Will cancer ever be cured?

Cancer is a disease characterized by the uncontrolled growth and spread of abnormal cells in the body. If left untreated, it can invade surrounding tissues and spread to distant organs, a process known as metastasis. Despite decades of intensive research and remarkable medical advances, a universal cure for cancer remains out of reach. This is not due to a lack of effort, but rather because cancer is an extraordinarily complex and adaptive set of diseases. Each type of cancer and often each individual tumour behaves differently, creating significant challenges for treatment. This article explores why curing cancer is so difficult, highlights the progress being made, and examines whether we might ever achieve a true cure.

Why Haven't We Cured Cancer Yet?

Genetic Complexity and Heterogeneity: Cancer is not a single disease but over 200 subtypes, each driven by unique genetic mutations. Even within a single tumour, cells often harbour different mutations (intratumor heterogeneity). This means a drug that works for one cancer patient might have absolutely no effect for another. Moreover, cancer cells rapidly develop evolutionary resistance through genetic changes, akin to antibiotic-resistant bacteria. Therapies that initially work may fail as resistant subclones emerge. (1)

Metastasis and Immune Evasion: Many cancers metastasize before detection, spreading via blood or lymphatic systems, which seeds the growth of a new tumour. This makes treatment harder as there are now multiple targets with varying characteristics and immunities to certain treatments. Furthermore, cancer’s ability of immunosuppression makes it even harder to treat. Cancer suppresses the immune system by producing abnormal proteins that trigger an immune response, leading to phagocytosis. Cancer cells in or metastasizing to bone marrow can inhibit white blood cell production, allowing cancer to evade immune detection. Treatments like chemotherapy, radiotherapy, and steroids can also weaken the immune system, compounding the challenge of treatment by creating artificially induced immunosuppression, making cancer harder to treat. (2)

Limitations of traditional cancer therapies: Traditional cancer treatments, particularly chemotherapy, are challenging due to their non-specific nature and significant side effects. While chemotherapy targets rapidly dividing cancer cells by interfering with processes like DNA replication, apoptosis, and metabolism, it also harms healthy cells, causing severe physical and mental side effects. Prolonged exposure often leads to drug resistance, making treatment less effective over time and increasing the risk of relapse. High doses required for treatment further exacerbate these issues. (3)

Progress and future outlook:

Major advances in treatment and diagnosis are steadily changing the landscape of cancer care. Modern therapies are increasingly able to control cancers long-term, transforming them into manageable chronic conditions rather than terminal illnesses:

Targeted therapies like Gleevec (imatinib) have shown that identifying specific gene mutations can lead to effective, long-term control of certain cancers. The use of next-generation sequencing is rapidly expanding the number of genetic alterations that can be matched to targeted treatments, improving outcomes for many patients.

Immunotherapy represents another groundbreaking area. By empowering the immune system, particularly through checkpoint inhibitors, some advanced cancers like melanoma have seen durable responses. However, these therapies are not universally effective yet, and new research into the gut microbiome may help expand their benefits to more people.

Combining treatments is also proving beneficial. Adjunct therapies, such as pairing immunotherapy with radiation, can trigger an "abscopal effect," where immune cells attack tumours far from the original radiation site, improving overall cancer control.

Innovations like nanotechnology offer promise for the future, with nanoscale devices potentially able to detect cancers at the earliest stages and deliver highly targeted treatments directly to tumours.

Additionally, cancer vaccines using mRNA technology, similar to COVID-19 vaccines, are being developed to train the immune system to recognize and eliminate cancer cells. Although clinical trials have shown mixed results, some promising outcomes suggest this approach could be part of future treatment strategies.

Finally, treatment of oligometastases—isolated rogue tumours that appear even when overall cancer is controlled—using techniques like stereotactic body radiotherapy (SBRT) is offering a way to further extend control and possibly eradicate resistant cancer sites. (4)

Will cancer ever be cured?

The concept of a cancer being "curable" is more complex than it might initially seem. In some cases, particularly when detected early, cancers can be effectively eradicated. For example, stage 0 cancers like ductal carcinoma in situ (DCIS) are often considered completely curable with appropriate treatment. Similarly, children treated successfully for acute lymphoblastic leukemia are often referred to as "cured," as the likelihood of recurrence later in life is very low.

Several types of cancer are considered more "curable" based on high five-year survival rates, including breast cancer, melanoma, thyroid cancer, Hodgkin lymphoma, testicular cancer, and prostate cancer. However, survival statistics can mask important nuances. For instance, oestrogen receptor-positive (ER+) breast cancers diagnosed at stages 1 to 3 are known to have a higher risk of recurrence five to ten years—or even decades—after initial treatment. In these cases, the cancer may be more "treatable" than definitively "curable," with ongoing therapies aimed at long-term control rather than permanent eradication.

The term "durable response" is often used in situations where a metastatic (stage 4) cancer has been controlled for an extended period, sometimes years, especially with newer treatments like immunotherapy. A durable response suggests that while the cancer is not completely eliminated, it remains suppressed to the point that it no longer causes harm or progresses. (4)

Ultimately, when oncologists speak of a "cure," they generally mean that a person has lived long enough without evidence of cancer recurrence that the risk of the cancer returning is extremely low—although technically, they may never be 100% certain that every last cancer cell has been destroyed. In many cases, cancer becomes a disease to be controlled rather than cured in the absolute sense. (1) However, with advancing therapies and earlier detection methods, the line between treatable and curable is steadily shifting, offering more people the hope of long-term survival and a life free from cancer. 

References:

Worldwidecancerresearch.org. (2024). Why Is Cancer So Hard To Cure? [online] Available at: https://www.worldwidecancerresearch.org/information-and-impact/cancer-myths-and-questions/why-is-cancer-so-hard-to-cure/. (1) 

Wheeler, L.D. (2023). Why is cancer so hard to cure? Essex Student Journal, [online] 14(1). doi:https://doi.org/10.5526/esj164.  (2)

Anand, U., Dey, A., Chandel, A.K.S., Sanyal, R., Mishra, A., Pandey, D.K., De Falco, V., Upadhyay, A., Kandimalla, R., Chaudhary, A., Dhanjal, J.K., Dewanjee, S., Vallamkondu, J. and Pérez de la Lastra, J.M. (2022). Cancer chemotherapy and beyond: Current status, drug candidates, associated risks and progress in targeted therapeutics. Genes & Diseases, [online] 10(4), pp.1367–1401. doi:https://doi.org/10.1016/j.gendis.2022.02.007. (3)

https://www.facebook.com/verywell (2019). Will Cancer Ever Be Cured? [online] Verywell Health. Available at: https://www.verywellhealth.com/will-cancer-ever-be-cured-4686392. (4)