7.4. Cancer

Cancer is one of the most dreaded diseases of human beings and is a major cause of death all over the globe. More than a million Indians suffer from cancer and a large number of them die from it annually. The mechanisms that underlie development of cancer or oncogenic transformation of cells, its treatment and control have been some of the most intense areas of research in biology and medicine.

Cancer is a significant global health issue and affects millions of people. It is characterized by uncontrolled cell growth due to the breakdown of regulatory mechanisms in our bodies. Unlike normal cells, which grow and differentiate in a highly regulated manner, cancer cells lose this control and begin to multiply uncontrollably, leading to serious health consequences.

Think of your body's cells like a well-organized factory, where each worker knows their job and follows strict rules. When cancer strikes, it’s like someone has removed all the rules; workers (cells) start doing whatever they want, ignoring the factory's order and creating chaos that can eventually lead to the factory being shut down (the body failing to function).

In our body, cell growth and differentiation is highly controlled and regulated. In cancer cells, there is breakdown of these regulatory mechanisms. Normal cells show a property called contact inhibition by virtue of which contact with other cells inhibits their uncontrolled growth. Cancer cells appears to have lost this property. As a result of this, cancerous cells just continue to divide giving rise to masses of cells called tumors. Tumors are of two types: benign and malignant.

Cells in our body grow and divide in a controlled fashion. Normal cells communicate with each other and stop growing when they touch another cell (this is called contact inhibition). Cancer cells ignore this rule and continue to divide, forming lumps of tissue known as tumors. Tumors can be benign (harmless and not spreading) or malignant (harmful and capable of invading surrounding tissues and spreading to other body parts).

Imagine a neighborhood where every house has a yard. Normally, everyone respects their property lines and keeps their yards neat. If one person decides to ignore the boundaries and builds their yard into the street, invading others' space, this is like cancer cells ignoring contact inhibition. Their unregulated growth can lead to chaos (malignancy) in the community (body).

The malignant tumors, on the other hand are a mass of proliferating cells called neoplastic or tumor cells. These cells grow very rapidly, invading and damaging the surrounding normal tissues. As these cells actively divide and grow they also starve the normal cells by competing for vital nutrients. Cells sloughed from such tumors reach distant sites through blood, and wherever they get lodged in the body, they start a new tumor there. This property called metastasis is the most feared property of malignant tumors.

Malignant tumors consist of rapidly dividing cancer cells that invade and destroy surrounding healthy tissues. These cells consume nutrients and energy that regular cells need, making them weaker. Moreover, malignant cells can break away from the original tumor and travel through the bloodstream to form new tumors in other parts of the body. This process, known as metastasis, is particularly dangerous as it complicates treatment and significantly worsens the patient’s prognosis.

Think of malignant tumors as weeds in a garden. Initially, a weed starts in one corner and can take all the water and nutrients from the neighboring plants (healthy cells). Sometimes, the weed seeds can blow away and settle in another part of the garden, starting a new weed patch (metastasis). If not controlled, the garden can become overrun with weeds, just like the body can be overwhelmed by cancer.

Transformation of normal cells into cancerous neoplastic cells may be induced by physical, chemical or biological agents. These agents are called carcinogens. Ionising radiations like X-rays and gamma rays and non-ionizing radiations like UV cause DNA damage leading to neoplastic transformation. The chemical carcinogens present in tobacco smoke have been identified as a major cause of lung cancer. Cancer causing viruses called oncogenic viruses have genes called viral oncogenes.

Cancer can develop due to a variety of causes known as carcinogens. These can be physical agents like certain types of radiation (e.g., UV rays from the sun, X-rays) that damage DNA; chemical agents like those found in tobacco smoke that can cause mutations; or biological agents like cancer-causing viruses that can insert their genes into human cells. This damage or alteration in DNA can lead to the uncontrolled division of cells, resulting in cancer.

Consider DNA as a book of instructions for building and maintaining your body. Carcinogens act like a vandal who scribbles in the book, changing important instructions or tearing out pages. This scribbling can lead to errors in how cells are built, causing them to grow uncontrollably, much like how a faulty manual might lead a machine to malfunction.

Early detection of cancers is essential as it allows the disease to be treated successfully in many cases. Cancer detection is based on biopsy and histopathological studies of the tissue and blood and bone marrow tests for increased cell counts in the case of leukemias. In biopsy, a piece of the suspected tissue cut into thin sections is stained and examined under microscope (histopathological studies) by a pathologist. Techniques like radiography (use of X-rays), CT (computed tomography) and MRI (magnetic resonance imaging) are very useful to detect cancers of the internal organs.

To treat cancer effectively, early detection is crucial. This can be achieved through several methods, including biopsies where a small sample of tissue is taken and examined for cancer cells. Imaging technologies like X-rays, CT scans, and MRIs help visualize internal structures to identify tumors. Detection methods are important because identifying cancer early significantly improves treatment success rates.

Think of early cancer detection like catching a small leak in a roof before it becomes a big problem. If you find and fix a small leak quickly, it can save you from losing a lot more to a major water damage later. In the same way, early cancer detection can prevent the disease from becoming more serious and harder to treat.

The common approaches for treatment of cancer are surgery, radiation therapy and immunotherapy. In radiotherapy, tumor cells are irradiated lethally, taking proper care of the normal tissues surrounding the tumor mass. Several chemotherapeutic drugs are used to kill cancerous cells. Some of these are specific for particular tumors. Majority of drugs have side effects like hair loss, anemia, etc. Most cancers are treated by combination of surgery, radiotherapy and chemotherapy.

Cancer treatment often involves a combination of methods such as surgery to remove tumors, radiation to destroy cancer cells, and chemotherapy, which uses drugs to target rapidly dividing cells. Each treatment has its pros and cons. While effective, these treatments can also have side effects, impacting the patient's quality of life. A personalized approach is often taken to select the most effective treatment plan for each individual.

Treating cancer is similar to repairing a car that has multiple problems. Just as you might need to change the oil, replace the tires, and fix the engine all at once to get it running smoothly, cancer treatment often requires using multiple methods to attack the cancer from different angles and improve the patient’s health.

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