Take these two opinions: “Most cancers are preventable”, Prof David Hunter, Harvard School of Public Health, and “The average cancer patient is just unlucky”, Prof. Hans Clevers, Utrecht University. Discuss the scientific evidence/mechanisms behind both statements. Conclude with your own opinion about the issue.

Introduction

Cancer remains one of the leading causes of mortality worldwide, with complex aetiology involving genetic, environmental, and lifestyle factors. This essay examines two contrasting opinions from prominent researchers in the field. The first, from Professor David Hunter of Harvard School of Public Health, asserts that “most cancers are preventable” (Hunter, 2014). The second, from Professor Hans Clevers of Utrecht University, suggests that “the average cancer patient is just unlucky” (Clevers, 2016). As a student studying Biomedical Science, I find this debate particularly relevant, as it bridges epidemiology, molecular biology, and public health. The purpose of this essay is to discuss the scientific evidence and mechanisms supporting each statement, drawing on peer-reviewed sources and official reports. The main body will explore preventable aspects of cancer, followed by the role of intrinsic randomness or ‘bad luck’. Finally, I will conclude with a summary and my own opinion, arguing for a balanced perspective that emphasises prevention while acknowledging unavoidable elements. This discussion highlights the multifaceted nature of cancer causation, informing potential strategies for reduction.

Evidence Supporting the Preventability of Most Cancers

The notion that most cancers are preventable is grounded in substantial epidemiological evidence linking modifiable risk factors to cancer incidence. Professor Hunter’s statement aligns with global health perspectives, such as those from the World Health Organization (WHO), which estimates that 30-50% of cancers could be prevented through lifestyle changes and environmental interventions (WHO, 2022). Key mechanisms involve external carcinogens and behavioural choices that damage DNA or promote cellular proliferation.

One primary mechanism is exposure to tobacco smoke, a well-established carcinogen responsible for approximately 22% of cancer deaths globally (WHO, 2022). Tobacco contains over 70 known carcinogens, such as polycyclic aromatic hydrocarbons and nitrosamines, which induce DNA adducts and mutations in genes like TP53, leading to uncontrolled cell growth (Hecht, 2012). For instance, lung cancer rates have declined in regions with stringent smoking bans, demonstrating preventability. In the UK, the NHS reports that smoking cessation could prevent around 64,000 cancer cases annually (NHS, 2021). This evidence supports Hunter’s view, as avoiding tobacco directly reduces mutational burden.

Furthermore, dietary and lifestyle factors contribute significantly. Obesity, linked to 4-8% of cancers, promotes chronic inflammation and hormonal imbalances that facilitate tumourigenesis (Lauby-Secretan et al., 2016). Mechanisms include elevated insulin-like growth factor-1 (IGF-1) levels, which stimulate cell division in tissues like the breast and colon. Alcohol consumption, meanwhile, metabolises into acetaldehyde, a mutagen that impairs DNA repair (Seitz and Stickel, 2007). The International Agency for Research on Cancer (IARC) classifies alcohol as a Group 1 carcinogen, with evidence from cohort studies showing dose-dependent risks for oesophageal and liver cancers (IARC, 2012). Physical inactivity exacerbates these risks by altering metabolic pathways, but regular exercise can mitigate them by enhancing immune surveillance and reducing inflammation (Moore et al., 2016).

Environmental and occupational exposures also underscore preventability. Asbestos, for example, causes mesothelioma through chronic inflammation and genetic alterations in mesothelial cells (Carbone et al., 2012). Regulatory measures, such as the UK’s Control of Asbestos Regulations 2012, have reduced incidence by limiting exposure. Similarly, ultraviolet (UV) radiation from sun exposure drives skin cancers via pyrimidine dimer formation in DNA, preventable through sunscreen and protective clothing (Armstrong, 2004). Vaccinations against oncogenic viruses, like human papillomavirus (HPV) for cervical cancer, represent another preventive mechanism, with HPV vaccines reducing infection rates by up to 90% in vaccinated populations (Drolet et al., 2019).

However, limitations exist; not all cancers respond equally to prevention. For example, while breast cancer has modifiable risks like hormone replacement therapy, genetic predispositions (e.g., BRCA mutations) complicate full preventability (Narod, 2011). Nonetheless, Hunter’s assertion is supported by modelling studies estimating that over 40% of UK cancers are linked to preventable causes, including smoking, diet, and infections (Parkin et al., 2011). This evidence, drawn from large-scale registries like those from Cancer Research UK, illustrates how interventions targeting these mechanisms could substantially lower cancer burden.

Evidence Supporting Cancer as Primarily a Matter of Bad Luck

In contrast, Professor Clevers’ opinion that the average cancer patient is “just unlucky” emphasises intrinsic, stochastic processes in carcinogenesis, independent of external factors. This perspective gained prominence from research by Tomasetti and Vogelstein (2015), who proposed that many cancers arise from random mutations during normal cell division, rather than solely from environmental insults.

The core mechanism involves errors in DNA replication during stem cell divisions. Each cell division carries a small risk of mutations due to imperfect proofreading by DNA polymerases, leading to oncogene activation or tumour suppressor inactivation (Tomasetti and Vogelstein, 2015). Their study correlated lifetime cancer risk with the number of stem cell divisions in various tissues, finding that two-thirds of cancer variability could be attributed to this ‘bad luck’ factor. For instance, colorectal cancer, with high stem cell turnover, shows elevated intrinsic risk compared to tissues with fewer divisions, like the brain.

This randomness is evident in childhood cancers, where environmental exposure is minimal. Paediatric leukaemias often result from spontaneous chromosomal translocations, such as the Philadelphia chromosome in chronic myeloid leukaemia, occurring de novo without clear preventable causes (Greaves, 2018). Mechanisms include replication stress in rapidly dividing haematopoietic cells, leading to genomic instability. Similarly, glioblastomas in adults frequently harbour random mutations in genes like IDH1, unrelated to lifestyle (Parsons et al., 2008).

Critics argue this model overlooks gene-environment interactions, but subsequent analyses refined it, showing that while extrinsic factors dominate in some cancers (e.g., lung), intrinsic mutations explain a significant portion in others (Wu et al., 2016). For example, prostate cancer’s incidence correlates weakly with modifiable risks, suggesting bad luck plays a larger role (Al Olama et al., 2014). Ageing amplifies this, as cumulative mutations accrue over time, explaining why cancer risk increases exponentially with age (Rozhok and DeGregori, 2019).

However, the ‘bad luck’ hypothesis has limitations; it does not negate prevention but highlights that not all cancers are avoidable. Evidence from twin studies shows that while heritability accounts for 5-10% of cancers, much of the remainder could be stochastic (Lichtenstein et al., 2000). This supports Clevers’ view, particularly for patients without obvious risk factors, who may indeed be unlucky victims of probabilistic cellular events.

Conclusion

In summary, Professor Hunter’s claim that most cancers are preventable is backed by robust evidence on modifiable risks like smoking, diet, and environmental exposures, which operate through mechanisms such as DNA damage and inflammation. Conversely, Professor Clevers’ emphasis on bad luck is supported by research on random mutations during cell division, explaining cancers with minimal external triggers. Both perspectives contribute to a comprehensive understanding in Biomedical Science, revealing cancer as a interplay of preventable and intrinsic factors.

In my opinion, while bad luck undeniably contributes—particularly in rare or childhood cancers—the evidence for preventability is compelling and actionable. As a Biomedical Science student, I believe prioritising prevention through public health measures could save more lives than fatalistically accepting unluckiness. However, integrating both views suggests a holistic approach: promoting lifestyle changes while advancing research into intrinsic mechanisms for early detection. This balanced strategy could reduce cancer’s global impact, though complete eradication remains unlikely due to stochastic elements. Ultimately, empowering individuals with knowledge of preventable risks arguably offers the greatest hope.

(Word count: 1,248 including references)

References

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