Optimal sequencing of docetaxel and abiraterone in men with metastatic castration-resistant prostate cancer

[Therapy sequences and duration in mCRPC: a retrospective review of the Lübeck mCRPC cohort]

BACKGROUND

Prostate cancer is one of the most common cancers in men in Europe. Several classes of agents can be considered for the treatment of metastatic prostate carcinoma, and their use is supported by extensive guidelines. In the treatment of metastatic castration-resistant prostate cancer (mCRPC), it is currently unclear which sequence of systemic therapies is most effective. Currently approved system therapies in the castration-resistant setting generally include hormone-manipulating agents, taxane-based chemotherapies, radioactive agents, or inhibitiors of DNA repair mechanisms. This study aims to summarize real world data of mCRPC therapy.

METHODS

Retrospectively, 90 mCRPC patients undergoing treatment at the University Hospital Schleswig-Holstein, Lübeck Campus between February 2006 and March 2020 were identified. The patient data were analyzed for their treatment sequence and disease progression. Due to the inclusion period, the mCRPC therapy sequences studied were limited to: Abiraterone, Cabazitaxel, Docetaxel, Enzalutamide, Lutetium-177-PSMA and Radium-223. The analysis includes the therapy sequences and their duration, clinical information of the respective cohort, overall and cancer-specific survival (OS/CSS) as well as time to second-line therapy in relation to the respective first-line therapy.

RESULTS

Approximately two-thirds of patients underwent a true therapy sequence (at least two of the drugs listed above), with this proportion halving by the third line.The majority of patients received the sequence (first/second line) abiraterone/docetaxel (n=13), followed by docetaxel/abiraterone (n=12) and abiraterone/enzalutamid (n=10) and docetaxel/docetaxel (n=8).Within the different docetaxel sequences, first-line (mean 4.7 months ± SD 3.1; median 4.0) and rechallenge (mean 5.3 months ± SD 5.9; median 3.0) therapy durations were the longest. The subjective side effect rate of docetaxel was lower in the second line, so that a better tolerability can be assumed here.The abiraterone/docetaxel sequence was used mainly in patients with metachronous metastases. Among the different sequences of abiraterone, first-line (mean 10.8 months ± SD 10.2; median 9.0) and second-line (mean 10.6 months ± SD 9.0; median 7.0) therapy durations were the longest.The sequence abiraterone/enzalutamide was prescribed mainly to older patients with synchronous metastases. Among the different enzalutamide sequences first-line (mean 9.6 months ± SD 7.1; median 7.0) and rechallenge (mean 11.0 ± SD 0.0; median 11.0) therapy durations were the longest.In contrast, the sequence docetaxel/docetaxel was used mainly in younger patients with a high initial PSA.The evaluation shows a trend that both abiraterone and enzalutamide can account for a survival advantage in the first line.

CONCLUSION

Ultimately, an optimal treatment sequence cannot be confidently derived from these data.However, it was found that only a small proportion of patients underwent fourth- or even fifth-line treatment at all. Thus, the focus on first- and second-line in this study seems reasonable. It could be shown in a trend that docetaxel as first-line therapy seems to be disadvantegous regarding OS as well as CSS when compared to abiraterone or enzalutamide. However, due to the small number of patients in this study, a clear significance cannot be derived. Moreover, the subjectively better tolerability of docetaxel in the second-line setting could provide an impetus for treatment planning in multimorbid elderly patients in the future. The sequence abiraterone/docetaxel may offer a beneficial option for initial mCRPC therapy.

Comparative analysis of real-world data of frequent treatment sequences in metastatic prostate cancer

Background

The incidence of prostate cancer is increasing worldwide. A significant proportion of patients develop metastatic disease and are initially prescribed androgen deprivation therapy (ADT). However, subsequent sequences of treatments in real-world settings that may improve overall survival remain an area of active investigation.

Materials and methods

Data were collected from 384 patients presenting with de novo metastatic prostate cancer from 2011 to 2015 at a tertiary cancer center. Patients were categorized into surviving (n = 232) and deceased (n = 152) groups at the end of 3 years. Modified sequence pattern mining techniques (Generalized Sequential Pattern Mining and Sequential Pattern Discovery using Equivalence Classes) were applied to determine the exact order of the most frequent sets of treatments in each group.

Results

Degarelix, as the initial form of ADT, was uniquely in the surviving group. The sequence of ADT followed by abiraterone and docetaxel was uniquely associated with a higher 3-year overall survival. Orchiectomy followed by fosfestrol was found to have a unique niche among surviving patients with a long duration of response to the initial ADT. Patients who received chemotherapy followed by radiotherapy and those who received radiotherapy followed by chemotherapy were found more frequently in the deceased group.

Conclusions

We identified unique treatment sequences among surviving and deceased patients at the end of 3 years. Degarelix should be the preferred form of ADT. Patients who received ADT followed by abiraterone and chemotherapy showed better results. Patients requiring palliative radiation and chemotherapy in any sequence were significantly more frequent in the deceased group, identifying the need to offer such patients the most efficacious agents and to target them in clinical trial design.

Radium-223 in combination with docetaxel in patients with castration-resistant prostate cancer and bone metastases: a phase 1 dose escalation/randomised phase 2a trial

PURPOSE

Radium 223 dichloride (radium-223) is an alpha particle-emitting bone-directed therapy that prolongs overall survival in men with bone-predominant metastatic castration-resistant prostate cancer (mCRPC). Docetaxel is an antimicrotubule cytotoxic agent that improves survival in mCRPC. We investigated whether combining these potentially cross-sensitising agents to dually target tumour and bone would be safe and effective.

PATIENTS AND METHODS

Phase 1 was a dose escalation study to define a recommended phase 2 dose (RP2D) of docetaxel and radium-223. In phase 2a, patients were randomised 2:1 to the recommended combination regimen or docetaxel at a dose of 75 mg/m2 every 3 weeks (q3w). Patients with bone-predominant mCRPC were eligible. End-points were safety, efficacy and treatment-related changes in serum and imaging biomarkers.

RESULTS

Twenty patients were enrolled in phase 1; 53 patients were randomised in phase 2a: 36 to combination treatment and 17 to docetaxel alone. The RP2D for the combination was radium-223 55 kBq/kg every six weeks × 5 doses, plus docetaxel 60 mg/m2 q3w × 10 doses. Febrile neutropenia was dose limiting. A higher rate of febrile neutropenia was seen in the docetaxel monotherapy arm (15% vs 0%); the safety profile of the treatment groups was otherwise similar. The combination arm had more durable suppression of prostate-specific antigen (median time to progression, 6.6 vs 4.8 months, respectively), alkaline phosphatase (9 vs 7 months) and osteoblastic bone deposition markers.

CONCLUSIONS

Radium-223 in combination with docetaxel at the RP2D was well tolerated. Exploratory efficacy data suggested enhanced antitumour activity for the combination relative to docetaxel alone. Comparative studies with end-points of clinical benefit are warranted. ClinicalTrials.gov number: NCT01106352.

Neuroendocrine differentiation markers guide treatment sequence selection in metastatic castration-resistant prostate cancer

BACKGROUND

To evaluate the value of the serum neuroendocrine differentiation (NED) markers in helping to select the best treatment sequence of abiraterone acetate (AA) and docetaxel-prednisone (DP) in mCRPC.

METHODS

Eighty-eight mCRPC patients were identified (42 in the DP-to-AA group and 46 in the AA-to-DP group). The serum levels of NED markers were measured before the first-line treatment in 88 patients and also before and after DP therapy in 38 patients. We determined their impact on OS, radiographic progression-free survival (rPFS), and PSA-PFS.

RESULTS

In men with an elevation of at least one NED marker (n = 46) before the first-line treatment, those who received AA and then DP had significantly better worse OS (21.7 months [95% CI 21.0-22.4] vs 19.9 months (95% CI 15.3-24.5); P = 0.023. In a multivariate Cox regression analysis, treatment sequencing selection (selecting DP-AA rather than AA-DP) independently predicted OS (HR 0.4, 95% CI 0.2-0.9, P = 0.035) in patients with an elevation of at least one NED marker. However, in the subgroup without NED marker elevation, there was no significant difference in clinical outcomes between AA-DP and DP-AA groups (all P > 0.05). In the group with continued NED marker evaluation during DP treatment, patients with higher baseline NED markers and obtaining PSA response to DP were more inclined to experience NED markers decline.

CONCLUSIONS

Elevated pretreatment serum NED markers might indicate mCRPC patients would get better clinical outcomes from DP-AA than AA-DP. In contrast, those without NED marker elevation had similar outcomes regardless of which agent was chosen first. mCRPC patients with elevated NED markers and chemotherapy response were more inclined to obtain NED markers decline during DP therapy, which could account for this phenomenon.

Impact of the introduction of novel hormonal agents on metastatic castration-resistant prostate cancer treatment choice

BACKGROUND

Docetaxel-based chemotherapy has been the cornerstone of the management of symptomatic metastatic castration-resistant prostate cancer (mCRPC) since 2004. This study aimed to describe how real-world clinical practice was changed with the public funding of novel hormonal agents (abiraterone and enzalutamide) in Quebec.

METHODS

We conducted a retrospective cohort study in two McGill University hospitals. Hospital-based cancer registries were used to select mCRPC patients in medical oncology departments from January 2010 to June 2014. Two groups according to mCRPC diagnosis year were built, with 2012 chosen as the cut-off year, corresponding to the year abiraterone was approved for public reimbursement in second-line in Quebec. Kaplan-Meier analysis was used to estimate time to first docetaxel prescription since mCRPC diagnosis before and after 2012. Cox regression was used to identify predictive factors of docetaxel and novel hormonal agent use.

RESULTS

In our cohort, 308 patients diagnosed with mCRPC were selected with 162 patients in the pre-2012 group and 146 patients in the post-2012 group. The median age at mCRPC was 74.0 years old. At 12 months from diagnosis, 69% of patients received a prescription for docetaxel in the pre-2012 group comparatively to 53% in the post-2012 group. Factors that decreased the likelihood of docetaxel utilization were: age older than 80 at mCRPC diagnosis (HR: 0.5; 95%CI: 0.3-0.7), mCRPC diagnosis after 2012 (HR: 0.6; 95%CI: 0.4-0.8), and asymptomatic disease at mCRPC diagnosis (HR: 0.5; 95%CI: 0.3-0.7).

CONCLUSION

The introduction of novel hormonal agents reduced first-line and overall docetaxel utilization and delayed time to its initiation.

Expression of AR-V7 and ARv567es in Circulating Tumor Cells Correlates with Outcomes to Taxane Therapy in Men with Metastatic Prostate Cancer Treated in TAXYNERGY

PURPOSE

Biomarkers aiding treatment optimization in metastatic castration-resistant prostate cancer (mCRPC) are scarce. The presence or absence of androgen receptor (AR) splice variants, AR-V7 and ARv567es, in mCRPC patient circulating tumor cells (CTC) may be associated with taxane treatment outcomes.Experimental Design: A novel digital droplet PCR (ddPCR) assay assessed AR-splice variant expression in CTCs from patients receiving docetaxel or cabazitaxel in TAXYNERGY (NCT01718353). Patient outcomes were examined according to AR-splice variant expression, including prostate-specific antigen (PSA)50 response and progression-free survival (PFS).

RESULTS

Of the 54 evaluable patients, 36 (67%) were AR-V7+, 42 (78%) were ARv567es+, 29 (54%) were double positive, and 5 (9%) were double negative. PSA50 response rates at any time were numerically higher for AR-V7- versus AR-V7+ (78% vs. 58%; P = 0.23) and for ARv567es- versus ARv567es+ (92% vs. 57%; P = 0.04) patients. When AR-V mRNA status was correlated with change in nuclear AR from cycle 1 day 1 to day 8 (n = 24), AR-V7+ patients (n = 16) had a 0.4% decrease versus a 12.9% and 26.7% decrease in AR-V7-/ARv567es- (n = 3) and AR-V7-/ARv567es+ (n = 5) patients, respectively, suggesting a dominant role for AR-V7 over ARv567es. Median PFS was 12.02 versus 8.48 months for AR-V7- versus AR-V7+ (HR = 0.38; P = 0.01), and 12.71 versus 7.29 months for ARv567es- versus ARv567es+ (HR = 0.37; P = 0.02). For AR-V7+, AR-V7-/ARv567es+, and AR-V7-/ARv567es- patients, median PFS was 8.48, 11.17, and 16.62 months, respectively (P = 0.0013 for trend).

CONCLUSIONS

Although detection of both CTC-specific AR-V7 and ARv567es by ddPCR influenced taxane outcomes, AR-V7 primarily mediated the prognostic impact. The absence of both variants was associated with the best response and PFS with taxane treatment.See related commentary by Dehm et al., p. 1696.

Systemic immune-inflammation index predicts the combined clinical outcome after sequential therapy with abiraterone and docetaxel for metastatic castration-resistant prostate cancer patients

OBJECTIVE

To compare the antitumor effect of abiraterone (AA) followed by docetaxel-prednisone (DP) or vice versa in metastatic castration-resistant prostate cancer (mCRPC) patients, and explored factors that might predict combined PSA-PFS, combined rPFS and OS.

PATIENTS AND METHODS

We retrospectively analyzed mCRPC patients treated with sequential therapy using DP followed by AA or vice versa. Patients who had received enzalutamide or cabazitaxel were excluded. The primary outcome measure was overall survival (OS). The combined PSA progression-free survival (PSA-PFS), combined radiographic PFS (rPFS), and OS of AA-to-DP were compared to the reverse sequence using Kaplan-Meier curves with log-rank statistics. Univariable and multivariable Cox regression analyses were performed to determine prognostic factors that were associated with combined PSA-PFS, combined rPFS and OS.

RESULTS

A total of 104 mCRPC patients who began treatment between 2013 and 2017 were identified: 42 were in the DP-to-AA group and 62 were in the AA-to-DP group. There was no significant difference of baseline clinical characteristics between AA-to-DP and DP-to-AA group. In addition, there was no significant difference in combined PSA-PFS (AA-to-DP: 12.5 [11.4-13.6] vs DP-to-AA: 13.2 [10.9-15.5] months [P = 0.127]), combined rPFS (AA-to-DP: 12.2 [10.9-13.4] vs DP-to-AA: 11.2 [8.9-13.5] months [P = 0.183]) and OS (AA-to-DP: 23.3 [19.7-26.9] vs DP-to-AA: 22.9 [22.1-23.7] months [P = 0.213]) between the two treatment sequences in Kaplan-Meier analysis. In multivariate Cox regression analysis, high systematic Immune-Inflammation Index (SII) level, which was calculated by P (platelet) × N (neutrophil)/L(lymphocyte), remained significant predictors of OS, combined rPFS and combined PSA-PFS.

CONCLUSION

In this study, we did not observe differences in clinical outcomes based on alternative sequencing of AA and DP in mCRPC patients. The ability to tolerate side effects and patient preference may be used to determine the treatment sequencing. In addition, high pretreatment SII level is a negative independent prognosticator of survival outcomes in mCRPC with sequential therapy using DP followed by AA or vice versa, which might guide clinicians select the best treatment.

p53 status in the primary tumor predicts efficacy of subsequent abiraterone and enzalutamide in castration-resistant prostate cancer

BACKGROUND

We tested whether tissue-based analysis of p53 and PTEN genomic status in primary tumors is predictive for subsequent sensitivity to abiraterone and enzalutamide in castration-resistant prostate cancer (CRPC).

METHODS

We performed a retrospective analysis of 309 consecutive patients with CRPC treated with abiraterone or enzalutamide. Of these, 101 men (33%) had available primary tumor tissue for analysis. We screened for deleterious TP53 missense mutations and PTEN deletions using genetically validated immunohistochemical assays for nuclear accumulation of p53 protein and PTEN protein loss, with sequencing confirmation of TP53 mutations in a subset. Overall survival (OS) and progression-free survival (PFS) were compared between patients with and without p53 and/or PTEN alterations.

RESULTS

Forty-eight percent of the evaluable cases had PTEN loss and 27% had p53 nuclear accumulation. OS and PFS did not differ according to PTEN status, but were significantly associated with p53 status. Median OS was 16.7 months (95% CI, 14-21.9 months) and 31.2 months (95% CI, 24.5-43.4) for men with and without p53 nuclear accumulation, respectively (HR 2.32; 95% CI 1.19-4.51; P = 0.0018). Similarly, median PFS was 5.5 months (95% CI, 3.2-9.9 months) and 10.9 months (95% CI, 8-15.2 months) in men with and without p53 nuclear accumulation, respectively (HR 2.14, 95%CI 1.20-3.81; P = 0.0008). In multivariable analyses, p53 status was independently associated with PFS (HR 2.15; 95% CI 1.03-4.49; P = 0.04) and a HR of 2.19 for OS (95% CI 0.89-5.40; P = 0.087).

CONCLUSIONS

p53 inactivation in the primary tumor (but not PTEN loss) may be predictive of inferior outcomes to novel hormonal therapies in CRPC.

Sequencing Treatment for Castration-Resistant Prostate Cancer

OPINION STATEMENT

Prostate cancer is the most common non-cutaneous cancer diagnosed in men and the second leading cause of male cancer deaths in the USA. While most cases are diagnosed in early stages, some will present as or progress to metastatic disease and eventually castration-resistant prostate cancer (mCRPC) which has a mortality rate exceeding 50 %. There are currently six approved systemic life-prolonging therapies for use in mCRPC, yet little data to guide sequencing. Clinical factors, including the presence or absence of symptoms and the presence or absence of visceral metastases, should help determine the best therapeutic choice at each treatment node. Those with asymptomatic bone-only disease could be considered for sipuleucel-T, abiraterone, enzalutamide, or docetaxel in the first-line setting. For symptomatic disease, docetaxel could be used or radium-223 if disease is only present in the bone. In the second-line setting, sipuleucel-T or radium-223 can be used in the appropriate clinical setting. Taxane chemotherapy could be used if a novel androgen-directed therapy was used in the first-line setting. Cabazitaxel, if docetaxel was previously used, should be considered. There is scarce data on best treatment options in the third-line setting. In general, we recommend alternating between androgen-targeting agents and taxane chemotherapy. Finally, consideration should be given to testing for the androgen receptor splice variant AR-V7, which may be a relevant treatment-specific biomarker to aid in the selection of androgen-targeting therapy versus chemotherapy at each treatment juncture. Mutation testing for DNA damage repair defects can also be considered, as such patients may benefit from investigational poly ADP ribose polymerase (PARP) inhibitors or platinum-based chemotherapies. Several ongoing studies have been designed to answer some of these sequencing questions, including the biomarker questions, and will hopefully continue to inform us about rational therapy selection in mCRPC.

Piecing the puzzle together: Docetaxel cycles and current considerations in the treatment of metastatic castration-resistant prostate cancer

Docetaxel is the current first line therapy for metastatic castration-resistant prostate cancer (mCRPC), but there is no standard number of docetaxel cycles given to patients. In their post hoc analysis of the Mainsail study, de Morrée et al. show that the number of docetaxel cycles administered to a patient is a significant factor contributing to overall survival. These findings warrant further investigation into the standardization of the number of docetaxel cycles administered.

Early use of chemotherapy in metastatic prostate cancer

Since 2010, five new antineoplastic therapies have been FDA approved for the treatment of metastatic prostate cancer. With additional treatment options, questions arose about the optimal sequence of these agents. Until recently, chemotherapy has been deferred until later in the disease course in favor of next-generation androgen deprivation therapy. Prior to the development of abiraterone acetate and enzalutamide, clinical trials were opened investigating the combination of chemotherapy with androgen deprivation therapy in patients with metastatic hormone-sensitive disease. With the development of new oral therapies used to treat castration-resistant disease, these trials were largely forgotten or felt to be obsolete. Recently, two trials have been reported showing an overall survival benefit of the early use of chemotherapy in patients with hormone-naive prostate cancer, changing the treatment paradigm for metastatic disease. Here we review the history of chemotherapy in treating prostate cancer and the emerging evidence favoring its use as first-line therapy against metastatic hormone-sensitive disease.

Targeting the N-Terminal Domain of the Androgen Receptor: A New Approach for the Treatment of Advanced Prostate Cancer

: Despite the recent approval and widespread use of abiraterone acetate and enzalutamide for the treatment of castration-resistant prostate cancer (CRPC), this disease still poses significant management challenges because of various tumor escape mechanisms, including those that allow androgen receptor (AR) signaling to remain active. These AR-related resistance mechanisms include AR gene amplification or overexpression, constitutively active ligand-independent AR splice variants, and gain-of-function mutations involving the AR ligand-binding domain (LBD), among others. Therefore, the development of AR-targeted therapies that function independently of the LBD represents an unmet medical need and has the potential to overcome many of these resistance mechanisms. This article discusses N-terminal domain (NTD) inhibition as a novel concept in the field of AR-directed therapies for prostate cancer. AR NTD-targeting agents have the potential to overcome shortcomings of current hormonal therapies by inhibiting all forms of AR-mediated transcriptional activity, and as a result, may affect a broader AR population including mutational and splice variant ARs. Indeed, the first clinical trial of an AR NTD inhibitor is now underway.

IMPLICATIONS FOR PRACTICE

Because of emerging resistance mechanisms that involve the ligand-binding domain of the androgen receptor (AR), there is currently no effective treatment addressing tumor escape mechanisms related to current AR-targeted therapies. Many patients still demonstrate limited clinical response to current hormonal agents, and castration-resistant prostate cancer remains a lethal disease. Intense research efforts are under way to develop therapies to target resistance mechanisms, including those directed at other parts of the AR molecule. A novel small-molecule agent, EPI-506, represents a new pharmaceutical class, AR N-terminal domain inhibitors, and shows preclinical promise to overcome many known resistance mechanisms related to novel hormonal therapies.

Use of early chemotherapy for hormone-sensitive prostate cancer: time for CHAARTED

CHAARTED was an ECOG-led phase III trial looking at early chemotherapy with the use of docetaxel in addition to androgen deprivation therapy (ADT) versus ADT alone in hormone-sensitive prostate cancer. The positive results of the trial showing marked improvement in overall survival in those who received chemotherapy with ADT have revolutionized the treatment of metastatic castration-sensitive prostate cancer. In addition to overall survival, secondary endpoints such as time to castration resistance, PSA response were also significant for the patients who received early chemotherapy.