Dosing chemotherapy in obese patients: Actual versus assigned body surface area (BSA)

Outcomes in obese and overweight acute myeloid leukemia patients receiving chemotherapy dosed according to actual body weight

Cytotoxic chemotherapy dosages are traditionally calculated according to body surface area (BSA). No guidelines exist for chemotherapy dosing of acute myeloid leukemia (AML) patients at extremes of weight. We investigated the efficacy and safety of chemotherapy dosed according to BSA based on actual body weight (ABW) among under/normal weight, overweight, and obese AML patients. AML patients (excluding acute promyelocytic leukemia) treated with anthracycline and cytarabine-based remission induction chemotherapy from 2002 to 2009 at Cleveland Clinic were divided into three body mass index (BMI) groups: under/normal weight (BMI ≤ 24.9), overweight (BMI 25.0-29.9), and obese (BMI ≥ 30.0). Among 247 AML patients, 81 (33%) were under/normal weight, 81 (33%) were overweight, and 85 (34%) were obese. Complete remission (CR) rates were similar among these groups (69.1, 79.0, and 76.5%, respectively; P = 0.321), as was median survival (10.7, 16.7, and 14.2 months, respectively, P = 0.352) and 30-day mortality (3.7, 2.5, 7.1%, respectively, P = 0.331). There was no difference among groups in days to neutrophil or platelet recovery, hospitalization days for induction chemotherapy, and bacteremia. After adjustment for confounders (age, sex, BMI, white blood cells, cytogenetic risk, etiology, and bacteremia), overall survival was significantly shorter for normal weight compared to overweight (P = 0.006) and obese (0.038) patients. Response rates and adverse events were not significantly different among AML patients of all weight classes when induction chemotherapy was dosed according to ABW. Induction chemotherapy in these patients can be safely dosed using ABW.

Relative dose intensity in early stage breast cancer chemotherapy: A retrospective analysis of incidence, risk factors and outcomes at a south-west Sydney cancer clinic

AIM

In early stage breast cancer chemotherapy relative dose intensity (RDI) of <85% leads to poorer outcomes. This study assesses what proportion of such patients at a south-west Sydney cancer clinic received optimal RDI and the reasons and risk factors contributing to RDI reduction, as well as comparing survival outcomes.

METHODS

A retrospective analysis of 308 patients treated with adjuvant chemotherapy for early stage breast cancer at the Macarthur Cancer Centre was undertaken, with an overall RDI calculated for each patient. The study analysed reasons for reductions in RDI as well as predictive factors for reduced RDI and overall and disease-free survival.

RESULTS

Mean RDI was 92%. Of the participants, 17% had an RDI less than 85%, 55% received 100% RDI. Hematological toxicity, infection and patient choice were the most common reasons for RDI reduction. Body surface area capping (BSA) was the most common cause of initial dose reduction. Obesity, increasing body mass index and age ≥65 years were risk factors for RDI reduction. Disease-free and overall survival were reduced with RDI < 50%; overall survival decreased when RDI < 65%.

CONCLUSION

Most patients attained the RDI benchmark; however dose intensity reducing events occurred frequently. Despite contrary recommendations in the literature, BSA capping and dose reduction due to patient choice were common. Implementation of focused patient and physician education strategies may improve these results, as could measures directed as supporting those at risk (i.e. elderly or obese).

Association between baseline body mass index and overall survival among patients over age 60 with acute myeloid leukemia

Acute myeloid leukemia (AML) is more common and more lethal among patients over the age of 60. Increased body mass index (BMI) has been associated with a higher incidence of various malignancies, including AML. We sought to determine whether patient BMI at the time of AML diagnosis is related to overall survival (OS) among elderly patients. We identified 97 patients with AML diagnosed after the age of 60 and treated with cytarabine-based induction chemotherapy. The median age was 68 years (range 60-87); 52% of patients were male, and our study population was predominantly white (89% of patients). The median OS for all patients was 316 days (95% CI 246-459). The hazard ratio for mortality was increased among patients with a BMI < 25 compared to BMI ≥ 30 (HR 2.14, P = 0.009, 95% CI 1.21-3.77), as well as with older age (HR 1.76, P = 0.015, 95% CI 1.12-2.79) and with secondary versus de novo disease (HR 1.95, P = 0.006, 95% CI 1.21-3.14). After multivariable analysis, we did not find a significant association between OS and other potential confounders such as coronary artery disease or diabetes among these patients. We conclude that increased BMI was independently associated with improved OS among older AML patients at our institution.

Chemotherapy dosing in overweight and obese patients with cancer

Retrospective and prospective preclinical and clinical data have demonstrated an association between chemotherapy dose intensity and both clinical efficacy and toxicity. The optimum tolerable and effective dose and schedule of chemotherapeutic agents is based on data from dose-finding studies and early clinical trials. There is considerable evidence that reductions in the recommended dose intensity often occurs in actual clinical practice, particularly among overweight and obese patients with cancer. With increasing rates of obesity, and variation and uncertainty about appropriate dosing of chemotherapy in obese patients, ASCO has generated clinical practice guidelines for appropriate chemotherapy dosing for obese adult patients with cancer. Without evidence of any increase in treatment-related toxicity among obese patients receiving chemotherapy, the guidelines recommend that, after considering any accompanying comorbidities, chemotherapy dosing should be calculated based on body surface area using actual weight, rather than an estimate or idealization of weight. While further research is needed, pharmacokinetic studies support the use of actual body weight to calculate chemotherapy doses for most chemotherapy drugs in obese patients. We highlight the issue of chemotherapy dosing in this population, how a more personalized approach can be achieved, as well as discussing areas for further research.

Does obesity have an effect on outcomes in triple-negative breast cancer?

BACKGROUND

Among patients with breast cancer, obesity has been associated with an increased likelihood of having triple-negative breast cancer (TNBC). This association has been thought to be due to the antiapoptotic effects of obesity-related proteins. However, the effect of obesity on the outcomes in patients with TNBC remains unclear. We hypothesized that obesity would be associated with decreased overall survival and disease-free survival in these patients.

MATERIALS AND METHODS

A retrospective review of a prospectively maintained database was conducted of patients treated for breast cancer at an academic medical center from March 1998 to September 2011. The body mass index (BMI) of patients with TNBC was calculated at diagnosis. The patients were categorized as normal (BMI < 25 kg/m(2)), overweight (BMI 25-30 kg/m(2)), or obese (BMI > 30 kg/m(2)). The endpoints of overall survival and disease-free survival were analyzed.

RESULTS

A total of 183 patients with TNBC were included for analysis. Of the 183 patients, 24 (13.1%) were normal (BMI < 25 kg/m(2)), 42 (23.1%) were overweight (BMI 25-30 kg/m(2)), and 117 (63.7%) were obese (BMI > 30 kg/m(2)). The median follow-up period was 42.5 months. Of the 183 patients, 2 (9.1%) died in the normal group, 10 (23.1%) died in the overweight group, and 25 (21.4%) died in the obese group (P = 0.28). The patients who were overweight or obese had larger tumors (P = 0.02), a higher T stage (P = 0.001), and higher tumor grade (P = 0.01) than the normal BMI patients. By Kaplan-Meier analysis, normal patients had higher overall survival than the overweight or obese patients, but this difference was not statistically significant (P = 0.29). Disease-free survival was also not significantly different (P = 0.91).

CONCLUSIONS

Despite an increased frequency of larger tumors, higher T stage, and higher tumor grade, obesity was not associated with decreased overall or disease-free survival in patients with TNBC.

Effect of obesity on toxicity in women treated with adjuvant chemotherapy for early-stage breast cancer: a systematic review

The purpose of this study is to provide more definite evidence regarding the role of dose modification of chemotherapy in obese women with breast cancer by systematically reviewing current literature regarding chemotherapy-induced toxicity rates in obese and non-obese women with early-stage breast cancer. A systematic search of Pubmed and EMBASE was conducted to identify original studies investigating chemotherapy-induced toxicity in obese women receiving adjuvant chemotherapy treatment for breast cancer. Ten studies were identified. We noted low rates of adjustment for confounders such as prophylactic hematopoietic growth factor use and empirical dose reductions. Seven studies found reduced toxicity in obese compared to non-obese women. Of four studies, where dose capping was precluded or statistically adjusted for, three found reduced toxicity in obese women. These outcomes include less febrile neutropenia (body mass index (BMI) >23.6; odds ratio (OR) 4.4; 95 % confidence interval (CI) 1.65-12.01), fewer hospital admissions (BMI >35; OR 0.61, 95 % CI 0.38-0.97), and fewer neutropenic events (BMI >25; OR 0.49; 95 % CI 0.37-0.66). Only a single study reported higher rates of toxicity in obese women, but this study had significant methodological issues. As a conclusion, we observed that obese patients tolerate chemotherapy better than lean patients. However, this may be confounded by poorly specified dose capping practices and the use of hematopoietic growth factors. Further research should focus on improved documentation of body size, of dose, and of use of growth factors, and analysis of how these affect recurrence rates, toxicity, and survival.

Appropriate chemotherapy dosing for obese adult patients with cancer: American Society of Clinical Oncology clinical practice guideline

PURPOSE

To provide recommendations for appropriate cytotoxic chemotherapy dosing for obese adult patients with cancer.

METHODS

The American Society of Clinical Oncology convened a Panel of experts in medical and gynecologic oncology, clinical pharmacology, pharmacokinetics and pharmacogenetics, and biostatistics and a patient representative. MEDLINE searches identified studies published in English between 1996 and 2010, and a systematic review of the literature was conducted. A majority of studies involved breast, ovarian, colon, and lung cancers. This guideline does not address dosing for novel targeted agents.

RESULTS

Practice pattern studies demonstrate that up to 40% of obese patients receive limited chemotherapy doses that are not based on actual body weight. Concerns about toxicity or overdosing in obese patients with cancer, based on the use of actual body weight, are unfounded.

RECOMMENDATIONS

The Panel recommends that full weight-based cytotoxic chemotherapy doses be used to treat obese patients with cancer, particularly when the goal of treatment is cure. There is no evidence that short- or long-term toxicity is increased among obese patients receiving full weight-based doses. Most data indicate that myelosuppression is the same or less pronounced among the obese than the non-obese who are administered full weight-based doses. Clinicians should respond to all treatment-related toxicities in obese patients in the same ways they do for non-obese patients. The use of fixed-dose chemotherapy is rarely justified, but the Panel does recommend fixed dosing for a few select agents. The Panel recommends further research into the role of pharmacokinetics and pharmacogenetics to guide appropriate dosing of obese patients with cancer.

Chemotherapy dose reductions in obese patients with colorectal cancer

BACKGROUND

In cancer patients with a large Body Surface Area, chemotherapy drug doses are often reduced, as studies have suggested that their pharmacokinetics may be altered. However, this strategy may result in underdosing obese patients.

PATIENTS AND METHODS

In three Medical Research Council trials of chemotherapy for advanced colorectal cancer, dose reductions were not mandated. This provided the opportunity to compare the toxicity levels in those obese patients fully dosed and to investigate if those under dosed experienced a worse survival. Body Mass Index (BMI) was used to classify patients as normal weight (BMI < 25), overweight (BMI 25-29), or obese (BMI 30+).

RESULTS

Of the 4781 patients, 2158 (45%) were classified as normal weight, 1753 (37%) as overweight, and 870 (18%) as obese. There was no evidence that, in those patients fully dosed, obese patients experienced more toxicity or that dose-reducing obese patients resulted in less toxicity. However, there was a suggestion that those obese patients who were given reduced doses had a worse progression-free survival [hazard ratio (HR) 1.21, 95% confidence interval (CI) 1.06-1.39, P = 0.006] and a slightly worse overall survival (HR 1.12, 95% CI 0.96-1.30, P = 0.152).

CONCLUSION

These results, although not a randomised comparison, do not support the policy of reducing chemotherapy doses for obese patients with colorectal cancer.

Body mass index does not influence post-treatment survival in early stage endometrial cancer: results from the MRC ASTEC trial

Body mass index (BMI) is a major risk factor for endometrial cancer incidence but its impact on post-treatment survival is unclear. We investigated the relationships of BMI (categorised using the WHO definitions) with clinico-pathological characteristics and outcome in women treated within the MRC ASTEC randomised trial, which provides data from patients who received standardised allocated treatments and therefore reduces biases. The impact of BMI on both recurrence-free survival (RFS) and overall survival (OS) was analysed using the Cox regression models. An apriori framework of evaluating potential biases was explored. From 1408 participants, there were 1070 women with determinable BMI (median=29.1 kg/m(2)). Histological types were endometrioid (type 1) in 893 and non-endometrioid (type 2) in 146 women; the proportion of the latter decreasing with increasing BMI (8% versus 19% for obese III WHO category versus normal weight, p(trend)=0.003). For type 1 carcinomas, increasing BMI was associated with less aggressive histopathological features (depth of invasion, p=0.006; tumour grade, p=0.015). With a median follow-up of 34.3 months, there was no influence of BMI on RFS - adjusted HRs per 5 kg/m(2) were 0.98 (95% CI 0.86, 1.13) and 0.95 (0.74, 1.24), for type 1 and 2 carcinomas; and no influence on OS - adjusted HRs per 5 kg/m(2) were 0.96 (0.81, 1.14) and 0.92 (0.70, 1.23), respectively. These findings demonstrate an important principle: that an established link between an exposure (here, obesity) and increased incident cancer risk, does not necessarily translate into an inferior outcome following treatment for that cancer.

Is obesity a prognostic factor for acute myeloid leukemia outcome?

Obesity adversely affects outcome in pediatric acute lymphocytic leukemia and acute myeloid leukemia (AML). We asked if obesity, measured by body mass index (BMI), affected outcome in 329 adult AML patients treated with high-dose cytarabine and idarubicin-containing regimens administered according to actual body weight. Age ≥ 60, unfavorable karyotype, secondary AML, and positive smoking status had adverse impact on overall survival in a multivariate analysis, while BMI did not. We conclude that high BMI should not be a barrier to administer high-dose cytarabine-containing regimens for AML induction.

The impact of obesity on receipt of adjuvant chemotherapy for breast cancer in the National Comprehensive Cancer Network (NCCN) centers

Disparities in the receipt of adjuvant chemotherapy for early stage breast cancer is an important factor influencing mortality. We investigated whether greater body mass index (BMI) decreases receipt of adjuvant chemotherapy among women with operable breast cancer. In the NCCN breast cancer outcomes database, we identified women aged ≤ 70 with newly diagnosed stage I, II, or III breast cancer between 1997 and 2007, for whom use of adjuvant chemotherapy was classified as either standard-of-care or discretionary based on their clinical characteristics. Body mass index was assessed in categories (<18.5 kg/m(2) [underweight], 18.5 to <25 kg/m(2) [normal], 25 to <30 kg/m(2) [overweight], 30-39 kg/m(2) [obese], ≥ 40 kg/m(2) [extreme obese]). Multivariable logistic regression analysis was used to examine the association between BMI and receipt of chemotherapy in each classification group. 9,527 women were eligible for the study; 40% normal weight or less; 31% overweight; 24% obese; and 5% extremely obese. In multivariable analysis, there was no significant association between BMI and receipt of chemotherapy in either classification group. Among women for whom chemotherapy would be considered standard-of-care, older age (P < 0.001), comorbidity (P < 0.001), and non-Hispanic black ethnicity (P = 0.002) were associated with a lower likelihood of receipt of chemotherapy; however, the effect of ethnicity was not modified by obesity. Among women treated for operable breast cancer in the NCCN centers, BMI had no impact on receipt of adjuvant chemotherapy and did not modify the lower likelihood of chemotherapy among non-Hispanic black patients. Further investigation is needed into other factors that contribute to patient disparities in the receipt of chemotherapy in major academic centers.

Influence of body mass index on outcome in advanced colorectal cancer patients receiving chemotherapy with or without targeted therapy

PURPOSE

Obesity is associated with an increased risk of development and recurrence of colorectal cancer. However, the role of obesity in advanced colorectal cancer (ACC) patients is unknown. We investigated the effect of body mass index (BMI) on overall survival (OS) in ACC patients receiving systemic treatment in two large phase III studies (CAIRO and CAIRO2).

PATIENTS AND METHODS

Treatment data were obtained and analysed from 796 ACC patients who were treated with chemotherapy in the CAIRO study, and from 730 ACC patients who were treated with chemotherapy plus targeted therapy in the CAIRO2 study. Baseline height and weight were used to assign patients to one of the following BMI categories: A (<18.5 kg/m(2)), B (18.5-24.9 kg/m(2)), C (25.0-29.9 kg/m(2)) and D (≥30.0 kg/m(2)).

RESULTS

In 796 patients of the CAIRO study a high BMI was associated with better median OS (8.0, 14.9, 18.4 and 19.5 months for BMI categories A, B, C, and D, respectively; P=0.001), and was an independent prognostic factor for OS in a multivariate analysis. BMI was not associated with OS in 730 patients who participated in the CAIRO2 study, although a trend was observed.

CONCLUSIONS

These results show that BMI is an independent prognostic factor for survival in patients receiving chemotherapy, but not in patients receiving chemotherapy and targeted therapy. The possible decreased efficacy of bevacizumab in obese patients may explain this discrepant result. The role of BMI in patients receiving targeted therapy should be further tested.

Effect of obesity on survival of women with breast cancer: systematic review and meta-analysis

Obesity is a risk factor for the development of new cases of breast cancer and also affects survival in women who have already been diagnosed with breast cancer. Early studies of obesity and breast cancer survival have been summarised in two meta-analyses, but the latest of these only included studies that recruited women diagnosed as recently as 1991. The primary aim of this study was to conduct a meta-analysis that included the more recent studies. A systematic search of MEDLINE, EMBASE and CINAHL was conducted to identify original data evaluating the effects of obesity on survival in newly diagnosed breast cancer patients. Adjusted hazard ratios (HR) from individual studies were pooled using a random effects model. A series of pre-specified sensitivity analyses were conducted on factors such as overall versus breast cancer survival and treatment versus observational cohort. The meta-analysis included 43 studies that enrolled women diagnosed with breast cancer between 1963 and 2005. Sample size ranged from 100 to 424168 (median 1192). The meta-analysis showed poorer survival among obese compared with non-obese women with breast cancer, which was similar for overall (HR = 1.33; 95% confidence interval (CI): 1.21, 1.47) and breast cancer specific survival (HR = 1.33; 95% CI: 1.19, 1.50). The survival differential varied only slightly, depending on whether body mass index (1.33; 1.21, 1.47) or waist-hip ratio (1.31; 1.08, 1.58) was used as the measure of obesity. There were larger differences by whether the woman was pre-menopausal (1.47) or post-menopausal (1.22); whether the cohort included women diagnosed before (1.31) or after 1995 (1.49); or whether the women were in a treatment (1.22) or observational cohort (1.36), but none of the differences were statistically significant. Women with breast cancer, who are obese, have poorer survival than women with breast cancer, who are not obese. However, no study has elucidated the causal mechanism and there is currently no evidence that weight loss after diagnosis improves survival. Consequently, there is currently no reason to place the additional burden of weight loss on women already burdened with a diagnosis of cancer. Further research should concentrate on assessing whether factors such as diabetes or type of chemotherapy modify the obesity effect and on understanding the causal mechanism, in particular the role of relative under-dosing.

Pharmacokinetics and Drug Dosing in Obese Children

OBJECTIVES

To review pharmacokinetics in obese children and to provide medication dosing recommendations.

METHODS

EMBASE, MEDLINE, and International Pharmaceutical Abstracts databases were searched using the following terms: obesity, morbid obesity, overweight, pharmacokinetics, drug, dose, kidney function test, creatinine, pediatric, and child.

RESULTS

We identified 10 studies in which the authors examined drug dosing or pharmacokinetics for obese children. No information was found for drug absorption or metabolism. Obese children have a higher percent fat mass and a lower percent lean mass compared with normal-weight children. Therefore, in obese children, the volume of distribution of lipophilic drugs is most likely higher, and that of hydrophilic drugs is most likely lower, than in normal-weight children. Serum creatinine concentrations are higher in obese than normal-weight children. Total body weight is an appropriate size descriptor for calculating doses of antineoplastics, cefazolin, and succinylcholine in obese children. Initial tobramycin doses may be determined using an adjusted body weight, although using total body weight in the context of monitoring serum tobramycin concentrations would also be an appropriate strategy. We found no information for any of the opioids; antibiotics such as penicillins, carbapenems, vancomycin, and linezolid; antifungals; cardiac drugs such as digoxin and amiodarone; corticosteroids; benzodiazepines; and anticonvulsants. In particular, we found no information about medications that are widely distributed to adipose tissue or that can accumulate there.

CONCLUSIONS

The available data are limited because of the small numbers of participating children, study design, or both. The number and type of drugs that have been studied limit our understanding of the pharmacokinetics in obese children. In the absence of dosing information for obese children, it is important to consider the nature and severity of a child's illness, comorbidities, organ function, and side effects and physiochemical properties of the drug. Extrapolating from available adult data is possible, as long as practitioners consider the effects of growth and development on the pharmacokinetics relevant to the child's age.

Diet-induced obesity alters vincristine pharmacokinetics in blood and tissues of mice

Obesity is associated with poorer outcome from many cancers, including leukemia. One possible contributor to this could be suboptimal chemotherapy dosing in obese patients. We have previously found that vincristine (VCR) is less effective in obese compared to non-obese mice with leukemia, despite weight-based dosing. In the present study, we administered (3)H-VCR to obese and control mice to determine whether obesity would cause suboptimal VCR exposure. Blood VCR concentrations were fitted with a three-compartment model using pharmacokinetic analysis (two-stage PK) in three subsets of VCR concentrations vs. time method. Tissue and blood VCR concentrations were also analyzed using non-compartmental modeling. Blood VCR concentrations showed a triexponential decay and tended to be slightly higher in the obese mice at all time-points. However, the t(1/2,beta) and t(1/2,gamma) were shorter in the obese mice (9.7 min vs. 44.5 min and 60.3h vs. 85.6h, respectively), resulting in a lower AUC(0-infinity) (13,099 ng/m Lh vs. 15,384 ng/mL h). Had the dose of VCR been "capped", as is done in clinical practice, the AUC(0-infinity) would have been 36% lower in the obese mice than the controls. Tissue disposition of VCR revealed a biexponential decay from spleen, liver, and adipose. Interestingly, VCR slowly accumulated in the bone marrow of control mice, but had a slow decay from the marrow in the obese mice. Thus, obesity alters VCR PK, causing a lower overall exposure in circulation and bone marrow. Given the high prevalence of obesity, additional PK studies should be performed in obese subjects to optimize chemotherapy dosing regimens.