Aspirin, NSAIDs, and Colorectal Cancer: Possible Involvement in an Insulin-Related Pathway

Nonsteroidal anti-inflammatory drugs but not aspirin are associated with a lower risk of post-colonoscopy colorectal cancer

BACKGROUND

Although nonsteroidal anti-inflammatory drugs (NSAIDs) reduce colorectal cancer (CRC) risk, their role in preventing post-colonoscopy CRC (PCCRC) remains undetermined.

AIMS

To investigate whether NSAIDs reduce PCCRC risk after a negative baseline colonoscopy METHODS: This is a retrospective cohort study based on a territory-wide healthcare database of Hong Kong. All patients (aged 40 or above) who underwent colonoscopies between 2005 and 2013 were identified. Exclusion criteria included CRC detected within 6 months of index colonoscopy, prior CRC, inflammatory bowel disease and prior colectomy. The primary outcome was PCCRC-3y diagnosed between 6 and 36 months after index colonoscopy. Sites of CRC were categorised as proximal (proximal to splenic flexure) and distal. The adjusted hazards ratio (aHR) of PCCRC-3y with NSAID and aspirin use (defined as cumulative use for ≥90 days within 5 years before index colonoscopy) was derived by propensity score (PS) regression adjustment of 22 covariates (including patient factors, concurrent medication use and endoscopy centre's performance).

RESULTS

Of 187 897 eligible patients, 21 757 (11.6%) were NSAID users. 854 (0.45%) developed PCCRC-3y (proximal cancer: 147 [17.2%]). NSAIDs were associated with a lower PCCRC-3y risk (aHR: 0.54, 95% CI: 0.41-0.70), but not CRC that developed >3 years (aHR: 0.78, 95% CI 0.56-1.09). The aHR was 0.48 (95% CI: 0.24-0.95) for proximal and 0.55 (95% CI: 0.40-0.74) for distal cancer. A duration- and frequency response relationship was observed (P_trend  < 0.001). For aspirin, the aHR was 1.01 (95% CI: 0.80-1.28).

CONCLUSIONS

Non-aspirin NSAIDs were associated with lower PCCRC risk after a negative baseline colonoscopy.

The effects of genetic variants related to insulin metabolism pathways and the interactions with lifestyles on colorectal cancer risk

OBJECTIVES

Genetic variants in metabolic signaling pathways may interact with lifestyle factors, such as dietary fatty acids, influencing postmenopausal colorectal cancer (CRC) risk, but these interrelated pathways are not fully understood.

METHODS

In this study, we examined 54 single-nucleotide polymorphisms (SNPs) in genes related to insulin-like growth factor-I/insulin traits and their signaling pathways and lifestyle factors in relation to postmenopausal CRC, using data from 6,539 postmenopausal women in the Women's Health Initiative Harmonized and Imputed Genome-Wide Association Studies. By employing a two-stage random survival forest analysis, we evaluated the SNPs and lifestyle factors by ranking them according to their predictive value and accuracy for CRC.

RESULTS

We identified four SNPs (IRS1 rs1801123, IRS1 rs1801278, AKT2 rs3730256, and AKT2 rs7247515) and two lifestyle factors (age and percentage calories from saturated fatty acids) as the top six most influential predictors for CRC risk. We further examined interactive effects of those factors on cancer risk. In the individual SNP analysis, no significant association was observed, but the combination of the four SNPs, age, and percentage calories from saturated fatty acid (≥11% per day) significantly increased the risk of CRC in a gene and lifestyle dose-dependent manner.

CONCLUSIONS

Our findings provide insight into gene-lifestyle interactions and will enable researchers to focus on individuals with risk genotypes to promote intervention strategies. Our study suggests the careful use of data on potential genetic targets in clinical trials for cancer prevention to reduce the risk for CRC in postmenopausal women.

Genetic variants and traits related to insulin-like growth factor-I and insulin resistance and their interaction with lifestyles on postmenopausal colorectal cancer risk

Genetic variants and traits in metabolic signaling pathways may interact with lifestyle factors such as obesity, physical activity, and exogenous estrogen (E), influencing postmenopausal colorectal cancer (CRC) risk, but these interrelated pathways are not fully understood. In this case-cohort study, we examined 33 single-nucleotide polymorphisms (SNPs) in genes related to insulin-like growth factor-I (IGF-I)/ insulin resistance (IR) traits and signaling pathways, using data from 704 postmenopausal women in Women’s Health Initiative Observation ancillary studies. Stratifying by the lifestyle modifiers, we assessed the effects of IGF-I/IR traits (fasting total and free IGF-I, IGF binding protein-3, insulin, glucose, and homeostatic model assessment–insulin resistance) on CRC risk as a mediator or influencing factor. Six SNPs in the INS, IGF-I, and IGFBP3 genes were associated with CRC risk, and those associations differed between non-obese/active and obese/inactive women and between E nonusers and users. Roughly 30% of the cancer risk due to the SNP was mediated by IGF-I/IR traits. Likewise, carriers of 11 SNPs in the IRS1 and AKT1/2 genes (signaling pathway–related genetic variants) had different associations with CRC risk between strata, and the proportion of the SNP–cancer association explained by traits varied from 30% to 50%. Our findings suggest that IGF-I/IR genetic variants interact with obesity, physical activity, and exogenous E, altering postmenopausal CRC risk, through IGF-I/IR traits, but also through different pathways. Unraveling gene–phenotype–lifestyle interactions will provide data on potential genetic targets in clinical trials for cancer prevention and intervention strategies to reduce CRC risk.

The role of aspirin in colorectal cancer chemoprevention

Considerable interest has emerged over the last decade regarding the role of aspirin in prevention of colorectal cancer. This disease is one of the commonest cancers in the Western World, therefore, the existence of a simple "everyday" agent, which could have the ability to prevent the disease, represents an invaluable opportunity clinicians may be able to exploit. Evidence from case-control and cohort studies, and recent updates of randomised controlled trials have been very encouraging-indicating benefit from long term use of aspirin at low dose. Possible mechanisms of chemoprevention include inhibition of the cyclooxygenase (COX) pathway, or COX-independent mechanisms, for example, the PIK3CA pathway, or therapy-induced senescence of cancer cells. The most serious side effect of prolonged aspirin treatment is haemorrhage, especially from the GI tract. This is likely to be less of a problem with chemoprevention at lower doses. One also needs to consider the impact if aspirin resistance, an increasingly recognised clinical entity.

Prevention and early detection of colorectal cancer--new horizons

Colorectal cancer is potentially one of the most preventable malignancies. Nutritional awareness (low fat, low red meat, high fruits and vegetables) and regular physical activity have major potential for primary prevention of this malignancy, while early detection technologies have the potential of both influencing mortality from colorectal cancer as well as enhancing primary prevention through detection and removal of lesions that could potentially develop into cancer. While the potential for prevention is large, its materialization is far from being optimal. The large-scale lifestyle changes in the population necessary to reduce colorectal cancer rates are hard to achieve, and most of the early detection technologies are either invasive or otherwise nonappealing to the population. Thus, without abandoning the proven prevention methods, new avenues need to be investigated to deal with this malignancy, which carries both high morbidity and high mortality. Such new avenues can now be followed, both in prevention and detection. Chemoprevention, or the use of medications to prevent disease, has now been extensively explored in colorectal cancer. Some of these interventions, such as supplemental fibers, have failed to demonstrate the anticipated effect, while others such as calcium supplementation have been shown to reduce formation of premalignant lesions, polyps, or adenomas. Data accumulating in recent years have suggested that aspirin, nonsteroidal anti-inflammatory drugs, and selective COX-II inhibitors all have a potential to reduce both colorectal cancer and colorectal adenomas. Issues of safety and therapeutic indexes have recently come up as barriers to the use of COX-II inhibitors, and have again drawn attention to aspirin as a potential drug of choice. Association studies have also shown a major potential role for statins in colorectal cancer prevention. New methodologies in cancer detection involve the introduction of colonography or virtual colonoscopy, and the development of methods of detection of genetic somatic mutations in feces or peripheral blood. While radiological techniques currently avoid the need for premedication and are less invasive, they currently still require similar gut cleansing to colonoscopy, can also lead to perforation, are costly, and carry a non-negligible exposure to radiation. Genetic analysis of the stool for mutations in tumor cells is evolving as a promising technique, struggling to achieve both high sensitivity and high specificity with the right combination of mutations sought. With all of these developments taking place, the near future will undoubtedly bring about the expected reduction in colorectal cancer mortality.