|LETTER TO EDITOR
|Year : 2020 | Volume
| Issue : 2 | Page : 414-415
Differentiating radiation necrosis vis-à -vis recurrence in brain metastasis
Utpal Gaikwad, Rakesh Jalali
Department of Radiation Oncology, Apollo Proton Cancer Centre, Chennai, Tamil Nadu, India
|Date of Submission||05-Mar-2020|
|Date of Decision||05-Mar-2020|
|Date of Acceptance||05-Mar-2020|
|Date of Web Publication||19-Jun-2020|
Department of Radiation Oncology, Apollo Proton Cancer Centre, Chennai, Tamil Nadu
Source of Support: None, Conflict of Interest: None
|How to cite this article:|
Gaikwad U, Jalali R. Differentiating radiation necrosis vis-à -vis recurrence in brain metastasis. Cancer Res Stat Treat 2020;3:414-5
With improvement in systemic chemotherapy, targeted therapy, the increasing role of immunotherapy, relatively lower threshold of imaging and availability of modern diagnostic modalities, the incidence of brain metastasis is increasing. High-precision radiation therapy techniques of stereotactic radiosurgery and fractionated radiotherapy with or without systemic agents have improved the survival and patient-reported outcomes in these patients, as well. Recursive partition analysis score and diagnosis-specific graded prognostic assessment score are frequently used in clinical practice to prognosticate and help define the most appropriate treatment strategies for these patients. Whole-brain radiotherapy (WBRT) is generally indicated in patients with multiple metastases, large metastases (>4 cm), poorly controlled systemic disease, and in low-performance status patients. Advances in radiotherapy techniques such as hippocampal-sparing WBRT have shown significant benefit in preserving cognitive functions and quality of life in these patients.
Postradiation changes can be acute, subacute, and late, which can be caused by vascular changes, glial changes, and damage to the blood-brain barrier causing edema, mass effects, etc. Postradiation changes may mimic disease progression and this is termed as pseudo-progression, typically observed in the first few months after treatment. Patients can sometimes also develop frank radiation-induced necrosis (RIN), which can be seen as late as 18–24 months postradiotherapy. Prior or concurrent systemic therapies (chemotherapy, targeted therapy, and immunotherapy) increase the risk of RIN. Postradiotherapy changes and RIN are often difficult to distinguish from true tumor progression and present a clinical challenge. The case in this issue exemplified this diagnostic dilemma of RIN versus tumor progression. Multiparametric magnetic resonance imaging (MRI) brain with perfusion assay and magnetic resonance spectroscopy (MRS) are helpful in differentiating radiation changes from disease recurrence. Currently, modified Response Assessment in Neuro-Oncology (RANO) criteria using various MRI features along with clinical assessment have been advocated to be used to help establish the correct diagnosis. Diffusion-weighted imaging with higher apparent diffusion coefficient (ADC) values, extensive lipid lactate peak on MRS and decreased relative cerebral blood volume values on perfusion scans favor the diagnosis of RIN, but both RIN and a recurrent lesion can show neuronal loss (low NAA), and abnormal cellular membrane attenuation (high choline). It is important to correlate all MRI findings with clinical signs and symptoms and also to assess the clinico-radiological features in chronological order. In the present case, the MRI features and clinical presentation were in favor of RIN.
Fluorodeoxyglucose positron-emission tomography-computed tomography, particularly with newer radiotracers is another option for RIN diagnosis, but low sensitivity and sensitivity with limited data, have precluded its routine use. In symptomatic patients with the empirical diagnosis of RIN, corticosteroids may be used with or without other measures such as medical decompression therapy, anti-angiogenic agents, and checkpoint inhibitors with surgical resection reserved for refractory cases.
It is important to rule out the diagnosis of RIN in brain metastases patients postradiotherapy with or without systemic therapy. With the help of modern imaging modalities, timely diagnosis and management of RIN will improve patient-related outcomes.
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Conflicts of interest
There are no conflicts of interest.
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