and is often related to geographic location and socioeconomic status. In this study, we review the demographic and geographic factors of patients treated with SBRT for prostate cancer for a single institution with over a decade of experience.

Methods

Patient zip codes from one thousand and thirty-five patients were derived from a large, prospectively maintained quality of life database for patients treated for prostate cancer with SBRT from 2008 to 2017. The geospatial distance between the centroid of each zip code to our institution was calculated using the R package Geosphere. Characteristics for seven hundred and twenty-one patients were evaluated at the time of analysis including: race, age, and insurance status. To assess the geographic reach of our institution, we evaluated the demographic features of each zip code using US Census data. Statistical comparisons for these features and their relation to distance traveled for treatment was performed using the Mann-Whitney U test. Finally, an unsupervised learning algorithm was performed to identify distinct clusters of patients with respect to median income, racial makeup, educational level, and rural residency.

Results

Patients traveled from 246 distinct zip codes at a median distance of 11.35 miles. Forty percent of patients were African American, 6.9% resided in a rural region, and 22% were over the age of 75. Using K-means cluster analysis, four distinct patient zip-code groups were identified based on the aforementioned demographic features: Suburban/high-income (45%), Urban (30%), Suburban/low-income (17%), and Rural (8%). For each of the clusters, the average travel distance for SBRT was significantly different at 11.17, 9.26, 11.75, and 40.2 miles, respectively (p-value: <0.001).

Conclusions

Distinct demographic features are related to travel distance for prostate SBRT. In our large cohort, travel distance did not prevent uptake of prostate SBRT in African American, elderly or rural patient populations. Prostate SBRT offers a diverse population modern treatment for their localized prostate cancer and particularly for those who live significant distances from a treatment center.

Evaluating the correlation between early and late quality-of-life declines using the Expanded Prostate Cancer Index Composite for Clinical Practice (EPIC-CP) after definitive stereotactic body radiotherapy, intensity-modulated radiotherapy, or brachytherapy for prostate cancer

214

Background: Multiple authorities including an NCI Taskforce have recommended routine evaluation of patient reported outcomes (PRO) in cancer care. The Expanded Prostate Cancer Index Composite for Clinical Practice (EPIC-CP) is a single-page quality-of-life (QOL) tool which is easily integrated into routine clinical practice. The EPIC-CP has 5 domains (each scored 0-12). The present study evaluated whether early clinically significant changes in EPIC-CP were correlated with later changes in patients undergoing definitive radiotherapy (RT) for prostate cancer. Methods: A cohort of 979 patients including the PROSTQA study and 3 other institutions with prospective QOL data pooled for analysis were evaluated for patient-reported outcomes. Patients were treated with definitive low-dose rate brachytherapy (n=284), intensity-modulated RT (n=251), or stereotactic body RT (n=444). EPIC-CP scores were derived based upon responses to the EPIC-26. Data were evaluated using minimal clinically important difference (MCID) thresholds to compare QOL at 1-2 months and 24 months from baseline. Univariate analysis was used to assess the correlation between early and late MCID changes. Results: On univariate analysis, early ≥1 MCID change from baseline was strongly associated with a late ≥1 MCID across all 5 domains (urinary incontinence, urinary irritation/obstruction, bowel, sexual, and vitality/hormonal) within EPIC-CP and for the overall EPIC-CP score (Table). When MCID was instead defined as 1 or 3, early toxicity remained predictive of late toxicity for all domains and the overall EPIC-CP score. Conclusions: The EPIC-CP is an easy-to-use QOL assessment with clinically relevant outcomes. Early QOL decline was strongly associated with late QOL decline in patients undergoing definitive RT for prostate cancer across all EPIC-CP domains. Patients with early QOL decline may be candidates for early QOL-based interventions to alleviate their late toxicity burden from treatment. [Table: see text]

Stereotactic Body Radiotherapy for High-Risk Localized Carcinoma of the Prostate (SHARP) Consortium: Analysis of 344 Prospectively Treated Patients

PURPOSE

To explore the efficacy and toxicity of stereotactic body radiation therapy (SBRT) in high-risk prostate cancer (HRPCa) in a consortium of 7 institutional phase 2 trials and prospective registries.

METHODS AND MATERIALS

Individual patient data were pooled for 344 patients with a minimum follow-up of 24 months. Biochemical recurrence-free survival (BCRFS) and distant metastasis-free survival (DMFS) were estimated using a Kaplan-Meier framework. Fine and Gray competing risk and Cox proportional hazards regression models were developed to assess the association between time to BCR and time to distant metastasis and prespecified variables of interest. Logistic regression models were developed to evaluate associations between acute and late grade ≥2 genitourinary and gastrointestinal and the following a priori-specified variables: age, dose per fraction, ADT use, and nodal radiation therapy.

RESULTS

Median follow-up was 49.5 months. Seventy-two percent of patients received ADT, with a median duration of 9 months, and 19% received elective nodal radiation therapy. Estimated 4-year BCRFS and DMFS rates were 81.7% (95% CI, 77.2%-86.5%) and 89.1% (95% CI, 85.3%-93.1%). The crude incidences of late grade ≥3 genitourinary and gastrointestinal toxicity were 2.3% and 0.9%.

CONCLUSIONS

These data support a favorable toxicity and efficacy profile for SBRT for HRPCa. Further prospective studies are needed to evaluate the optimal dose and target volume in the context of SBRT for HRPCa.

Rationale for Involved Field Stereotactic Body Radiation Therapy-Enhanced Intermittent Androgen Deprivation Therapy in Hormone-Sensitive Nodal Oligo-Recurrent Prostate Cancer Following Prostate Stereotactic Body Radiation Therapy

Lymph node recurrent prostate cancer is a common clinical scenario that is likely to increase significantly with the widespread adoption of novel positron emission tomography (PET) agents. Despite increasing evidence that localized therapy is disease modifying, most men with lymph node recurrent prostate cancer receive only systemic therapy with androgen deprivation therapy (ADT). For men who receive localized therapy the intent is often to delay receipt of systemic therapy. Little evidence exists on the optimal combination of local and systemic therapy in this patient population. In this hypothesis generating review, we will outline the rationale and propose a framework for combining involved field SBRT with risk adapted intermittent ADT for hormone sensitive nodal recurrent prostate cancer. In patients with a limited number of nodal metastases, involved field stereotactic body radiation therapy (SBRT) may have a role in eliminating castrate-resistant clones and possibly prolonging the response to intermittent ADT. We hypothesize that in a small percentage of patients, such a treatment approach may lead to long term remission or cure.

Utilization of Iodinated SpaceOAR Vue™ During Robotic Prostate Stereotactic Body Radiation Therapy (SBRT) to Identify the Rectal-Prostate Interface and Spare the Rectum: A Case Report

We describe the utilization of SpaceOAR Vue™, a new iodinated rectal spacer, during Robotic Stereotactic Body Radiation Therapy (SBRT) for a Prostate Cancer Patient with a contraindication to Magnetic Resonance Imaging. A 69-year-old Caucasian male presented with unfavorable intermediate risk prostate cancer and elected to undergo SBRT. His medical history was significant for atrial fibrillation on Rivaroxaban with a pacemaker. He was felt to be at increased risk of radiation proctitis following SBRT due to the inability to accurately contour the anterior rectal wall at the prostate apex without a treatment planning MRI and an increased risk of late rectal bleeding due to prescribed anticoagulants. In this case report, we discuss the technical aspects of appropriate placement and treatment planning for utilizing SpaceOAR Vue™ with Robotic SBRT.

Stereotactic Body Radiation Therapy: A Versatile, Well-Tolerated, and Effective Treatment Option for Extracranial Metastases From Primary Ovarian and Uterine Cancer

Purpose

Single extracranial metastases from ovarian and uterine malignancies have historically been treated with surgery or conventional radiation. We report mature local control (LC), overall survival (OS), progression free survival (PFS), and toxicity for patients who completed 5-fraction stereotactic body radiation therapy (SBRT).

Methods

Patients with biopsy-proven, single extracranial metastases from primary ovarian and uterine malignancies treated with 5-fraction SBRT were included. Patients were stratified based on tumor volume (small < 50 cc or large ≥ 50 cc) and dose (low dose < 35 Gy or high ≥ 35 Gy). Kaplan–Meier method was used to estimate LC, OS, and PFS.

Results

Between July 2007 and July 2012, 20 patients underwent SBRT to a single extracranial metastasis. Primary site was divided evenly between ovarian and uterine (n = 10 each). Metastases involved the liver (30%), abdominal lymph nodes (25%), lung (20%), pelvic lymph nodes (10%), spine (10%), and extremity (5%). The median gross tumor volume (GTV) was 42.5 cc (range, 5–273 cc) and the median dose to the GTV was 35 Gy (range, 30–50 Gy). At a median follow-up of 56 months, the 5-year LC and OS estimates were 73 and 46%. When stratified by tumor volume, the 5-year LC and OS for small tumors were significantly better at 100% (p < 0.01) and 65% (p < 0.02). When stratified by dose, the 5-year LC was 87.5% with high dose and 53.6% with low dose (p = 0.035). The 5-year PFS for the entire cohort was 20%. Four patients with small metastases who had complete response remained disease free at study completion and were considered cured (median PFS > 10 years). Treatment was generally well tolerated, and only one patient experienced a late grade III musculoskeletal SBRT related toxicity.

Conclusions

SBRT is a versatile, well-tolerated, and effective treatment option for single extracranial metastases from ovarian and uterine primary tumors. 35 Gy in five fractions appears to be a practical minimum effective dose. Four patients with small metastases were disease free at the study completion and considered cured. However, patients with larger metastases (≥50 cc) may require higher SBRT dosing or alternative treatments.

Management of Isolated Local Failures Following Stereotactic Body Radiation Therapy for Low to Intermediate Risk Prostate Cancer

Background: Stereotactic body radiation therapy (SBRT) is a safe and effective treatment option for patients with low to intermediate risk prostate cancer (1). SBRT results in very low PSA nadirs secondary to the delivery of high biologically effective doses. Studies reporting on the diagnosis, confirmation, and management of salvageable isolated local failures (ILF) are limited. This study aims to determine the incidence and management approach of ILF after SBRT in a large single institution cohort. Method: All patients with low or intermediate risk localized prostate cancer treated with SBRT at Georgetown University Hospital were eligible for this study. Treatment was delivered using robotic SBRT with doses of 35-36.25 Gy in five fractions. ILF were diagnosed using multiparametric MRI and/or biopsy prompted by rising PSA levels after achieving long-term nadir. Patient's characteristics were extracted from a prospective institutional quality of life trial (IRB 2009-510). Type of salvage therapy and post-salvage PSA were determined on subsequent follow-up and chart review. Results: Between December 2008 to August 2018, 998 men with low to intermediate risk prostate cancer were eligible for inclusion in this analysis. Twenty-four patients (low risk, n = 5; intermediate risk, n = 19) were found to have ILF within the prostate on either MRI (n = 19) and/or biopsy (n = 20). Median pre-treatment PSA was 7.55 ng/ml. Median time to diagnosis of ILF was 72 months (24-110 months) with median PSA at the time of ILF of 2.8 ng/ml (0.7-33 ng/ml). Median PSA doubling time was 17 months (5-47 months). Thirteen patients with biopsy proven ILF proceeded with salvage therapy (cryotherapy n = 12, HIFU n = 1). Of 12 patients who underwent cryotherapy, 7 had a post-treatment PSA of <0.1 ng/ml. One patient experienced a urethral-cutaneous fistula (grade 3 toxicity). Conclusion: The incidence of isolated local recurrence is rare in our cohort. Diagnosis and management of isolated local failures post-SBRT continues to evolve. Our report highlights the importance of early utilization of MRI and confirmatory biopsy at relatively low PSA levels and long PSA doubling time (1). Additionally, undetectable PSA levels after salvage therapy supports the role of early treatment in ILF (1). Further research is needed to determine appropriate patient selection and salvage modality in this population.

Dose-response with stereotactic body radiotherapy for prostate cancer: A multi-institutional analysis of prostate-specific antigen kinetics and biochemical control

BACKGROUND AND PURPOSE

The optimal dose for prostate stereotactic body radiotherapy (SBRT) is still unknown. This study evaluated the dose-response relationships for prostate-specific antigen (PSA) decay and biochemical recurrence (BCR) among 4 SBRT dose regimens.

MATERIALS AND METHODS

In 1908 men with low-risk (50.0%), favorable intermediate-risk (30.9%), and unfavorable intermediate-risk (19.1%) prostate cancer treated with prostate SBRT across 8 institutions from 2003 to 2018, we examined 4 regimens (35 Gy/5 fractions [35/5, n = 265, 13.4%], 36.25 Gy/5 fractions [36.25/5, n = 711, 37.3%], 40 Gy/5 fractions [40/5, n = 684, 35.8%], and 38 Gy/4 fractions [38/4, n = 257, 13.5%]). Between dose groups, we compared PSA decay slope, nadir PSA (nPSA), achievement of nPSA ≤0.2 and ≤0.5 ng/mL, and BCR-free survival (BCRFS).

RESULTS

Median follow-up was 72.3 months. Median nPSA was 0.01 ng/mL for 38/4, and 0.17-0.20 ng/mL for 5-fraction regimens (p < 0.0001). The 38/4 cohort demonstrated the steepest PSA decay slope and greater odds of nPSA ≤0.2 ng/mL (both p < 0.0001 vs. all other regimens). BCR occurred in 6.25%, 6.75%, 3.95%, and 8.95% of men treated with 35/5, 36.25/5, 40/5, and 38/4, respectively (p = 0.12), with the highest BCRFS after 40/5 (vs. 35/5 hazard ratio [HR] 0.49, p = 0.026; vs. 36.25/5 HR 0.42, p = 0.0005; vs. 38/4 HR 0.55, p = 0.037) including the entirety of follow-up, but not for 5-year BCRFS (≥93% for all regimens, p ≥ 0.21).

CONCLUSION

Dose-escalation was associated with greater prostate ablation and PSA decay. Dose-escalation to 40/5, but not beyond, was associated with improved BCRFS. Biochemical control remains excellent, and prospective studies will provide clarity on the benefit of dose-escalation.

Prostate-specific antigen kinetics and biochemical control following stereotactic body radiation therapy, high dose rate brachytherapy, and low dose rate brachytherapy: A multi-institutional analysis of 3502 patients

BACKGROUND AND PURPOSE

Stereotactic body radiation therapy (SBRT), low dose rate brachytherapy (LDR-BT) and high dose rate brachytherapy (HDR-BT) are ablative-intent radiotherapy options for prostate cancer (PCa). These vary considerably in dose delivery, which may impact post-treatment prostate-specific antigen (PSA) patterns and biochemical control. We compared PSA kinetics between SBRT, HDR-BT, and LDR-BT, and assessed their relationships to biochemical recurrence-free survival (BCRFS).

METHODS AND MATERIALS

Retrospective PSA data were analyzed for 3502 men with low-risk (n = 2223; 63.5%), favorable intermediate-risk (n = 869; 24.8%), and unfavorable intermediate-risk (n = 410; 11.7%) PCa treated with SBRT (n = 1716; 49.0%), HDR-BT (n = 512; 14.6%), or LDR-BT (n = 1274; 36.4%) without upfront androgen deprivation therapy at 10 institutions from 1990 to 2017. We compared nadir PSA (nPSA), time to nPSA, achievement of nPSA <0.2 ng/mL and <0.5 ng/mL, rates of nPSA <0.4 ng/mL at 4 years, and BCRFS.

RESULTS

Median follow-up was 72 months. Median nPSA and nPSA <0.2 ng/mL were stratified by risk group (interaction p ≤ 0.001). Median nPSA and time to nPSA were 0.2 ng/mL at 44 months after SBRT, 0.1-0.2 ng/mL at 37 months after HDR-BT, and 0.01-0.2 ng/mL at 51 months after LDR-BT (mean log nPSA p ≤ 0.009 for LDR-BT vs. SBRT or HDR-BT for low/favorable intermediate-risk). There were no differences in nPSA <0.4 ng/mL at 4 years (p ≥ 0.51). BCRFS was similar for all three modalities (p ≥ 0.27). Continued PSA decay beyond 4 years was predictive of durable biochemical control.

CONCLUSION

LDR-BT led to lower nPSAs with longer continued decay compared to SBRT and HDR-BT, but no differences in BCRFS.

Stereotactic Body Radiation Therapy (SBRT) for Prostate Cancer in Men With a High Baseline International Prostate Symptom Score (IPSS ≥ 15)

Background: Patients with a high pretreatment IPSS may have higher rates of late urinary morbidity after radiation therapy for prostate cancer (1). Stereotactic body radiation therapy (SBRT) delivers fewer high-dose fractions of radiation, which may be radiobiologically favorable to the conventional low-dose external beam fractions. The urinary toxicity associated with SBRT, however, remains unclear in patients with a high IPSS (1). We report our experience using SBRT for localized prostate cancer in patients with pretreatment IPSS ≥ 15.

Methods: Localized prostate cancer patients with a pre-treatment IPSS ≥ 15 treated with SBRT at Georgetown University Hospital from 2009 to 2016 were included in this retrospective review of prospectively collected data. These patients were treated to 35–36.25 Gy in five fractions delivered via CyberKnife (Accuray Inc., Sunnyvale, CA). Urinary toxicity was assessed using the Common Terminology Criteria for Adverse Events version 4.0 (CTCAE v4). Urinary quality of life was assessed using validated questionnaires (IPSS and EPIC-26).

Results: 53 patients at a median age of 71 years (range 57–89 years) received SBRT with a minimum follow up of 3 years. The median prostate size was 37 cm³ (range 12–100 cm³) and 30.2% patients received ADT. The 3-years incidence rate of Grade 3 urinary toxicity was 7.5% with median time to toxicity of 2.9 years. There were no Grade 4 or 5 toxicities. A mean baseline IPSS score of 19.8 significantly decreased to 12.9 at 3 months post-SBRT (p = 0.002) and remained stable at 36 months (13.7). A mean baseline EPIC-26 obstructive/irritative score of 64.1 significantly improved to 80.2 at 3 months (p = 0.002). This improvement was maintained to 36 months. There was no significant change from the mean baseline EPIC-26 urinary incontinence score at any point during follow up.

Conclusions: SBRT for clinically localized prostate cancer was well-tolerated in men with baseline IPSS ≥ 15 (1). Grade 3 toxicities occurred but resolved with time. Our data suggest that poor baseline urinary function does not worsen following SBRT and may even improve. High baseline IPSS score should not be considered a contraindication to SBRT.

Urinary Morbidity in Men Treated With Stereotactic Body Radiation Therapy (SBRT) for Localized Prostate Cancer Following Transurethral Resection of the Prostate (TURP)

Background: Clinical data suggest that stereotactic body radiation therapy (SBRT) provides similar clinical outcomes as other radiation modalities for prostate cancer. However, data reporting on the safety of SBRT after TURP is limited. Herein, we report our experience using SBRT to deliver hypofractionated radiotherapy in patients with a history of TURP including physician-reported toxicities and patient-reported quality of life.

Methods: Forty-seven patients treated with SBRT from 2007 to 2016 at Georgetown University Hospital for localized prostate carcinoma with a history of prior TURP were included in this retrospective analysis. Treatment was delivered using the CyberKnife® (Accuray Incorporated, Sunnyvale, CA) with doses of 35 Gy or 36.25 Gy in 5 fractions without prostatic urethral sparing. Toxicities were recorded and scored using the CTCAE v.4. Cystoscopy findings were retrospectively reviewed. Urinary quality of life data was assessed using the International Prostate Symptom Scoring (IPSS) and Expanded Prostate Cancer Index Composite 26 (EPIC-26). A Wilcoxon signed-rank sum test was used to determine if there was a statistically significant increase or decrease in IPSS or EPIC scores between timepoints. Minimally important differences were calculated by obtaining half the standard deviation at time of start of treatment.

Results: Forty-seven patients at a median age of 72 years (range 63–84) received SBRT. The mean follow-up was 4.7 years (range 2–10 years). Late Grade 2 and grade 3 urinary toxicity occurred in 23 (48.9%) and 3 (6.4%) men, respectively. There were no Grade 4 or 5 toxicities. Approximately 51% of patients experienced hematuria following treatment. Mean time to hematuria was 10.5 months. Twenty-five cystoscopies were performed during follow-up and the most common finding was hyperemia, varices of the bladder neck/TURP defect, and/or necrotic tissue in the TURP defect. Baseline urinary QOL composite scores were low, but they did not clinically significantly decline in the first 2 years following treatment.

Conclusions: In patients with prior TURP, prostate SBRT was well-tolerated. GU toxicity rates were comparable to similar patients treated with conventionally fractionated radiation therapy. Urinary quality of life was poor at baseline, but did not worsen clinically over time. Stricter dosimetric criteria could potentially improve the rate of high-grade late toxicity, but may increase the risk of peri-urethral recurrence.

Metabolomics-Based Biosignatures of Prostate Cancer in Patients Following Radiotherapy

Metabolomics offers new promise for research on prostate cancer (PCa) and its personalized treatment. Metabolomic profiling of radiation-treated PCa patients is particularly important to reveal their new metabolomic status, and evaluate the radiation effects. In addition, bioinformatics-integrated metabolomics-based approaches for disease profiling and assessment of therapy could help develop precision biomarkers in a context of PCa. We report mass spectrometry-based untargeted (global) serum metabolomics findings from patients with PCa (n = 55) before and after treatment with stereotactic body radiation therapy (SBRT), and intensity-modulated radiation therapy (IMRT) with SBRT, and using parsimony phylogenetic analysis. Importantly, the radiation-treated serum metabolome of patients represented a unique robust cluster on a cladogram that was distinct from the pre-RT metabolome. The altered radiation responsive serum metabolome was defined by predominant aberrations in the metabolic pathways of nitrogen, pyrimidine, purine, porphyrin, alanine, aspartate, glutamate, and glycerophospholipid. Our findings collectively suggest that global metabolomics integrated with parsimony phylogenetics offer a unique and robust systems biology analytical platform for powerful unbiased determination of radiotherapy (RT)-associated biosignatures in patients with PCa. These new observations call for future translational research for evaluation of metabolomic biomarkers in PCa prognosis specifically, and response to radiation treatment broadly. Radiation metabolomics is an emerging specialty of systems sciences and clinical medicine that warrants further research and educational initiatives.

Self-Reported Burden in Elderly Patients With Localized Prostate Cancer Treated With Stereotactic Body Radiation Therapy (SBRT)

Purpose: Retaining quality of life in patients treated with SBRT for prostate cancer remains paramount. As such, balancing the benefits of treatment against the effects of therapy on elderly patients is essential. The EORTC QLQ-ELD14 (ELD-14) is a validated questionnaire with a domain dedicated to burden of illness and treatment in the elderly. The Expanded Prostate Cancer Index Composite (EPIC)-26 is a validated questionnaire which measures urinary, bowel, sexual, and hormonal symptoms. This study reports trends in self-reported burden in patients with prostate cancer treated with SBRT and reveals convergence of self-reported burden with treatment related side effects obtained from the EPIC-26 questionnaire.

Methods: All patients ≥70 years old, with localized prostate cancer treated with SBRT ± ADT at Medstar Georgetown University Hospital from 2013 to 2018 and had completed the ELD-14 were eligible for inclusion in this cross-sectional cohort study. Percentage of responses to questions related to disease and treatment burden were counted for each category (“not at all” and “a little” vs. “quite a bit” and “very much”). Additional demographic features were derived from available medical records. A total of 111 patients (median age of 74) responded to the ELD-14 questionnaire at onset of treatment and at the 2-year mark. Responses to EPIC questionnaires at matched follow-ups were scored and correlated with the self-reported burden domain of the ELD-14 using the Spearman correlation coefficient.

Results: Number of patients reporting “quite a bit” or “very much” burden from prostate cancer was 6.3% prior to treatment. This was highest at 1-month (10.8%) and decreased to 9.0% at 24 months post-SBRT (X² = 3.836, p = 0.6986). By comparison, 3.6 and 5.4% reported “quite a bit” or “very much” burden from treatment at start of treatment and 24 months, respectively (X² = 1.046, p = 0.9838). Patient reported treatment burden was found to converge well with individual domains of EPIC-26. Patients undergoing ADT experienced more burden than their non-ADT counterparts.

Conclusions: This cross-sectional study suggests a minority of patients reported high burden from their clinically localized prostate cancer or from their SBRT treatment. Self-reported burden converged well with lower EPIC scores in multiple domains.

MicroRNA-214 targets PTK6 to inhibit tumorigenic potential and increase drug sensitivity of prostate cancer cells

Prostate cancer is the most commonly diagnosed cancer in men with African American men disproportionally suffering from the burden of this disease. Biomarkers that could discriminate indolent from aggressive and drug resistance disease are lacking. MicroRNAs are small non-coding RNAs that affect numerous physiological and pathological processes, including cancer development and have been suggested as biomarkers and therapeutic targets. In the present study, we investigated the role of miR-214 on prostate cancer cell survival/migration/invasion, cell cycle regulation, and apoptosis. miR-214 was differentially expressed between Caucasian and African American prostate cancer cells. Importantly, miR-214 overexpression in prostate cancer cells induced apoptosis, inhibiting cell proliferation and colony forming ability. miR-214 expression in prostate cancer cells also inhibited cell migration and 3D spheroid invasion. Mechanistically, miR-214 inhibited prostate cancer cell proliferation by targeting protein tyrosine kinase 6 (PTK6). Restoration of PTK6 expression attenuated the inhibitory effect of miR-214 on cell proliferation. Moreover, simultaneous inhibition of PTK6 by ibrutinib and miR-214 significantly reduced cell proliferation/survival. Our data indicates that miR-214 could act as a tumor suppressor in prostate cancer and could potentially be utilized as a biomarker and therapeutic target.

Multi-Institutional Analysis of Prostate-Specific Antigen Kinetics After Stereotactic Body Radiation Therapy

PURPOSE

Understanding prostate-specific antigen (PSA) kinetics after radiation therapy plays a large role in the management of patients with prostate cancer (PCa). This is particularly true in establishing expectations regarding PSA nadir (nPSA) and PSA bounces, which can be disconcerting. As increasingly more patients are being treated with stereotactic body radiation therapy (SBRT) for low- and intermediate-risk PCa, it is imperative to understand the PSA response to SBRT.

METHODS AND MATERIALS

PSA data from 5 institutions were retrospectively analyzed for patients with localized PCa treated definitively with SBRT alone from 2004 to 2016. Patients received 35 to 40 Gy in 5 fractions, per institutional standards. Patients who had less than 12 months of PSA data or received androgen deprivation therapy were excluded from this study. Linear and logistic multivariable analysis were performed to identify predictors of nPSA, bounce, and biochemical recurrence, and joint latent class models were developed to identify significant predictors of time to biochemical failure.

RESULTS

A total of 1062 patients were included in this study. Median follow-up was 66 months (interquartile range [IQR], 36.4-89.9 months). Biochemical failure per the Phoenix criteria occurred in 4% of patients. Median nPSA was 0.2 ng/mL, median time to nPSA was 40 months, 84% of patients had an nPSA ≤0.5 ng/mL, and 54% of patients had an nPSA ≤0.2 ng/mL. On multivariable analysis, nPSA was a significant predictor of biochemical failure. Benign PSA bounce was noted in 26% of patients. The median magnitude of PSA bounce was 0.52 ng/mL (IQR, 0.3-1.0 ng/mL). Median time to PSA bounce was 18.1 months (IQR, 12.0-31.1 months). On multivariable analysis, age and radiation dose were significantly associated with a lower incidence of bounce. Joint latent class models modeling found that nPSA and radiation dose were significantly associated with longer time to biochemical failure.

CONCLUSIONS

In this multi-institutional cohort of patients with long-term follow-up, we found that SBRT led to low nPSAs. In turn, lower nPSAs are associated with reduced incidence of, and longer time to, biochemical failure. Benign PSA bounces occurred in a quarter of patients, as late as several years after treatment. Further studies are needed to directly compare the PSA response of patients who receive SBRT versus other treatment modalities.

Management of isolated local failures following stereotactic body radiation therapy for low to intermediate risk prostate cancer

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Background: SBRT is a safe and effective treatment option for patients with low to intermediate risk prostate cancer (PCa). SBRT delivers high biologically effective doses resulting in very low PSA nadirs. Strategies to diagnose and confirm salvageable isolated local failures (ILF) are needed. This study aims to examine the incidence and approach to management of ILF after SBRT in a large single institution cohort. Methods: All patients with low or intermediate risk PCa treated with SBRT at our institution were eligible for this study. Treatment was delivered using the robotic SBRT with doses of 35-36.25 Gy in five fractions. ILF were diagnosed using mpMRI and/or biopsy prompted by PSA rise after achieving long-term nadir. Choice of salvage therapy and post-salvage PSA were ascertained on follow up. Results: Between December, 2008 to August, 2018, 998 men with low to intermediate risk prostate cancer were eligible for analysis. Twenty patients (low risk, n = 4; intermediate risk, n = 16) were found to have ILF on either MRI (n = 15) and/or biopsy (n = 17). Three patients with MRI-identified ILF elected active surveillance in lieu of biopsy. Median pre-treatment PSA was 7.5 ng/ml. Median time to diagnosis of ILF was 72 months (37-96 months) with median PSA at the time of ILF of 2.3 ng/ml (1.1-10 ng/ml). Median PSA doubling time was 17 months (5-22 months). Thirteen patients with biopsy proven ILF proceeded with salvage therapy (cryotherapy n = 12, HIFU n = 1). Of 12 patients who underwent cryotherapy, 8 had a post-treatment PSA of < 0.1ng/ml, two patient’s results were unavailable, one patient had a PSA nadir of 0.7 ng/ml and one patient had yet to undergo post-salvage PSA test at the time of this report. Conclusions: The incidence of ILF is rare in our series. Diagnosis and management of ILF post-SBRT continues to evolve in the era of successful salvage therapy. Our report suggests an important role for early utilization of MRI and confirmatory biopsy at relatively low PSA levels and long PSA doubling time. Additionally, undetectable PSA post-salvage therapy supports early treatment after identifying ILF. Larger trials are needed for refinement of patient selection and most appropriate salvage modality.

Multi-institutional analysis of high-risk prostate cancer patients treated with stereotactic body radiotherapy

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Background: Stereotactic Body Radiotherapy (SBRT) delivers ablative doses of radiation (RT) over a course of five treatments and has been increasingly used as a definitive RT option for low- and intermediate-risk prostate cancer (PCa). Ongoing prospective trials are evaluating the efficacy of SBRT for high-risk PCa, but clinical outcomes reports are limited. Methods: Patients treated for high-risk PCa between 2006-2017 at any of five institutions were included. SBRT doses ranged from 35-40 Gy in 5 fractions per institutional standards, with one institution using an integrated boost approach. The Phoenix definition was used to define biochemical failure (BCR). Physician-reported genitourinary (GU) and gastrointestinal (GI) toxicity outcomes were scored using the Radiation Therapy Oncology Group or Common Terminology Criteria for Adverse Events systems. Results: In total, 182 patients were included in this study with a median follow-up time of 38.4 months (mos). The median age was 72. Most patients (72%) had Gleason 8-10 disease. Sixty-eight percent of patients received androgen deprivation therapy (ADT) for a median of 9 mos (interquartile range 6-9 mos). The rate of distant metastases was 3.8%. There were no acute Grade 3 (G3) or higher GU or GI toxicities. Three patients (1.6%) experienced a late G3 GU toxicity and one patient (0.5%) experienced a late G3 GI toxicity. The incidence of BCR was significantly higher in patients who did not receive ADT (30% vs. 15%, p = 0.02 by Chi-square). Conclusions: In this multi-institutional study, SBRT demonstrated an acceptable safety profile for the treatment of high-risk PCa. Longer term follow-up is necessary to evaluate the oncologic efficacy of this approach, but given the potentially higher incidence of BCR without ADT, ADT likely has an important oncologic role even with SBRT regimens.