Partially Ablative Radiotherapy for Bulky Tumors: A Narrative Review of a Developing Concept

The management of large bulky tumors is very challenging. The current treatment options for effective palliation of symptoms are limited. These tumors often present a large burden at the time of diagnosis, growing along critical bony and neural structures and preventing surgical resection in most of the cases. These tumors are also known to be relatively resistant to chemotherapy, with very low response rates. In addition, conventional photon-based radiotherapy has a limited effect due to their radioresistance, the use of large treatment fields, and the impossibility of delivering high doses because of the higher risk of normal tissue toxicity. Therefore, more effective radiation treatments for palliation are needed to achieve greater local control rates. A recent approach called partial ablative radiotherapy (PART) has been shown to be potentially able to improve the effectiveness of radiotherapy. This technique is based on the ability of recent advanced delivery techniques to deliver a high "ablative" dose to the central part of the tumor, maintaining a very low and safe dose profile at the periphery to spare the surrounding organs at risk. Although this technique has been evaluated only in small studies and case reports, it showed notable treatment responses and safety profiles. The present narrative review describes the rationale for PART, the current and forthcoming state of evidence, the existing studies, and the future directions for the development of this approach, including the associated challenges.