Cancer FAQ: Straight Answers to 20 Common Questions

An oncologist is a doctor who diagnoses cancer, works out exactly what type and stage it is, and then plans and delivers treatment. A medical oncologist uses drug-based treatments — chemotherapy, targeted therapy, hormonal therapy, and immunotherapy — and coordinates with surgeons and radiation oncologists so the whole plan fits together. In practice, my job is also to explain the disease in language you understand, weigh the realistic options against your goals and tolerance, and stay with you through treatment, side-effect management, and follow-up.

See an oncologist once a biopsy or scan raises a real concern about cancer, when a diagnosis has already been made and you need a treatment plan, or when you want a second opinion before starting or changing treatment. You do not need a confirmed diagnosis to come — many patients are referred with an abnormal report or a suspicious lump, and part of the visit is deciding whether it is cancer at all. If reports are conflicting or a major decision is coming up, an early oncology opinion usually saves time and prevents wrong turns.

Cancer is what happens when normal cells pick up faults in their instructions and start dividing without the usual controls. Instead of growing, doing their job, and dying on schedule, these cells keep multiplying, ignore stop signals, and can invade nearby tissue or spread to other parts of the body. It is not one disease but hundreds, each behaving differently depending on the organ it starts in and the molecular changes driving it — which is why treatment is never one-size-fits-all.

Worldwide the most common cancers are breast, lung, colorectal, prostate, and stomach. In India, breast and cervical cancers lead among women, while oral cavity, lung, and other tobacco-related cancers are especially common in men — reflecting the heavy burden of tobacco use here. Blood cancers such as leukaemia, lymphoma, and multiple myeloma are less common but important. See the full list of cancers treated.

The commonest early warnings are a new lump, unexplained weight loss, unusual bleeding (in stool, urine, between periods, or when coughing), a sore or ulcer that does not heal, a persistent cough or change in voice, a change in bowel or bladder habit, and a mole that changes in size, shape, or colour. Persistent fatigue, fever, or bone pain without a clear cause also deserve attention. Most of these turn out not to be cancer — but if a symptom is new, unexplained, and lasts more than two to three weeks, it should be checked rather than watched.

Most cancers arise from a mix of factors accumulating over years rather than a single cause. Tobacco in every form is the biggest avoidable driver in India, followed by alcohol, obesity, chronic infections (HPV, hepatitis B and C, H. pylori), certain occupational and environmental exposures, and ageing itself, since faults build up in cells over time. A smaller share is driven by inherited gene changes. Importantly, in many patients we never find a single "reason" — and developing cancer is very rarely something a patient did wrong.

All cancer is genetic in the sense that it is caused by changes in a cell's genes — but only about 5 to 10 percent is hereditary, meaning a faulty gene passed down through the family that raises risk. Clues to a hereditary pattern include several close relatives with the same or related cancers, cancers at unusually young ages, or a known family mutation such as BRCA. If that pattern fits your family, genetic counselling and testing can guide screening and, sometimes, prevention. For most people, though, cancer is not inherited and does not mean their children will get it.

You cannot remove all risk, but you can lower a large share of it. The highest-impact steps are: avoid all forms of tobacco and limit alcohol; keep a healthy weight and stay physically active; eat more vegetables, fruit, and whole grains and less processed and red meat; get vaccinated against HPV and hepatitis B; protect your skin from excess sun; and attend recommended screenings so anything that does develop is caught early. Roughly a third to a half of cancers are linked to modifiable risks — so these habits genuinely matter, even though no single change guarantees prevention.

Diagnosis usually moves through three steps. First, something is found — on examination, a scan, or a routine test. Second, imaging (ultrasound, CT, MRI, or PET) maps where it is and whether it has spread. Third, and most important, a biopsy takes a sample of the tissue so a pathologist can confirm whether it is cancer and, if so, exactly what type. Blood tests and molecular testing on the biopsy then refine the picture. Only after this is complete can a reliable treatment plan be made — which is why rushing to treat before the diagnosis is fully confirmed is a mistake.

The main categories are imaging, tissue sampling, and laboratory tests. Imaging includes ultrasound, X-ray, CT, MRI, and PET-CT to locate the disease and check for spread. Tissue sampling — a needle biopsy, endoscopic biopsy, or surgical biopsy — provides the definitive answer, and the sample is examined under the microscope and tested for specific markers. Laboratory tests include blood counts, organ-function tests, tumour markers, and increasingly molecular and genetic tests that identify targetable mutations. Bone marrow tests are added for suspected blood cancers. No single test "catches everything"; they are chosen in sequence for the situation.

A biopsy is the only test that can say for certain whether a growth is cancer, because it lets a pathologist look at the actual cells. Scans can strongly suspect cancer but cannot confirm the type, grade, or molecular features that decide treatment — and some things that look worrying on a scan turn out to be benign. The biopsy also guides which targeted therapy or immunotherapy might work. A common fear is that a biopsy "spreads" cancer; in modern practice this risk is extremely low and is far outweighed by the danger of treating blind. If you want help interpreting one, read how to read a pathology report.

Staging describes how much cancer there is and how far it has travelled — the size of the tumour, whether nearby lymph nodes are involved, and whether it has spread to distant organs. It matters because stage, more than almost anything else, shapes the treatment plan and the likely outcome. The same cancer treated at an early stage and a late stage can call for completely different approaches. Getting the stage right — using examination, imaging, and sometimes surgery — is one of the most important steps before treatment begins.

Most solid cancers are grouped into stages 0 through IV. Stage 0 is very early, confined to where it started. Stages I and II are generally localised and often larger or slightly deeper. Stage III usually means spread to nearby lymph nodes or surrounding tissue. Stage IV means the cancer has spread to distant parts of the body. Doctors often use the more detailed TNM system (tumour, nodes, metastasis) behind these numbers. Blood cancers are staged differently, using their own systems. A higher stage does not automatically mean untreatable — many stage III and even stage IV cancers are treated with excellent, sometimes curative, results.

The main tools are surgery, radiation therapy, and drug-based treatments — and most plans combine them. Drug treatments include chemotherapy, targeted therapy (drugs aimed at a specific molecular fault), hormonal therapy, and immunotherapy (which harnesses the immune system). For some blood cancers, bone marrow transplant and CAR-T cell therapy are options. The right combination depends on the cancer type, stage, molecular profile, and the patient's overall health and priorities. The goal may be cure, long-term control, or comfort — and that goal is agreed with the patient, not assumed.

Chemotherapy is treatment with medicines that kill or slow rapidly dividing cancer cells throughout the body. Because it works everywhere, it is especially useful when cancer has spread or has a high risk of spreading. It is used before surgery to shrink a tumour, after surgery to clear away stray cells and lower relapse risk, as the main treatment for many blood cancers, and to control advanced disease. It is usually given in cycles, with recovery time built in between. Modern anti-nausea and supportive medicines have made it far more tolerable than its reputation suggests — see the full chemotherapy guide.

Because chemotherapy also affects fast-growing normal cells, common side effects include fatigue, nausea, hair loss, low blood counts (raising the risk of infection, anaemia, or bleeding), mouth sores, and changes in appetite or bowels. Which ones occur, and how strongly, depends entirely on the specific drugs and doses — many patients continue working and daily life through treatment. Most side effects are temporary and reversible, and the majority are now preventable or manageable with supportive medicines. Report fever, uncontrolled vomiting, or breathlessness promptly, as these need same-day attention.

Radiation is a local treatment, so most side effects are limited to the area being treated. The commonest are tiredness and a sunburn-like reaction of the skin over the treated site, plus effects specific to the region — for example a sore throat with head-and-neck radiation, or bowel and bladder irritation with pelvic radiation. These tend to build up over the course of treatment and settle in the weeks after it finishes. A smaller number of late effects can appear months later, which is why follow-up matters. Your radiation oncologist tailors the plan to spare healthy tissue as much as possible.

Yes — many cancers can be cured, especially when caught early and treated properly. Some, such as certain leukaemias, lymphomas, testicular cancer, and early-stage solid tumours, are curable even when advanced. For others, cure may not be realistic, but the cancer can often be controlled for years as a long-term condition, with good quality of life. Doctors sometimes prefer words like "remission" or "no evidence of disease" because we monitor for recurrence, but for practical purposes many patients are cured. The honest answer always depends on the specific cancer, its stage, and how it responds — and that is a conversation worth having directly.

It can. A recurrence means cancer returns after a period of being undetectable, either at the original site, nearby, or elsewhere in the body. It happens because a small number of cancer cells can survive treatment while being too few to detect — which is exactly why follow-up visits, scans, and sometimes maintenance treatment continue after the main course ends. The risk of recurrence varies widely by cancer type and stage, and it falls the longer you stay disease-free. If cancer does return, it is not a dead end; there are often effective further treatments.

Yes — screening aims to find cancer early or prevent it, before symptoms appear, and it saves lives for several common cancers. In general: breast cancer screening (mammography) for women from around age 40 to 50; cervical screening (Pap or HPV testing) for women from their 20s or 30s; and colorectal screening from age 45 for average-risk adults. People with a strong family history or known risk factors should start earlier and screen more often, guided by a doctor. Screening is for people without symptoms; if you already have a symptom, that needs evaluation, not screening.