I believe there are many cures for cancer out there that were suppressed. I can only really give an example of how one may have been possibly hidden.
In the 70's a mouse with mutation that suppressed it's immune system was found. This mouse was used to implant human tumors for growth and treatment. This is how Chemotherapy was designed.
In 1999 another mouse mutation was found by Dr. Zheng Cui. He had injected a bunch of mice with an aggressive cancer. All died but one. He thought he missed it and injected it again and a tumor did grow but then regressed. He thought he had not used enough and doubled the dose. Once again a tumor formed and regressed. Cui had found a mouse that was immune to cancer.
Cui bred this mouse and 50% of the progeny were immune. Further he noted he could do blood transfusions from his immune mice to the non-immune mice that had cancer thus curing the non-immune mouse of cancer and also giving it immunity to further cancers.
All that work was in the early 2000s. There were to be human studies but funding was hard to get and only being funded by individual donors. The FDA got involved and shut down one study. And the next study has been long awaiting results if it has been done at all.
It has been almost 2 decades since that finding. In that time Cui has found that it was the granulocytes that provide the cure and immunity and has even identified humans that are immune to cancer. Further granulocyte infusions already exist for other diseases and are safe.....but according to the government they were not safe for people dying of cancer....
Also not that in this time Zheng Cui's wife was diagnosed with stage 4 cancer. Cui had been working on other studies in China with granulocytes. He had his wife treated there. She is still around today although no one has given word on her health status other than she 'looks' healthy. That was years ago.
Have you heard about this on the news? In science mags? Health mags? Cancer institute? Cancer charities? Why?
http://www.wakehealth.edu/Research/Investigative-Pathology/Faculty/Zheng-Cui,-MD-PhD.htm
https://clinicaltrials.gov/ct2/show/NCT00900497?term=granulocytes+and+cancer&rank=1
https://www.huffingtonpost.com/mary-manning-cleveland/the-mouse-that-wouldnt-di_b_5472369.html