More than two dozen cancer groups say that about half the world's population doesn't have adequate access to painkillers because of restrictive laws meant to combat drug abuse.
In a global survey released on Thursday, The European Society for Medical Oncology and partners estimated millions of cancer patients aren't able to get seven cheap medicines considered essential for pain relief, including codeine and morphine.
The survey was largely based on questionnaires sent to doctors not linked to the government in more than 100 developing countries, asking about the availability of painkillers.
Nathan Cherny, the report's lead author, said it was "catastrophically difficult" in many countries to relieve cancer pain. He said the drugs were also needed for other things like palliative care, obstetric and chronic pain.