Predicting response to radiotherapy of intracranial metastases with hyperpolarized $$^{13}$$C MRI
Casey Y. Lee, Hany Soliman, Nadia Bragagnolo, Arjun Sahgal, Benjamin Geraghty, Albert P. Chen, Ruby Endre, William J. Perks, Jay Detsky, Eric Leung, Michael W.Y. Chan, Chris Heyn, Charles H. Cunningham
Abstract
Abstract Background Stereotactic radiosurgery (SRS) is used to manage intracranial metastases in a significant fraction of patients. Local progression after SRS can often only be detected with increased volume of enhancement on serial MRI scans which may lag true progression by weeks or months. Methods Patients with intracranial metastases (N = 11) were scanned using hyperpolarized $$^{13}$$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:msup> <mml:mrow/> <mml:mn>13</mml:mn> </mml:msup> </mml:math> C MRI prior to treatment with stereotactic radiosurgery (SRS). The status of each lesion was then recorded at six months post-treatment follow-up (or at the time of death). Results The positive predictive value of $$^{13}$$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:msup> <mml:mrow/> <mml:mn>13</mml:mn> </mml:msup> </mml:math> C-lactate signal, measured pre-treatment, for prediction of progression of intracranial metastases at six months post-treatment with SRS was 0.8 $$p < 0.05$$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:mrow> <mml:mi>p</mml:mi> <mml:mo><</mml:mo> <mml:mn>0.05</mml:mn> </mml:mrow> </mml:math> , and the AUC from an ROC analysis was 0.77 $$p < 0.05$$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:mrow> <mml:mi>p</mml:mi> <mml:mo><</mml:mo> <mml:mn>0.05</mml:mn> </mml:mrow> </mml:math> . The distribution of $$^{13}$$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:msup> <mml:mrow/> <mml:mn>13</mml:mn> </mml:msup> </mml:math> C-lactate z -scores was different for intracranial metastases from different primary cancer types (F = 2.46, $$p = 0.1$$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:mrow> <mml:mi>p</mml:mi> <mml:mo>=</mml:mo> <mml:mn>0.1</mml:mn> </mml:mrow> </mml:math> ). Conclusions Hyperpolarized $$^{13}$$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:msup> <mml:mrow/> <mml:mn>13</mml:mn> </mml:msup> </mml:math> C imaging has potential as a method for improving outcomes for patients with intracranial metastases, by identifying patients at high risk of treatment failure with SRS and considering other therapeutic options such as surgery.