At 5am on Saturday, April 20, Amelia Brown, Issy Simmons, Mia Smart and Taylor Dury set off on foot from Birmingham Children's Hospital back towards their Newport homes.
Just two months ago their friend, Anmol Basi, was diagnosed with Hodgkin lymphoma at just 15 years old.
In no time at all, the group of girls banded together in support of Amnol and organised the mammoth undertaking to raise money for Cancer Research UK.
Originally aiming to raise just £500, the teens have exceeded all expectations and raised a staggering £4,092.
After 37 miles on roads, tow paths and public ways, the teens made it back to Burton Borough School at 9pm.
Lisa Kane, the lead practitioner for whole school teaching and learning at the school, was one of many members of staff who greeted the girls at their finish line.
"Everybody was so emotional," Mrs Kane explained: "it was so amazing to see them appear walking down the road.
"Even after all those miles, they were still in really good spirits and all very proud of what they've achieved.
"They still can't believe how much they've raised, it's amazing. When you think their original goal was just £500 - it's really incredible.
"Their families, friends and staff here at the school are so proud of them and what they've achieved."
The charity has expressed its thanks to the teens for their huge undertaking.
Paula Young, spokesperson for Cancer Research UK in Shropshire, said: “We’d like to say a huge congratulations to the girls for their incredible achievement.
"Tackling that distance in one go is quite remarkable for anyone, but to do it at such a young age in response to their friend’s cancer diagnosis shows great compassion and strength of character.
"Every step our researchers make towards beating cancer relies on every pound, every hour and every person so we’d like to thank the girls from the bottom of our hearts.”
The group's fundraising page is still open for donations, which can be made at fundraise.cancerresearchuk.org/page/amelias-giving-page-152544.