Inverse Association between Statin Use and Cancer Mortality Relates to Cholesterol Level

Cholesterol and Immune Microenvironment: Path Towards Tumorigenesis

PURPOSE OF REVIEW

Since obesity is a major risk factor for many different types of cancer, examining one of the most closely associated comorbidities, such as hypercholesterolemia, is crucial to understanding how obesity causes cancer. Hypercholesterolemia is usually associated with many cardiovascular complications such as hypertension, angina, and atherosclerosis. In addition, cholesterol may be a major factor in increasing cancer risk. Cancer patients who received statins, an anti-hypercholesteremic medicine, demonstrated improved prognosis possibly through its effect on tumor proliferation, apoptosis, and oxidative stress. Cholesterol could also aid in tumor progression through reprogramming tumor immunological architecture and mediators. This review focuses on the immunomodulatory role of cholesterol on cellular and molecular levels, which may explain its oncogenic driving activity. We look at how cholesterol modulates tumor immune cells like dendritic cells, T cells, Tregs, and neutrophils. Further, this study sheds light on the modification of the expression pattern of the common cancer-related immune mediators in the tumor immune microenvironment, such as programmed cell death 1 (PD-1), cytotoxic T lymphocyte antigen-4 (CTLA-4), transforming growth factor-beta (TGF-β), interleukin 12 (IL-12), IL-23, and forkhead box protein P3 (FOXP3).

RECENT FINDINGS

We highlight relevant literature demonstrating cholesterol's immunosuppressive role, leading to a worse cancer prognosis. This review invites further research regarding the pathobiological role of cholesterol in many obesity-related cancers such as uterine fibroids, post-menopausal breast, colorectal, endometrial, kidney, esophageal, pancreatic, liver, and gallbladder cancers. This review suggests that targeting cholesterol synthesis may be a fruitful approach to cancer targeting, in addition to traditional chemotherapeutics.

Statin Use, Cholesterol Level, and Mortality Among Females With Breast Cancer

Importance

Several studies have reported an association between the use of statins and breast cancer (BC) mortality. However, most of these studies did not take into account the underlying cholesterol level.

Objective

To investigate the association between serum cholesterol, statin use, and BC mortality.

Design, Setting, and Participants

This cohort study included females with invasive BC that was newly diagnosed between January 1, 1995, and December 31, 2013, in Finland. The cohort had available hormone receptor data and at least 1 cholesterol measurement. All data were obtained from Finnish national registries. Statistical analyses were performed from January to May 2022.

Exposure

Use of statins; statin dose; and serum cholesterol, low-density lipoprotein, high-density lipoprotein, and triglyceride levels measured separately before and after BC diagnosis.

Main Outcomes and Measures

Breast cancer mortality and overall mortality between date of BC diagnosis and December 31, 2015.

Results

A total of 13 378 female patients with BC (median [IQR] age, 62 [54-69] years) participated in the study. The median (IQR) follow-up was 4.5 (2.4-9.8) years after BC diagnosis, during which 16.4% of patients died and 7.0% died of BC. Prediagnostic statin use was a risk factor for BC death even after adjustment for total cholesterol level (hazard ratio [HR], 1.22; 95% CI, 1.02-1.46; P = .03). Reduced risk for BC death was seen for postdiagnostic statin use (HR, 0.85; 95% CI, 0.73-1.00; P = .05). The risk reduction was robust in participants whose cholesterol level decreased after starting statins (HR, 0.49; 95% CI, 0.32-0.75; P = .001) but was nonsignificant if cholesterol level did not subsequently decrease (HR, 0.69; 95% CI, 0.34-1.40; P = .30). Reduced BC mortality among statin users was also observed in females with estrogen receptor-positive tumors (HR, 0.82; 95% CI, 0.68-0.99; P = .03). Overall mortality was lower among statin users vs nonusers when adjusted for serum cholesterol level (HR, 0.80; 95% CI, 0.72-0.88; P < .001).

Conclusions and Relevance

Results of this cohort study showed that postdiagnostic use of statins was associated with reduced BC mortality compared with nonuse, and the risk was associated with subsequent change in serum cholesterol level. This finding suggests that cholesterol-lowering interventions with statins may be beneficial for patients with BC.

A Systematic Review and Meta-analysis on the Role of Statins in the Prevention of Mortality Following Pancreatic Cancer

BACKGROUND

Pancreatic cancer (PC) is a type of cancer with a high incidence and case-fatality rate.

OBJECTIVE

This study aimed to evaluate the role of statins in preventing mortality following PC based on scientific evidence with systematic review and meta-analysis method.

METHODS

This meta-analysis considered studies published from 1980 till the end of 2022 in ISI Web of Science, Scopus, PubMed, Cochrane, Science Direct, Google Scholar, and Embase databases. Funnel diagrams and Begg's and Egger's tests were used to assess the publication bias.

RESULTS

In general, this meta-analysis has included 19 studies (13 cohort studies, 4 case-control, and 2 randomized clinical trials (RCTs)) and a total of 100,888 patients with PC. The risk of mortality of PC in statin users in total was 0.86 (95% CI: 0.80 - 0.92, P-value <0.001); in the case-control studies, it was equal to 0.53 (0.34-0.83); in the cohort studies, it was equal to 0.87 (0.82-0.92, P-value <0.001); in RCTs, it was equal to 1.19 (0.99-1.42, P-value <0.001); in studies with good quality score category, it was equal to 0.92 (0.86-0.99, P-value <0.001), and in articles of the moderate quality score category, it was equal to 0.73 (0.64-0.84, P-value <0.001). The results of statistical tests indicated the existence of publication bias (Begg's test (P-value = 0.002) and Egger's test (P-value = 0.004)).

CONCLUSION

Statins reduce the risk of mortality in patients with PC. However, no significant relation has been observed in RCTs. Therefore, it is necessary to be cautious in interpreting the results.

Statin Use and Survival Among Men Receiving Androgen-Ablative Therapies for Advanced Prostate Cancer: A Systematic Review and Meta-analysis

IMPORTANCE

Epidemiological evidence supports a role for statins in improving survival in advanced prostate cancer, particularly among men receiving androgen-ablative therapies.

OBJECTIVE

To study the association between statin use and survival among men with prostate cancer receiving androgen deprivation therapy (ADT) or androgen receptor axis-targeted therapies (ARATs).

DATA SOURCES

This systemic review and meta-analysis used sources from MEDLINE, EMBASE, Epub Ahead of Print, Cochrane Clinical Trials, Cochrane Systematic Reviews, and Web of Science from inception to September 6, 2022.

STUDY SELECTION

Observational studies reporting associations of concurrent statin use and survival outcomes (in hazard ratios [HRs]).

DATA EXTRACTION AND SYNTHESIS

Two authors independently abstracted all data. Summary estimates pooled multivariable HRs with 95% CIs using the generic inverse variance method with random-effects modeling. A priori specified subgroup and sensitivity analyses were undertaken, and heterogeneity, study quality, and publication bias were evaluated. Confidence in the evidence was assessed using the GRADE (Grading of Recommendations Assessment, Development, and Evaluation) approach.

MAIN OUTCOMES AND MEASURES

Overall mortality and prostate cancer-specific mortality (PCSM).

RESULTS

Twenty-five cohorts of 119 878 men (65 488 statin users [55%]) with more than 74 416 deaths were included. Concurrent statin use was associated with a 27% reduction in the risk of overall mortality (HR, 0.73 [95% CI, 0.66-0.82]; I2 = 83%) and a 35% reduction in the risk of PCSM (HR, 0.65 [95% CI, 0.58-0.73]; I2 = 74%), with substantial heterogeneity in both estimates. Subgroup analyses identified a PCSM advantage associated with statins for men receiving ARATs compared with ADT alone (HR, 0.40 [95% CI, 0.30-0.55] vs 0.68 [95% CI, 0.60-0.76]; P = .002 for difference). Confidence in the evidence was rated low for both outcomes.

CONCLUSIONS AND RELEVANCE

The findings of this meta-analysis show that concurrent statin use was associated with reduced overall mortality and PCSM among men receiving androgen-ablative therapies for advanced prostate cancer. These findings are limited by the observational nature of the data and residual unexplained interstudy heterogeneity. Randomized clinical trials are warranted to validate these results.