Fasting insulin and outcome in early-stage breast cancer: results of a prospective cohort study

PURPOSE

Insulin, a member of a family of growth factors that includes insulin-like growth factor (IGF)-I and IGF-II, exerts mitogenic effects on normal and malignant breast epithelial cells, acting via insulin and IGF-I receptors. Because of this and because of its recognized association with obesity, an adverse prognostic factor in breast cancer, we examined the prognostic associations of insulin in early-stage breast cancer.

PATIENTS AND METHODS

A cohort of 512 women without known diabetes, who had early-stage (T1 to T3, N0 to N1, and M0) breast cancer, was assembled and observed prospectively. Information on traditional prognostic factors and body size was collected, and fasting blood was obtained.

RESULTS

Fasting insulin was associated with distant recurrence and death; the hazard ratios and 95% confidence intervals (CI) for those in the highest (> 51.9 pmol/L) versus the lowest (< 27.0 pmol/L) insulin quartile were 2.0 (95% CI, 1.2 to 3.3) and 3.1 (95% CI, 1.7 to 5.7), respectively. There was some evidence to suggest that the association of insulin with breast cancer outcomes may be nonlinear. Insulin was correlated with body mass index (Spearman r = 0.59, P <.001), which, in turn, was associated with distant recurrence and death (P <.001). In multivariate analyses that included fasting insulin and available tumor- and treatment-related variables, adjusted hazard ratios for the upper versus lower insulin quartile were 2.1 (95% CI, 1.2 to 3.6) and 3.3 (95% CI, 1.5 to 7.0) for distant recurrence and death, respectively.

CONCLUSION

Fasting insulin level is associated with outcome in women with early breast cancer. High levels of fasting insulin identify women with poor outcomes in whom more effective treatment strategies should be explored.

The effect of group psychosocial support on survival in metastatic breast cancer

BACKGROUND

Supportive-expressive group therapy has been reported to prolong survival among women with metastatic breast cancer. However, in recent studies, various psychosocial interventions have not prolonged survival.

METHODS

In a multicenter trial, we randomly assigned 235 women with metastatic breast cancer who were expected to survive at least three months in a 2:1 ratio to an intervention group that participated in weekly supportive-expressive group therapy (158 women) or to a control group that received no such intervention (77 women). All the women received educational materials and any medical or psychosocial care that was deemed necessary. The primary outcome was survival; psychosocial function was assessed by self-reported questionnaires.

RESULTS

Women assigned to supportive-expressive therapy had greater improvement in psychological symptoms and reported less pain (P=0.04) than women in the control group. A significant interaction of treatment-group assignment with base-line psychological score was found (P</=0.003 for the comparison of mood variables; P=0.04 for the comparison of pain); women who were more distressed benefited, whereas those who were less distressed did not. The psychological intervention did not prolong survival (median survival, 17.9 months in the intervention group and 17.6 months in the control group; hazard ratio for death according to the univariate analysis, 1.06 [95 percent confidence interval, 0.78 to 1.45]; hazard ratio according to the multivariate analysis, 1.23 [95 percent confidence interval, 0.88 to 1.72]).

CONCLUSIONS

Supportive-expressive group therapy does not prolong survival in women with metastatic breast cancer. It improves mood and the perception of pain, particularly in women who are initially more distressed.

Risk of menopause during the first year after breast cancer diagnosis

PURPOSE

Premenopausal women with breast cancer often enter a premature menopause during initial treatment of their malignancy, with resulting loss of childbearing capacity, onset of menopausal symptoms, and subsequent prolonged exposure to long-term risks of menopause. Adjuvant therapy is believed to contribute to this early menopause.

PATIENTS AND METHODS

One hundred eighty-three premenopausal women with locoregional breast cancer (tumor-node-metastasis staging system classification, T1-3 N0-1 M0) who had undergone surgical treatment and provided information on menopausal status at diagnosis and 1 year later were enrolled. Systemic adjuvant therapy was recorded. Univariate and multivariate predictors of menopause were examined.

RESULTS

Age, weight gain, tumor stage, nodal stage, and systemic adjuvant therapy (chemotherapy, tamoxifen) were all significant univariate correlates of menopause. In multivariate analysis, age, chemotherapy, and hormone therapy (tamoxifen) made significant independent contributions to the onset of menopause.

CONCLUSION

Age and systemic chemotherapy are the strongest predictors of menopause in women with locoregional breast cancer. They independently contribute to menopause. A graphic representation of our multivariate model allows an estimation of risk of menopause according to patient age and planned adjuvant treatment, and it may facilitate clinical decision-making.

Prognostic factors in osteosarcoma: a critical review

PURPOSE

The purpose of this critical appraisal was to determine the prognostic factors that influence survival in patients with nonmetastatic, high-grade osteosarcoma of the extremities.

DESIGN

A computerized literature search of reports published from January 1973 to March 1992 was conducted to determine those eligible for inclusion in the review. Reports were reviewed blindly by two of the authors; inclusion and scoring were determined according to preestablished criteria.

RESULTS

Eight reports were included in the appraisal. The prognostic variables evaluated were age, sex, anatomic tumor location, tumor size, and tumor necrosis. Tumor size and necrosis following preoperative chemotherapy were significant prognostic variables in relation to survival in univariate analysis. However, only tumor necrosis maintained its significance in multivariate modeling.

CONCLUSION

The most important prognostic variable for patients with osteosarcoma of the extremity was tumor necrosis evident following preoperative chemotherapy. There is no consensus as to any prognostic variable that might be used to stratify patients before the onset of therapy.

Understanding the benefit of metformin use in cancer treatment

Biguanides have been developed for the treatment of hyperglycemia and type 2 diabetes. Recently, metformin, the most widely prescribed biguanide, has emerged as a potential anticancer agent. Epidemiological, preclinical and clinical evidence supports the use of metformin as a cancer therapeutic. The ability of metformin to lower circulating insulin may be particularly important for the treatment of cancers known to be associated with hyperinsulinemia, such as those of the breast and colon. Moreover, metformin may exhibit direct inhibitory effects on cancer cells by inhibiting mammalian target of rapamycin (mTOR) signaling and protein synthesis. The evidence supporting a role for metformin in cancer therapy and its potential molecular mechanisms of action are discussed.

Metformin in cancer: translational challenges

The anti-diabetic drug metformin is rapidly emerging as a potential anti-cancer agent. Metformin, effective in treating type 2 diabetes and the insulin resistance syndromes, improves insulin resistance by reducing hepatic gluconeogenesis and by enhancing glucose uptake by skeletal muscle. Epidemiological studies have consistently associated metformin use with decreased cancer incidence and cancer-related mortality. Furthermore, numerous preclinical and clinical studies have demonstrated anti-cancer effects of metformin, leading to an explosion of interest in evaluating this agent in human cancer. The effects of metformin on circulating insulin levels indicate a potential efficacy towards cancers associated with hyperinsulinaemia; however, metformin may also directly inhibit tumour growth. In this review, we describe the mechanism of action of metformin and summarise the epidemiological, clinical and preclinical evidence supporting a role for metformin in the treatment of cancer. In addition, the challenges associated with translating preclinical results into therapeutic benefit in the clinical setting will be discussed.

Obesity and Breast Cancer Prognosis: Evidence, Challenges, and Opportunities

Purpose To summarize the evidence of an association between obesity and breast cancer prognosis. Methods We reviewed the literature regarding overweight and obesity and breast cancer survival outcomes, overall and with regard to breast cancer subtypes, breast cancer therapies, biologic mechanisms, and possible interventions. We summarize our findings and provide clinical management recommendations. Results Obesity is associated with a 35% to 40% increased risk of breast cancer recurrence and death and therefore poorer survival outcomes. This is most clearly established for estrogen receptor-positive breast cancer, with the relationship in triple-negative and human epidermal growth factor receptor 2-positive subtypes less well established. A range of biologic mechanisms that may underlie this association has been identified. Weight loss and lifestyle interventions, as well as metformin and other obesity-targeted therapies, are promising avenues that require further study. Conclusion Obesity is associated with inferior survival in breast cancer. Understanding the nature and mechanisms of this effect provides an important opportunity for interventions to improve the diagnosis, treatment, and outcomes of obese patients with breast cancer.

Prognostic effects of 25-hydroxyvitamin D levels in early breast cancer

PURPOSE

Vitamin D has been linked to breast cancer risk, but prognostic effects are unknown. Such effects are biologically plausible given the presence of vitamin D receptors in breast cancer cells, which act as nuclear transcription factors to regulate gene activity.

PATIENTS AND METHODS

The study was conducted in a prospective inception cohort of 512 women with early breast cancer diagnosed 1989 to 1996. Vitamin D levels were measured in stored blood. Clinical, pathologic, and dietary data were accessed to examine prognostic effects of vitamin D.

RESULTS

Mean age was 50.4 years, mean vitamin D was 58.1 +/- 23.4 nmol/L. Vitamin D levels were deficient (< 50 nmol/L) in 37.5% of patients, insufficient (50 to 72 nmol/L) in 38.5% of patients, and sufficient (> 72 nmol/L) in 24.0% of patients. There was little variation in mean vitamin D levels between summer and winter months. Mean follow-up was 11.6 years; 116 women had distant recurrences, and 106 women died. Women with deficient vitamin D levels had an increased risk of distant recurrence (hazard ratio [HR] = 1.94; 95% CI, 1.16 to 3.25) and death (HR = 1.73; 95% CI, 1.05 to 2.86) compared with those with sufficient levels. The association remained after individual adjustment for key tumor and treatment related factors but was attenuated in multivariate analyses (HR = 1.71; 95% CI, 1.02 to 2.86 for distant recurrence; HR = 1.60; 95% CI, 0.96 to 2.64 for death).

CONCLUSION

Vitamin D deficiency may be associated with poor outcomes in breast cancer.

Adjuvant treatment and onset of menopause predict weight gain after breast cancer diagnosis

PURPOSE

Weight gain is common during the first year after breast cancer diagnosis. In this study, we examined clinical factors associated with body size at diagnosis and weight gain during the subsequent year.

PATIENTS AND METHODS

An inception cohort of 535 women with newly diagnosed locoregional breast cancer underwent anthropometric measurements at baseline and 1 year. Information was collected on tumor- and treatment-related variables, as well as diet and physical activity.

RESULTS

Mean age was 50.3 years; 57% of women were premenopausal. Mean baseline body mass index (weight [kg] divided by height [m] squared) was 25.5 kg/m2. Overall, 84.1% of the patients gained weight. Mean weight gain was 1.6 kg (95% confidence interval, 1.2 to 1.9 kg), 2.5 kg (95% confidence interval, 1.8 to 3.2 kg) in those receiving chemotherapy, 1.3 kg (95% confidence interval, 0.7 to 1.8 kg) in those receiving tamoxifen only, and 0.6 kg (95% confidence interval, 0.01 to 1.3 kg) in those receiving no adjuvant treatment. Menopausal status at diagnosis (P = .02), change in menopausal status over the subsequent year (P = .002), axillary nodal status (P = .009), and adjuvant treatment (P = .0002) predicted weight gain in univariate analysis. In multivariate analysis, onset of menopause and administration of chemotherapy were independent predictors of weight gain (all P < or = .05). Caloric intake decreased (P < .01) and physical activity increased (P < .05) during the year after diagnosis; these factors did not explain the observed weight gain.

CONCLUSION

Weight gain is common after breast cancer diagnosis; use of adjuvant chemotherapy and onset of menopause are the strongest clinical predictors of this weight gain.

The role of obesity in cancer survival and recurrence

Obesity and components of energy imbalance, that is, excessive energy intake and suboptimal levels of physical activity, are established risk factors for cancer incidence. Accumulating evidence suggests that these factors also may be important after the diagnosis of cancer and influence the course of disease, as well as overall health, well-being, and survival. Lifestyle and medical interventions that effectively modify these factors could potentially be harnessed as a means of cancer control. However, for such interventions to be maximally effective and sustainable, broad sweeping scientific discoveries ranging from molecular and cellular advances, to developments in delivering interventions on both individual and societal levels are needed. This review summarizes key discussion topics that were addressed in a recent Institute of Medicine Workshop entitled, "The Role of Obesity in Cancer Survival and Recurrence"; discussions included (i) mechanisms associated with obesity and energy balance that influence cancer progression; (ii) complexities of studying and interpreting energy balance in relation to cancer recurrence and survival; (iii) associations between obesity and cancer risk, recurrence, and mortality; (iv) interventions that promote weight loss, increased physical activity, and negative energy balance as a means of cancer control; and (v) future directions.

Insulin and related factors in premenopausal breast cancer risk

BACKGROUND

Insulin and insulin-like growth factor I (IGF-I) are important mitogens in vitro and in vivo. It has been hypothesized that these factors may play an important role in the development of breast cancer.

METHODS

A case-control study comparing plasma insulin levels in 99 premenopausal women with newly diagnosed node-negative invasive carcinoma of the breast and 99 age-matched controls with incident biopsied non-proliferative breast disease (NP) was conducted. Women with known diabetes were excluded.

RESULTS

For the entire study group, mean age was 42.6 +/- 5.1 years and mean weight was 62.9 +/- 10.3 kg. After adjustment for age and weight, elevated insulin levels were significantly associated with breast cancer, Odds Ratio (OR) for women in the highest insulin quintile versus the lowest quintile = 2.83 (95% Confidence Interval [CI] 1.22-6.58). There were no statistically significant differences between cases and controls for IGF-I and IGFBP-1 levels. However, after adjustment for age, the association between plasma levels of insulin-like growth factor binding protein 3 (IGFBP-3) and breast cancer approached statistical significance; OR for highest quintile versus lowest quintile of IGFBP-3 being 2.05 (95% CI, 0.93-4.53). All results were independent of diet and other known risk factors for breast cancer.

CONCLUSION

Circulating insulin levels and possibly IGFBP-3 levels are elevated in women with premenopausal breast cancer. This association may reflect an underlying syndrome of insulin resistance that is independent of obesity.

Metformin in early breast cancer: a prospective window of opportunity neoadjuvant study

Metformin may exert anti-cancer effects through indirect (insulin-mediated) or direct (insulin-independent) mechanisms. We report results of a neoadjuvant "window of opportunity" study of metformin in women with operable breast cancer. Newly diagnosed, untreated, non-diabetic breast cancer patients received metformin 500 mg tid after diagnostic core biopsy until definitive surgery. Clinical (weight, symptoms, and quality of life) and blood [fasting serum insulin, glucose, homeostasis model assessment (HOMA), C-reactive protein (CRP), and leptin] attributes were compared pre- and post-metformin as were terminal deoxynucleotidyl transferase-mediated dUTP nick end labeling (TUNEL) and Ki67 scores (our primary endpoint) in tumor tissue. Thirty-nine patients completed the study. Mean age was 51 years, and metformin was administered for a median of 18 days (range 13-40) up to the evening prior to surgery. 51 % had T1 cancers, 38 % had positive nodes, 85 % had ER and/or PgR positive tumors, and 13 % had HER2 overexpressing or amplified tumors. Mild, self-limiting nausea, diarrhea, anorexia, and abdominal bloating were present in 50, 50, 41, and 32 % of patients, respectively, but no significant decreases were seen on the EORTC30-QLQ function scales. Body mass index (BMI) (-0.5 kg/m(2), p < 0.0001), weight (-1.2 kg, p < 0.0001), and HOMA (-0.21, p = 0.047) decreased significantly while non-significant decreases were seen in insulin (-4.7 pmol/L, p = 0.07), leptin (-1.3 ng/mL, p = 0.15) and CRP (-0.2 mg/L, p = 0.35). Ki67 staining in invasive tumor tissue decreased (from 36.5 to 33.5 %, p = 0.016) and TUNEL staining increased (from 0.56 to 1.05, p = 0.004). Short-term preoperative metformin was well tolerated and resulted in clinical and cellular changes consistent with beneficial anti-cancer effects; evaluation of the clinical relevance of these findings in adequately powered clinical trials using clinical endpoints such as survival is needed.

Insulin-lowering effects of metformin in women with early breast cancer

BACKGROUND

Obesity has been associated with poor breast cancer outcomes. Insulin may mediate this effect, interacting with insulin receptors on breast cancer cells. Metformin, a biguanide derivative used in the treatment of diabetes, reduces insulin levels in subjects with type 2 diabetes and other insulin-resistant states. If metformin lowers insulin levels in women with breast cancer, it may also improve breast cancer outcomes.

PATIENTS AND METHODS

We administered metformin (1500 mg per day) to 32 women with early breast cancer whose baseline insulin levels were at least 45 pmol/L to determine its effect on insulin levels.

RESULTS

Twenty-two (69%) women completed the 6-month intervention. Four women (12.5%) dropped out because of gastrointestinal side effects; the others withdrew for reasons not related to toxicity. Completers were similar to noncompleters for all baseline characteristics apart from global health, overall physical condition, overall quality of life, physical function, and social function (HRQOL), which was decreased in noncompleters. Metformin significantly lowered fasting insulin levels by 15.8 pmol/L (22.4%; P=.024) and improved insulin sensitivity by 25.6% (P=.018), total cholesterol by 5.3%, and low-density lipoprotein (LDL) cholesterol by 9.1%. Metformin reduced weight by 1.9 kg (2.5%; P=.01), and it had no significant effects on HRQOL or specific gastrointestinal symptoms (appetite, nausea/vomiting, diarrhea, constipation).

CONCLUSION

Metformin significantly lowers insulin levels, and it improves insulin resistance in nondiabetic women with breast cancer. A phase III randomized trial to evaluate its effects on breast cancer outcomes is recommended.

Health-related quality-of-life measurement in randomized clinical trials in breast cancer--taking stock

Measurement of health-related quality-of-life (HRQOL) in randomized clinical trials in breast cancer has become common. In this review, we take stock of the contribution that HRQOL measurement in breast cancer clinical trials makes to clinical decision making regarding selection of optimal treatment. A series of MEDLINE searches was conducted to identify all randomized trials in breast cancer that included self-reported HRQOL or psychosocial outcomes. A total of 256 citations were identified that included HRQOL or psychosocial outcomes in breast cancer patients, and 66 of these involved randomized clinical trials of treatment. These 66 reports of breast cancer clinical trials of treatment are discussed in this review. Forty-six of the trials evaluated biomedical interventions, and 20 evaluated psychosocial interventions. Among the biomedical trials, eight trials evaluated HRQOL in primary management of breast cancer, seven trials evaluated HRQOL in adjuvant therapy of breast cancer patients, 20 trials involved metastatic breast cancer, eight trials involved symptom control/supportive care, and three trials evaluated different approaches to investigation or follow-up of breast cancer patients. Among the psychosocial trials, 13 trials evaluated HRQOL in adjuvant therapy of breast cancer patients, and their partners or spouses, six trials involved metastatic breast cancer, and one trial focused on symptom control. We found that the contribution of HRQOL measurement to clinical decision making depended on the clinical setting. In primary management of breast cancer, where medical outcomes of several treatment options are equivalent, HRQOL measurement provided added information for clinical decision making beyond that of traditional medical outcomes. In trials in the adjuvant setting, HRQOL measurement did not influence clinical decision making. In metastatic disease, HRQOL outcomes provided little information beyond that obtained from traditional medical outcomes, including toxicity. In the symptom control/supportive care setting, results of HRQOL questionnaires targeting specific symptoms (e.g., emesis) guided treatment decisions. In psychosocial intervention trials, psychosocial and/or HRQOL measurements often provided the only outcome information; therefore, selection of instruments that captured attributes likely to be altered by the intervention was essential. Until results of ongoing trials in breast cancer are available, caution is recommended in initiating new HRQOL studies unless treatment equivalency is expected, or unless the HRQOL questions target unique or specific issues that can only be addressed through patient self-report, including outcomes of psychosocial interventions.

Counting the costs of chemotherapy in a National Cancer Institute of Canada randomized trial in nonsmall-cell lung cancer

An economic evaluation was undertaken of a previously reported National Cancer Institute of Canada (NCIC) trial of chemotherapy in advanced nonsmall-cell lung cancer (NSCLC). That trial had demonstrated a survival benefit associated with the use of either vindesine and cisplatin (VP) or cyclosphosphamide, doxorubicin, and cisplatin (CAP) in relation to best supportive care (BSC). The economic technique used in this evaluation was cost-effectiveness analysis (CEA). All costs were determined from the viewpoint of two provincial health care plans. When compared with BSC, the survival benefit of 8 weeks in favor of patients receiving CAP chemotherapy was associated with an economic saving of $949.49 (in 1984 Canadian dollars). This translated into a savings of $6,171.69 per year of life gained. The mean survival benefit of 12.8 weeks that was obtained with VP chemotherapy compared with BSC was associated with an increased cost of $3,637.60 per patient, or $14,777.75 per year of life gained. The economic evaluation demonstrated that the majority of costs on each of the three treatment arms was related to hospitalization and not to the use of chemotherapy agents. These results compare favorably with estimates of cost-effectiveness (CE) of commonly used treatments for other diseases and demonstrate that a policy of supportive care is associated with costs that may exceed those of active treatment. It is concluded that economic factors should not adversely affect decisions regarding the use of chemotherapy in advanced NSCLC.

Insulin- and obesity-related variables in early-stage breast cancer: correlations and time course of prognostic associations

PURPOSE

To investigate patterns of prognostic associations over time of insulin- and obesity-related variables measured at diagnosis of early breast cancer (BC), focusing on whether the prognostic associations with distant recurrence and death changed over time.

PATIENTS AND METHODS

Five hundred thirty-five nondiabetic women with T1-3, N0-1, M0 invasive BC diagnosed from 1989 to 1996 were included in the study. Insulin-related variables included fasting insulin, Homeostasis Model Assessment, C-peptide, and glucose. Obesity-related variables included weight, body mass index (BMI), waist and hip circumference, and leptin. Correlations were examined using the Pearson correlation coefficient and prognostic associations using the Cox model.

RESULTS

There was evidence that associations of baseline insulin-related variables with distant recurrence and death were not constant over time; univariable adverse prognostic associations were significant only during the first 5 years (eg, insulin quartile 4 v 1: hazard ratio [HR], 2.32; 95% CI, 1.39 to 3.86; P < .001 for distant disease-free survival [DDFS]; and HR, 2.85; 95% CI, 1.48 to 5.50; P = .002 for overall survival [OS], with little attenuation of this pattern in multivariable analyses). In contrast, obesity-related variables (BMI, weight, leptin) exerted significant adverse univariable associations that were constant over time (eg, BMI quartile 4 v 2: HR, 1.40; 95% CI, 1.07 to 1.82 for DDFS; P = .014; and HR, 1.50; 95% CI, 1.16 to 1.93; P < .001 for OS); prognostic associations of leptin remained significant in multivariable analyses.

CONCLUSION

Baseline insulin- and obesity-related variables exert different patterns of prognostic associations over time in early BC.

Catalytic and biophysical properties of a nitrogenase Apo-MoFe protein produced by a nifB-deletion mutant of Azotobacter vinelandii

A Zn-immobilized metal-affinity chromatography technique was used to purify a poly-histidine-tagged, FeMo-cofactorless MoFe protein (apo-MoFe protein) from a nifB-deletion mutant of Azotobacter vinelandii. Apo-MoFe protein prepared in this way was obtained in sufficient concentrations for detailed catalytic, kinetic, and spectroscopic analyses. Metal analysis and electron paramagnetic resonance spectroscopy (EPR) were used to show that the apo-MoFe protein does not contain FeMo-cofactor. The EPR of the as-isolated apo-MoFe protein is featureless except for a minor S = 1/2 signal probably arising from the presence of either a damaged P cluster or a P cluster precursor. The apo-MoFe protein has an alpha2beta2 subunit composition and can be activated to 80% of the theoretical MoFe protein value by the addition of isolated FeMo-cofactor. Oxidation of the as-isolated apo-MoFe protein by indigodisulfonate was used to elicit the parallel mode EPR signal indicative of the two-electron oxidized form of the P cluster (P2+). The midpoint potential of the PN/P2+ redox couple for the apo-MoFe protein was shown to be shifted by -63 mV when compared to the same redox couple for the intact MoFe protein. Although the apo-MoFe protein is not able to catalyze the reduction of substrates under turnover conditions, it does support the hydrolysis of MgATP at 60% of the rate supported by the MoFe protein when incubated in the presence of Fe protein. The ability of the apo-MoFe protein to specifically interact with the Fe protein was also shown by stopped-flow techniques and by formation of an apo-MoFe protein-Fe protein complex. Finally, the two-electron oxidized form of the apo-MoFe protein could be reduced to the one-electron oxidized form (P1+) in a reaction that required Fe protein and MgATP. These results are interpreted to indicate that the apo-MoFe protein produced in a nifB-deficient genetic background [corrected] contains intact P clusters and P cluster polypeptide environments. Small changes in the electronic properties of P clusters contained within the apo-MoFe protein are most likely caused by slight perturbations in their polypeptide environments.

The impact of diabetes on survival following breast cancer

PURPOSE

It has been suggested that type 2 diabetes may affect breast cancer prognosis, possibly due to increased diabetes-related comorbidity, or direct effects of insulin resistance and/or hyperinsulinemia. The purpose of this study was to examine the impact of diabetes on survival following breast cancer.

METHODS

Using population-based health databases from Ontario, Canada, this retrospective cohort study compared deaths between women with breast cancer aged 55-79 years with diabetes and without diabetes. Women were followed for all cause mortality from breast cancer diagnosis until March 31st 2006.

RESULTS

Of the 6,107 women with breast cancer, 1,011 had diabetes and 5,096 did not have diabetes. Women with diabetes were slightly older, were more likely to reside in a lower income neighborhood, and had greater comorbidity compared to women without diabetes. After a mean follow-up of 5.0 years and adjustment for age, prior mammograms and other covariates, mortality following breast cancer was significantly higher among women with versus without diabetes (hazard ratio, HR 1.39, 95% confidence interval, CI 1.22-1.59, P < 0.0001). The effect of diabetes on mortality was comparable to that seen in women with diabetes without breast cancer over a 7-year follow-up.

CONCLUSION

This study found that diabetes was associated with a close to 40% increase in mortality within the first 5 years following breast cancer, which was similar to that seen in women with diabetes without breast cancer. These findings suggest that early survival following breast cancer is reduced in women with diabetes, possibly due to diabetes-related causes.

Impact of the obesity epidemic on cancer

There is growing appreciation that the current obesity epidemic is associated with increases in cancer incidence at a population level and may lead to poor cancer outcomes; concurrent decreases in cancer mortality at a population level may represent a paradox, i.e., they may also reflect improvements in the diagnosis and treatment of cancer that mask obesity effects. An association of obesity with cancer is biologically plausible because adipose tissue is biologically active, secreting estrogens, adipokines, and cytokines. In obesity, adipose tissue reprogramming may lead to insulin resistance, with or without diabetes, and it may contribute to cancer growth and progression locally or through systemic effects. Obesity-associated changes impact cancer in a complex fashion, potentially acting directly on cells through pathways, such as the phosphoinositide 3-kinase (PI3K) and Janus kinase-signal transducer and activator of transcription (JAK-STAT) pathways, or indirectly via changes in the tumor microenvironment. Approaches to obesity management are discussed, and the potential for pharmacologic interventions that target the obesity-cancer link is addressed.

Body size and breast cancer prognosis: a critical review of the evidence

There is currently controversy about the effect of body size on the prognosis of patients with breast cancer. In order to clarify the prognostic importance of body size, and to determine whether the effect varies across subgroups of patients, a critical appraisal of the published literature was undertaken. Thirteen cohort studies and one case-control study were identified that examined the prognostic effect of body size. Methodologic standards were developed that reflected those features of study design considered most important in studies of prognosis in breast cancer, and were independently applied to each report by each of the authors. When the effects of methodologic differences among the studies were controlled, a modest prognostic effect of body size was identified. This effect appeared to be greatest in postmenopausal women, in those with little or no involvement of axillary nodes, and to be independent of other prognostic factors. Additional investigation is recommended to determine the prognostic effects of body size in postmenopausal women with axillary node negative breast cancer and in women receiving systemic adjuvant therapy, and to determine the pathophysiological basis for these effects. Intervention studies to determine the effects of altering body size may also be indicated.

Randomized trial of a telephone-based weight loss intervention in postmenopausal women with breast cancer receiving letrozole: the LISA trial

PURPOSE

Obesity is associated with poor outcomes in women with operable breast cancer. Lifestyle interventions (LIs) that help women reduce their weight may improve outcomes.

PATIENTS AND METHODS

We conducted a multicenter randomized trial comparing mail-based delivery of general health information alone or combined with a 24-month standardized, telephone-based LI that included diet (500 to 1,000 kcal per day deficit) and physical activity (150 to 200 minutes of moderate-intensity physical activity per week) goals to achieve weight loss (up to 10%). Women receiving adjuvant letrozole for T1-3N0-3M0 breast cancer with a body mass index (BMI) ≥ 24 kg/m(2) were eligible. Weight was measured in the clinic, and self-report physical activity, quality-of-life (QOL), and diet questionnaires were completed. The primary outcome was disease-free survival. Accrual was terminated at 338 of 2,150 planned patients because of loss of funding.

RESULTS

Mean weight loss was significantly (P < .001) greater in the LI arm versus the comparison arm (4.3 v 0.6 kg or 5.3% v 0.7% at 6 months and 3.1 v 0.3 kg or 3.6% v 0.4% at 24 months) and occurred consistently across strata (BMI 24 to < 30 v ≥ 30 kg/m(2); prior v no prior adjuvant chemotherapy). Weight loss was greatest in those with higher baseline levels of moderate-intensity physical activity or improvement in QOL. Hospitalization rates and medical events were similar.

CONCLUSION

A telephone-based LI led to significant weight loss that was still evident at 24 months, without adverse effects on QOL, hospitalizations, or medical events. Adequately powered randomized trials with cancer end points are needed.