Wessex Cancer Trust, which is a self-funded charity, has launched an appeal to raise the funds by 31st January, 2020, or risk closure.
The Trust provides free emotional and practical support to anyone living with cancer in Hampshire, Dorset and the Isle of Wight.
The charity has supported local families for close to 40 years and has seen a 30% increase in demand for its services this year.
They have also been hit by a 65% reduction in people leaving a gift in their will, while shop sales have fallen by 15%.
The Trust supports around 11,000 people annually through four cancer support centres.
Professional counselling, complementary therapies and support groups are among the services provided.
Barry Rinaldi, Wessex Cancer Trust’s Chairman, said:
“Since 1981 Wessex Cancer Trust has been there for local people at a particularly tough time in their lives.
"Being told you have cancer is devastating. Living with it can be incredibly lonely and affects all aspects of your life.
"We work tirelessly to give people a safe place to get support regardless of age, gender or type of cancer, away from a hospital environment.
"We do not receive any Government funding and rely on voluntary donations and fundraising to run our services.
"One in two of us will get cancer and an increasing number of us are living longer after a cancer diagnosis meaning more and more people will need us in the future.
"Throughout 2019, we have been working hard to ensure we can continue to meet the growing and diverse needs of people living with cancer in the future.
"We have recently launched a new strategy which outlines how we will evolve our services to care for every single person in a way that best meets their individual needs.
"In the long term, this will enable us to help more people and improve our financial sustainability. But we’ve been struggling to stabilise our financial situation.
"We have worked tirelessly to explore all income sources and make cost savings, but now have no other option than to ask for urgent help.
"This is not a Christmas appeal or a planned campaign, it is a last resort.
"We have never needed to run a crisis appeal before but now urgently need to raise £600,000 by 31 January 2020. If we fail, we will not be there for the 165,000 people who will be facing a cancer diagnosis by 2030 and their loved ones.
"This would be a heartbreaking end to almost four decades of crucial support and it is particularly upsetting given our plans for the future of local cancer care.
"For almost 40 years we have supported local families through their toughest times.
"Now we are facing ours and urge you to help us if you can.”
For more information about the appeal, you can visit www.wessexcancer.org.uk/savewessexcancertrust.