Phase I trial of weekly docetaxel, total androgen blockade, and image-guided intensity-modulated radiotherapy for localized high-risk prostate adenocarcinoma

Harnessing the potential of multimodal radiotherapy in prostate cancer

Radiotherapy in combination with androgen deprivation therapy (ADT) is a standard treatment option for men with localized and locally advanced prostate cancer. However, emerging clinical evidence suggests that radiotherapy can be incorporated into multimodality therapy regimens beyond ADT, in combinations that include chemotherapy, radiosensitizing agents, immunotherapy and surgery for the treatment of men with localized and locally advanced prostate cancer, and those with oligometastatic disease, in whom the low metastatic burden in particular might be treatable with these combinations. This multimodal approach is increasingly recognized as offering considerable clinical benefit, such as increased antitumour effects and improved survival. Thus, radiotherapy is becoming a key component of multimodal therapy for many stages of prostate cancer, particularly oligometastatic disease.

Phase I Trial of Weekly Cabazitaxel with Concurrent Intensity Modulated Radiation and Androgen Deprivation Therapy for the Treatment of High-Risk Prostate Cancer

PURPOSE

Cabazitaxel has been demonstrated to improve the overall survival for men with metastatic castrate-resistant prostate cancer. The purpose of this study was to determine the maximum tolerated dose for concurrent cabazitaxel with androgen deprivation and intensity modulated radiation therapy in men with high-risk prostate cancer.

METHODS AND MATERIALS

Twenty men were enrolled in this institutuional review board-approved phase I clinical trial using a 3 + 3 design. Patients were followed prospectively for safety, efficacy, and health-related quality of life (Expanded Prostate Index Composite). Efficacy was assessed biochemically using the Phoenix definition.

RESULTS

With a median follow-up time of 56 months, the maximum tolerated dose of concurrent cabazitaxel was 6 mg/m². The 5-year biochemical disease-free survival was 73%, despite 75% of patients having very high risk prostate cancer per the National Comprehensive Cancer Network guidelines. Four patients were unable to complete chemotherapy owing to dose-limiting toxicities (eg, rectal bleeding, diarrhea, and elevated transaminase). There was no significant minimally important difference in Expanded Prostate Index Composite patient-reported outcomes for either the urinary or bowel domains; however, there was a significant decrease in the sexual domain.

CONCLUSIONS

This is the first clinical trial of prostate cancer to report on the combination of cabazitaxel and radiation therapy. The maximum tolerated dose of concurrent cabazitaxel with radiation and androgen deprivation therapy was determined to be 6 mg/m². Despite the aggressive nature of the disease, robust biochemical control was observed.

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.

Docetaxel-titanate nanotubes enhance radiosensitivity in an androgen-independent prostate cancer model

Around 40% of high-risk prostate cancer patients who undergo radiotherapy (RT) will experience biochemical failure. Chemotherapy, such as docetaxel (DTX), can enhance the efficacy of RT. Multidrug resistance mechanisms often limit drug efficacy by decreasing intracellular concentrations of drugs in tumor cells. It is, therefore, of interest to develop nanocarriers of DTX to maintain the drug inside cancer cells and thus improve treatment efficacy. The purpose of this study was to investigate the use of titanate nanotubes (TiONts) to develop a TiONts-DTX nanocarrier and to evaluate its radiosensitizing in vivo efficacy in a prostate cancer model. In vitro cytotoxic activity of TiONts-DTX was evaluated using an MTS assay. The biodistribution of TiONts-DTX was analyzed in vivo by single-photon emission computed tomography. The benefit of TiONts-DTX associated with RT was evaluated in vivo. Eight groups with seven mice in each were used to evaluate the efficacy of the nanohybrid combined with RT: control with buffer IT injection ± RT, free DXL ± RT, TiONts ± RT and TiONts-DXL ± RT. Mouse behavior, health status and tumor volume were monitored twice a week until the tumor volume reached a maximum of 2,000 mm³. More than 70% of nanohybrids were localized inside the tumor 96 h after administration. Tumor growth was significantly slowed by TiONts-DTX associated with RT, compared with free DTX in the same conditions (P=0.013). These results suggest that TiONts-DTX improved RT efficacy and might enhance local control in high-risk localized prostate cancer.

A phase 2 trial of salvage radiation and concurrent weekly docetaxel after a rising prostate-specific antigen level after radical prostatectomy

PURPOSE/OBJECTIVES

We sought to assess the utility of docetaxel administered concurrently with salvage radiation therapy (SRT) following postprostatectomy biochemical failure (BF).

METHODS AND MATERIALS

Men with postprostatectomy BF were accrued on a single-arm phase 2 clinical trial. SRT doses ranged from 64.8 to 70.2 Gy and were delivered in 1.8-Gy fractions to the prostate bed alone as the clinical target volume with a +1-cm uniform planning target volume expansion. The primary endpoint was progression-free survival at 4 years compared with the Stephenson nomogram estimate. Kaplan-Meier methods were used to assess late toxicity, BF, and distant metastases. An unplanned matched-pair analysis was performed with 19 patients treated with SRT alone.

RESULTS

Nineteen men were accrued and treated. Median follow-up was 4.8 years. Median pre-RT prostate-specific antigen level was 0.7 ng/mL (interquartile range, 0.4-1.3 ng/mL). All 8 cycles of docetaxel were completed in 17 (89%) patients. Acute grade 1-4 toxicities were observed in 79%, 50%, 58%, and 11%, respectively. A total of 68% of acute grade 1 toxicities were related to fatigue, urinary, or bowel symptoms. For grade 2 toxicities, 76% were related to neutropenia, fatigue, or urinary symptoms. Acute grade 3 and 4 toxicities were most commonly neutropenia (84% and 100%, respectively). All late toxicities were grade 1 to 2 with 89% related to bowel or urinary function. Predicted 4-year progression-free survival was 39% and observed was 42% (90% confidence interval [CI], 24-60). Matched-pair analysis demonstrated no significant improvement in BF (P = .96, hazard ratio, 0.98; 90% CI, 0.4-2.3) or distant metastases (P = .09; hazard ratio, 0.3; 90% CI, 0.07-1.2), and no difference between late bowel (P = .60) or urinary toxicity (P = .41).

CONCLUSIONS

Docetaxel can safely be administered concurrently with SRT without significantly impacting posttreatment toxicity. Neutropenia was the most significant acute toxicity. Given the small sample size, no clear clinical benefit was observed. Larger studies are needed to determine the efficacy of concurrent docetaxel in this setting.

Concurrent chemoradiation for high-risk prostate cancer

There are estimated to be 220800 cases of prostate cancer diagnosed in 2015, making up 26% of all cancer diagnoses. Fortunately, adenocarcinoma of the prostate is often a highly treatable malignancy. Even though the majority of prostate cancer patients present with localized disease, prostate cancer still accounts for over 27000 deaths a year. There is a subset of patients that are likely to recur after locoregional treatment that is thought of as a “high-risk” population. This more aggressive subset includes patients with clinical stage greater than T2b, Gleason score greater than 7, and prostate specific antigen greater than 20 ng/dL. The rate of biochemical relapse in this high risk group is 32%-70% within five years of definitive focal therapy. Given these discouraging outcomes, attempts have been made to improve cure rates by radiation dose escalation, addition of androgen depravation therapy, and addition of chemotherapy either sequentially or concurrently with radiation. One method that has been shown to improve clinical outcomes is the addition of chemotherapy to radiotherapy for definitive treatment. Concurrent chemoradiation with 5-fluorouracil, estramustine phosphate, vincristine, docetaxel, and paclitaxel has been studied in the phase I and/or II setting. These trials have identified the maximum tolerated dose of chemotherapy and radiation that can be safely delivered concurrently and established the safety and feasibility of this technique. This review will focus on the addition of concurrent chemotherapy to radiotherapy in the definitive management of high-risk prostate cancer.