The epidemiological study – presented at study at the 11th Annual AACR International Conference – suggests that the risk for developing pediatric acute lymphoblastic leukaemia increases when babies are fed formula for longer.
"For every month that a child was fed formula, taking into account other feeding practices, we found that the risk for this type of cancer was higher," said Jeremy Schraw of the University of Texas, USA.
"If a baby is fed only formula, he or she will not be getting any immune factors from the mother, which could be leading to this greater risk," he suggested.
The team found that the risk for developing acute lymphoblastic leukaemia (ALL) increased by 16% for every month of formula feeding.
In addition, for each month the introduction of solid foods was delayed, the risk increased by 14%.
Schraw and his team analysed data from 284 control children and 142 children who had been diagnosed with ALL.
Compared with controls, children diagnosed with ALL started solid foods significantly later, more of their mothers smoked during pregnancy and they had a longer duration of formula feeding.
"One explanation for this co-risk may be that it's the same effect being picked up twice," said Schraw. "Children being given solid foods later may be receiving formula longer."
Future research should address the factors influencing prolonged formula feeding and delay in solid food introduction, according to the researchers.