What to know about cobalt radiotherapy

The radioactive source stays inside the treatment machine; it does not enter the body during external-beam treatment. The machine directs radiation from planned angles while the patient remains still on the treatment couch.

Radiation damages genetic material within cells. Cancer cells are often less able than healthy cells to repair that damage, so repeated carefully calculated treatments can reduce or control a tumour. Healthy tissue in the beam path can still be affected, which is why planning, positioning and dose checks matter.

Cobalt machines produce radiation from natural decay rather than generating high-energy X-rays electrically. This changes the equipment and some planning characteristics, but the clinical aim remains targeted radiation delivery. Suitability depends on the tumour site, depth, treatment goal, available technology and the radiation oncologist's plan.

Planning usually includes imaging and a reproducible position. A fitted mask or body support may help keep the target aligned. Follow instructions about skin care, eating, bladder filling or bowel preparation because these vary with the treated area.

During delivery, staff leave the room but continue to see and hear you. Radiation cannot be felt as the beam is given. External cobalt treatment does not make you radioactive afterward, so ordinary contact with family is generally possible unless the clinical team gives separate precautions for another therapy.

Effects depend on the body area treated and can build over a course. Tiredness and a skin reaction within the treatment field are possible; treatment near the head, chest, abdomen or pelvis can cause different local symptoms. Report changes early so the team can check the cause and provide relief.

Contact the treatment service urgently for fever when the team has warned of infection risk, uncontrolled vomiting, inability to drink, rapidly worsening pain, severe breathlessness, sudden neurological symptoms or a moist, blistered skin reaction. Call emergency services for collapse, a seizure, sudden weakness or major breathing difficulty.

Ask why a cobalt machine suits the target, whether treatment aims to cure, control or relieve symptoms, which nearby organs influence planning, what preparation is required and how side effects will be managed. Confirm whom to contact if symptoms arise between appointments and whether any medicines need adjustment.