Putting it to the test
The clinical trial that Dr. Reed and colleagues have initiated, officially titled “Evolutionary Inspired Therapy for Newly Diagnosed, Metastatic, Fusion Positive Rhabdomyosarcoma,” (NCT04388839) contains four arms: three experimental and one active comparator arm.
“We won’t randomize; we don’t feel that it would be fair to randomize patients, because these arms are so different from each other,” Dr. Reed said.
Arm A is the experimental first-strike arm, a 42-week course containing cyclophosphamide delivered intravenously over 60 minutes at a dose ranging from 220 mg to 1200 mg, vinorelbine delivered in an IV push over 6-10 minutes with a dose ranging from 4 mg to 25 mg, and actinomycin D administered via IV over 3-5 minutes at a dose ranging from 0.025 mg to 0.04 mg.
“The idea is that we take the standard of care, and we add a drug – vinorelbine – to make it stronger,” Dr. Reed said. “The idea is that the resistant cell, the cell that escapes, if we start hitting it on day 1 with vinorelbine, we might be able to drive it to extinction.”
Arm B, the second experimental arm, is the second-strike and maintenance arm, in which patients will receive conventional doses of vincristine, actinomycin D, and cyclophosphamide (VAC) until complete response (CR) for 12-42 weeks, and will then be switched to up to 2 years of maintenance with vinorelbine and oral cyclophosphamide.
“Vinorelbine will be added when the cancer is declining or first goes into remission. We try not to wait 42 weeks, which is too long we think, by which time the cancer may be fully adapted and resistant,” he explained.
Arm C is the adaptive therapy arm, in which patients will receive VAC that starts and stops based on response, with the goal of prolonging time to disease progression rather than achieving CR.
Arm D is the active comparator arm, consisting of conventional chemotherapy based on published clinical trials, such as VAC for 42 weeks, or other standard-of-care regimens that may include irinotecan, doxorubicin, ifosfamide, and/or etoposide.
A change in thinking
Dr. Reed acknowledges that Arm C, the adaptive therapy arm, “definitely represents a change in thinking for pediatric oncology.”
“The idea is that if you could do this perfectly well, you would be able to take a patient who is diagnosed today and essentially ‘pause’ their disease for a while. Then 5 years from now, if there is a better medicine, you would have gotten that patient to that medicine.”
The optimal approach to treating metastatic fusion-positive rhabdomyosarcoma may be similar to that used for treatment of acute lymphoblastic leukemia, with induction, consolidation, and maintenance and the option of delayed intensification, he said.
“But we’re so far away from knowing which series to do that we just need to show that any series – any changing it up – is helpful.”
Dr. Reed said that when he started presenting the concept of adaptive therapy in clinical meetings in 2017, “I was told to come up with a better idea. There were several people who instantly got it, but most people would instantly get angry.”
The common refrain was that adaptive therapy was “giving up.”
But minds began to change in 2018, following presentation at the annual meeting of the American Society of Clinical Oncology of a European study showing that adding 6 months of low-dose chemotherapy maintenance to standard therapy improved the 5-year overall survival rate of pediatric rhabdomyosarcoma from 73.7% to 86.6%.2
Before presenting the idea of adaptive therapy to his colleagues, he ran it by the parents of children with advanced sarcomas, and many were on board with it, he said.
Ricky Huff said that had the option of adaptive therapy been available for Theo, he and his wife would have been willing to try it.
“Of course, everyone has the ability in hindsight to apply critical thinking to decisions that you made or could have made,” he said. “I think is true for many parents, who if they’re presented with information about options will say ‘well if there’s a 1 percent chance, I want that chance for my child, especially for a 5-month-old.”
The decision to choose adaptive therapy is a difficult decision to make, whether for oneself or for one’s son, because it isn’t curative.
“My wife and I have since had a conversation about this, and I do think we would have considered it, although through a lot of difficult conversations,” he said.
“After we got the pathology, knowing that it was metastatic, fusion-positive, and given his age, just doing a brief literature review on my own, I knew what we were up against using 20-year-old treatments, and that the chance of a cure was very, very small.”
If parents of children with metastatic, poor-prognosis rhabdomyosarcoma could be made to understand that adaptive therapy would entail shorter and fewer hospital stays, and cumulatively less toxic chemotherapy, and could prolong the lives of their children, the option might be more acceptable, he said.
And as Dr. Reed mentioned, prolonging time to progression offers hope of additional therapies to come.
“The whole time that my son was being treated, I hoped that there was going to be something else that came out, that a new trial would be launched because they found a way to drug a mutation, or treat it with immunotherapy – something that was going to give us a better option.”
Asked whether he would be willing to share his experiences in this article, Mr. Huff said that “I am willing to, in whatever small way I can, make an impact, and hopefully save another family from what we experienced.”