Challenges in radiological evaluation of brain metastases, beyond progression.

MRI is the cornerstone in the evaluation of brain metastases. The clinical challenges lie in discriminating metastases from mimickers such as infections or primary tumors and in evaluating the response to treatment. The latter sometimes leads to growth, which must be framed as pseudo-progression or radionecrosis, both inflammatory phenomena attributable to treatment, or be considered as recurrence. To meet these needs, imaging techniques are the subject of constant research. However, an exponential growth after radiotherapy must be interpreted with caution, even in the presence of results suspicious of tumor progression by advanced techniques, because it may be due to inflammatory changes. The aim of this paper is to familiarize the reader with inflammatory phenomena of brain metastases treated with radiotherapy and to describe two related radiological signs: "the inflammatory cloud" and "incomplete ring enhancement", in order to adopt a conservative management with close follow-up.

Los retos en la evaluación radiológica de las metástasis cerebrales, más allá de la progresión / Challenges in radiological evaluation of brain metastases, beyond progression

La resonancia magnética es la piedra angular en la evaluación de las metástasis cerebrales. Los retos clínicos residen en discriminar las metástasis de imitadores como infecciones o tumores primarios y en evaluar la respuesta al tratamiento. Este, en ocasiones, condiciona un crecimiento, que debe encuadrarse como una pseudoprogresión o una radionecrosis, ambos fenómenos inflamatorios atribuibles al mismo, o bien considerarse como una recurrencia. Para responder a estas necesidades, las técnicas de imagen son objeto de constantes investigaciones. No obstante, un crecimiento exponencial tras la radioterapia debe interpretarse con cautela, incluso ante resultados sospechosos de progresión por técnicas avanzadas, ya que puede tratarse de una radionecrosis. El objetivo de este trabajo es familiarizar al lector con los fenómenos inflamatorios de las metástasis cerebrales tratadas con radioterapia y describir dos signos radiológicos relacionados: la «nube inflamatoria» y el «realce en anillo incompleto», con el fin de adoptar un manejo conservador en estos casos.(AU)

MRI is the cornerstone in the evaluation of brain metastases. The clinical challenges lie in discriminating metastases from mimickers such as infections or primary tumors and in evaluating the response to treatment. The latter sometimes leads to growth, which must be framed as pseudo-progression or radionecrosis, both inflammatory phenomena attributable to treatment, or be considered as recurrence. To meet these needs, imaging techniques are the subject of constant research. However, an exponential growth after radiotherapy must be interpreted with caution, even in the presence of results suspicious of tumor progression by advanced techniques, because it may be due to inflammatory changes. The aim of this paper is to familiarize the reader with inflammatory phenomena of brain metastases treated with radiotherapy and to describe two related radiological signs: «the inflammatory cloud» and «incomplete ring enhancement», in order to adopt a conservative management with close follow-up.(AU)