In 1859, Charles Darwin published “On the Origin of Species,” which outlined his world-shaking theory of evolution and its core principle of natural selection caused by environmental pressures that may determine whether an organism adapts and survives, or remains static, languishes, and eventually dies out.
The same forces that have influenced the size and shape of the beaks of finches in the Galapagos Islands, the length of giraffe necks in Africa, and the intestinal microbiomes of the nearly 8 billion human inhabitants of this planet also control whether malignant cells thrive and multiply, wither and die when assaulted by chemotherapy, or go into hiding, mutating and waiting for their next opportunity to erupt again and metastasize.
The ability of malignant cells to adapt to environmental pressures is “cancer’s most lethal and sophisticated property,” said Damon R. Reed, MD, program leader of the adolescent/young adult program at Moffitt Cancer Center in Tampa, Fla.
Dr. Reed and colleagues are developing methods to meet cancer on its own terms, applying evolutionary principles to the treatment of childhood fusion-positive rhabdomyosarcoma in an innovative, and some would say audacious, clinical trial.
Adaptive versus conventional therapy
The trial, now recruiting, is designed to evaluate each of four different strategies for chemotherapy schedules in patients with newly diagnosed metastatic fusion-positive rhabdomyosarcoma.
The trial contains four arms, three of which consist of either conventional chemotherapy based on published clinical trials, moving a second-line therapy to the first line, or adding maintenance therapy, all of which have the goal of inducing as many complete remissions as possible.
The remaining adaptive therapy arm, however, is entirely novel in approach, with therapy using a combination of chemotherapy drugs that will be started and interrupted based on tumor responses, with resumption of therapy on an adaptive schedule unique to each patient. The goal of treatment for patients enrolled in this arm will be prolongation of the time to disease progression, rather than complete remission.
Although some people might consider the adaptive therapy approach to be sacrificing the hope for a cure in exchange for palliation, the hard truth is that patients with fusion-positive rhabdomyosarcoma (in contrast to those with fusion-negative disease) have a dismal prognosis following relapse after up-front intensified therapy.
Instead, because a cure is exceedingly unlikely in patients with metastatic disease, the conventional idea of delivering the maximum tolerated dose of chemotherapy until disease progression could be replaced by an approach based on understanding of the evolution of cancer cells under selective pressures, Dr. Reed and colleagues contend.
“Although adaptive therapy would represent a major paradigm shift in pediatric oncology, this approach would exploit the chemotherapy-sensitive population to prevent the emergence of resistant populations, optimizing tumor control with less toxicity,” they wrote in a commentary published online in the journal Cancer.1
Poor survival with advanced disease
Childhood rhabdomyosarcoma (RMS) is a form of soft tissue sarcoma of mesenchymal origin. Approximately 25% of cases are parameningeal, arising from sites adjacent to the meninges of the nasopharynx, middle ear, paranasal sinuses, orbit, and other regions of the head and neck. Approximately 31% of cases arise in the genitourinary tract and 13% in the extremities, and other tumors occur less commonly in the trunk, chest wall, perineal/anal region, and abdomen.