As researchers learn more in the fight against cancer, the next big advancement in treatment could actually be a vaccine which can shrink tumours and stop cancer from coming back, according to experts in the US.
After decades of trying with limited success, scientists say their research has reached a turning point, with predictions that more vaccines will be available in as little as five years.
Though they're being called vaccines, they aren't traditional vaccines that prevent disease. Instead, these jabs shrink tumours and stop cancer from coming back.
Types of cancer being targeted with the experimental treatment include breast and lung cancer, with gains reported this year for melanoma, the deadly skin cancer, and pancreatic cancer. Volunteer patients have said they are taking part not only in the hopes of shrinking their own tumours, but to help future cancer patients.
Dr James Gulley helps lead a centre at the National Cancer Institute which develops immune therapies, including cancer treatment vaccines. He said: "We're getting something to work. Now we need to get it to work better."
After years of research, scientists have a better understanding than ever of how cancer hides from the body's immune system. Cancer vaccines, like other immunotherapies, boost the immune system so it can find and kill cancer cells. Some new ones use mRNA, which was developed for cancer but used first for Covid vaccines.
For a vaccine to work, it needs to teach the immune system's T cells to recognise cancer as a danger, explained Dr Nora Disis of UW Medicine's Cancer Vaccine Institute in Seattle. Once the T cells have been trained, they can travel anywhere in the body to hunt down danger.
"If you saw an activated T cell, it almost has feet," Dr Disis explained. "You can see it crawling through the blood vessel to get out into the tissues."
Patient volunteers, such as 50-year-old Kathleen Jade, are vital for the research. She learned she had breast cancer in February, just weeks before she and her husband were set to leave Seattle for an around-the-world adventure.
But, instead of sailing their 46ft boat, Shadowfax, through the Great Lakes toward the St Lawrence Seaway, she was sat on a hospital bed waiting for her third dose of an experimental vaccine. She's been receiving the vaccine therapy to see if it will shrink her tumour before surgery.
"Even if that chance is a little bit, I felt like it's worth it," she said.
Progress has been challenging for the treatment vaccines. The first, Provenge, was approved in the US in 2010 to treat prostate cancer that had spread.
It requires processing a patient's own immune cells in a lab before giving them back intravenously. There are also treatment vaccines for early bladder cancer and advanced melanoma.
Early cancer vaccine research faltered as cancer outwitted and outlasted patients' weakened immune systems, said vaccine researcher Olja Finn, based at the University of Pittsburgh School of Medicine.
"All of these trials that failed allowed us to learn so much," Ms Finn said.
As a result, she now focusing on patients with earlier disease since the experimental vaccines did not help with more advanced patients. Her group is planning a vaccine study in women with a low-risk, non-invasive breast cancer called ductal carcinoma in situ.
More vaccines that prevent cancer may appear in the future too. Decades-old hepatitis B vaccines present liver cancer, and HPV vaccines, introduced in 2006, prevent cervical cancer.
In Philadelphia, Dr Susan Domchek, director of the Basser Center at Penn Medicine, is recruiting 28 healthy people with the BRCA mutation for a vaccine test. The mutation is known to increase the risk of breast and ovarian cancer.
The idea is to kill very early abnormal cells before they cause problems. She likens it to periodically weeding a garden or erasing a whiteboard.
Others are developing vaccines to prevent cancer in people with precancerous lung nodules and other inherited conditions that increase cancer risk.
"Vaccines are probably the next big thing" in the fight to reduce cancer deaths, said Dr Steve Lipkin, a medical geneticist at New York's Weill Cornell Medicine. He is leading one effort funded by the National Cancer Institute. "We're dedicating our lives to that", he added.
People with the inherited condition Lynch syndrome have a 60 to 80 per cent lifetime risk of developing cancer. Recruiting them for cancer vaccine trials has been remarkable easy, according to Dr Eduardo Vilar-Sanchez of MD Anderson Cancer Centre in Houston, who is leading two government-funded studies on vaccines for Lynch-related cancers.
"Patients are jumping on this in a surprising and positive way," he said.
Moderna and Merck are jointly developing a personalised mRNA vaccine for patients with melanoma, with a large study to begin this year. The vaccines are customised to each patient, based on the numerous mutations in their cancer tissue.
A vaccine personalised in this way can train the immune system to hunt for the cancer's mutation fingerprint and kill those cells. However, these vaccines will be expensive.
"You basically have to make every vaccine from scratch," said Dr Patrick Ott of Dana-Farber Cancer Institute in Boston. "If this was not personalised, the vaccine could probably be made for pennies, just like the Covid vaccine."
The vaccines under development at UW Medicine are designed to work for many patients, not just a single patient. Tests are under way in early and advanced breast cancer, lung cancer and ovarian cancer. Some results could be seen as soon as next year.
56-year-old Todd Pieper, from suburban Seattle, is taking part in testing for a vaccine intended to shrink lung cancer tumours. His cancer spread to his brain, but he's hoping to live long enough to see his daughter graduate from nursing school next year.
"I have nothing to lose and everything to gain, either for me or for other people down the road," he said.
One of the first to receive the ovarian cancer vaccine in a safety study was Jamie Crase or nearby Mercer Island 11 years ago. She was diagnosed with ovarian cancer at 34, and thought she would die young.
Ms Crase made a will, bequeathing a favourite necklace to her best friend. Now aged 50, she has no sign of cancer, and still wears the necklace.
She doesn't know for sure if the vaccine helped, "but I'm still here."
