Comparative overall survival of CDK4/6 inhibitors in combination with endocrine therapy in advanced breast cancer

Individual trials of abemaciclib, palbociclib, and ribociclib show a similar impact on progression-free survival yet differing statistical significance for overall survival (OS). A robust comparative evaluation of OS, safety, and tolerability of the three drugs is warranted. A systematic literature search identified phase 3 randomized clinical trials reporting OS of CDK4/6 inhibitors (CDK4/6i) in combination with endocrine therapy in ER-positive/HER2-negative advanced breast cancer. Trial-level data on OS and common and serious adverse events (AE) were extracted for each drug. In the absence of direct comparisons, a network meta-analysis was performed to evaluate pairwise comparative efficacy, safety, and tolerability of each of the CDK4/6i. Seven studies comprising of 4415 patients met the inclusion criteria. Median follow-up was 73.3 months (range: 48.7-97.2 months). There were no statistically significant differences in OS between any of the CDK4/6i. Compared to palbociclib, ribociclib and abemaciclib both showed significantly higher GI toxicity (grade 1-2 vomiting OR 1.87 [95% CI 1.37-2.56] and OR 2.27 [95% CI 1.59-3.23] respectively). Compared to palbociclib, abemaciclib was associated with more grade 3-4 diarrhea OR 118.06 [95% CI 7.28-1915.32]. In contrast, palbociclib was associated with significantly more neutropenia than ribociclib and abemaciclib but significantly lower risk of grade 3-4 infections. Abemaciclib had significantly less grade 3-4 transaminitis and grade 3-4 neutropenia than ribociclib. Treatment discontinuation and death due to AE were significantly higher with abemaciclib than palbociclib and ribociclib. There is no statistically significant difference in OS between CDK4/6i despite differing statistical significance levels of individual trials. Real-world data analyses may help to identify if there is a meaningful inter-drug difference in efficacy. Significant differences between CDK4/6i are observed for safety and tolerability outcomes.

Magnitude of effect and sample size justification in trials supporting anti-cancer drug approval by the US Food and Drug Administration

Approval of drugs is based on randomized trials observing statistically significant superiority of an experimental agent over a standard. Statistical significance results from a combination of effect size and sampling, with larger effect size more likely to translate to population effectiveness. We assess sample size justification in trials supporting cancer drug approvals. We identified US FDA anti-cancer drug approvals for solid tumors from 2015 to 2019. We extracted data on study characteristics, statistical plan, accrual, and outcomes. Observed power (Pobs) was calculated based on completed study characteristics and observed hazard ratio (HRobs). Studies were considered over-sampled if Pobs > expected with HRobs similar or worse than expected or if Pobs was similar to expected with HRobs worse than expected. We explored associations with over-sampling using logistic regression. Of 75 drug approvals (reporting 94 endpoints), 21% (20/94) were over-sampled. Over-sampling was associated with immunotherapy (OR: 5.5; p = 0.04) and associated quantitatively but not statistically with targeted therapy (OR: 3.0), open-label trials (OR: 2.5), and melanoma (OR: 4.6) and lung cancer (OR: 2.17) relative to breast cancer. Most cancer drug approvals are supported by trials with justified sample sizes. Approximately 1 in 5 endpoints are over-sampled; benefit observed may not translate to clinically meaningful real-world outcomes.

Meta-analysis of sex and racial subgroup participation rates and differential treatment effects for trials in solid tumor malignancies leading to US Food and Drug Administration registration between 2010 and 2021

BACKGROUND

The lack of sociodemographic diversity in clinical trials limits the generalizability of results. The authors examined participation rates and effect modification by sex and race in oncology trials.

METHODS

The authors extracted outcome data stratified by sex and race for registration trials supporting US Food and Drug Administration (FDA) approval (2010-2021). Effect modification by race and sex was examined using quantitative and qualitative methods. A random-effects meta-analysis and pairwise comparison of progression-free survival (PFS) and overall survival (OS) outcomes was conducted by sex and race.

RESULTS

Ninety-five trials with 123 end points and 54,365 patients provided information on sex. Trial patients were more often male (n = 35,482; 65% vs. 56% male patients in US Surveillance, Epidemiology, and End Results [SEER] data), although the proportion of male patients was similar after adjusting by tumor type (60% in FDA data vs. 58% in SEER data). There was no difference in pooled outcomes among male versus female patients (PFS: hazard ratio, 0.99; 95% confidence interval, 0.92-1.07; p = .89; OS: hazard ratio, 0.99; 95% confidence interval, 0.93-1.07; p = .90). In total, 111 trials including 74,217 patients provided information on race, and 68% of patients identified as White, compared with 72.3% in US SEER incidence data. Black patients were under-represented compared with US SEER incidence data, although ethnicity was poorly reported throughout the data set. In the authors' network meta-analysis by race, there were no statistically significant differences in PFS or OS outcomes.

CONCLUSIONS

No significant differences in PFS or OS outcomes were identified when the analyses were stratified by sex or race. Certain racial minorities remain under-represented, and clearer reporting of race and ethnicity is needed. Representation of female patients in FDA trials is similar to that in SEER data after adjusting for tumor type.

Differential treatment effect between younger and older adults for new cancer therapies in solid tumors supporting US Food and Drug Administration approval between 2010 and 2021

BACKGROUND

Over one half of cancer diagnoses occur in patients aged 65 and older. The authors quantified how treatment effects differ between older and younger patients in oncology registration trials.

METHODS

The authors performed a retrospective cohort study of registration trials supporting US Food and Drug Administration approval of cancer drugs (from January 2010 to December 2021). The primary outcome was differential treatment effect by age (younger than 65 years vs. 65 years or older) for progression-free survival and overall survival. Random effects meta-analysis and a pairwise comparison of outcomes by age group also were performed.

RESULTS

Among 263 trials that met the inclusion criteria, 120 trials with 153 end points and 83,152 patients presented age-specific outcome data. Among the included randomized patients, 38% were aged 65 years and older compared with an incidence proportion of 55% in data from the National Cancer Institute's Surveillance, Epidemiology, and End Results program. Studies evaluating prostate cancer had the highest representation of patients aged 65 years or older (73%), whereas breast cancer studies had the lowest (20%). There were no changes in the proportion of patients aged 65 years or older over time (p = .86). Only 7% of end points showed a statistically significant interaction between outcome and age group. In a pooled analysis, there was an association between treatment effect and age for progression-free survival that approached but did not meet significance (hazard ratio, 0.95; p = .06), and there was no difference for overall survival (hazard ratio, 0.97; p = .79).

CONCLUSIONS

Older adults remain under-represented in oncology registration trials. Significant differences in outcomes by age group were uncommon in individual trials and pooled analyses. However, clinical trial participants differ from real-world patients older than 65 years, and increased enrollment and ongoing research into differential treatment effects by age are needed.

State of research, feasibility, safety, acceptability, and outcomes examined on remotely delivered exercises using technology for older adult with cancer: a scoping review

INTRODUCTION

Technology-based exercise is gaining attention as a promising strategy for increasing physical activity (PA) in older adults with cancer (OACA). However, a comprehensive understanding of the interventions, their feasibility, outcomes, and safety is limited. This scoping review (1) assessed the prevalence and type of technology-based remotely delivered exercise interventions for OACA and (2) explored the feasibility, safety, acceptability, and outcomes in these interventions.

METHODS

Studies with participant mean/median age ≥ 65 reporting at least one outcome measure were included. Databases searched included the following: PubMed, CINAHL, Embase, Cochrane Library Online, SPORTDiscus, and PsycINFO. Multiple independent reviewers completed screening and data abstractions of articles in English, French, and Spanish.

RESULTS

The search yielded 2339 citations after removing duplicates. Following title and abstract screening, 96 full texts were review, and 15 were included. Study designs were heterogeneous, and sample sizes were diverse (range 14-478). The most common technologies used were website/web portal (n = 6), videos (n = 5), exergaming (n = 2), accelerometer/pedometer with video and/or website (n = 4), and live-videoconferencing (n = 2). Over half (9/15) of the studies examined feasibility using various definitions; feasibility outcomes were reached in all. Common outcomes examined include lower body function and quality of life. Adverse events were uncommon and minor were reported. Qualitative studies identified cost- and time-savings, healthcare professional support, and technology features that encourage engagement as facilitators.

CONCLUSION

Remote exercise interventions using technology appear to be feasible and acceptable in OACA.

IMPLICATIONS FOR CANCER SURVIVORS

Some remote exercise interventions may be a viable way to increase PA for OACA.

Perceived guideline clarity impacts guideline-concordant care for breast cancer screening in women age 40-49

BACKGROUND

Canadian and US Task Forces recommend against routine mammography screening for women age 40-49 at average breast cancer risk as harms outweigh benefits. Both suggest individualized decisions based on the relative value women place on potential screening benefits and harms. Population-based data reveal variation in primary care professionals (PCPs) mammography rates in this age group after adjusting for sociodemographic factors, highlighting the need to explore PCP screening perspectives and how this informs clinical behaviours. Results from this study will inform interventions that can improve guideline concordant breast screening for this age group.

METHODS

Qualitative semi-structured interviews were performed with PCPs in Ontario, Canada. Interviews were structured using the theoretical domains framework (TDF) to explore determinants of breast cancer screening best-practice behaviours: (1) risk assessment; (2) discussion regarding benefits and harms; and (3) referral for screening.

ANALYSIS

Interviews were transcribed and analyzed iteratively until saturation. Transcripts were coded deductively by behaviour and TDF domain. Data that did not fit within a TDF code were coded inductively. The research team met repeatedly to identify potential themes that influenced or were important consequences of the screening behaviours. The themes were tested against further data, disconfirming cases, and different PCP demographics.

RESULTS

Eighteen physicians were interviewed. The theme of perceived guideline clarity (a lack of clarity on guideline-concordant practices) influenced all behaviours and moderated the extent to which the risk assessment and discussion occurred. Many were unaware of how risk-assessment factored into the guidelines and/or did not perceive that a shared-care discussion was guideline-concordant. Deferral to patient preference (screening referral without a complete discussion of benefits and harms) occurred when the PCPs had low knowledge regarding harms and/or if they experienced regret (TDF domain: emotion) resulting from prior clinical experiences. Older providers described patient's influence impacting their decisions and physicians trained outside Canada, practicing in higher-resourced areas, and female physicians described being influenced by beliefs about consequences of benefits of screening.

CONCLUSION

Perceived guideline clarity is an important driver of physician behaviour. Improving guideline concordant care should start by clarifying the guideline itself. Thereafter, targeted strategies include building skills in identifying and overcoming emotional factors and communication skills important for evidence-based screening discussions.

Determinants of guideline-concordant breast cancer screening by family physicians for women aged 40-49 years: a qualitative analysis

BACKGROUND

Although the current Canadian Task Force on Preventive Health Care guideline recommends that physicians should inform women aged 40-49 years of the potential benefits and harms of screening mammography to support individualized decisions, previous reports of variation in clinical practice at the physician level suggest a lack of guideline-concordant care. We explored determinants (barriers and facilitators) of guideline-concordant care by family physicians regarding screening mammography in this age group.

METHODS

We conducted qualitative semi-structured interviews by phone with family physicians in the Greater Toronto Area from January to November 2020. We structured interviews using the Theoretical Domains Framework to explore determinants (barriers and facilitators) of 5 physician screening behaviours, namely risk assessment, discussion regarding benefits and harms, decision or referral for mammography, referral for genetic counselling and referral to high-risk screening programs. Two independent researchers iteratively analyzed interview transcripts and deductively coded for each behaviour by domain to identify key behavioural determinants until saturation was reached.

RESULTS

We interviewed 18 physicians (mean age 48 yr, 72% self-identified as women). Risk assessment was influenced by physicians' knowledge of risk factors, skills to synthesize risk and beliefs about utility. Physicians had beliefs in their capabilities to have informed patient-centred discussions, but insufficient knowledge regarding the harms of screening. The decision or referral for mammography was affected by emotions related to past patient outcomes, social influences of patients and radiology departments, and knowledge and beliefs about consequences (benefits and harms of screening). Referrals for genetic counselling and to high-risk screening programs were facilitated by their availability and by the knowledge and skills to complete forms. Lack of knowledge regarding which patients qualify and beliefs about consequences were barriers to referral.

INTERPRETATION

Insufficient knowledge and skills for performance of risk assessment, combined with a tendency to overestimate benefits of screening relative to harms affected provision of guideline-concordant care. These may be effective targets for future interventions to improve guideline-concordant care.

A retrospective analysis of changes in distant and breast cancer related disease-free survival events in adjuvant breast cancer trials over time

Disease-free survival (DFS) comprises both breast cancer and non-breast cancer events. DFS has not been validated as a surrogate endpoint for overall survival (OS) in most breast cancer subtypes. We assessed changes to the type of events contributing to DFS over time. We identified adjuvant studies in breast cancer (BC) from 2000 to 2020 where the endpoint was DFS. We examined change in distant DFS events and the BC-related DFS using univariable and multivariable linear regression. Data were reported quantitatively using the Burnand criteria irrespective of statistical significance. We included 84 studies (88 cohorts), comprising 212,191 participants, 41,604 DFS events and 23,205 distant DFS events. The DFS event rate/100 participants/year has declined modestly over time (ß - 0.34, p = 0.001). Start year was negatively associated with distant DFS events (ß - 0.58, p < 0.0001); however, the effect was lost after adjusting for follow-up time (ß - 0.18, p = 0.096). The average number of BC-related events/100 participants/year also declined over time (ß - 0.28, p = 0.009). In multivariable analysis, start year and ER expression were quantitatively associated with distant DFS events and BC-related DFS events. DFS events have declined over time driven by a reduction in BC related events. As DFS events are increasingly defined by non-BC events, there will be limited surrogacy between DFS and OS.

Platinum-based chemotherapy in early-stage triple negative breast cancer: A meta-analysis

PURPOSE

The addition of platinum agents to anthracycline and taxane-based chemotherapy in early-stage triple negative breast cancer (TNBC) patients improves pathological complete response (pCR). Long-term outcomes, such as disease-free survival (DFS) and overall survival (OS), have not been well-established.

METHODS

A systematic literature review identified studies using platinum-based treatment in TNBC patients in the neoadjuvant or adjuvant setting with reportable long-term outcomes. Hazard ratios (HR) from collected data were pooled in a meta-analysis using generic inverse-variance and random effects modeling. Subgroup analyses were conducted based on treatment setting and study design.

RESULTS

Fourteen studies comprising 3518 patients met the inclusion criteria. Median follow up was 56.2 months. All studies reported DFS and 9 studies (64%) reported OS. DFS was significantly better in platinum-based treatment (HR 0.71, 95% confidence interval (CI) 0.56-0.89; p = 0.03). However, OS was no different (HR 0.98, 95% CI 0.75-1.27; p = 0.87). There was a non-significant difference between platinum exposure in the adjuvant compared to neoadjuvant setting for both DFS (HR 0.75 vs 0.62, p = 0.43) and for OS (HR 0.90 vs 1.10, p = 0.58). The addition of platinum was associated with more thrombocytopenia and all-grade neuropathy and non-significant increases in neutropenia and grade 3-4 neuropathy.

CONCLUSIONS

Platinum-based treatment improves DFS but not OS. The reporting of toxicity was suboptimal, but in general adding platinum increased toxicity. The discordant effect of platinum-based treatment on DFS and OS suggest the potential development of platinum resistance and worse outcomes after recurrence. Platinum-based chemotherapy cannot be recommended in unselected patients with early TNBC.

Quantifying Withdrawal of Consent, Loss to Follow-Up, Early Drug Discontinuation, and Censoring in Oncology Trials

BACKGROUND

Censoring due to early drug discontinuation (EDD) or withdrawal of consent or loss to follow-up (WCLFU) can result in postrandomization bias. In oncology, censoring rules vary with no defined standards. In this study, we sought to describe the planned handling and transparency of censoring data in oncology trials supporting FDA approval and to compare EDD and WCLFU in experimental and control arms.

METHODS

We searched FDA archives to identify solid tumor drug approvals and their associated trials between 2015 and 2019, and extracted the planned handling and reporting of censored data. We compared the proportion of WCLFU and EDD between the experimental and control arms by using generalized estimating equations, and performed logistic regression to identify trial characteristics associated with WCLFU occurring more frequently in the control group.

RESULTS

Censoring rules were defined adequately in 48 (59%) of 81 included studies. Only 14 (17%) reported proportions of censored participants clearly. The proportion of WCLFU was higher in the control group than in the experimental group (mean, 3.9% vs 2.5%; β-coefficient, -2.2; 95% CI, -3.1 to -1.3; P<.001). EDD was numerically higher in the experimental arm in 61% of studies, but there was no statistically significant difference in the proportion of EDD between the experimental and control groups (mean, 21.6% vs 19.9%, respectively; β-coefficient, 0.27; 95% CI, -0.32 to 0.87; P=.37). The proportion of EDD due to adverse effects (AEs) was higher in the experimental group (mean, 13.2% vs 8.5%; β-coefficient, 1.5; 95% CI, 0.57-2.45; P=.002). WCLFU was higher in the control group in studies with an active control group (odds ratio [OR], 10.1; P<.001) and in open label studies (OR, 3.00; P=.08).

CONCLUSIONS

There are significant differences in WCLFU and EDD for AEs between the experimental and control arms in oncology trials. This may introduce postrandomization bias. Trials should improve the reporting and handling of censored data so that clinicians and patients are fully informed regarding the expected benefits of a treatment.

Patient and provider determinants of breast cancer screening among Ontario women aged 40-49: a population-based retrospective cohort study

PURPOSE

Canadian breast cancer screening guidelines state that mammography screening for women 40-49 should be individualized based on risk assessment and preferences. This retrospective cohort study describes the frequency of screening in women aged 40-49 and identifies patient and provider-level associations with screening.

METHODS

Administrative databases were linked. The overall cohort included Ontario women aged 40-49 between April 1, 2009 and March 31, 2019. Subgroups were created: the "screen" group included women who received a mammogram defined as screening (using a set of exclusion criteria) and the "routine screen" group included women with three or more screening mammograms. A multivariable multilevel logistic regression model accounting for patient and provider characteristics was fit to determine characteristics associated with routine screening. The intracluster correlation co-efficient was used to quantify the degree of variation across providers.

RESULTS

Of approximately 2 million eligible women, there were 532,596 (25.5%) in the screen group and 90,651 (4.3%) the routine screen group. There was an average of 0.30 and 0.52 screening mammograms per woman year, in the screen and routine screen groups, respectively. Routine screening was associated with periodic health exams (OR 1.21, 95% CI 1.20-1.22), receiving pap smears (OR 1.38, 95% CI 1.37-1.39), and fee-for-service models of care (OR 1.32, 95% CI 1.27-1.36). Over 20% of the variation in screening was due to systematic between-provider differences.

CONCLUSIONS

Approximately 4.3% of women aged 40-49 in Ontario received routine breast cancer screening with substantial variation across providers. Routine screening is associated with periodic health examinations, receipt of pap smears, and fee-for-service models of care.

Development of an evidence-informed recommendation guide to facilitate physical activity counseling between oncology care providers and patients in Canada

Decision support aids help reduce decision conflict and are reported as acceptable by patients. Currently, an aid from the American College of Sports Medicine exists to help oncology care providers advise, assess, and refer patients to physical activity (PA). However, some limitations include the lack of specific resources and programs for referral, detailed PA, and physical function assessments and not being designed following an international gold standard (Appraisal of Guidelines for Research and Evaluation [AGREE] II). This study aimed to develop a recommendation guide to facilitate PA counseling by assessing the risk for PA-related adverse events and offering a referral to an appropriate recommendation. Recommendation guide development followed AGREE II, and an AGREE methodologist was consulted. Specifically, a stakeholder group of oncology care providers and cancer survivors were engaged to develop the assessment criteria for comorbidities, PA levels, and physical function. Assessment criteria were developed from published PA interventions, consultations with content experts, and targeted web-based searches for cancer-specific PA programs. Feedback on the recommendation guide was solicited from stakeholders and external reviewers with relevant knowledge and clinical experience. Independent AGREE methodologists appraised the development process. The recommendation guide is a five-page document, including a preamble, assessment criteria for absolute contraindications to PA, comorbidities, and PA/functional capacity with a list of appropriate resources. Independent AGREE methodologists rated the development process as strong and recommended the guide for use. The recommendation guide has the potential to facilitate PA counseling between oncology care providers and cancer survivors, thus, potentially impacting PA behavior.

Fragility of randomized trials supporting cancer drug approvals stratified by approval pathway and review designations

BACKGROUND

It has been suggested that the results from fragile trials are less likely to translate into benefit in routine clinical practice.

METHODS

We searched the Food and Drug Administration (FDA) archives to identify drug approvals for solid organ malignancies between 2010 and 2019. We calculated the Fragility Index (FI) supporting each approval, using methods to account for time-to-event. We compared FI and trial and approval characteristics using Mann-Whitney U and Kruskal-Wallis test. Using logistic regression, we examined study characteristics associated with withdrawal of consent or lost to follow-up (WCLFU) exceeding the calculated FI.

RESULTS

The median FI among 125 included studies was 23 (range 1-322). The FI was ≤10 in 35 studies (28%), 11-20 in 21 (17%), and >20 in 69 (55%). The median FI/Nexp was 7.7% (range 0.1-51.7%). The median FI was significantly lower among approvals processed through the accelerated vs regular pathway (5.5 vs 25, p = 0.001), but there was no difference in median FI/Nexp. The WCLFU exceeded FI in 42% of studies. Overall survival endpoints were more likely to have a WCLFU exceeding FI (OR 3.16, p = 0.003). WCLFU exceeding FI was also associated with a lesser magnitude of effect (median HR 0.69 vs 0.55, p < 0.001). In a sensitivity analysis including only studies with 1:1 randomization, 51% of studies had WCLFU >FI.

CONCLUSION

The median FI among all trials was 23, and WCLFU exceeded FI in 42%. Comparative trials in solid tumors supporting approval through the accelerated pathway are more fragile compared to trials approved through the regular pathway, an observation likely explained by a lower sample size in the experimental arm.

Network Meta-analysis Comparing Efficacy, Safety and Tolerability of Anti-PD-1/PD-L1 Antibodies in Solid Cancers

Background: Multiple anti-PD-1/PD-L1 antibodies have been approved, and in some diseases, there is a choice of more than one. Comparative efficacy, safety and tolerability are unknown.

Methods: Randomized trials (RCTs) supporting the registration of single agent anti-PD1 or anti-PDL1 inhibitors between 2015-2019 were identified. We extracted the hazard ratio (HR) for overall survival (OS) and calculated the odds ratio (OR) for commonly reported safety and tolerability outcomes. We then performed a network meta-analysis, reporting multiple pair-wise comparisons between different anti-PD-1/PD-L1 antibodies.

Results: Sixteen RCTs comprising 10673 patients were included; 10 in non-small-cell lung cancer, 2 in melanoma, 2 in head and neck squamous cell carcinoma and 2 in urothelial cancer. Compared to pembrolizumab, efficacy was similar for nivolumab (HR: 1.02 95% CI: 0.91-1.14) and for atezolizumab (HR: 0.97 95% CI: 0.85-1.10), however, avelumab appeared inferior (HR: 1.30, 95% CI: 1.06-1.56). Pembrolizumab showed similar odds of serious adverse events (SAEs) as nivolumab (OR: 1.12, 95% CI: 0.56-2.27) and atezolizumab (OR: 1.05, 95% CI: 0.55-2.04). Compared to nivolumab, atezolizumab was associated with more SAEs (OR: 2.14, 95% CI: 1.47-3.12). Avelumab had the lowest odds of grade 3-4 adverse events compared to pembrolizumab (OR: 0.42, 95% CI: 0.24-0.74), nivolumab (OR: 0.38, 95% CI: 0.24-0.62) and atezolizumab (OR: 0.21, 95% CI: 0.14-0.33). The odds of treatment discontinuation without progression were similar between nivolumab and atezolizumab (OR: 1.20, 95% CI: 0.73-2.00), and between pembrolizumab and nivolumab (OR: 1.35, 95% CI: 0.83-2.17), but was higher with atezolizumab compared to nivolumab (OR: 2.56, 95% CI: 1.29-5.00). Pembrolizumab was associated with higher OR of immune-related adverse events (IRAEs) compared to nivolumab (OR: 2.12, 95% CI: 1.49-3.03) and atezolizumab (OR: 1.63, 95% CI: 1.09-2.43).

Conclusions: Pembrolizumab, nivolumab, and atezolizumab have similar efficacy. Avelumab appears less efficacious. Safety and tolerability seem better with avelumab, but worse with atezolizumab and pembrolizumab.

Abstract PS7-30: Differential efficacy, safety and tolerability of low-dose versus standard dose tamoxifen as breast cancer prophylaxis: A network meta-analysis

BACKGROUND: Despite reduction in the risk of breast cancer occurrence, the use of prophylactic tamoxifen does not improve longer term outcomes such as survival and comes at the cost of toxicity. As such, chemoprophylaxis is utilized poorly in routine practice. Lower dose tamoxifen has been proposed as a more acceptable alternative for breast cancer prevention. Here, we explore efficacy and treatment-related adverse events (TRAEs) comparing the two tamoxifen dosing regimens in a network meta-analysis.

METHOD: We searched PubMed to identify randomized trials (RCTs) of tamoxifen for breast cancer prophylaxis in high-risk patients (as defined in individual trials). Low-dose tamoxifen was defined as less than 20mg per day. We extracted the hazard ratio (HR) for breast cancer events relative to placebo. We also collected data on common and serious TRAE, and calculated odd ratios (OR) for each TRAE relative to placebo. Data were then included in a network meta-analysis comparing low-dose (experimental group) to standard dose tamoxifen (control group). Associations between TRAEs and patient charactericstics were explored using meta-regression which comprised a weighted linear regression using mixed effects modelling.

RESULTS: Ten RCTs comprising 35,505 patients were included in the analysis (4 low-dose trials (n=3712 patients) and 6 standard dose trials (n=31,793 patients). There were no significant differences between low-dose and standard dose trials in age (53.3 vs 50.8, p=0.25), post-menopausal status (77.5% vs 49%, p=0.63) or BMI (24.1kg/m2 vs 26.95 kg/m2, p=0.40). Efficacy was similar between the two dosage regimens (HR for breast cancer recurrences: 1.04, 95% CI 0.77-1.41, p=0.78 and for invasive breast cancer: 1.04, 95% CI 0.69-1.56, p=0.85). Differences in TRAEs are shown in the Table. There was a statistically significant reduction in headache with low-dose tamoxifen, and a non-significant reduction in endometrial cancers, other cancers, cardiovascular diseases and all-cause deaths. Hot flashes, vaginal bleeding and endometrial polyps were non-significantly higher with low-dose tamoxifen. In meta-regression analysis, age was associated with lower risk of endometrial carcinoma (p=0.049) and hot flashes (p=0.03).

CONCLUSION: The use of prophylactic low-dose tamoxifen provides similar efficacy to standard dosing, but may reduce the risk of certain common and serious TRAEs.

TRAEOR95% CIp-valueDeaths0.630.14-2.860.55Endometrial cancer0.320.08-1.240.10Endometrial polyps1.660.84-3.280.15Other cancer0.710.40-1.260.24DVT or PE0.900.12-7.580.93

Coronary heart disease0.720.24-2.150.56Cerebrovascular disease1.600.29-8.970.59Hot flashes1.340.63-2.860.45Vaginal dryness0.840.34-2.030.69Vaginal bleeding1.260.52-3.060.61Vaginal discharge1.080.58-1.990.81Headache0.110.05-0.860.04

Citation Format: Alexandra Desnoyers, Michelle B Nadler, Brooke E Wilson, Eitan Amir. Differential efficacy, safety and tolerability of low-dose versus standard dose tamoxifen as breast cancer prophylaxis: A network meta-analysis [abstract]. In: Proceedings of the 2020 San Antonio Breast Cancer Virtual Symposium; 2020 Dec 8-11; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2021;81(4 Suppl):Abstract nr PS7-30.

Abstract PS3-17: Patient and provider determinants of breast cancer screening among Ontario women age 40-49: A population based retrospective cohort study

Background: For women aged 40-49, Canadian guidelines recommend individualized-decision making (based on risk assessment, values, and preferences) rather than routine screening mammography (SM). In this age group, family physicians are the gatekeepers to access SM; however, studies indicate substantial variability in practice patterns. There are few population-based data regarding uptake and patient/provider determinants of SM in this age group. We describe the uptake and frequency of SM and identify patient and provider level associations with SM in Ontario women aged 40-49. We hypothesized that SM would vary by provider characteristics and women’s demographics, suggesting lack of guideline-concordant care.

Methods: This population-based retrospective cohort study linked health administrative databases to form a cohort of all Ontario women aged 40-49 between April 1, 2009 to March 31, 2019. Mammograms were identified using Ontario Health Billing codes. In order to identify mammograms that were specifically for screening, women were excluded if they had any prior breast MRI, mammogram, cancer diagnosis, oncologist visit, or breast surgical procedure. Sub-cohorts were created to identify women who had (a) at least one SM (“screen cohort”) and (b) 3 or more SM (“routine screen cohort”). Following SM, women were censored from cohorts if they had any cancer diagnosis, breast surgical procedure, oncologist visit, or death; however, breast cancer related outcomes were tracked for 6 months following SM, regardless of whether a censoring event occurred. Patient and provider characteristics were extracted for women in each cohort. A multivariable regression model was used to identify predictors of routine SM.

Results: Of 2 million eligible women, 743 274 (35.6%) received a mammogram, 532 782 (25.5%) received at least one SM, and 90 651 (4.3%) received routine SM (3 or more). Table 1 demonstrates cohort characteristics. There were 0.32 and 0.52 mammograms per woman per year in the screen and routine screen cohort respectively. Call-backs were similar for women after the first SM compared to the third SM (9.5% vs 9.3%); however, there were more biopsies (3.2% vs 1.8%) and breast cancers diagnosed (1.2% vs 0.45%) within six months of the first SM. Compared to the full cohort, women in the routine screen cohort were more likely to have a family physician at cohort entry, be in higher-income quintiles, receive annual health exams, and receive have pap smears (p&lt;0.001). Women in the screen cohort were more likely to have female providers and providers that were primarily paid fee for service versus capitation (p&lt;0.001). Multivariable analysis will be reported at the meeting.

Conclusions: Less than 5% of Ontario women 40-49 undergo routine SM. SM is associated with patient demographics related to higher socioeconomic status which could be related to higher risk of breast cancer and/or increased access to care. SM is also associated with some provider demographics which could be independent of breast cancer risk, suggesting lack of individualized risk assessment. Qualitative work is ongoing to explore this hypothesis. This information can inform guideline implementation strategies.

Table 1: Patient and Provider Characteristics of ScreeningCharacteristicpercent (%) unless otherwise notedAll Women 40-49Screen Cohort (1 or more SM)Routine Screen Cohort (3 or more SM)Patient CharacteristicsAge at Cohort entryMean (median)42.5 (40)42.8 (42)41.7 (41)Age at Cohort exitMean (median)47.3 (50)48.5 (50)49.1 (50)Family Physician at Cohort entry90.0 %92.3%94.8%Income – top quintile20.7%22.3%24%Rurality Category – most urban76.3%79.0%81.2%Birth Location – Canada74.4%72.2%71.6%Annual Health Exams: at least one51.1%72.1%75.3%Pap Smear: at least one68.4%86.6%92.9%Provider CharacteristicsFemale44.8%47.2%52.1%Canadian Graduates70.3%70.3%72.1%Fee for Service model48.0%55.0%58.8%

Citation Format: Michelle B Nadler, Alex Marchand-Austin, Peter C. Austin, Alexandra Desnoyers, Brooke E. Wilson, Aisha Lofters, Noah Ivers, Eitan Amir. Patient and provider determinants of breast cancer screening among Ontario women age 40-49: A population based retrospective cohort study [abstract]. In: Proceedings of the 2020 San Antonio Breast Cancer Virtual Symposium; 2020 Dec 8-11; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2021;81(4 Suppl):Abstract nr PS3-17.

Increasing Referrals of Patients With Gastrointestinal Cancer to a Cancer Rehabilitation Program: A Quality Improvement Initiative

BACKGROUND

People with cancer are at risk for initial, late, and long-term effects of cancer and its treatments. Cancer rehabilitation (CR) focuses on prevention/treatment of these sequelae and optimization of physical, social, and vocational functioning. Our center has a multidisciplinary impairment-driven outpatient CR program, but referrals of patients with GI cancer were low.

AIMS

We aimed (for 2019, relative to 2018) (1) to increase CR referrals of patients with GI cancer by 50% and (2) to increase the proportion of referrals coming from oncologists. Balancing measures included inappropriate referrals and cancellations.

METHODS

A rapid cycle improvement approach was used to optimize GI referrals to the CR program. Barriers to CR referral were identified through a literature review and informal interviews of GI clinicians. Barriers included (a) knowledge of CR program existence, (b) awareness of the referral process, (c) time, and (d) lack of CR program exposure. The team used Plan-Do-Study-Act (PDSA) cycles every 2 months from January to December 2019 to address barriers. A p-chart was used to analyze the results.

RESULTS

PDSA cycles included CR program advertisement, a presentation to GI staff, nurse-led patient identification, patient-facing posters, and clinician thank-you emails. The p-chart showed a 100% relative increase in referral numbers and an improvement in the percentage of patients referred by oncologists from 51% to 75%. There was no significant change in inappropriate referrals or cancellations.

CONCLUSION

Through PDSA cycles, we improved the total number of patients with GI cancer and percentage referred by an oncologist to a CR program. Future work will assess sustainability.

Comparison of treatment-related adverse events of different Cyclin-dependent kinase 4/6 inhibitors in metastatic breast cancer: A network meta-analysis

BACKGROUND

Palbociclib, ribociclib and abemaciclib have all been approved in combination with endocrine therapy in hormone-receptor positive, HER2 negative metastatic breast cancer. While the efficacy of these drugs appears similar, differences in safety and tolerability are apparent.

METHODS

We searched PubMed and ASCO, ESMO and SABCS proceedings to identify randomized trials of palbociclib, ribociclib and abemaciclib. Data on common and serious adverse events (AE) were extracted for each approved drug. The odds ratio for each AE and the hazard ratio for progression-free survival were calculated relative to endocrine therapy alone. A network meta-analysis was then performed for each endocrine therapy backbone (aromatase inhibitor (AI) or fulvestrant) to compare ribociclib and abemaciclib to palbociclib.

RESULTS

8 trials were included in the analysis and comprised 2799 patients receiving cyclin-dependent kinase 4/6 inhibitors palbociclib: 873 patients; ribociclib: 1153 patients; abemaciclib: 773 patients. In 5 trials (1524 patients), the endocrine therapy backbone was an AI and in 3 trials (1275 patients) it was fulvestrant. Compared to palbociclib, ribociclib and abemaciclib showed significantly lower grade 3-4 neutropenia, but significantly higher GI toxicity. Treatment discontinuation was higher with abemaciclib than other drugs. Efficacy of the 3 drugs was similar. Compared to palbociclib, for AI backbone, the HR for PFS for ribociclib was 0.98 and for abemaciclib 1.02. For fulvestrant backbone, the HR were 0.88 and 0.93 respectively.

CONCLUSIONS

Palbociclib, ribociclib and abemaciclib have comparable efficacy, but differences in safety and tolerability. Abemaciclib has worse tolerability with significantly higher treatment discontinuation likely due to GI toxicity.

Influence of Competing Risks on Estimates of Recurrence Risk and Breast Cancer-specific Mortality in Analyses of the Early Breast Cancer Trialists Collaborative Group

Early-stage breast cancer (BC) is a curable disease with many patients dying of causes other than BC. The influence of non-BC death and other competing risks on the interpretation of Kaplan-Meier (KM)-based analyses for BC-specific outcomes are unknown. We searched the Oxford University website to identify all meta-analyses published by the Early Breast Cancer Trialists Collaborative Group (EBCTCG) between 2005 and 2018. The potential influence of competing risks was estimated using a validated multivariable linear model that predicts the difference between KM and cumulative incidence function (CIF) on estimates of BC-specific outcomes. The initial search identified 14 EBCTCG papers, 10 (71%) reported data on BC and competing events. Eight (80%) had a relative difference between KM and the competing risk adjusted estimates exceeding 10%. The median relative difference was 28.4% for local-recurrence; 16.8% for distant-recurrence, and 6.7% for BC-specific mortality. There was a 18.9% relative difference between KM and CIF adjusted analyses beyond 10 years. The use of KM-based methods when competing risks are present biases risk estimates in studies of early BC especially for uncommon outcomes such as local recurrence. The use of CIF to calculate BC-specific outcomes may be preferable in this setting.

Abstract P4-14-09: Platinum-based chemotherapy in early-stage triple negative breast cancer: A meta-analysis

Background: The addition of platinum agents to anthracycline and taxane-based chemotherapy in early-stage triple negative breast cancer (TNBC) patients improves pathological complete response (pCR). Long-term outcomes, such as disease-free survival (DFS) and overall survival (OS), have not been well-established.

Methods: A systematic literature review identified studies using platinum-based treatment in TNBC patients in the neoadjuvant or adjuvant setting with reportable long-term outcomes. Hazard ratios (HR) from collected data were pooled in a meta-analysis using generic inverse-variance and random effects modeling. Subgroup analyses were conducted based on treatment setting (neoadjuvant vs. adjuvant) and study design (retrospective vs. randomized controlled trials). When available, odds ratios (OR) for commonly reported safety and tolerability measures such as treatment-related death, treatment discontinuation without progression, dose reduction, neuropathy, renal impairment and hematological toxicity were calculated.

Results: Seven studies comprising 1699 patients met the inclusion criteria. Median follow up was 54.5 months. All studies reported DFS and 4 studies reported OS. DFS was significantly better in platinum-based treatment (HR 0.71, 95% confidence interval (CI) 0.53-0.96; P = 0.03). However, OS was no different with a higher number of events in the platinum-based treatment arm (HR 1.17, 95% CI 0.81-1.69; P = 0.42). There was no significant difference between treatment settings (p = 0.74) or between study designs (p = 0.74), although a higher HR for OS was observed for studies in the adjuvant (HR 1.34, 95% CI 0.54-3.35) compared to neoadjuvant setting (HR 1.14, 95% CI 0.76-1.70). The reporting of toxicity was suboptimal with most studies not reporting safety and tolerability metrics clearly. Platinum-based treatment was associated with more neutropenia and thrombocytopenia and treatment discontinuation, however, the magnitude of this effect could not be estimated accurately.

Conclusions: Platinum-based treatment improves DFS but has no effect on OS and increases toxicity. The discordant effect of platinum-based treatment on DFS and OS suggest the potential development of platinum resistance and worse outcomes after recurrence. The higher magnitude of discordance in adjuvant compared to neoadjuvant studies suggests an effect of platinum-based therapy on loco-regional control prior to surgery rather than prevention of distant metastatic disease. Platinum-based chemotherapy cannot be recommended in unselected patients with TNBC.

Citation Format: Ramy Saleh, Michelle B Nadler, Alexandra Desnoyers, Rouhi Fazelzad, Eitan Amir. Platinum-based chemotherapy in early-stage triple negative breast cancer: A meta-analysis [abstract]. In: Proceedings of the 2019 San Antonio Breast Cancer Symposium; 2019 Dec 10-14; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2020;80(4 Suppl):Abstract nr P4-14-09.

Abstract P4-15-01: Fragility index of trials supporting approval of breast cancer drugs

Background: Decisions on regulatory approval and reimbursement of drugs are based typically on the observation of statistically significant results showing superiority over an established standard. The Fragility Index (FI) quantifies the reliability of statistically significant results by estimating the number of events which would change statistically significant results to non-significant results. Here, we calculate the FI of trials supporting approval of breast cancer drugs.

Methods: We searched Drugs@FDA to identify randomized controlled trials (RCT) supporting breast cancer drug approvals by the US Food and Drug Administration (FDA) between January 2010 and December 2018. We adapted the FI framework (Walsh et al. J Clin Epidemiol 2014) to allow input comprising of time to event data. First, we reconstructed survival tables from reported data using the Parmar Toolkit (Parmar et al. Stat Med 1998). Then, the FI was calculated as the number of events for each arm which would result in a non-significant effect for the primary endpoint of each trial. The FI was then compared quantitatively to the number of patients in each respective trial who withdrew consent or were lost to follow-up.

Results: We identified 15 RCT with a median of 724 patients (range, 302-4084) and 318 events (range, 210-635). The median FI was 18 (range, 4 to 33 - see Table). The FI was 10 or fewer patients in 3 trials (20%) and 20 or fewer in 11 trials (73%). Among the 13 RCTs (87%) reporting data, the median number of patients who withdrew consent and were lost to follow up was 16 (range, 2-103). The number of patients who withdrew consent or were lost to follow-up was greater than the FI in 7 trials (54%). There was no association between trial sample size or reported P-value and the FI.

Conclusion: Statistical significance of trials supporting breast cancer drug approval rely often on a small number of events. In over one half of trials the FI was lower than the number of patients withdrawing consent or being lost to follow-up. Post-approval randomized trials or real-world data analyses should be performed to ensure that effects observed in registration trials are robust.

Main resultsFDA-Approved DrugYear of approvalPhase 3 TrialPrimary EndpointWithdrew consent and lost to follow-upFragility IndexAbemaciclib2018MONARCH 3PFS415Abemaciclib2017MONARCH 2PFS1020Eribulin2010EMBRACEPFS238Eribulin2010EMBRACEOS2316Everolimus2012BOLERO-2PFS3818Neratinib2017ExteNETIDFS827Olaparib2018OlympiADPFS1610Palbociclib2017PALOMA-2PFS1918Palbociclib2016PALOMA-3PFS718Pertuzumab2017APHINITYIDFS1034Pertuzumab2012CLEOPATRAPFS4125Ribociclib2018MONALEESA-7PFS227Ribociclib2018MONALEESA-3PFSn/a19Ribociclib2017MONALEESA-2PFSn/a22T-DM12013EMILIAOS333T-DM12013EMILIAPFS326Talazoparib2018EMBRACAPFS7013

Citation Format: Alexandra Desnoyers, Michelle B. Nadler, Ramy Saleh, Eitan Amir. Fragility index of trials supporting approval of breast cancer drugs [abstract]. In: Proceedings of the 2019 San Antonio Breast Cancer Symposium; 2019 Dec 10-14; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2020;80(4 Suppl):Abstract nr P4-15-01.

The Effect of Exercise on Quality of Life, Fatigue, Physical Function, and Safety in Advanced Solid Tumor Cancers: A Meta-analysis of Randomized Control Trials

BACKGROUND

People with metastatic cancers experience poor quality of life (QoL), fatigue, and decreased physical function. Exercise improves these symptoms in the curative setting, but the efficacy and safety of exercise in the metastatic setting is uncertain.

METHODS

Prospective, randomized trials of moderate/high-intensity aerobic exercise or resistance training vs. control in patients with advanced/metastatic solid cancers were identified from prior reviews and updated using a search of PubMed. The mean and SD for validated outcome measures (QoL, physical function, and fatigue) were extracted for intervention and control groups at baseline and postintervention. The Mann-Whitney test was used to evaluate the effect of exercise on the pooled change between baseline and postintervention. Safety was evaluated qualitatively.

RESULTS

Sixteen trials were analyzed. Among patients with scores at the mean or 2SD above, exercise was not associated with significant or clinical difference in QoL or fatigue. In patients with baseline scores 2SD below mean, exercise was associated with nonsignificant difference meeting minimal clinical important difference in QoL (-2.8 vs. 4.6, P = 0.28). For function, patients at the mean had nonstatistically significant, but clinically meaningful difference in the six-minute walk test (6-MWT) (14.7 vs. 29.0 m, P = 0.44). In patients 2 SD below the mean, there was a clinically meaningful difference in two patient-reported functional subscales (0.1 vs. 5.3, P = 0.076 and 0.44 vs. 8.5, P = 0.465) and a clinically meaningful improvement in the 6-MWT (-7.5 vs. 27.0 m, P = 0.34), although none of these associations met statistical significance. There were no differences in falls, fractures, or pain.

DISCUSSION

Exercise is associated with clinically meaningful improvements in QoL, function, and 6-MWT in some patients with metastatic cancer. Despite poor reporting of safety, there was no signal of increased harm from exercise in this setting.