From the Guest Editor: New Lenses, New Visions for Radiotherapy in the Molecular-Genetic-Immunomodulator Era of Oncology.

A new moment in oncology has arrived. It might not have appeared overnight, but the dizzying rush of fantastical discoveries over the last few years leaves us all wondering howmuch we even need to remember of yesterday’s old-world order of cancer diagnosis and therapy, before molecular targeted agents and next-generation sequencing and immune checkpoint inhibitors. High-profile popular media coverage of these advances reinforces the narrative that we have reached an epochal tipping point in the war against unbridled neoplasia. The optimism is justifiable. After decades of charging into the seemingly impenetrable line of defenses put forth by so many malignancies, more and more avenues of attack have been recognized. Crizotinib, for example, improves quality of life and doubles the time to disease progression and triples the response rate in patients with metastatic non–small cell lung cancer that harbors an ALK gene rearrangement. Similarly, ipilimumab came on strong to the scene when a randomized trial showed it yielded a 10 months’median survival for patients with advancedmelanoma, significantly better than the 6 months provided by a tumor vaccine therapy, arguably the first time ever improving the overall survival curve in this disease by means of a systemic therapy. Nevertheless, enthusiasm is tempered by the sobering reality that there are still very few long-term survivors in either situation, and recalcitrant foci of disease invariably, defiantly persist and eventually lead to the patient’s demise. And so we have a new moment of opportunity for radiation oncology to reinvent itself and look ahead to the horizon through the lens of modern cancer biology and today’s health care economics toward greener, better places for patients. This particular medical specialty should not, however, discard all of the technological advances that so many investigators worked so hard to nurture and develop over the last few decades, because we will need them in the future more than ever. This special issue starts with a review of a topic formally introduced into the medical literature a little more than 20 years ago by 2 radiation oncologists of great stature, Hellman and Weichselbaum. The term oligometastases is now part of the everyday cancer-speak parlance, and David Palma and colleagues put this concept in perspective relative to current theories of the metastatic process and offer insight into the role radiotherapy can play in this setting. JimWelsh and his group follow with a thoughtful introduction into the exciting possibilities for exploiting the impact of radiation on the adaptive immune response to cancer to good effect in combination with modern immunotherapeutic agents. David Kirsch and his team complete the triad of translational science–infused articles with a thorough consideration of how the tenets of classic radiobiology might still inform our approach to clinical treatment in the current era of stereotactic body radiation therapy (SBRT). The remainder of the issue is populated by reviews of the use of SBRT for specific primary or recurrent cancers. The senior authors are all well-known and well-qualified experts in SBRTwho share their perspectives on their own work and the related published literature. Stereotactic body radiation therapy itself is directly descended from a combination of principles applied for many years in cranial radiosurgery and new delivery technology that allows for a concentrated dose of radiation to be deposited confidently in a tightly constrained region inside a patient, and its early history is well chronicled. Once seen as a disruptive, rule-bending, somewhat risky if not downright dangerous strategy has now gained widespread acceptance and evolved into an acceptable, costeffective alternative mode of management for numerous cancers. Indeed, it might eventually be the case