By Dr. Sanjay Gupta, lead physician at the Binaytara Foundation Cancer Center
What is cancer?
A neoplasm is an abnormal mass of tissue, the growth of which exceeds and is uncoordinated with that of the normal tissues and persists in the same excessive manner after cessation of the stimuli which evoked the change.
All tumor cells show the six hallmarks of cancer. These characteristics are required to produce a malignant tumor. They include:
- Cell growth and division absent the proper signals
- Continuous growth and division even given contrary signals
- Avoidance of programmed cell death
- Limitless number of cell divisions
- Promoting blood vessel construction
- Invasion of tissue and formation of metastases
Sign and Symptoms
Cancer has no symptoms at the initial stage. Signs and symptoms appear as the mass grows and ulcerate. The sign and symptoms vary according to site and nature of the cancer. Symptoms may be local, systemic and distant due to metastasis.
Local Symptoms: Local symptoms may occur due to the mass of the tumor or its ulceration. Mass causes local symptoms due to pressure effect (eg. Narrowing of oesophagus due to oesophageal carcinoma) and ulceration causes local bleeding(eg. Incase of bladder & vaginal carcinoma).
Systemic Symptoms: General symptoms occur due to effects that are not related to direct or metastatic spread. These may include: unintentional weight loss, fever, excessive fatigue and changes to the skin. Some cancers may cause specific groups of systemic symptoms, termed paraneoplastic syndrome. Examples include the appearance of myasthenia gravis in thymoma and clubbing in lung cancer.
Metastasis: Cancer can spread from its original site by local spread, lymphatic spread to regional lymph nodes or by hematogenous spread via the blood to distant sites, known as metastasis. The symptoms due to metastasis are based on the site it has metastasized. Eg. Low back pain in case of prostate cancer.
Causes
The majority of cancers, some 90–95% of cases, are due to genetic mutations from environmental factors. The remaining 5–10% are due to inherited genetics. Common environmental factors that contribute to cancer death include tobacco (25–30%), diet and obesity (30–35%), infections (15–20%), radiation (both ionizing and non-ionizing, up to 10%), stress, lack of physical activity and pollution.
Diagnosis
Most cancers are initially recognized either because of the appearance of signs or symptoms or through screening. Neither of these leads to a definitive diagnosis, which requires the examination of a tissue sample by a pathologist. People with suspected cancer are investigated with medical tests. These commonly include blood tests, X-rays, (contrast) CT scans and endoscopy.
Prevention
Cancer prevention is defined as active measures to decrease cancer risk. The vast majority of cancer cases are due to environmental risk factors. Many of these environmental factors are controllable lifestyle choices. Thus, cancer is generally preventable. Between 70% and 90% of common cancers are due to environmental factors and therefore potentially preventable.
Greater than 30% of cancer deaths could be prevented by avoiding risk factors including: tobacco, excess weight/obesity, poor diet, physical inactivity, alcohol, sexually transmitted infections and air pollution. Not all environmental causes are controllable, such as naturally occurring background radiation and cancers caused through hereditary genetic disorders and thus are not preventable via personal behavior.
Screening
Unlike diagnostic efforts prompted by symptoms and medical signs, cancer screening involves efforts to detect cancer after it has formed, but before any noticeable symptoms appear. This may involve physical examination, blood or urine tests or medical imaging.
Cancer screening is not available for many types of cancers. Even when tests are available, they may not be recommended for everyone. Universal screening or mass screening involves screening everyone. Selective screening identifies people who are at higher risk, such as people with a family history
Treatment
The treatment of cancer depends upon the type, nature and site of cancer. Following options are available for the treatment, single or in combination.
- Chemotherapy
- Radiotherapy
- Surgery
- Immunotherapy
- Hormonal therapy