Musician Bethan Doci, 38, told people she needed the money to pay for treatment but spent it on holidays, handbags and cars.
Swansea Crown Court heard she was fit and well and made £24,000 a year playing with orchestras.
Doci, of Swansea, admitted 11 counts of fraud from 2010 to 2013 and was jailed for 32 months.
She conned three men out of £357,000 after putting an advert on the Craigslist website saying she needed the cash for treatment.
But she used it to fund holidays to Florida, Spain and the five-star luxury Me Melia hotel in Mexico.
Retired chartered accountant Liam Donnelly, 64, handed over £170,000 and retired businessman Bruce Pilley, 58, was defrauded by £168,000.
She also conned retired Royal Navy officer Neil McKelvie, 56, out of £30,000 - although she repaid some of the cash.
Doci, who has performed with the Royal Shakespeare Company and concerts "around the world", would show people fake doctors' notes.
Mr Donnelly told police Doci caught him at a "terrible time in his life" after his wife died from skin cancer, so he handed over his life savings.
Doci - who performs under the name of Bethan Morgan - would exchange emails and texts with her victims, but they rarely spoke to her.
Prosecutor Catherine Richards said: "Her lies and deception became more and more elaborate."
Paul Spreadborough, defending, said: "She has feelings of true remorse and guilt over the years. She was gaining a professional reputation as a violinist and was a dedicated performer.
"But she was caught in a classic spiral of lies, debt and deceit. She fell into a pattern and fell deeper and deeper."
Judge Keith Thomas said: "You committed these offences in a callous and heartless manner, saying you were suffering from cancer and needed treatment which you couldn't afford.
"Your victims were devastated, especially Mr Donnelly who you treated particularly cruelly by taking all his life savings."
The court heard Doci spent all the money and had no assets, so she was ordered to repay a nominal £1.
A violinist has been jailed for conning £350,000 out of people after pretending to have cancer.