The anticancer treatment modality tumor treating fields (TTFields; Optune, Novocure) use the lower frequency range of the electromagnetic spectrum to destroy tumor cells during mitosis. This treatment has been evaluated in several trials of patients with glioblastoma. In these patients, TTFields are delivered through 4 transducer arrays applied to the scalp. In a phase 3 clinical trial of patients with recurrent glioblastoma, TTFields were as effective as chemotherapy, and were associated with fewer and milder systemic toxicities. Data from a phase 3 trial in newly diagnosed glioblastoma suggested that the addition of TTFields to postoperative radiation therapy and chemotherapy represents an important advance in the management of newly diagnosed glioblastoma. Ongoing clinical trials are investigating the efficacy and safety of TTFields in other tumor types, including pancreatic cancer, mesothelioma, ovarian cancer, and non–small cell lung cancer. Other recent advances in the management of cancer have been seen with immunomodulatory therapy, including immune checkpoint inhibitors. Further study will be necessary to evaluate whether TTFields will enhance or impair other established and newly emerging therapies.