Second-Generation Antiandrogen Therapy Radiosensitizes Prostate Cancer Regardless of Castration State through Inhibition of DNA Double Strand Break Repair

(1) Background: The combination of the first-generation antiandrogens and radiotherapy (RT) has been studied extensively in the clinical setting of prostate cancer (PCa). Here, we evaluated the potential radiosensitizing effect of the second-generation antiandrogens abiraterone acetate, apalutamide and enzalutamide. (2) Methods: Cell proliferation and agarose-colony forming assay were used to measure the effect on survival. Double strand break repair efficiency was monitored using immunofluorescence staining of γH2AX/53BP1. (3) Results: We report retrospectively a minor benefit for PCa patients received first-generation androgen blockers and RT compared to patients treated with RT alone. Combining either of the second-generation antiandrogens and 2Gy suppressed cell growth and increased doubling time significantly more than 2Gy alone, in both hormone-responsive LNCaP and castration-resistant C4-2B cells. These findings were recapitulated in resistant sub-clones to (i) hormone ablation (LNCaP-abl), (ii) abiraterone acetate (LNCaP-abi), (iii) apalutamide (LNCaP-ARN509), (iv) enzalutamide (C4-2B-ENZA), and in castration-resistant 22-RV1 cells. This radiosensitization effect was not observable using the first-generation antiandrogen bicalutamide. Inhibition of DNA DSB repair was found to contribute to the radiosensitization effect of second-generation antiandrogens, as demonstrated by a significant increase in residual γH2AX and 53BP1 foci numbers at 24h post-IR. DSB repair inhibition was further demonstrated in 22 patient-derived tumor slice cultures treated with abiraterone acetate before ex-vivo irradiation with 2Gy. (4) Conclusion: Together, these data show that second-generation antiandrogens can enhance radiosensitivity in PCa through DSB repair inhibition, regardless of their hormonal status. Translated into clinical practice, our results may help to find additional strategies to improve the effectiveness of RT in localized PCa, paving the way for a clinical trial.

Prediction of Organ-confined Disease in High- and Very-high-risk Prostate Cancer Patients Staged with Magnetic Resonance Imaging: Implications for Clinical Trial Design

BACKGROUND

High-risk (HR) prostate cancer (PCa) is a heterogeneous disease leading to difficulties in designing appropriate inclusion criteria for clinical trials.

OBJECTIVE

To describe clinical predictors of organ-confined disease in HR or very-high-risk (VHR) PCa patients staged with multiparametric magnetic resonance imaging with endorectal coil (mp-MRI-ER).

DESIGN, SETTING, AND PARTICIPANTS

We reviewed 366 HR/VHR PCa patients who had preoperative mp-MRI-ER, and underwent radical prostatectomy and extended pelvic lymph node dissection between 2006 and 2015.

INTERVENTION

Radical prostatectomy with preoperative mp-MRI-ER.

OUTCOME MEASUREMENTS AND STATISTICAL ANALYSIS

We used multivariable logistic regression modeling to assess for associations with ≤ pT2N0 stage and multivariable cox modeling to assess for associations with biochemical failure.

RESULTS AND LIMITATIONS

Of 366 patients, 132 had ≤ pT2N0 disease. For the entire cohort, negative staging mp-MRI-ER (odds ratio [OR] 1.73, 95% confidence interval [CI] 1.06-2.83, p =  0.03), lower prostate-specific antigen (PSA; OR 0.98, 95% CI 0.97-1.00, p =  0.02), and fewer cores of Gleason ≥8 cancer (OR 0.86, 95% CI 0.79-0.93, p =  0.0002) were associated with ≤pT2N0 disease. In HR patients only, negative mp-MRI-ER (OR 3.41, 95% CI 1.73-6.72, p =  0.0004) and fewer than four cores of Gleason ≥8 disease (OR 3.38, 95% CI 1.20-9.56, p =  0.02) were still associated with ≤pT2N0 disease. Lack of non-organ-confined disease on MRI was associated with superior biochemical recurrence-free survival (p =  0.02). Limitations of this study include lack of a central review or quality control of the MRI reporting.

CONCLUSIONS

In HR PCa, negative staging mp-MRI-ER, fewer positive cores of Gleason >8, and lower PSA were significant predictors of pathologic organ-confined disease. Improved prediction of organ-confined disease in HR patients may allow for their inclusion into studies evaluating treatments from which they would otherwise be excluded based solely on their HR status.

PATIENT SUMMARY

In patients with high-risk prostate cancer, prostate magnetic resonance imaging along with other clinical parameters may help determine which patients are likely to have disease confined to the prostate and thus be eligible for clinical trials that they otherwise might be excluded from based on their high-risk status alone.

Recent advances in radiation oncology: multimodal targeting of high risk and recurrent prostate cancer

PURPOSE OF REVIEW

The overview summarizes recent developments in radiation oncology for high risk and recurrent prostate cancer.

RECENT FINDINGS

A number of well known phase III prostate hypofractionated radiation therapy (HFxRT) trials were finally published with long-term follow-ups. These trials demonstrate patterns of equivalent tumor control with several showing worse toxicity rates. The ASCENDE-RT randomized trial demonstrated the superiority of brachytherapy boost in intermediate and high-risk prostate cancer. Important randomized trials show a clear benefit to androgen deprivation therapy (ADT) in both intermediate-risk prostate cancer and postprostatectomy patients with rising PSA. Finally, the first randomized trial of metastasis-directed therapy showed a delay in time to ADT and biochemical failures in oligometastatic prostate cancer.

SUMMARY

The use of brachytherapy boost in high-risk disease and ADT in locally recurrent cancer after prostatectomy are practice changing given the magnitude of benefit seen in the randomized trials. The benefit of metastasis-directed therapy in oligometastatic prostate cancer must be validated in a larger randomized trial. However, hypofractionated radiation therapy requires further long-term follow-up so that late toxicity risk can be accurately assessed before it becomes a standard of care in prostate cancer.

Systematic Review of Systemic Therapies and Therapeutic Combinations with Local Treatments for High-risk Localized Prostate Cancer

CONTEXT

Systemic therapies, combined with local treatment for high-risk prostate cancer, are recommended by the international guidelines for specific subgroups of patients; however, for many of the clinical scenarios, it remains a research field.

OBJECTIVE

To perform a systematic review, and describe current evidence and perspectives about the multimodal treatment of high-risk prostate cancer.

EVIDENCE ACQUISITION

We performed a systematic review of PubMED, Embase, Cochrane Library, European Society of Medical Oncology/American Society of Clinical Oncology Annual proceedings, and clinicalTrial.gov between January 2010 and February 2018 following the Preferred Reporting Items for Systematic Reviews and Meta-analysis statement.

EVIDENCE SYNTHESIS

Seventy-seven prospective trials were identified. According to multiple randomized trials, combining androgen deprivation therapy (ADT) with external-beam radiotherapy (EBRT) outperforms EBRT alone for both relapse-free and overall survival. Neoadjuvant ADT did not show significant improvement compared with prostatectomy alone. The role of adjuvant ADT after prostatectomy in patients with high-risk disease is still debated, with lack of data from phase 3 trials in pN0 patients. Novel androgen pathway inhibitors have been tested only in early-phase trials in addition to primary treatment. GETUG 12, RTOG 0521, and nonmetastatic subgroup of the STAMPEDE trial showed improved relapse-free survival for docetaxel in patients treated with EBRT plus ADT, although mature metastasis-free survival data are still pending. Both the SPCG-12 and the VACSP#553 trial showed no improvement in relapse-free survival for adjuvant docetaxel after prostatectomy.

CONCLUSIONS

In contrast to the clearly demonstrated survival benefits of long-term adjuvant ADT when used with EBRT, its role after prostatectomy remains unclear especially in pN0 patients. Adding docetaxel to EBRT-ADT improves relapse-free survival, with immature results on overall survival. Novel androgen receptor pathway inhibitors are currently being tested in the neoadjuvant and adjuvant setting.

PATIENT SUMMARY

Treatment of high-risk prostate cancer is based on a multimodality approach that includes systemic treatments. The best treatment or therapy combination remains to be defined.

Phase 1-2 Study of Stereotactic Ablative Radiotherapy Including Regional Lymph Node Irradiation in Patients With High-Risk Prostate Cancer (SATURN): Early Toxicity and Quality of Life

PURPOSE

Five-fraction stereotactic ablative radiation therapy appears to be gaining popularity in treatment of prostate cancer, but it has not been extensively tested in the context of pelvic radiation. The objective of this prospective prostate and pelvic SABR study is to report the acute toxicity, late toxicity, and quality of life (QoL) after study completion.

METHODS AND MATERIALS

A phase 1/2 study was conducted for patients with high-risk prostate cancer. Radiation therapy was planned to deliver 25 Gy to pelvis and seminal vesicles (SV) and a simultaneous integrated boost (SIB) of up to 40 Gy to the prostate in 5 fractions, weekly, over 29 days. Androgen deprivation therapy was used for 12 to 18 months. Common Terminology Criteria for Adverse Events version 3.0 was used to assess worst acute and late toxicities. QoL data was captured using the Expanded Prostate Cancer Index Composite questionnaire (EPIC).

RESULTS

Thirty patients completed the planned treatment with a median follow-up of 25.7 months (range, 18.5-30.7 months). The following "worst" acute and late toxicities were observed: grade 2 genitourinary toxicity, 46.7% and 52%, respectively; grade 2 gastrointestinal toxicity, 3.3% and 32%, respectively. No grade 3 or higher toxicities were noted. Mean (95% confidence interval) EPIC urinary QoL scores were 86.6 (81.9-91.3), 87.1 (81.4-92.6), and 87.9 (80.1-95.7) at baseline, 3 months and 24 months; bowel scores were 94.1 (91.3-97.0), 93.2 (89.1-97.2), and 92.4 (87.7- 97.1), respectively.

CONCLUSIONS

This gantry-based novel fractionation schedule incorporating pelvic radiation for high-risk prostate cancer in combination with androgen deprivation therapy is feasible and well tolerated.

Impact of time to testosterone rebound and comorbidity on the risk of cause-specific mortality in men with unfavorable-risk prostate cancer

BACKGROUND

Herein, the authors evaluated how the time to testosterone rebound (TTR) after radiotherapy (RT) and 6 months of androgen deprivation therapy (ADT) impacted the risk of prostate cancer-specific mortality (PCSM) and cardiovascular-specific mortality (CVM) among men with varying comorbidity extent.

METHODS

Between 1995 and 2001, a total of 206 men who were randomized to receive RT either alone or with 6 months of ADT for unfavorable-risk PC and who had a comorbidity score assigned using the Adult Comorbidity Evaluation 27 metric comprised the study cohort. Multivariable competing risk regression was used to evaluate the impact of and possible interaction between comorbidity and TTR on PCSM and CVM.

RESULTS

After a median follow-up of 18.19 years, 30 men (18.6%), 39 men (24.2%), and 92 men (57.1%), respectively, had died of PC, CV disease, or other causes. As TTR increased, PCSM significantly decreased in men with no or minimal (adjusted hazard ratio [AHR], 0.53, 95% confidence interval [95% CI], 0.34-0.84 [P =.007]) and moderate to severe (AHR, 0.37; 95% CI, 0.14-0.99 [P = .048]) comorbidity. However, increasing TTR significantly increased the risk of CVM among men with moderate to severe comorbidity (AHR, 1.87; 95% CI, 1.40-2.49 [P <.001]), but not those with no or minimal comorbidity (AHR, 0.86; 95% CI, 0.57-1.29 [P =.46]), leading to a significant interaction between TTR and comorbidity (P = .001).

CONCLUSIONS

The results of the current study indicate that considering an intermittent course of ADT such that the TTR approaches 18 months, instead of continuous long-term administration of ADT, in men with moderate to severe comorbidity and high-risk PC may reduce the increased risk of CVM without increasing the risk of PCSM. Cancer 2018;124:1391-9. © 2018 American Cancer Society.

Optimizing androgen deprivation therapy with radiation therapy for aggressive localized and locally advanced prostate cancer

Radiation therapy with androgen deprivation therapy (ADT) has historically been one of the mainstays of treatment for intermediate- and high-risk prostate cancer. The benefit of ADT likely derives from both enhancing local control and inhibiting micrometastatic disease. While level 1 evidence has demonstrated the benefits of 4-6 months of ADT for all men with intermediate-risk disease, further stratification of intermediate-risk prostate cancer into favorable and unfavorable subgroups indicates that ADT may not be necessary for favorable intermediate-risk disease but likely still provides a survival advantage for unfavorable intermediate-risk disease, even in the dose escalation era. Long-course ADT, consisting of 2-3 years of treatment, is the standard of care for high-risk prostate cancer managed with RT based on phase III trials. However, emerging data from a randomized trial raises the possibility that 18 months of ADT could be sufficient for select high-risk patients. The desire to minimize exposure to ADT lies in its many adverse effects, including the potential for cardiovascular harm in certain patients with significant coexisting comorbidity, possibly increased risk for neurocognitive and psychiatric events, and the well-documented metabolic changes. Providers need to carefully weigh these potential risks with the known survival benefits of ADT in aggressive localized and locally advanced prostate cancer.