A recently published case study from an ongoing clinical trial has revealed an experimental immunotherapy treatment has cured a breast cancer patient. The 49-year-old patient with advanced breast cancer was given three months to live before enrolling into the trial. Within weeks her tumors had disappeared and 22 months later she is still in complete remission.

The treatment being trialed is a modified form of what is called adoptive immunotherapy. The technique generally works by harvesting a person's immune cells. Once collected, the cells are armed with cancer-recognizing molecules so that when they are reintroduced into the patient's body they can home in on the tumors and kill them off.

This form of immunotherapy has frustratingly been inconsistent in early clinical trials, working well with some patients on certain cancers but proving less effective on others. In particular, the treatment hasn't been hugely successful in treating common epithelial cancers. These cancers tend to harbor lower levels of mutations that are fundamental to programming the immune cells to hit their targets.

The specific form of adoptive immunotherapy being trialed here recruits cells called tumor-infiltrating lymphocytes (TILs). The treatment involves sequencing the DNA and RNA from a patient's tumor to find mutations that are unique to it. The extracted TILs from the patient are then tested against the particular mutations to find lymphocytes that can specifically recognize and attack those mutations.

Once the most effective TILs are identified they are replicated in enormous numbers before being infused back into the patient. In this case study the researchers observed the tumors disappearing at a remarkable rate. Judy Perkins, the patient in the trial, recently remarked to the BBC, "About a week after [the therapy] I started to feel something, I had a tumor in my chest that I could feel shrinking. It took another week or two for it to completely go away."

Steven Rosenberg, who is leading the ongoing clinical trial, suggests this is an exciting early result, highlighting that this kind of treatment is not cancer-type specific but can be applied to a broad variety of different cancers.

"All cancers have mutations, and that's what we're attacking with this immunotherapy," says Rosenberg. "It is ironic that the very mutations that cause the cancer may prove to be the best targets to treat the cancer."

Despite this extraordinary case study it is still very early days for the treatment, with the current clinical trial due to run until at least 2023. After that, a Phase 3 trial will need to broaden the volume of patients treated to verify any positive results. So, realistically a broad clinical application could be up to a decade away ... and that's assuming everything goes right.

An early form of adoptive immunotherapy, called CAR-T therapy, exhibited severe side effects across many of its clinical trials, including some deaths. The therapy also displayed some impressively positive response rates, promising at the very least an extra possibility for patients where pre-existing treatments have failed.

Last year, the first immunotherapy of this kind was approved for use by the FDA. The treatment's approval was undeniably a milestone for this new kind of therapy, but alongside the approval came a striking price tag. Kymriah, for young patients with a type of blood and bone marrow cancer, was initially costed at nearly half a million US dollars per treatment.

The company making the drug, Novartis, suggested a single treatment takes 22 days to produce. This ushered in a fleet of questions over the future of personalized medicines, and whether they can ever be widely implemented. Each treatment is hugely labor-intensive to produce and will inevitably come with these kinds of hefty price tags.

This truly impressive case study is an undeniably exciting early report from an ongoing clinical trial. Scientists are certainly on the right track to finding an effective way to battle cancer, but a lot more work lies ahead to verify these treatments are safe and effective for a large number of people.

The case study was published in the journal Nature Medicine.

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