Balancing risk and benefit
Long-term follow-up is not just for transplant survivors. Many cancer therapies are tracked for years or decades after patients receive treatment. For some, like immunotherapy and other therapies that involve genetically modified cells, the U.S. Food and Drug Administration strongly recommends a 15-year follow-up period to understand the new therapies’ possible delayed effects, Martin said.
Long-term tracking studies are necessary to understand whether a cure is really a cure. When bone marrow transplantation was first developed at the Hutch in the 1960s and ‘70s, it took several years of tracking survivors for researchers to understand that the procedure was working to cure leukemia.
And sometimes, following patients who were treated with older therapies lays the groundwork for a better understanding of new treatments, too. Fred Hutch clinical researcher Dr. Mazyar Shadman led a study published earlier this week in the Journal of Clinical Oncology, describing 10 years of follow-up data from a large clinical trial for patients with follicular lymphoma.
Known as SWOG S0016, the trial was led by former Fred Hutch lymphoma researcher, the late Dr. Oliver Press, who holds the David and Patricia Giuliani/Oliver Press Endowed Chair in Cancer Research. The trial started in 2001 and included more than 500 patients with previously untreated, advanced follicular lymphoma. SWOG S0016 compared a standard combination of chemotherapy drugs commonly referred to by the acronym CHOP, combined with either the immunotherapy drug rituximab, a lymphoma-specific antibody, or a similar antibody-bearing a radioactive molecule. R-CHOP, as the combination of the chemotherapies and rituximab is called, had newly become the standard of care at the time, although it’s not used as frequently these days.
This blood cancer is generally very slow-growing, Shadman said, making lengthy tracking of follicular lymphoma treatments especially important. The study’s initial results, published in 2013, found that both groups of patients — those who’d received rituximab and those who had received the radioimmunotherapy — did very well, with no significant difference in overall survival. Approximately 90 percent of patients were still alive five years after treatment.
Now, after having followed the patients for 10 years, the longer-term results aren’t turning any of those older findings on their head, Shadman said. The two groups continue to do well — about 80 percent of the trial participants were still alive in 2016. Those who’d received rituximab had a slightly higher chance of their cancer coming back as compared to those treated with the radiolabeled antibody, but that didn’t affect their overall survival, the researchers found.
Multiple levels of reassurance
Shadman, who also treats patients with lymphoma and other blood disorders at Seattle Cancer Care Alliance, Fred Hutch’s clinical care partner, finds multiple levels of reassurance from tracking this study for so long. For one, he now can tell his patients exactly what they can expect in terms of their chances for long-term survival if they are treated with the type of combination therapy studied in SWOG S0016, more broadly known as chemoimmunotherapy.
But the follow-up is important not just for patients treated exactly like those in the study, he said. The findings will also be useful as a baseline for comparison. There are a lot of new targeted therapies for follicular lymphoma on the scene or coming down the pike, drugs such as lenalidomide, venetoclax, ibrutinib, and idelalisib, all of which either boost the immune system to act against cancer cells or target specific proteins involved in some follicular lymphomas and other blood cancers.
Researchers and patients alike are excited about the potential of these drugs to improve cancer treatment, but studies like Shadman’s are necessary to provide the context, he said.
“It’s very important to know what are your historical data, what’s your benchmark,” he said. “If you don’t know how well you can do with chemoimmunotherapy, you don’t know if there’s any room for improvement.”
Likewise, similar studies will be needed for those new therapies themselves.
“If I have a new drug today and I give it to my patients and their lymphoma goes away, but I’ve only followed them for six months, what do I know about the risk of other types of cancers five years from now? What if their lymphoma comes back? How difficult is it going to be to treat? These are real issues,” Shadman said. “In medicine, there should be an ongoing assessment of risk and benefit. If you don’t know your long-term risks, you don’t know how reasonable it is to accept that short-term benefit.”