Side effects, symptom first

Fatigue is the most common side effect of cancer treatment and is different from ordinary tiredness: rest does not fix it. It usually improves after treatment ends. Anaemia, thyroid problems, poor sleep and low mood make it worse and are treatable.

Feeling or being sick is expected with many treatments and is usually well controlled with the anti-sickness medicines given with them. Uncontrolled vomiting leads to dehydration and missed oral medicines.

Neutrophils are the white cells that fight bacteria. Chemotherapy and some targeted drugs lower them for a few days after each dose, which is when infections take hold.

Loose or frequent stools are common with many chemotherapies, kinase inhibitors, ADCs and immunotherapy. The danger is dehydration, and with immunotherapy the possibility of colitis.

Rashes are among the most common side effects: acne-like with EGFR inhibitors, itchy or blotchy with immunotherapy, sun-sensitive with some kinase inhibitors. Rarely a rash is the start of a severe blistering reaction that is a medical emergency.

Many drugs stress the liver. Blood tests usually pick this up before symptoms appear, which is why they are checked before each dose. Immunotherapy can cause a hepatitis that needs steroids.

Red cells carry oxygen. When treatment lowers them, people feel tired, breathless on stairs, dizzy or cold.

Many treatments lower the white blood cells that fight infection. A fever can then be the only sign of a serious infection, and it can become life-threatening within hours.

Aching joints and muscles are common with aromatase inhibitors, taxanes, growth-factor injections and immunotherapy. Usually manageable, but with immunotherapy they can signal inflammatory arthritis or myositis.

Cancer treatment weakens several parts of the immune system at once, so infections start more easily and can progress faster than in healthy people.

Antibodies and some chemotherapies can trigger a reaction during or within hours of the infusion: flushing, chills, fever, itching, breathlessness, back pain. Most are mild and happen in the unit, where they are treated at once.

Drugs that block VEGF (bevacizumab, most multi-kinase inhibitors) raise blood pressure in most people who take them. It is usually controllable with tablets and needs checking regularly.

Platelets stop bleeding. When they fall, small bruises appear without injury and cuts and nosebleeds take longer to stop.

Taxanes, platinums, vinca alkaloids, bortezomib and MMAE-containing ADCs damage the long nerves to the hands and feet, causing tingling, numbness, pain or clumsiness. It can be permanent if the drug is continued, so early reporting matters.

After CAR-T cells or bispecific T-cell engagers, activated immune cells release a flood of signalling proteins. It starts with fever, then sometimes low blood pressure and low oxygen. It is treated with tocilizumab and steroids and is why the first doses are given in hospital.

Many chemotherapies and some ADCs cause partial or complete hair loss; it usually regrows within months of finishing treatment. Scalp cooling reduces it with some regimens.

Chemotherapy, mTOR inhibitors and some ADCs damage the fast-dividing lining of the mouth, causing soreness and ulcers that make eating hard and let infection in.

Immunotherapy, some ADCs (especially the deruxtecan family), EGFR inhibitors, mTOR inhibitors and radiotherapy can inflame the lungs. Early it looks like a mild dry cough; late it can be fatal, so the labels say to report symptoms immediately.

Blood tests often show changes with no symptoms: low potassium, magnesium or phosphate, high cholesterol or triglycerides, low albumin, or high white cells. The team uses them to adjust treatment or add a supplement.

Fluid can collect in the ankles, around the eyes, in the abdomen or around the lungs with steroids, docetaxel, imatinib, dasatinib, some IDH inhibitors and heart or kidney strain.

Capecitabine, fluorouracil, liposomal doxorubicin and multi-kinase inhibitors cause redness, tenderness, peeling and sometimes blisters on the palms and soles.

Some kinase inhibitors (including ribociclib, vandetanib and many others) lengthen the QT interval on the ECG, which can trigger dangerous rhythms. BTK inhibitors raise the risk of atrial fibrillation.

Appetite falls with many treatments and with the cancer itself. Losing weight during treatment weakens the body and makes side effects harder to tolerate.

Immunotherapy and some kinase inhibitors can make the thyroid overactive briefly and then underactive, usually permanently. It is picked up on blood tests and treated with a daily tablet.

Low platelets, blood thinners, BTK inhibitors and VEGF inhibitors all make bleeding more likely. Most bleeding is minor (gums, nose, bruises) but some is not.

After CAR-T or bispecific T-cell engagers, the brain can become inflamed (ICANS): trouble finding words, confusion, drowsiness, shaky handwriting, and rarely seizures. It usually starts within the first two weeks and is treated with steroids. Some chemotherapies (ifosfamide, high-dose cytarabine) cause a different reversible encephalopathy.

Anthracyclines and HER2-targeted drugs can weaken the heart's pumping (cardiomyopathy); immunotherapy can inflame it (myocarditis), which is rare but can be fatal and usually starts within the first weeks.

Some ADCs (belantamab, tisotumab, mirvetuximab) damage the surface of the eye; MEK and FGFR inhibitors can cause fluid under the retina; steroids cause cataracts. Eye checks before and during treatment are part of the plan for these drugs.

Cisplatin, some antibodies, radioligands and immunotherapy can strain or inflame the kidneys. Protein in the urine is an early sign with VEGF inhibitors. Dehydration from vomiting or diarrhoea makes all of this worse.

Some treatments lower all three blood cell lines at once: white cells (infection), red cells (tiredness and breathlessness) and platelets (bleeding). After CAR-T and some radioligands this can last for weeks or months.

Shortness of breath has many possible causes during treatment: anaemia, infection, fluid around the lungs, a blood clot, heart strain or lung inflammation. New breathlessness always needs a reason.

A small number of people treated with certain drugs (alkylating chemotherapy, PARP inhibitors, some CAR-T products, tamoxifen, BRAF inhibitors) develop a second, different cancer years later. The risk is small and is weighed against the benefit of treatment.

Headaches are common with many drugs and with anti-sickness medicines. Rarely they signal high blood pressure, a bleed, brain swelling or an inflamed pituitary gland on immunotherapy.

Steroids, PI3K and AKT inhibitors, enfortumab vedotin and, rarely, immunotherapy raise blood sugar. Immunotherapy can cause sudden insulin-dependent diabetes.

Trials report the share of people who had at least one severe (grade 3 or higher) side effect of any kind. Grade 3 means severe or medically significant, often needing hospital treatment; grade 4 is life-threatening; grade 5 is death.

Cancer itself, surgery, some chemotherapies, hormone therapies (tamoxifen), immunomodulators (lenalidomide) and CDK4/6 inhibitors raise the risk of clots in the leg veins, which can travel to the lungs.

Intravesical treatments (BCG, gene therapy, drug-eluting devices) irritate the bladder lining; cyclophosphamide and ifosfamide can cause bleeding from it. Burning, urgency and frequency are common and usually settle.

Anti-sickness medicines, opioid painkillers, vincristine and some other drugs slow the bowel. Untreated it causes pain, nausea and, rarely, a blocked bowel.

With IDH inhibitors, menin inhibitors, arsenic trioxide and retinoids, leukaemia cells maturing all at once can trigger fever, breathlessness, fluid retention and organ strain. It carries a boxed warning on these drugs and is treated with steroids; it can be fatal if missed.

Hormone therapies for breast and prostate cancer and some chemotherapies cause hot flushes, vaginal dryness, loss of libido, erectile difficulty, and can reduce fertility. These affect quality of life and are worth raising even though they are not dangerous.

Radioligand therapy that reaches the salivary glands (PSMA-targeted) and radiotherapy to the head and neck reduce saliva. It affects taste, swallowing and dental health.

Checkpoint inhibitors release the immune system, which can then attack any organ: skin, bowel, liver, lungs, glands, joints, heart or nerves. Most reactions are treatable with steroids if they are reported early, and they can start months after the last dose.

Taxanes, EGFR inhibitors and some ADCs cause ridged, discoloured, loose or infected nails. It usually recovers after treatment.

Immunotherapy can make the immune system attack the lining of the bowel, causing diarrhoea, cramps and sometimes blood. It is treatable with steroids if caught early and can perforate the bowel if it is not.

Heartburn, bloating and cramps are common with oral targeted drugs. Somatostatin analogues can cause gallstones.

Lymphocytes are the white cells that fight viruses and some fungi. Low counts raise the risk of shingles, pneumonia and other opportunistic infections, often for months.

Metallic or absent taste is common with chemotherapy and with the GPRC5D bispecific talquetamab. It usually recovers after treatment but can reduce appetite meanwhile.

Immunotherapy can inflame the pituitary or adrenal glands, and abiraterone or long steroid courses can suppress them. The result is too little cortisol, which is dangerous if it is not replaced, especially during illness.

Treatments that remove B cells (CAR-T, bispecifics, anti-CD20 antibodies) also remove the cells that make antibodies, so ordinary infections become more frequent and last longer. Replacement immunoglobulin is sometimes given.

Dehydration, infection, cytokine release syndrome, bleeding and some drugs can lower blood pressure. Fainting always needs a cause.

Aromatase inhibitors, androgen deprivation, steroids and early menopause thin the bones over years. Bone density scans, calcium, vitamin D, exercise and bone-protecting drugs reduce fracture risk.

A rare reaction, seen with some immunotoxins and cytokines, in which fluid leaks out of small blood vessels: swelling, rapid weight gain, low blood pressure and low albumin. It is treated in hospital.

Cisplatin and, less often, carboplatin can cause permanent hearing loss and ringing in the ears, particularly at high frequencies and in children. Hearing tests are part of monitoring.

Difficulty concentrating, forgetfulness and low mood are common during and after chemotherapy and hormone therapy. They are real, usually improve with time, and respond to exercise, sleep and psychological support.

Some kinase inhibitors, asparaginase and immunotherapy can inflame the pancreas. Blood tests often show it before symptoms do.

Some intensive treatments carry a measurable risk of death from the treatment itself, mainly from infection during profound neutropenia, bleeding, or organ toxicity. Trials report this so that it can be weighed against the benefit.

When many cancer cells die quickly (venetoclax, some chemotherapies, bispecifics in bulky disease), their contents flood the blood and can damage the kidneys and heart. It is why venetoclax is started with a slow dose ramp, fluids and blood tests.

Steroids, hormone therapies and some targeted drugs cause weight gain. Sudden gain over days is fluid rather than fat and can signal heart, kidney or liver strain.

A rare but life-threatening hole in the bowel wall, seen mainly with drugs that block blood-vessel growth (VEGF inhibitors) and with severe immune colitis.

Rare muscle destruction that releases muscle protein into the blood and can damage the kidneys. Seen with some kinase inhibitors, immunotherapy myositis and statin interactions.

Pain from the cancer or the treatment should be controlled. Untreated pain is not a sign of strength, and telling the team early gives more options.

Drugs that block blood-vessel growth (VEGF inhibitors) slow healing of surgical wounds. They are normally stopped for several weeks around any operation.

A temporary worsening of symptoms (bone pain, a swelling lymph node, a rash) in the first weeks of some hormone therapies and immunomodulators as the treatment starts to act. It settles, but it can be mistaken for progression.

Hoarseness is common with VEGF-pathway kinase inhibitors and with some ADCs. It is rarely dangerous but can signal vocal-cord or thyroid problems.