Hundreds lined up Saturday at a Cambridge stem cell clinic for Katie Herron, a four-year-old girl battling cancer for the second time.

“We’re praying to God Almighty that this works and we can get our little girl back home and she can lead a normal life,” says Paul Herron, Katie’s dad.

He notes his daughter, who was diagnosed with acute lymphoblastic leukemia, can’t beat the disease with chemotherapy and medication alone.

Her only hope is a stem cell donor.

“If someone needs a stem cell transplant it’s usually their last hope of survival for the disease that they’re trying to combat,” says Char Cairns with the One Match Stem Cell and Marrow Network.

Fortunately for Katie and her family, there is no shortage of eager would-be donors – many people cued up at Saturday’s clinic before it even opened its doors.

“It’s not that long when it comes down it,” says Dave Partridge, who stood in line for 50 minutes. “When you think about what somebody is suffering through. An hour wait? Not a problem.”

Even an Olympian turned out to get swabbed.

“She has been through so much and she is such a fighter,” says gymnast and Cambridge resident Victoria Moors. “It changes me as a person. She’s just an inspiration to me,”

According to officials with One Match, the optimal donor is a male between the ages of 17 and 35. Those who were unable to attend Saturday’s clinic are encouraged to register online.