In this article, I will cover some basics of oncology that would be useful for a layperson to be aware of. I will try to answer some common questions that I frequently get asked from patients and family members. Answers to these questions will make us more aware and informed about the fundamentals of oncology. So first, let’s start with what is cancer.
What is cancer?
The National Cancer Institute defines cancer as a disease “in which some of the body’s cells grow uncontrollably and spread to other parts of the body”. First, we need to understand that our body is made up of several trillions of cells (more than 30 trillion, probably). These cells continue to reproduce and replicate, a process known as cell division. Almost 1% of our body cells (300 billions) are replaced every day by cell division. So, when I meet you today, I meet a you that is different from yesterday’s you by several billions of cells.
This cell division is a complex process. The genetic information are carried out in our DNAs and these DNAs are located in chromosomes. These chromosomes get replicated during the cell division process. Any small error during this process changes the genetic makeup and this is called mutation. A mutation is defined as a change in DNA sequence, due to mistakes in copying process during cell division.
As you can imagine, such mutations and errors in copying the DNA occur very frequently since hundreds of billions of our cells are dividing literally every day. So, why don’t we see the effects of such errors more commonly? Why is everyone not dying of cancer everyday?
That’s because every mutation or change in DNA sequence is not harmful. There are several mutations that don’t make a difference. The other more important reason is that our body has a wonderful repair mechanism. Our body is really smart in identifying cells that have such mistakes in their chromosomes and correcting or killing these cells. I always feel wonderful imagining how marvelous our body is in correcting these mistakes. When such staggering number of cells are dividing everyday, it’s almost a miracle that everybody does not have cancer.
Ok, so what happens in cancer is that, some cells with mutations do not get repaired or killed, they escape our body’s defense, and they continue to divide and divide. These cells outsmart our body’s smart mechanism. Our normal cells divide at a specific rate, and also undergo cell-death when they have aged, called “apopotosis”. Apoptosis is a process by which the cells in our body kill themselves (cell-suicide) when they are no longer useful. However, these cells with mutations do not undergo suicide and keep dividing. When cells are dividing uncontrollably, they will result in a mass of tissue. This is called tumor.
Some tumors stay at a local place and do not migrate, these are called benign tumors. Some other tumors, however, aren’t happy with just forming a mass at a place. They start invading nearby other tissues and might even migrate to other parts of the body. These tumors are called malignant tumors. These malignant tumors are called cancers. They are also called neoplasia.
Thus, cancer refers to tumors (abnormal growth of cells) that invade and migrate to other tissues. This neoplastic process is usually due to errors during cell-division or mutations.
What causes cancer?
So, we have our answer. Mutation is what causes cancer. But another important follow-up question would be what causes mutations?
As we just discussed, mutations happen during cell divisions due to some error in DNA copying. Thus, this is mostly bad luck. I know this is not a very satisfying answer, but most of the cancers happen due to bad luck. For some reason, an error gets introduced during copying of the DNA, and the cell becomes abnormal, and stops dying and just keeps dividing and dividing until it becomes a mass of tissue and starts migrating. That’s the reason why we can’t prevent cancer- because how do you prevent bad luck? Thus, bad luck is the answer for the cause of almost one-third cancers.
For the other one-third, it is the hereditary causes. Some of these mutations can pass from parents to children. Depending on the type of mutations, some of them may not always pass from parents to children, but may skip one generation and show up in grandkids. That’s why we take a thorough family history of cancer- not only whether your parents had cancer, but also your grandparents, and your parent’s siblings history is important. For example, such hereditary causes are quite common in patients with breast, ovarian, colorectal cancers.
For the remaining one-third, environmental causes lead to mutations and cause cancer. For example, smoking is responsible for several cancers. Alcohol is also now known to be responsible for some cancers. Human papilloma virus leads to mutations causing head and neck, and cervical, and penile cancers. Hepatitis virus makes one susceptible to liver cancer.
Thus, in summary, although mutations lead to cancer, there are three major causes for mutations such as hereditary passing of genes, environmental factors causing mutations, and bad luck.
Some patients are confused when they get lung cancer because they have never smoked in their lives. That is explained by bad luck. Although they didn’t smoke, they still got some errors during cell division. Also, some people smoke their who lives without getting cancer because the mutations may have been corrected by other repair mechanisms. There are other scientific answers but that is beyond the scope of this article.
So, what can we do to reduce the risk of cancer?
Because you can’t prevent bad luck, you can’t prevent cancer. You also can’t control the genetics you inherit from your patients. But you can reduce the risk of cancer by controlling the environmental factors. Of several risk factors identified for increasing the risk of cancer, the most responsible ones are smoking and obesity.
So, the best thing you can do to prevent the risk of cancer, is to not smoke or stop smoking if you have already started smoking. The next best thing would be to keep your body weight under control by staying active and eating proper diet.
Also, for cervical cancer prevention, HPV vaccination is important.
What about screening? Should I get screened for cancer?
This is a difficult question because the answer differs for different cancer types. But in general, “screening packages” of blood work and whole-body scans are not useful, and can even be harmful by picking up small tumors that may not need treatment. We call this overdiagnosis, which can lead to unnecessary biopsies and surgeries, known as overtreatment. So, please avoid these “screening packages” and whole-body scans that are popularized by private hospitals in Nepal.
However, there maybe some use to some cancer screenings based on your age. It will need a detailed discussion with your doctor. Also, if you have a family history of cancer, you will need screening from a relatively early age.
What do you mean by stage of cancer?
Cancers are usually divided into 4 stages, which affect their prognosis and treatment goals. They are staged based on scans and pathology reports. They range from stage 1 to stage 4. Stage 1 is very small tumor detected early, so that just taking that tumor out cures the disease and you do not need anything else. The tumor is cured.
Stage 4 is cancer that has spread from its original location. For example, a colon cancer that has migrated to lungs. A lung cancer that also shows up in liver, etc. This migration of cancer from one organ to another is called metastasis. A cancer that has metastasized is called stage 4 cancer, and generally this cannot be cured. Surgery, radiation, and chemotherapy are still useful but the goal of treatment usually is to increase the life expectancy and improve quality of life, but not cure.
Stage 2 and 3 are in between. They are bigger than stage 2 but have not metastasized, except to nearby lymph nodes. They usually are treated with surgery, and may need radiation and chemo after or before the surgery. The goal of chemotherapy here is to eliminate any cancer cells still circulating in the body after surgery. Chemotherapy and radiation after surgery is called adjuvant treatment, and before surgery is called neoadjuvant treatment.
However, some cancers like brain tumors, do not often metastasize but still kill patients due to invasion and growth. Thus, brain tumors are defined by grades (grade 1 to 4) rather than stages.
So, all patients with stage 4 cancer are going to die?
Yes, but all of us are also going to die even without cancer. What people usually mean when they ask this question is whether people with stage 4 cancer die sooner than normally expected of them. In Nepal, this question also means whether it’s worth spending on treatment if it cannot be cured. Thanks to medical advances, we can achieve long term control of such disease for several cancers. For example, with breast cancers and colorectal cancers, skin cancers, etc we can expect very good outcomes. It’s always difficult to predict the outcomes for a given patient, but the long-term outcomes are really good nowadays for several cancers despite being stage 4. Some cancers like testicular cancers can even be cured after being stage 4. There are some cancers, however, where we haven’t been able to make much progress. Brain tumors, pancreatic cancers, gall bladder cancers still have very dismal prognosis.
For most cancers, even in stage 4, I’d recommend undergoing treatment- at least the first line treatment, and assess treatment response before making any predictions of life expectancy. However, whether a person is fit for chemo will depend on several factors including comorbidities and functionally fit status. This needs to be discussed with the oncologist.
In summary, my message for the public is to do things in their capacity to prevent the risk of cancer (not smoking, reducing weight), be aware about screening being a double-edged sword (not all screening tests are useful), be aware of their family history of cancer, and help your loved ones make appropriate informed treatment decisions when they have cancer. For example, stages 1-3 may be cured if treated properly and in time. So, do not waste precious time seeking alternative treatments if the cancer is still in stages 1-3. Even for stage 4, several cancers can be treated and patients quality of life (functional status, ability to live a normal-ish life) can be maintained for quite a long time. If fit for chemo, trying at least first-line treatment is useful in many cases. However, there are several drugs which are quite expensive and may not provide any meaningful benefit, specially in later lines. If your oncologist recommends you a treatment, directly ask how many extra months in average does this drug provide and what your quality of life will be like while you are on that drug. If the drug shrinks tumor but doesn’t extend your life or improve your symptoms, in most cases, it may not be worth selling your house and also suffering the side-effects.
Dr. Bishal Gyawali 
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