Considerations involving reirradiation

Reirradiation is commonly employed in settings where patients experience locoregional failure after definitive intent or palliative intent treatment. Both clinical situations have slightly different goals but the overall objective is to mitigate symptoms from tumor progression without exposing the patient to excessive toxicity. To that end, patients and physicians face several challenges in the consideration of reirradiation. From a biological standpoint, progression after the initial radiation course may suggest that the original dose was insufficient to control the tumor, either due to treatment constraints or intrinsic tumor biology. This implies that any additional courses of radiation therapy should aim to deliver a higher biological effective dose (BED) to achieve the goal of treatment, whether this is local control or palliation of a particular symptom. However, from a treatment planning perspective, initial courses of radiation are often designed to meet normal tissue constraints, leaving little room for additional radiation therapy. As such, highly conformal radiation therapy techniques can often be used to deliver sufficient doses of radiation while simultaneously sparing critical structures adjacent to the intended target. Such techniques include proton therapy, stereotactic body radiation therapy, and brachytherapy. Furthermore, there is evidence to support time-dependent recovery of normal tissues after radiation, suggesting that if the time interval between radiation courses can be maximized, there is a lower risk of severe toxicity. All of these radiation techniques have been increasingly studied across a wide range of disease sites with variable tolerability and efficacy, providing some guidelines by which patients can be safely and reasonably retreated. Ultimately, the decision to offer reirradiation must remain patient-centered, with overall goals of care in mind, and with full informed consent.