TP53 structure-function relationships in metastatic castrate-sensitive prostate cancer and the impact of APR-246 treatment.

PURPOSE: Despite well-informed work in several malignancies, the phenotypic effects of TP53 mutations in metastatic castration-sensitive prostate cancer (mCSPC) progression and metastasis are not clear. We characterized the structure-function and clinical impact of TP53 mutations in mCSPC. PATIENTS AND METHODS: We performed an international retrospective review of men with mCSPC who underwent next-generation sequencing and were stratified according to TP53 mutational status and metastatic burden. Clinical outcomes included radiographic progression-free survival (rPFS) and overall survival (OS) evaluated with Kaplan-Meier and multivariable Cox regression. We also utilized isogenic cancer cell lines to assess the effect of TP53 mutations and APR-246 treatment on migration, invasion, colony formation in vitro, and tumor growth in vivo. Preclinical experimental observations were compared using t-tests and ANOVA. RESULTS: Dominant-negative (DN) TP53 mutations were enriched in patients with synchronous (vs. metachronous) (20.7% vs. 6.3%, p < 0.01) and polymetastatic (vs. oligometastatic) (14.4% vs. 7.9%, p < 0.01) disease. On multivariable analysis, DN mutations were associated with worse rPFS (hazards ratio [HR] = 1.97, 95% confidence interval [CI]: 1.31-2.98) and overall survival [OS] (HR = 2.05, 95% CI: 1.14-3.68) compared to TP53 wild type (WT). In vitro, 22Rv1 TP53 R175H cells possessed stronger migration, invasion, colony formation ability, and cellular movement pathway enrichment in RNA sequencing analysis compared to 22Rv1 TP53 WT cells. Treatment with APR-246 reversed the effects of TP53 mutations in vitro and inhibited 22Rv1 TP53 R175H tumor growth in vivo in a dosage-dependent manner. CONCLUSIONS: DN TP53 mutations correlated with worse prognosis in prostate cancer patients and higher metastatic potential, which could be counteracted by APR-246 treatment suggesting a potential future therapeutic avenue.

Outcomes of therapeutic plasma exchange for the treatment of patients with multiple myeloma cast nephropathy.

Current treatment guidelines of myeloma cast nephropathy (MCN) recommend the institution of plasma cell-directed therapy and consideration of therapeutic plasma exchange (TPE), with the goal of rapid reduction of the serum free light chain (sFLC). However, the role of TPE continues to remain a subject of debate. The goal of this retrospective bi-institutional study was to evaluate the clinical outcomes of TPE in combination with systemic therapy. Eighty patients were included in this analysis, of whom 72.5% had ≥50% drop in their initial involved sFLC. At 3 months from TPE initiation, the overall hematologic response rate (ORR) was 67.5% with a very good partial response or better (≥VGPR) rate of 40%. At 6 months, ORR was 57.5%, with ≥VGPR rate of 49%. The renal response rate at 3 and 6 months was 47.5% and 43.75%, respectively; the overall renal response rate was 48.75%. On multivariable analysis, every one unit increase in baseline creatinine (odds ratio [OR] 0.76, p = 0.006), and achievement of ≥VGPR (OR 21.7 p < 0.0001) were significantly associated with renal response. Also, a ≥50% drop in sFLC was favorably associated with renal response (OR 3.39, p = 0.09). With a median follow-up of 36.4 months, the median overall survival (OS) was 11 months. On multivariable analysis, achievement of renal response (hazard ratio [HR] 0.3, p < 0.0001) and newly diagnosed disease (NDMM; HR 0.43, p = 0.0055) were associated with improved OS. Among NDMM patients, those treated with daratumumab-based regimens had a trend for better OS (p = 0.15), compared to other regimens, but the difference was not significant. At the end of follow-up, an estimated 40.4% of patients who were on dialysis were able to become dialysis independent. In conclusion, our study highlights the poor survival of patients with MCN. Achievement of early renal response is crucial for prolonged OS, with daratumumab-based therapies showing promise.

A lower fibrinogen threshold does not lead to increased bleeding risk in patients receiving therapeutic plasma exchange: A prospective single-center analysis.

BACKGROUND: Plasma exchange (PLEX) therapy is indicated for several disorders. The 5% albumin is often used as a sole replacement fluid during most PLEX. However, each 1.0 plasma volume exchange depletes coagulation factors by ~65%. Although most coagulation factors recover to hemostatic levels within 24 h post-PLEX, fibrinogen requires 48-72 h to recover. Fibrinogen is the key coagulation protein for hemostasis. Therefore, fibrinogen is often monitored during the acute course of PLEX, and plasma is supplemented to prevent bleeding if fibrinogen is <100 mg/dL. STUDY DESIGN AND METHODS: We conducted a prospective, single-center, observational study to evaluate bleeding risk in adults who received an acute course of PLEX with a fibrinogen level of 80-100 mg/dL without plasma supplementation during the procedure or before central venous catheter removal. The study group was compared to patients with plasma fibrinogen >100 mg/dL. RESULTS: Among the 275 patients who received 1406 PLEXes, 62 patients (23%) who underwent 323 PLEXes met the inclusion criteria, and only 2 (3%) patients had bleeding while on oral anticoagulants. In contrast, out of 275 patients, 143 (52%) with fibrinogen levels >100 mg/dL received 751 PLEX treatments, and bleeding occurred in 2 (1%) while on low-molecular-weight heparin. CONCLUSIONS: Our findings suggest that a pre-procedure fibrinogen threshold of 80-100 mg/dL without plasma supplementation does not increase bleeding risk unless patients were on anticoagulation.

ELK1/MTOR/S6K1 Pathway Contributes to Acquired Resistance to Gefitinib in Non-Small Cell Lung Cancer.

The development of acquired resistance to small molecule tyrosine kinase inhibitors (TKIs) targeting epidermal growth factor receptor (EGFR) signaling has hindered their efficacy in treating non-small cell lung cancer (NSCLC) patients. Our previous study showed that constitutive activation of the 70 kDa ribosomal protein S6 kinase 1 (S6K1) contributes to the acquired resistance to EGFR-TKIs in NSCLC cell lines and xenograft tumors in nude mice. However, the regulatory mechanisms underlying S6K1 constitutive activation in TKI-resistant cancer cells have not yet been explored. In this study, we recapitulated this finding by taking advantage of a gefitinib-resistant patient-derived xenograft (PDX) model established through a number of passages in mice treated with increasing doses of gefitinib. The dissociated primary cells from the resistant PDX tumors (PDX-R) displayed higher levels of phosphor-S6K1 expression and were resistant to gefitinib compared to cells from passage-matched parental PDX tumors (PDX-P). Both genetic and pharmacological inhibition of S6K1 increased sensitivity to gefitinib in PDX-R cells. In addition, both total and phosphorylated mechanistic target of rapamycin kinase (MTOR) levels were upregulated in PDX-R and gefitinib-resistant PC9G cells. Knockdown of MTOR by siRNA decreased the expression levels of total and phosphor-S6K1 and increased sensitivity to gefitinib in PDX-R and PC9G cells. Moreover, a transcription factor ELK1, which has multiple predicted binding sites on the MTOR promoter, was also upregulated in PDX-R and PC9G cells, while the knockdown of ELK1 led to decreased expression of MTOR and S6K1. The chromatin immunoprecipitation (ChIP)-PCR assay showed the direct binding between ELK1 and the MTOR promoter, and the luciferase reporter assay further indicated that ELK1 could upregulate MTOR expression through tuning up its transcription. Silencing ELK1 via siRNA transfection improved the efficacy of gefitinib in PDX-R and PC9G cells. These results support the notion that activation of ELK1/MTOR/S6K1 signaling contributes to acquired resistance to gefitinib in NSCLC. The findings in this study shed new light on the mechanism for acquired EGFR-TKI resistance and provide potential novel strategies by targeting the ELK1/MTOR/S6K1 pathway.

A Proof-of-Concept Pilot Test of a Behavioral Intervention to Improve Adherence to Dietary Recommendations for Cancer Prevention.

OBJECTIVES: Prevention programs that can help adults improve the quality of their diets to reduce cancer risk are needed. This Phase IIa study prospectively tested a mHealth intervention designed to improve adherence to dietary quality guidelines for cancer prevention. METHODS: All participants (N = 62) received nutrition education and a self-regulation skills curriculum, with a primary target of changing grocery shopping behavior. Using a randomized, factorial design, the study varied whether each of the following 4 components were added to the 20-week intervention: (1) location-triggered app messaging, delivered when individuals arrived at grocery stores, (2) reflections on benefits of change, delivered with extra coaching time and tailored app messages, (3) coach monitoring, in which food purchases were digitally monitored by a coach, and (4) involvement of a household member in the intervention. RESULTS: Benchmarks were successfully met for recruitment, retention, and treatment acceptability. Across conditions, there were significant reductions in highly processed food intake (P < .001, η2 = .48), red and processed meat intake (P < .001, η2 = .20), and sugar-sweetened beverage intake (P = .008, η2 = .13) from pre-to post-treatment. Analyses examining whether each intervention component influenced change across time found that participants who received coach monitoring increased their intake of fruits, vegetables, and fiber, whereas those with no coach monitoring had less improvement (P = .01, η2 = .14). The improvement in red and processed meat was stronger among participants with household support ON, at a marginally significant level, than those with household support OFF (P = .056, η2 = .07). CONCLUSION: This study showed feasibility, acceptability, and preliminary signals of efficacy of a remotely delivered intervention to facilitate adherence to dietary guidelines for cancer prevention and that coach monitoring and household support may be especially effective strategies. A fully powered clinical trial is warranted to test an optimized version of the intervention that includes nutrition education, self-regulation skills training, coach monitoring, and household member involvement. TRIAL REGISTRATION: ClinicalTrials.gov NCT04947150.

Hemoglobin S target of <50% as compared to 30% in chronic red cell exchange for secondary stroke prevention in sickle cell disease.

BACKGROUND: Sickle cell disease (SCD) patients with a history of stroke are encouraged to receive chronic red blood cell exchange (RBCx) for stroke prevention. The American Society of Hematology guideline published in 2020 recommends an HbS target of <30%. However, this approach necessitates more frequent RBCx and more RBC units. UT Southwestern has devised a chronic exchange protocol that elevates the HbS target to <50% in patients with a low risk of stroke. STUDY DESIGN: This retrospective chart review study reviewed the medical records of patients receiving chronic RBCx with a target of HbS <50% over the past 10-year period to assess the safety of maintaining higher HbS targets in SCD patients with a low risk of cerebrovascular accidents (CVA). RESULTS: Among 49 SCD patients in the chronic RBCx program for secondary stroke prevention, 33 patients were maintained on an HbS target of <50% (average measured: 35.4%) for the duration of RBCx program enrollment (median 93.0 months, 95% CI, 83-99). Stroke or transient ischemic attack (TIA) clearly attributable to changing target HbS had not been identified among the 33 study subjects. Seven patients experienced conversion between the HbS targets of <50% and <30% HbS target. Significant reductions were observed in the frequency of RBCx and usage of blood volume in four of them. CONCLUSION: The findings suggest that liberalizing the HbS target could confer clinical flexibility without increasing the risk of CVA in a selective population. Further studies to fully evaluate the potential benefits of this approach are indicated.

Perceptions of and barriers to cancer screening by the sexual and gender minority community: a glimpse into the health care disparity.

PURPOSE: A disparity exists in cancer screening rates for the Sexual and Gender Minority (SGM) community. We sought to understand the perceptions and baseline knowledge of cancer screening among SGM community members. METHODS: Survey administered via social media from June 2018 to October 2018. We asked 31 questions focused on cancer screening, human papillomavirus, emotional distress, and experience with the health care system. Those included were 18 years or older. Cancer screening attitudes and knowledge, as well as perceptions of the health care system were investigated. RESULTS: There were 422 respondents analyzed: 24.6% identified as female, 25.5% as male, 40.1% transgender, and 9.6% as other. 65.4% of the SGM community is not certain what cancer screening to do for themselves. Only 27.3% and 55.7% knew that HPV was a risk factor associated with head and neck cancer and anal cancer, respectively. Half stated their emotional distress prevents them from getting cancer screening. It was identified that process changes in making appointments, comforts during the visit, and formal training for physicians and nurses could increase cancer screening compliance for this community. The transgender population had a trend in more gaps in knowledge of appropriate cancer screening and significant excess emotional distress. CONCLUSION: Gaps in cancer screening knowledge and emotional and financial distress may be responsible for the disparity of lower cancer screening rates for the SGM population and the transgender population may be most at risk. Appreciating the cancer screening concerns of the SGM population can help shape future clinical and institutional approaches to improve health care delivery.

High versus low fixed-dose four factor-prothrombin complex concentrate for warfarin reversal in patients with intracranial hemorrhage.

BACKGROUND: Four-factor prothrombin complex concentrate 4F-PCC is the standard of care for warfarin reversal in patients with major bleed or requiring urgent surgery. Although the 4F-PCC dose is weight and international normalized ratio (INR) based, for practical purposes, a fixed-dose approach has been explored, especially for rapid reversal. We report our experience using two different fixed-dose 4F-PCC for warfarin reversal in patients presenting with intracranial hemorrhage (ICH). STUDY DESIGN AND METHODS: We completed a retrospective chart review comparing high (4000 units) versus low (2000 units) dose 4F-PCC by evaluating patient characteristics, laboratory data, and pre-and post-4F-PCC brain imaging. RESULTS: There was no significant difference between patient characteristics or INR correction (≤1.5) between the two groups. Eighty percent (12/15) of patients who received the low dose 4F-PCC had either improved or stable brain imaging as compared to 88% (14/16) of patients who received the high dose PCC. When the eight patients (4 from each arm of the study) who required neurosurgery were excluded, only two patients in each arm had worse imaging after 4F-PCC. CONCLUSION: There was no significant difference between the INR correction and the brain imaging changes in patients with an ICH who received either the high or the low fixed-dose 4F-PCC for warfarin reversal.

Chronoradiobiology of Breast Cancer: The Time Is Now to Link Circadian Rhythm and Radiation Biology.

Circadian disruption has been linked to cancer development, progression, and radiation response. Clinical evidence to date shows that circadian genetic variation and time of treatment affect radiation response and toxicity for women with breast cancer. At the molecular level, there is interplay between circadian clock regulators such as PER1, which mediates ATM and p53-mediated cell cycle gating and apoptosis. These molecular alterations may govern aggressive cancer phenotypes, outcomes, and radiation response. Exploiting the various circadian clock mechanisms may enhance the therapeutic index of radiation by decreasing toxicity, increasing disease control, and improving outcomes. We will review the body's natural circadian rhythms and clock gene-regulation while exploring preclinical and clinical evidence that implicates chronobiological disruptions in the etiology of breast cancer. We will discuss radiobiological principles and the circadian regulation of DNA damage responses. Lastly, we will present potential rational therapeutic approaches that target circadian pathways to improve outcomes in breast cancer. Understanding the implications of optimal timing in cancer treatment and exploring ways to entrain circadian biology with light, diet, and chronobiological agents like melatonin may provide an avenue for enhancing the therapeutic index of radiotherapy.

Is a 20 gauge fenestrated intravenous catheter non-inferior to a 18 gauge standard catheter for apheresis procedures? A pilot study.

BACKGROUND: Peripheral venous access has been promoted as the safest, quickest, and most easily achievable route for performing apheresis procedures by the American Society for Apheresis' Choosing Wisely campaign. The current literature regarding catheter size and selection for both draw and return access is limited. Furthermore, the Infusion Nurses Society recommends using the smallest gauge catheter possible for the prescribed therapy in order to limit vein trauma and phlebitis. Since there is a lack of evidence to guide selection of catheter size for return access during therapeutic apheresis procedures (TAPs) for patients with chronic conditions, this pilot study seeks to compare the performance of a 20-gauge fenestrated (20G) catheter to a standard 18-gauge (18G) intravenous catheter. METHODS: This non-inferiority pilot study randomized 26 subjects during 74 TAPs to either 20G fenestrated catheter or 18G standard catheter. RESULTS: There were no statistically significant differences for variables associated with the efficiency of the TAPs comparing 20G to 18G catheter for inlet rate (P = .8666), return pressure (P = .9427), blood processed (P = .4318), or total procedure time (P = .3184). CONCLUSION: The results from this pilot study suggest that 20G fenestrated catheter is non-inferior to 18G standard catheters. Additional studies with increased power are warranted to confirm these findings.

Immune checkpoint inhibitor toxicity: A new indication for therapeutic plasma exchange?

Novel immune-modulating anticancer drugs are being used with increasing frequency. With increased use, there are more frequent cases of toxicities caused by these drugs, termed immune-related adverse events (irAEs). We present a case in which we successfully treated a case of severe, steroid-refractory, nivolumab-induced myocarditis with therapeutic plasma exchange (TPE). Nivolumab is an immune checkpoint inhibitor (ICI) which blocks programmed death receptor-1 (PD-1). This blockade allows for enhanced T-cell function and increased anti-tumor response. The patient presented with signs and symptoms of heart failure and was found to have a significantly depressed cardiac ejection fraction. Over the course of her five TPE procedures, she improved clinically and was discharged home with improved left ventricular ejection function. This case suggests an emerging role of TPE in the management of severe ICI-induced toxicity, such as myocarditis.

Personalized Nutrition as a Key Contributor to Improving Radiation Response in Breast Cancer.

Understanding metabolic and immune regulation inherent to patient populations is key to improving the radiation response for our patients. To date, radiation therapy regimens are prescribed based on tumor type and stage. Patient populations who are noted to have a poor response to radiation such as those of African American descent, those who have obesity or metabolic syndrome, or senior adult oncology patients, should be considered for concurrent therapies with radiation that will improve response. Here, we explore these populations of breast cancer patients, who frequently display radiation resistance and increased mortality rates, and identify the molecular underpinnings that are, in part, responsible for the radiation response and that result in an immune-suppressive tumor microenvironment. The resulting immune phenotype is discussed to understand how antitumor immunity could be improved. Correcting nutrient deficiencies observed in these populations should be considered as a means to improve the therapeutic index of radiation therapy.

BPG: Seamless, automated and interactive visualization of scientific data.

BACKGROUND: We introduce BPG, a framework for generating publication-quality, highly-customizable plots in the R statistical environment. RESULTS: This open-source package includes multiple methods of displaying high-dimensional datasets and facilitates generation of complex multi-panel figures, making it suitable for complex datasets. A web-based interactive tool allows online figure customization, from which R code can be downloaded for integration with computational pipelines. CONCLUSION: BPG provides a new approach for linking interactive and scripted data visualization and is available at http://labs.oicr.on.ca/boutros-lab/software/bpg or via CRAN at https://cran.r-project.org/web/packages/BoutrosLab.plotting.general.

Prolonged partial thromboplastin time: To mix or not to mix - is that the question?

Routine mixing studies are frequently used to evaluate patients presenting with prolonged partial thromboplastin times (PTT) and/or prothrombin times (PT). Unfortunately, mixing studies have a number of inherent limitations including lack of standardization in terms of what defines normal pooled plasma (NPP), the processing of a patient's plasma for platelet removal (platelet poor plasma versus platelet-free plasma), performance of appropriate controls, conducting an incubation step to evaluate for a time and temperature dependent inhibitor, and finally interpretation of test results. Moreover, misinterpretation of study results can lead to a delayed or incorrect diagnosis or worse, inappropriate treatment. Within this manuscript, we present four cases illustrating the shortcomings associated with inappropriate utilization and interpretation of routine mixing studies; and present practical steps for managing abnormal PT or PTT results.

Role of plasma exchange in stiff person syndrome.

OBJECTIVE: Stiff person syndrome (SPS) is commonly associated with antibodies directed against 65-kDa glutamic acid decarboxylase (GAD65). Therapeutic Plasma Exchange (TPE) has been used as an adjunct therapy in patients who do not respond well to conventional treatment, which includes immunosuppression therapies, anti-anxiety medications, muscle relaxants, anticonvulsants, and pain relievers. METHODS: We retrospectively analyzed the clinical data and outcomes of ten patients with the clinical diagnosis of anti-GAD65 positive SPS in which TPE was employed to improve symptoms refractory to conventional treatment during an eight-year period. RESULTS: TPE was initiated as complementary therapy in patients with worsening of symptoms characteristic of SPS. Six patients underwent chronic treatment with TPE following an initial course, of which the frequency of TPE was guided by the clinical response. Two patients only had transient improvements with further disease progression. Four patients developed a relapse of symptoms when the interval between procedures was increased. One of the four patients dependent on TPE had worsening of symptoms following complete cessation of TPE due to lack of insurance coverage. Four patients underwent only an acute hospitalized course of treatment with TPE; one demonstrated complete resolution of symptoms; one had a partial response; and two experienced no improvement. CONCLUSION: Our study supports previous reports that TPE may be beneficial for the management of patients with anti-GAD65 positive SPS, both for acute exacerbations and long-term maintenance, either as an adjunct therapy, or in lieu of treatment with disease modifying agents.

Single-needle: an effective alternative to dual-needle peripheral access in therapeutic plasma exchange.

Apheresis treatments, which involve the removal of a component of blood, generally require one access and one return line to continuously draw and return blood into the extracorporeal circuit. At our center, we prefer to use peripheral venous access to avoid central line-related complications, especially infection. Motivated by patient-centered care, the single-needle (SN) option for therapeutic plasma exchange (TPE) offered on the Spectra Optia (Terumo BCT, Lakewood, CO) was evaluated. Five patients underwent procedures using both SN and dual-needle (DN) plasma exchange procedures using the Spectra Optia. TPE procedures ran a median of 51 (range:10-102) minutes longer using the SN-TPE option. Inlet flow rates, plasma removal efficiency, and incidence of citrate reactions were similar between SN- and DN-procedures. Patients reported great satisfaction with SN-TPE.

Onco-metabolism: defining the prognostic significance of obesity and diabetes in women with brain metastases from breast cancer.

PURPOSE: Metabolic dysregulation has been implicated as a molecular driver of breast cancer in preclinical studies, especially with respect to metastases. We hypothesized that abnormalities in patient metabolism, such as obesity and diabetes, may drive outcomes in breast cancer patients with brain metastases. METHODS: We retrospectively identified 84 consecutive patients with brain metastases from breast cancer treated with intracranial radiation therapy. Radiation was delivered as whole-brain radiation to a median dose of 3000 cGy or stereotactic radiosurgery to a median dose of 2100 cGy. Kaplan Meier curves were generated for overall survival (OS) data and Mantel-Cox regression was performed to detect differences in groups. RESULTS: At analysis, 81 survival events had occurred and the median OS for the entire cohort was 21.7 months. Despite similar modified graded prognostic assessments, resection rates, and receptor status, BMI ≥ 25 kg/m2 (n = 45) was associated with decreased median OS (13.7 vs. 30.6 months; p < 0.001) and median intracranial progression-free survival (PFS) (7.4 vs. 10.9 months; p = 0.04) compared to patients with BMI < 25 kg/m2 (n = 39). Similar trends were observed among all three types of breast cancer. Patients with diabetes (n = 17) had decreased median OS (11.8 vs. 26.2 months; p < 0.001) and median intracranial PFS (4.5 vs. 10.3 months; p = 0.001) compared to non-diabetics (n = 67). On multivariate analysis, both BMI ≥ 25 kg/m2 [HR 2.35 (1.39-3.98); p = 0.002] and diabetes [HR 2.77 (1.454-5.274); p = 0.002] were associated with increased mortality. CONCLUSIONS: Elevated BMI or diabetes may negatively impact both overall survival and local control in patients with brain metastases from breast cancer, highlighting the importance of the translational development of therapeutic metabolic interventions. Given its prognostic significance, BMI should be used as a stratification in future clinical trial design in this patient population.

A tale of two ports: an in vitro comparison of flow characteristics for therapeutic plasma exchange.

Tunneled central venous catheters with ports are increasingly used for therapeutic apheresis procedures. Vortex ports have been used as access for therapeutic apheresis procedures, but are not ideal for therapeutic plasma exchange (TPE) procedures due to lower flow rates. We performed an in vitro experiment to compare flow characteristics of the single-lumen Vortex port (AngioDynamics) with the single-lumen TidalPort (Norfolk Medical). We used expired red blood cell units and adjusted the hematocrit to 40% with normal saline in a 2-L bag. We programmed the Spectra Optia (Terumo BCT) to run a 1.0-volume TPE with 5% albumin as replacement fluid. The TidalPort achieved flow rates of up to 110 mL/min without triggering alarms. Due to crucial alarms, the Vortex Port was not able to run at a flow rate higher than 90 mL/min, and multiple caution alarms were triggered at flow rates of 80 to 90 mL/min. These findings suggest that the TidalPort may be a suitable access option that provides flow rates similar to peripheral or central venous catheters for TPE procedures.

Mathematical calculation of lifespan of transfused RBCs in sickle cell disease patients.

BACKGROUND: Transfusion of donor red blood cells (RBCs) remains an important part of management of sickle cell disease (SCD). However, the survival characteristics of transfused donor RBCs in SCD patients have not been well studied. We sought to calculate survival kinetics of transfused RBCs in SCD patients since it is unclear whether transfused RBCs get destroyed at faster rate as innocent bystander or persist longer due to decreased destruction capacity such as functional splenectomy. STUDY DESIGN: and methods Forty-one SCD patients who had undergone at least 3 RBC exchange procedures were inlcuded. Interval between the procedures, both pre-procedure and post procedure hematocrits, HbA% and HbS% were collected. We developed a mathematical model to calculate RBC lifespan for donor RBCs. RESULTS: Donor RBCs exhibited average lifespan of about 120days (121.1±13.9 days), which was similar to reported survival of RBCs in normal recipients. However, significant variation between patients were observed with lifespan ranging from 75.6-148.5 days. Intrapersonal variations were small in most cases. CONCLUSION: The calculated survival of donor RBCs in SCD recipient, based on certain laboratory values, appears to be similar to that of normal recipient. However, inter-personal variations were large, suggesting different RBC kinetics in a subset of patients, which calls for further research to better understand underlying pathophysiology. This knowledge of RBC survival would be very helpful in individualized management of patients on chronic RBCx.