Abstract 196: Gender-based Differences in Presentation and Treatment of Patients Undergoing Peripheral Vascular Intervention

Introduction: While men and women are at equal risk for peripheral arterial disease (PAD), studies suggest that women present at an older age and with more advanced disease. The purpose of this analysis is to evaluate gender-based differences in disease presentation and its effect on treatment modality among patients who underwent peripheral vascular intervention (PVI) for PAD. Methods: Using national registry data from the Vascular Quality Initiative, univariate analysis, of patient-, limb- and artery-specific characteristics were performed by gender for procedures from 2010-2013. Statistical significance was determined by the Student’s T-test or Chi-squared test. Results: In this real-world cohort, there were 26,873 eligible procedures for 23,940 patients that had 30,668 limbs and 44,927 arteries treated. Compared to men, women presented at an older age (69 vs 71 years, p&lt;0.001) and with more rest pain and tissue loss than claudication (RR=1.13, 95% CI: 1.10-1.16). Women had more severe lesions than men, as measured by TASC classification (TASC C or D RR= 1.81, 95% CI: 1.74-1.87) ( Table 1 ). There were no meaningful gender-based differences in artery treated or treatment modality ( Figure 1 ). Treatment modality was determined by disease severity (indication and TASC classification) and artery treated rather than gender. Conclusion: Although gender-based differences in PAD presentation exist, these differences do not extend to treatment modality, which is determined by disease severity and artery treated. Further investigation is required to appreciate the effect of disease severity and treatment modality on patient outcomes after PVI. </jats:p

Abstract 21234: Patient and Lesion Predictors of Stenting and Atherectomy for Peripheral Arterial Disease

Introduction: Endovascular management of peripheral arterial disease (PAD) has become popular in the past two decades. But little is understood about the practice patterns of different endovascular treatment modalities and the factors that influence their use. Objective: Identify predictors for stenting and atherectomy treatment, compared to angioplasty (PTA) for PAD. Methods: We abstracted data from all endovascular procedures for PAD during January 2010- October 2016 in the Vascular Quality Initiative clinical registry. Adjusted logistic regression models built using backward elimination with a random-effects component for patient clustering were used to identify factors predictive of stenting or atherectomy compared to PTA at the artery level. Results: Eligible patients (n=58,231) had 106,039 arteries treated (median=2, IQR=1 to 3). The majority (50%) of these arteries were treated with stents, 39% with PTA and 11% with atherectomy. Compared to PTA, those receiving stents are more likely to smoke and have iliac treatment. In atherectomy, we see more distal treatment (SFA and tibial) compared to PTA. Artery location was a significant (p&lt;0.05) effect modifier. In multivariable models, there were no significant predictors for atherectomy; TASC C trended to significance in femoropopliteal (OR 6.6 [p=0.08]) and tibial arteries (OR 11.1 [p=0.06]). TASC C and D predicted stenting in all arteries (Figure 1). Current smoking (OR 1.49 [1.32-1.68]), obesity (OR 1.30 [1.17-1.44]), and age 70-79 (OR 1.36 [1.07-1.17]) predicted stenting in femoropopliteal arteries. These factors also predicted stenting in tibial arteries: current smoking (OR 1.40 [1.04-1.88]), obesity (OR 1.50 [1.15-1.44]), and age 80-89 (OR 1.56 [1.14-2.17]). Conclusion: TASC C and D trended toward significance as predictors of atherectomy in tibial and femoropopliteal arteries. TASC C and D, artery type, smoking status, age, and obesity are significant predictors of stenting in all arteries. </jats:p

Association of rurality and race with surgical treatment and outcomes for nonmetastatic colon cancer.

e18536 Background: Rural cancer patients face limited access to care due to greater travel distance and lack of specialty cancer care. Little is known about the intersection of rurality with well-documented racial disparities in colon cancer treatment and outcomes. Methods: We used fee-for-service Medicare claims to study patients age 65+ diagnosed with incident colon cancer without evidence of metastases who underwent cancer-directed surgery between 04/01/2016 and 09/30/2018. The primary exposure was rurality of patient’s residence categorized as metropolitan (metro), micropolitan, and small town/rural. Outcomes were non-elective surgery (emergency department visit or transfer within 2 days of surgery), receipt of minimally invasive surgery (laparoscopic or robotic), 90-day surgical complications, and 90-day mortality. Logistic regression adjusted for patient demographics, cancer side (right vs left), comorbidities, and Area Deprivation Index. We assessed effect modification by race/ethnicity. Results: Of 57,710 patients with incident non-metastatic colon cancer, 37,691 (65%) underwent surgery. In this surgical cohort, small town/rural and micropolitan residents were more likely to be older, white, and Medicare-Medicaid dual-eligible than metro residents. After risk adjustment, patients in small town/rural areas had higher odds of non-elective surgery (OR=1.24, 95% CI:1.13-1.36) and lower odds of minimally invasive surgery (OR=0.75, 95% CI:0.71-0.80) than patients living in metro areas. Similar results were seen for micropolitan areas. The association between rurality and 90-day outcomes differed by race/ethnicity (p-interaction=0.001 for surgical complications and mortality, see Table). Hispanics and other races had higher odds of 90-day surgical complications in non-metro versus metro areas but there was no notable difference for white patients. Likewise, compared to metro areas, racial/ethnic minorities had higher odds of 90-day mortality in small town/rural areas but white patients had lower odds. Conclusions: Small town/rural-residing Medicare beneficiaries undergoing surgery for non-metastatic colon cancer were less likely to receive optimal surgical management and worse outcomes, especially among non-white patients. The compounded effect of sociodemographic factors should be further studied to develop targeted policies and improve care for rural cancer patients.[Table: see text] </jats:p

Abstract 17018: Amputation After Atherectomy: Studying Long-Term Outcomes Using an Instrumental Variable Method

Introduction: Outcomes for atherectomy remain poorly characterized. Our objective was to use instrumental variable (IV) analysis to compare long-term amputation rates in patients receiving atherectomy versus other traditional peripheral vascular interventions (PVI) approaches. Methods: We queried the Medicare-linked Vascular Quality Initiative registry for patients undergoing PVI from 2010-2015. The exposure was treatment: atherectomy (+/- balloon angioplasty) versus other PVI types. The primary outcome was amputation. We used the proportion of atherectomy procedures of all PVIs performed at each hospital as an IV and compared the estimates from IV analysis to multivariable Cox regression and propensity-matched estimates. Results: In this cohort of 19693 patients, 2103 (10%) received atherectomy. Compared to patients receiving other PVI, patients receiving atherectomy were more likely to have a femoropopliteal artery (65% vs 48%, p&lt;0.001) treated with worse disease severity (TASC B and greater: 77% vs 69%, p&lt;0.001). The 5-year overall amputation rate was 31% (158 amputations per 1000 patients/year) in patients receiving atherectomy versus 24% (105 amputations per 1000 patients/year) for other PVIs (log-rank p&lt;0.001). Without adjustment, patients undergoing atherectomy were 40% more likely to have an amputation (Figure 1). After adjusting for patient demographics, comorbidities, and disease characteristics, this effect was mitigated to 15% and 16% for multivariable Cox and propensity-matched approaches, respectively. However, after the IV adjusted analysis accounted for unmeasured confounders, patients receiving atherectomy versus non-atherectomy PVI were 78% more likely to have an amputation. Conclusions: Patients receiving atherectomy were more likely to have an amputation. Unmeasured confounders such as selection bias may play an important role in the long-term risk of amputation for patients undergoing atherectomy. </jats:p

Abstract 171: User Beware: Understanding the Adjusted Estimates of Propensity Score Methods

Background: Propensity score methods are used in observational studies to compensate for the lack of random allocation by balancing measured baseline characteristics between treated and untreated patients. Yet default implementations of propensity score methods may lead to contradictory findings. Our goal was to illustrate differences in treatment effect estimates produced using propensity score methods such as matching and inverse probability weighting (IPW). Methods: We used data from a retrospective analysis of the Northern New England Cardiovascular Disease Study Group registry that studied reintervention after single internal mammary artery (SIMA) versus bilateral internal mammary artery (BIMA) conduit use in 41,481 coronary artery bypass grafting (CABG) procedures from 1992-2014. Results: The mean duration of follow-up was 13.2 (IQR: 7.4-17.7) years. In our standard multivariable Cox regression analysis, the adjusted HR for reintervention was 0.83 (95% confidence interval (CI): 0.75-0.92) in patients receiving BIMA compared to SIMA (Table). The 1:1 propensity matched analysis (HR=0.79, 95% CI: 0.69-0.91) and IPW estimate among the treated (HR=0.83, 95% CI: 0.75-0.92) show a similar protective treatment effect of BIMA use on reintervention. However, the IPW approach for the overall population effect unusually showed no difference between BIMA and SIMA on reintervention-free survival (HR=1.08, 95% CI: 0.94-1.24). Conclusions and Relevance: The adjusted HR for reintervention after BIMA versus SIMA use in CABG was remarkably different for the two IPW estimates. This difference is attributed to the population represented by the two IPW approaches- the IPW among the treated estimate represents the effect in the average study population, whereas the IPW in the treated represents the effect in the treated population alone. Determining how the study population is balanced (weighted to look like the overall study population versus treated group) is a large driver of treatment effect, and a key element of propensity score methods. Ultimately, the treatment effect estimate desired should drive the choice of propensity score adjustment method. </jats:p

Association of rurality and race with surgical treatment and outcomes for nonmetastatic colon cancer.

78 Background: Rural cancer patients face limited access to care due to greater travel distance and lack of specialty cancer care. Little is known about the intersection of rurality with well-documented racial disparities in colon cancer treatment and outcomes. Methods: We used fee-for-service Medicare claims to study patients age 65+ diagnosed with incident colon cancer without evidence of metastases who underwent cancer-directed surgery between 04/01/2016 and 09/30/2018. The primary exposure wasrurality of patient’s residence categorized as metropolitan (metro), micropolitan, and small town/rural. Outcomes were non-elective surgery (emergency department visit or transfer within 2 days prior to surgery), receipt of minimally invasive surgery (laparoscopic or robotic), 90-day surgical complications, and 90-day mortality. Logistic regression adjusted for patient demographics, cancer side (right vs left), comorbidities, and Area Deprivation Index. We assessed effect modification by race/ethnicity. Results: Of 57,710 patients with incident non-metastatic colon cancer, 37,691 (65%) underwent surgery. In this surgical cohort, small town/rural and micropolitan residents were more likely to be older, white, and Medicare-Medicaid dual-eligible than metro residents. After risk adjustment, patients in small town/rural areas had higher odds of non-elective surgery (OR =1.24, 95% CI:1.13-1.36) and lower odds of minimally invasive surgery (OR = 0.75, 95% CI:0.71-0.80) than patients living in metro areas. Similar results were seen for micropolitan areas. White rural patients had lower mortality than white urban patients, whereas black rural patients had higher mortality than black metro patients (see Table). Increasing area deprivation was associated with higher odds of non-elective surgery, surgical complications and mortality, and lower odds of minimally invasive surgery, even after adjusting for race and rurality. Conclusions: Small town/rural-residing Medicare beneficiaries undergoing surgery for non-metastatic colon cancer were less likely to receive optimal surgical management and had worse outcomes, especially among non-white patients. The compounded effect of rurality, race/ethnicity, and social deprivation should be incorporated in developing policies and interventions to improve care for rural cancer patients.[Table: see text] </jats:p