CAR T cell therapy has been called transformative and a “miracle,” and has garnered as much excitement as any cancer breakthrough in recent memory. The treatment—in which a patient’s immune cells are removed, reengineered and placed back into the body—has a success rate as high as 90% in some blood cancers, offering a full recovery for many who had given up hope.

Some believe that CAR T can be pushed even further. In “The Solid Tumor Barrier,” Proto explores efforts to marshal this therapy beyond blood cancers to solid tumors, which make up the vast majority of cancer cases. Marcela Maus, director of cellular immunotherapy at Massachusetts General Cancer Center, is working both on ways to target solid tumors with greater precision and on reducing the considerable costs of CAR T manufacture, which remain a major obstacle.

If successful, these efforts will present a revolution not only in cancer treatment but in care delivery. Immunotherapies such as CAR T therapy don’t come off the shelf, ready to use. Each treatment must be personalized to the patient, a labor-intensive process that calls for close work between many divisions of the hospital. Patients often remain on site for weeks to be monitored. In 2020 Massachusetts General Hospital aims to break ground on a building that will house six floors of new inpatient beds, with a focus on cancer and cardiac care, in part to be ready for the future in which moving patients through this and other processes will be far more common.

The first generation of this therapy is also not without complications. About three-quarters of the people who receive CAR T experience side effects, often severe and sometimes fatal. To understand these effects and set new standards in their treatment, MGH created a Severe Immunotherapy Complications Service. This pioneering team of 41 doctors and researchers from 22 areas of the hospital both treats these off-target effects and discovers ways to keep them from happening, in part by identifying which patients might be genetically disposed toward them.

The fight against cancer has many fronts, and the end is not likely to come soon. But we must prepare to press every advantage. As CAR T moves forward, the health care field must prepare not only for its vast promise to cure but also for its new and complex demands.