Bottlenecks of the field

There is barely enough of the radioactive metal actinium-225 in the world to treat a few hundred patients a year, even though several new cancer drugs need it. New ways of making it are being built, but they are not yet running at full scale.

There are so many new radioactive cancer drugs now being tested that the trials themselves compete with each other, and with approved treatments, for the same scarce radioactive material, the same specially licensed hospital rooms, and the same trained staff. Sometimes a trial has to pause enrolling new patients simply because the isotope has run out.

Making the pure form of lutetium-177 used in cancer drugs like Pluvicto requires starting from a rare, heavily purified metal called ytterbium-176. Almost all of the world's supply of that starting material has come from one country, which is a risky place for the whole medicine to depend on.

Even where the radioactive medicine itself is available, giving it to a patient needs a specially shielded room, lead-lined equipment, and a toilet that can hold radioactive waste safely. Most hospitals only have one or two of these set up, which limits how many patients they can treat each week.

Cell therapies take weeks to make for one patient and cost hundreds of thousands of dollars. Isotopes run short.

Most of the world's everyday nuclear medicine scans depend on a radioactive metal, molybdenum-99, made in a handful of ageing research reactors. When one of them breaks down, hospitals thousands of miles away run short of scans within days because the material decays so fast it cannot be stockpiled.

Radioactive cancer treatments need specially trained technologists and physicists to prepare and check every dose, and there simply are not enough of them. Hospitals in Europe, the US and Canada are all reporting job vacancies that stay open for months.

Getting a patient from 'this treatment might help you' to actually receiving it can take weeks or months, because the scan, the specialist review and the treatment often happen at different places, and not every hospital is equipped to give the treatment at all.

Most drug doses were chosen as the highest a person can tolerate, which is often more than they need.

In the US, only specially trained doctors are legally allowed to give radioactive cancer treatments. Whether there are enough of these doctors to keep up with demand is genuinely disputed: regulators and physician groups have looked at the numbers and reached different conclusions.

Radioactive medicines keep losing strength from the moment they are made, so a doctor prescribes a specific amount to arrive at a specific time. If a flight is delayed, an airline refuses the cargo, or customs holds the package for even a few hours, the dose can decay below the amount a patient needs and has to be thrown away.

Doctors give almost every patient the same fixed amount of radioactive drug, rather than measuring how much radiation each person's tumour and organs actually absorb and adjusting the dose. Personalising the dose might work better for some patients, but nobody has yet proven it clearly enough for it to become the standard of care.

Every radioactive treatment leaves behind radioactive waste, such as used vials and, for a short time, the patient's own urine, which has to be safely stored until it stops being radioactive. The rules and the physical space needed for this differ from hospital to hospital and country to country, and building enough of that safe storage takes time.

In the US, insurance pays extra for a new radioactive scan for a couple of years, then that extra payment can suddenly stop, even though the drug still costs the same to make. That cliff has already made at least one scan much harder for patients to get.