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Calendar time-specific propensity scores and comparative effectiveness research for stage III colon cancer chemotherapy.

ABSTRACT: Nonexperimental studies of treatment effectiveness provide an important complement to randomized trials by including heterogeneous populations. Propensity scores (PSs) are common in these studies but may not adequately capture changes in channeling experienced by innovative treatments. We use calendar time-specific (CTS) PSs to examine the effect of oxaliplatin during dissemination from off-label to widespread use.Stage III colon cancer patients aged 65+ years initiating chemotherapy between 2003 and 2006 were examined using cancer registry data linked with Medicare claims. Two PS approaches for receipt of oxaliplatin versus 5-flourouricil were constructed using logistic models with key components of age, sex, substage, grade, census-level income, and comorbidities: (i) a conventional, year-adjusted PS and (ii) a CTS PS constructed and matched separately within 1-year intervals, then combined. We compared PS-matched hazard ratios (HRs) for mortality using Cox models.Oxaliplatin use increased significantly; 8% (n?=?86) of patients received it in the first time period versus 52% (n?=?386) in the last. Channeling by comorbidities, income, and age appeared to change over time. The CTS PS improved covariate balance within calendar time strata and yielded an attenuated estimated benefit of oxaliplatin (HR?=?0.75) compared with the conventional PS (HR?=?0.69).In settings where prescribing patterns have changed and calendar time acts as a confounder, a CTS PS can characterize changes in treatment choices and estimating separate PSs within specific calendar time periods may result in enhanced confounding control. To increase validity of comparative effectiveness research, researchers should carefully consider drug lifecycles and effects of innovative treatment dissemination over time.

SUBMITTER: Mack CD

PROVIDER: S-EPMC3659185 | biostudies-literature | 2013 Aug

REPOSITORIES: biostudies-literature

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Calendar time-specific propensity scores and comparative effectiveness research for stage III colon cancer chemotherapy.

Mack Christina DeFilippo CD Glynn Robert J RJ Brookhart M Alan MA Carpenter William R WR Meyer Anne Marie AM Sandler Robert S RS Stürmer Til T

Pharmacoepidemiology and drug safety 20130107 8

<h4>Purpose</h4>Nonexperimental studies of treatment effectiveness provide an important complement to randomized trials by including heterogeneous populations. Propensity scores (PSs) are common in these studies but may not adequately capture changes in channeling experienced by innovative treatments. We use calendar time-specific (CTS) PSs to examine the effect of oxaliplatin during dissemination from off-label to widespread use.<h4>Methods</h4>Stage III colon cancer patients aged 65+ years ini ...[more]

PMID: 23296544

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Project description:BackgroundThe addition of oxaliplatin to adjuvant 5-fluorouracil (5-FU) improves survival of patients with stage III colon cancer in randomized clinical trials (RCTs). However, RCT participants are younger, healthier, and less racially diverse than the general cancer population. Thus, the benefit of oxaliplatin outside RCTs is uncertain.Subjects and methodsPatients younger than 75 years with stage III colon cancer who received chemotherapy within 120 days of surgical resection were identified from five observational data sources-the Surveillance, Epidemiology, and End Results registry linked to Medicare claims (SEER-Medicare), the New York State Cancer Registry (NYSCR) linked to Medicaid and Medicare claims, the National Comprehensive Cancer Network (NCCN) Outcomes Database, and the Cancer Care Outcomes Research & Surveillance Consortium (CanCORS). Overall survival (OS) was compared among patients treated with oxaliplatin vs non-oxaliplatin-containing adjuvant chemotherapy. Overall survival for 4060 patients diagnosed during 2004-2009 was compared with pooled data from five RCTs (the Adjuvant Colon Cancer ENdpoinTs [ACCENT] group, n = 8292). Datasets were juxtaposed but not combined using Kaplan-Meier curves. Covariate and propensity score adjusted proportional hazards models were used to calculate adjusted survival hazard ratios (HR). Stratified analyses examined effect modifiers. All statistical tests were two-sided.ResultsThe survival advantage associated with the addition of oxaliplatin to adjuvant 5-FU was evident across diverse practice settings (3-year OS: RCTs, 86% [n = 1273]; SEER-Medicare, 80% [n = 1152]; CanCORS, 88% [n = 129]; NYSCR-Medicaid, 82% [n = 54]; NYSCR-Medicare, 79% [n = 180]; and NCCN, 86% [n = 438]). A statistically significant improvement in 3-year overall survival was seen in the largest cohort, SEER-Medicare, and in the NYSCR-Medicare cohort (non-oxaliplatin-containing vs oxaliplatin-containing adjuvant therapy, adjusted HR of death: pooled RCTs: HR = 0.80, 95% CI = 0.70 to 0.92, P = .002; SEER-Medicare: HR = 0.70, 95% CI = 0.60 to 0.82, P < .001; NYSCR-Medicare patients aged ?65 years: HR = 0.58, 95% CI = 0.38 to 0.90, P = .02). The association between oxaliplatin treatment and better survival was maintained in older and minority group patients, as well as those with higher comorbidity.ConclusionThe addition of oxaliplatin to 5-FU appears to be associated with better survival among patients receiving adjuvant colon cancer treatment in the community.

Project description:BackgroundChanneling occurs when a medication and its potential comparators are selectively prescribed based on differences in underlying patient characteristics. Drug safety advisories can provide new information regarding the relative safety or effectiveness of a drug product which might increase selective prescribing. In particular, when reported adverse effects vary among drugs within a therapeutic class, clinicians may channel patients toward or away from a drug based on the patient's underlying risk for an adverse outcome. If channeling is not identified and appropriately managed it might lead to confounding in observational comparative effectiveness studies.ObjectiveTo demonstrate channeling among new users of second generation antipsychotics following a Food and Drug Administration safety advisory and to evaluate the impact of channeling on cardiovascular risk estimates over time.Data sourceFlorida Medicaid data from 2001-2006.Study designRetrospective cohort of adults initiating second generation antipsychotics. We used propensity scores to match olanzapine initiators with other second generation antipsychotic initiators. To evaluate channeling away from olanzapine following an FDA safety advisory, we estimated calendar time-specific propensity scores. We compare the performance of these calendar time-specific propensity scores with conventionally-estimated propensity scores on estimates of cardiovascular risk.Principal findingsIncreased channeling away from olanzapine was evident for some, but not all, cardiovascular risk factors and corresponded with the timing of the FDA advisory. Covariate balance was optimized within period and across all periods when using the calendar time-specific propensity score. Hazard ratio estimates for cardiovascular outcomes did not differ across models (Conventional PS: 0.97, 95%CI: 0.81-3.18 versus calendar time-specific PS: 0.93, 95%CI: 0.77-3.04).ConclusionsChanges in channeling over time was evident for several covariates but had limited impact on cardiovascular risk estimates, possibly due to unmeasured confounding. Although calendar time-specific propensity scores appear to improve covariate balance, the impact on comparative effectiveness results is limited in this setting.

Project description:BackgroundColon cancer incidence is rising in low- and middle-income countries (LMICs), where resource limitations and cost often dictate treatment decisions. In this study, we evaluate the cost-effectiveness of adjuvant chemotherapy for high-risk stage II and stage III colon cancer treatment in South Africa (ZA) and illustrate how such analyses can inform cancer treatment recommendations in a LMIC.MethodsWe created a decision-analytic Markov model to compare lifetime costs and outcomes for patients with high-risk stage II and stage III colon cancer treated with three adjuvant chemotherapy regimens in a public hospital in ZA: capecitabine and oxaliplatin (CAPOX) for 3 and 6 months, and capecitabine for 6 months, compared to no adjuvant treatment. The primary outcome was the incremental cost-effectiveness ratio (ICER) in international dollars (I$) per disability-adjusted life-year (DALY) averted, at a willingness-to-pay (WTP) threshold equal to the 2021 ZA gross domestic product per capita (I$13,764/DALY averted).ResultsCAPOX for 3 months was cost-effective for both patients with high-risk stage II and patients with stage III colon cancer (ICER = I$250/DALY averted and I$1042/DALY averted, respectively), compared to no adjuvant chemotherapy. In subgroup analyses of patients by tumor stage and number of positive lymph nodes, for patients with high-risk stage II colon cancer and T4 tumors, and patients with stage III colon cancer with T4 or N2 disease. CAPOX for 6 months was cost-effective and the optimal strategy. The optimal strategy in other settings will vary by local WTP thresholds. Decision analytic tools can be used to identify cost-effective cancer treatment strategies in resource-constrained settings.ConclusionColon cancer incidence is increasing in low- and middle-income countries, including South Africa, where resource constraints can impact treatment decisions. This cost-effectiveness study evaluates three systemic adjuvant chemotherapy options, compared to surgery alone, for patients in South African public hospitals after surgical resection for high-risk stage II and stage III colon cancer. Doublet adjuvant chemotherapy (capecitabine and oxaliplatin) for 3 months is the cost-effective strategy and should be recommended in South Africa.

Project description:BackgroundSince 2004, a regimen of 6 months of treatment with oxaliplatin plus a fluoropyrimidine has been standard adjuvant therapy in patients with stage III colon cancer. However, since oxaliplatin is associated with cumulative neurotoxicity, a shorter duration of therapy could spare toxic effects and health expenditures.MethodsWe performed a prospective, preplanned, pooled analysis of six randomized, phase 3 trials that were conducted concurrently to evaluate the noninferiority of adjuvant therapy with either FOLFOX (fluorouracil, leucovorin, and oxaliplatin) or CAPOX (capecitabine and oxaliplatin) administered for 3 months, as compared with 6 months. The primary end point was the rate of disease-free survival at 3 years. Noninferiority of 3 months versus 6 months of therapy could be claimed if the upper limit of the two-sided 95% confidence interval of the hazard ratio did not exceed 1.12.ResultsAfter 3263 events of disease recurrence or death had been reported in 12,834 patients, the noninferiority of 3 months of treatment versus 6 months was not confirmed in the overall study population (hazard ratio, 1.07; 95% confidence interval [CI], 1.00 to 1.15). Noninferiority of the shorter regimen was seen for CAPOX (hazard ratio, 0.95; 95% CI, 0.85 to 1.06) but not for FOLFOX (hazard ratio, 1.16; 95% CI, 1.06 to 1.26). In an exploratory analysis of the combined regimens, among the patients with T1, T2, or T3 and N1 cancers, 3 months of therapy was noninferior to 6 months, with a 3-year rate of disease-free survival of 83.1% and 83.3%, respectively (hazard ratio, 1.01; 95% CI, 0.90 to 1.12). Among patients with cancers that were classified as T4, N2, or both, the disease-free survival rate for a 6-month duration of therapy was superior to that for a 3-month duration (64.4% vs. 62.7%) for the combined treatments (hazard ratio, 1.12; 95% CI, 1.03 to 1.23; P=0.01 for superiority).ConclusionsAmong patients with stage III colon cancer receiving adjuvant therapy with FOLFOX or CAPOX, noninferiority of 3 months of therapy, as compared with 6 months, was not confirmed in the overall population. However, in patients treated with CAPOX, 3 months of therapy was as effective as 6 months, particularly in the lower-risk subgroup. (Funded by the National Cancer Institute and others.).

Project description:BackgroundThe survival impact of multi-agent (MAC) compared with single-agent (SAC) adjuvant chemotherapy (AC) in elderly patients with stage III colon cancer (CC) remains controversial. The aim of this study was to compare survival outcomes of MAC and SAC in this population utilizing the National Cancer Database (NCDB).Patients and methodsPatients aged ≥70 years with pathological stage III CC diagnosed in 2004-2015 were identified in the NCDB. Univariate and multivariable analyses were conducted, and Kaplan-Meier analysis and Cox proportional hazard models were used to identify associations between MAC vs. SAC and overall survival (OS).ResultsAmong 41 707 elderly patients (≥70 years old) with stage III CC, about half (n = 20 257; 48.5%) received AC; the majority (n = 12 923, 63.8%) received MAC. The median age was 79 (range 70-90). The majority were female (n = 11 201, 55.3%), Caucasians (88%) and had moderately differentiated tumor grade (n = 12 619, 62.3%), tumor size >4 cm (11 785, 58.2%), and negative surgical margins (18 496, 91.3%). Low-risk stage III CC constituted 50.6% (n = 10 264) of the study population. High-risk stage III CC was associated with worse OS compared with low-risk disease (HR 0.35, 0.34-0.36, P < .001). Multi-agent chemotherapy was associated with a better 5-year OS compared with SAC (P < .001). High-risk stage III patients who received MAC vs. SAC had an OS of 4.2 vs. 3.4 years, respectively (P < .001). Low-risk stage III patients who received MAC vs. SAC had a median OS of 8.5 vs. 7 years (P < .001). In univariate and multivariable analyses, male sex, positive surgical margin, insurance and facility types, age, year of diagnosis, tumor size, and Charlson-Deyo score of >2 were associated with worse OS (P < .05).ConclusionsAny adjuvant chemotherapy has a trend of survival benefits. Multi-agent chemotherapy seems to have an enhanced benefit in the 70-75 age group. Multi-agent chemotherapy seemed to have similar efficacy as SAC in those aged >76 years.

Project description:BackgroundThe benefit of chemotherapy in colon cancer patients is well documented but depends largely on whether patients complete the planned treatment regimen. We evaluated predictors of early discontinuation (EDChemo) and dose reduction of chemotherapy, especially the role of adverse treatment effects, in stage III patients who received adjuvant chemotherapy.MethodsStage III colon cancer patients who were diagnosed in 2003-2014 and recruited into a population-based study in Germany and received FOLFOX [5-fluorouracil (5-FU), leucovorin (LV), and oxaliplatin], capecitabine monotherapy (CapMono), or 5-FU/LV were included. We assessed determinants of EDChemo and dose reduction using multivariable logistic regression. Also, we estimated proportions of EDChemo and dose reduction that are attributable to adverse effects using attributable fractions.ResultsEDChemo and dose reduction rates were 52% and 17% for FOLFOX, 28% and 9% for CapMono, and 45% and 6% for 5-FU/LV, respectively. Predictors of EDChemo were low-grade tumor and treatment in a medium-volume hospital (for FOLFOX), obesity (for CapMono), and increasing age, T4 stage, and treatment in a medium-volume hospital (for 5-FU/LV). Adverse effects were particularly strongly associated with EDChemo and contributed to about 63%, 51%, and 32% of EDChemo of FOLFOX, CapMono, and 5-FU/LV, respectively. Of the various adverse effects, gastrointestinal events showed the strongest associations with EDChemo and accounted for about 7%, 26%, and 20% of EDChemo of FOLFOX, CapMono, and 5-FU/LV, respectively. Adverse effects were, moreover, a strong determinant of dose reduction and accounted for about 82% of all cases.ConclusionsEDChemo is common in stage III colon cancer patients receiving chemotherapy and more than half of the cases of EDChemo and dose reduction are due to adverse treatment effects. Further research should address the potential for reducing EDChemo and dose reduction rates by close monitoring of patients for early signs and enhanced management of adverse effects, especially gastrointestinal events.

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Calendar time-specific propensity scores and comparative effectiveness research for stage III colon cancer chemotherapy.

Publications

Calendar time-specific propensity scores and comparative effectiveness research for stage III colon cancer chemotherapy.

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