The two deaths that appear to be the greater source of concern in the study were one patient with acute heart failure and another with respiratory failure.

FORBES: Pfizer's Key Drug Walks A Tightrope

The septic shock had left her with heart and respiratory failure as well as dry gangrene of her foot, which would have to be amputated.

NEWYORKER: Letting Go

Both are cancer patients but opioids are equally needed to help patients with a range of other debilitating conditions such as heart failure, kidney and respiratory illness and neurodegenerative disorders.

BBC: Morphine and pain control