Real-world effectiveness of palbociclib in HR+/HER2- metastatic breast cancer: a literature review

Approximately 70% of newly diagnosed breast cancers are of the HR+/HER2- subtype. For the treatment of patients with HR+/HER2- metastatic breast cancer, current guidelines recommend the use of a CDK4/6 inhibitor (palbociclib, ribociclib or abemaciclib) in combination with endocrine therapy. In this review we assess existing literature concerning real-world effectiveness of palbociclib. Survival outcomes in terms of progression-free survival and overall survival are discussed and compared among the included real-world studies and in relation to the phase III PALOMA trials.

CDK4/6i-treated HR+/HER2- breast cancer tumors show higher ESR1 mutation prevalence and more altered genomic landscape

As CDK4/6 inhibitor (CDK4/6i) approval changed treatment strategies for patients with hormone receptor-positive HER2-negative (HR+/HER2-) breast cancer (BC), understanding how exposure to CDK4/6i affects the tumor genomic landscape is critical for precision oncology. Using real-world data (RWD) with tumor genomic profiling from 5910 patients with metastatic HR+/HER2- BC, we investigated the evolution of alteration prevalence in commonly mutated genes across patient journeys. We found that ESR1 is more often altered in tumors exposed to at least 1 year of adjuvant endocrine therapy, contrasting with TP53 alterations. We observed a similar trend after first-line treatments in the advanced setting, but strikingly exposure to aromatase inhibitors (AI) combined with CDK4/6i led to significantly higher ESR1 alteration prevalence compared to AI alone, independent of treatment duration. Further, CDK4/6i exposure was associated with higher occurrence of concomitant alterations in multiple oncogenic pathways. Differences based on CDK4/6i exposure were confirmed in samples collected after 2L and validated in samples from the acelERA BC clinical trial. In conclusion, our work uncovers opportunities for further treatment personalization and stresses the need for effective combination treatments to address the altered tumor genomic landscape following AI+CDK4/6i exposure. Further, we demonstrated the potential of RWD for refining patient treatment strategy and guiding clinical trial design.

Cabozantinib in the Routine Management of Renal Cell Carcinoma: A Systematic Literature Review of Real-World Evidence

Real-world cabozantinib use has increased since its approval to treat patients with advanced renal cell carcinoma (RCC) in 2016. We reviewed cabozantinib use in real-world clinical practice and compared outcomes with pivotal cabozantinib randomized control trials (RCTs). This PRISMA-standard systematic literature review evaluated real-world effectiveness and tolerability of cabozantinib in patients with RCC (PROSPERO registration: CRD42021245854). Systematic MEDLINE, Embase, and Cochrane database searches were conducted on November 2, 2022. Eligible publications included ≥ 20 patients with RCC receiving cabozantinib. After double-screening for eligibility, standardized data were abstracted, qualitatively summarized, and assessed for risk of bias using the Newcastle-Ottawa Scale. Of 353 screened publications, 41 were included, representing approximately 11,000 real-world patients. Most publications reported cabozantinib monotherapy cohort studies (40/41) of retrospective (39/41) and multicenter (32/41) design; most included patients from North America and/or Europe (30/41). Baseline characteristics were demographically similar between real-world and pivotal RCT populations, but real-world populations showed greater variation in prevalence of prior nephrectomy, multiple-site/brain metastasis, and nonclear-cell RCC histology. Cabozantinib activity was reported across real-world treatment lines and tumor types. Overall survival, progression-free survival, and objective response rate values from pivotal RCTs were within the ranges reported for equivalent outcomes across real-world studies. Common real-world grade ≥ 3 adverse events were consistent with those in pivotal RCTs (fatigue, palmar-plantar erythrodysesthesia syndrome, diarrhea, hypertension), but less frequent. No new tolerability concerns were identified. Real-world RCC survival outcomes for cabozantinib monotherapy were broadly consistent with pivotal RCTs, despite greater heterogeneity in real-world populations.

Transporting observational study results to a target population of interest using inverse odds of participation weighting

Inverse odds of participation weighting (IOPW) has been proposed to transport clinical trial findings to target populations of interest when the distribution of treatment effect modifiers differs between trial and target populations. We set out to apply IOPW to transport results from an observational study to a target population of interest. We demonstrated the feasibility of this idea with a real-world example using a nationwide electronic health record derived de-identified database from Flatiron Health. First, we conducted an observational study that carefully adjusted for confounding to estimate the treatment effect of fulvestrant plus palbociclib relative to letrozole plus palbociclib as a second-line therapy among estrogen receptor (ER)-positive, human epidermal growth factor receptor (HER2)-negative metastatic breast cancer patients. Second, we transported these findings to the broader cohort of patients who were eligible for a first-line therapy. The interpretation of the findings and validity of such studies, however, rely on the extent that causal inference assumptions are met.

Real-world study of overall survival with palbociclib plus aromatase inhibitor in HR+/HER2- metastatic breast cancer

Data on real-world effectiveness of cyclin-dependent kinase 4/6 inhibitor combination therapy versus endocrine therapy alone are limited. The Flatiron Health Analytic Database was used to assess overall survival (OS) in patients with hormone receptor–positive/human epidermal growth factor receptor 2–negative (HR+/HER2−) metastatic breast cancer (MBC) treated with first-line palbociclib plus an aromatase inhibitor (AI) versus an AI alone in routine US clinical practice. In total, 2888 patients initiated treatment during February 3, 2015–March 31, 2020, with a potential ≥6-month follow-up (cutoff date, September 30, 2020). After stabilized inverse probability treatment weighting, median OS (95% CI) is significantly longer among palbociclib versus AI recipients (49.1 [45.2–57.7] versus 43.2 [37.6–48.0] months; hazard ratio, 0.76 [95% CI, 0.65–0.87]; P < 0.0001). Progression-free survival (95% CI) is 19.3 (17.5–20.7) versus 13.9 (12.5–15.2) months, respectively (hazard ratio, 0.70 [95% CI, 0.62–0.78]; P < 0.0001). These data support first-line palbociclib plus an AI treatment for HR+/HER2− MBC.

(Trial number NCT05361655).

Real-World Safety and Efficacy Outcomes with Abiraterone Acetate Plus Prednisone or Prednisolone as the First- or Second-Line Treatment for Metastatic Castration-Resistant Prostate Cancer: Data from the Prostate Cancer Registry

BACKGROUND

Despite standard-of-care androgen-deprivation therapy and an increasing number of treatment options, the mortality rate for prostate cancer remains high. Progress to metastatic castration-resistant prostate cancer (mCRPC) necessitates additional treatments. Abiraterone acetate plus prednisone or prednisolone (AAP) prolongs survival in chemotherapy-naive and docetaxel-experienced patients.

OBJECTIVE

To evaluate the real-world safety and efficacy of AAP as first-line and second-line [post-docetaxel only (AAP-PD)] treatment in patients with mCRPC.

PATIENTS AND METHODS

The Prostate Cancer Registry (PCR) was a prospective, international, observational study of patients with mCRPC in routine clinical practice. Men aged ≥ 18 years with confirmed mCRPC were included. Baseline characteristics, safety (treatment-emergent adverse events, treatment-emergent severe adverse events), and efficacy [progression-free survival (PFS) and overall survival (OS)] were analyzed.

RESULTS

At baseline, patients who received first-line AAP (n = 754) were generally older than patients who received AAP-PD (n = 354); median age was 76 years and 70 years, respectively. However, the rate of visceral metastasis was higher in the AAP-PD cohort than in the AAP cohort (17.7% vs. 9.6%, respectively). Demographics and disease characteristics of patients with baseline cardiovascular disease were similar to those of the overall registry population. Efficacy outcomes were similar for all patients, regardless of the line of AAP therapy. For first-line AAP and AAP-PD, respectively, the median PFS was 8.9 and 5.8 months for all patients and 9.1 and 6.0 months for patients with cardiovascular comorbidities; median OS was 27.1 and 23.4 months for all patients, and 27.4 and 23.1 months for patients with cardiovascular comorbidities. There were no unexpected adverse events in any patient subgroup.

CONCLUSIONS

These real-world data complement the findings from randomized controlled trials, indicating that first- and second-line AAP is well tolerated and effective in patients with mCRPC, including those with underlying CV comorbidities.

TRIAL REGISTRATION NUMBER

NCT02236637, registered 8 September 2014.

Comparative effectiveness of first-line palbociclib plus letrozole versus letrozole alone for HR+/HER2- metastatic breast cancer in US real-world clinical practice

BACKGROUND

Findings from randomized clinical trials may have limited generalizability to patients treated in routine clinical practice. This study examined the effectiveness of first-line palbociclib plus letrozole versus letrozole alone on survival outcomes in patients with hormone receptor-positive (HR+)/human epidermal growth factor receptor-negative (HER2-) metastatic breast cancer (MBC) treated in routine clinical practice in the USA.

PATIENTS AND METHODS

This was a retrospective observational analysis of electronic health records within the Flatiron Health Analytic Database. A total of 1430 patients with ≥ 3 months of follow-up received palbociclib plus letrozole or letrozole alone in the first-line setting between February 3, 2015, and February 28, 2019. Stabilized inverse probability treatment weighting (sIPTW) was used to balance baseline demographic and clinical characteristics. Real-world progression-free survival (rwPFS) and overall survival (OS) were analyzed.

RESULTS

After sIPTW adjustment, median follow-up was 24.2 months (interquartile range [IQR], 14.2-34.9) in the palbociclib group and 23.3 months (IQR, 12.7-34.3) in those taking letrozole alone. Palbociclib combination treatment was associated with significantly longer median rwPFS compared to letrozole alone (20.0 vs 11.9 months; hazard ratio [HR], 0.58; 95% CI, 0.49-0.69; P < 0.0001). Median OS was not reached in the palbociclib group and was 43.1 months with letrozole alone (HR, 0.66; 95% CI, 0.53-0.82; P = 0.0002). The 2-year OS rate was 78.3% in the palbociclib group and 68.0% with letrozole alone. A propensity score matching analysis showed similar results.

CONCLUSIONS

In this "real-world" population of patients with HR+/HER2- MBC, palbociclib in combination with endocrine therapy was associated with improved survival outcomes compared with patients treated with letrozole alone in the first-line setting.

TRIAL REGISTRATION

Clinicaltrials.gov; NCT04176354.

A comparison between the assessments of progression-free survival by local investigators versus blinded independent central reviews in phase III oncology trials

PURPOSE

In this study, we compared the assessments of progression-free survival (PFS) carried out by the local investigator or by a blinded independent central review in the framework of phase III registration randomized controlled trials (RCT) in oncology.

METHODS

We carried out a search in the clinicatrials.gov database, looking at the RCTs reporting the results of both independently assessed and investigator-assessed PFS. The hazard ratios (HRs) of investigator-assessed PFS and independently assessed PFS were recorded, and a discrepancy index was obtained by calculating the ratio of their respective HRs. Moreover, we investigated possible factors of discrepancy by analyzing the trials in different groups (by year, by tumor type, by drug type, by study design).

RESULTS

We analyzed 28 RCTs meeting the search criteria. The estimated mean discrepancy index was 0.98 (confidence interval 0.927-1.032 (n = 32)). Subgroup analysis showed that the confidence intervals in all cases included the value 1, except in the subgroup of studies started in the period 2003-2006.

CONCLUSION

In phase III oncology trials, we found no significant differences between the hazard ratios estimated by local investigators and those estimated by blinded independent central reviews. A relatively higher variability, in terms of large CI, was found in trials with biological agents.

Approaches to Capturing Value in Oncology

This article sets out to describe different value frameworks in the field of new developments in oncology. Since the costs of new oncological therapies follow a steep path, their implementation and financing demand a thorough assessment. This is an ambitious task due to the complex nature of oncological treatments within overall health policy. Five value frameworks were reviewed: European Society for Medical Oncology (ESMO) Magnitude of Clinical Benefit Scale, American Society of Clinical Oncology (ASCO) Value Framework (version 2.0), National Comprehensive Cancer Network (NCCN) Evidence Blocks, Memorial Sloan Kettering Cancer Center DrugAbacus, and the Institute for Clinical and Economic Review Value Assessment Framework. They are all based on a large set of criteria. However, all these frameworks differ considerably in their outcomes. Among the main differences one has to cite are the inclusion of costs and the use of different outcomes, as well as the fact that they address different target stakeholders, etc. Despite these shortcomings, the value frameworks serve the necessity to introduce more rationality in health decision making seen from the perspective of physicians, patients, and financing bodies.