PMC6034356_01
A 60-year-old Caucasian male presented with a left-sided weakness including dragging his left foot, and the inability to write for about 6 weeks. Brain magnetic resonance imaging showed a solitary 2.3 cm brain lesion in the right frontal lobe, and subsequent positron emission tomography/computed tomography study showed multiple fludeoxyglucose avid bilateral pulmonary nodules and mediastinal adenopathy. Biopsy of a mediastinal lymph node revealed metastatic adenocarcinoma, negative for epidermal growth factor receptor mutation. Brain magnetic resonance images, T1-weighted contrast-enhanced (axial = left image; sagittal = middle image; coronal = right image), before (a) and 1 month after stereotactic radiosurgery (b) showed the right frontal lobe metastasis (cross-hair). Normalized subtraction result of A and B overlaid with the magnetic resonance image (c), demonstrated small areas of mixed interval decrease (purple) and increase (orange-red) of contrast enhancement, and other areas with no interval change. Corresponding fludeoxyglucose positron emission tomography scans (axial = left image; sagittal = middle image; coronal = right image) before (d) and 1 month (e) after stereotactic radiosurgery showed the brain metastasis (cross-hair). NS result of D and E, overlaid with the positron emission tomography image (f), showed interval decrease (purple) in lesional fludeoxyglucose uptake. The residual uptake, however, was still greater than that in the surrounding and contralateral brain parenchyma suggestive of partial treatment response.
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F1
Brain MRI and FDG PET images before his 1st SRS and chemotherapy showed a ring-enhancing brain lesion with intense FDG avidity [Figure 1 a and d]. One month after SRS, MRI images showed small areas of both interval decrease and increase in contrast enhancement as well as other areas with no interval change, as seen on the NS images [Figure 1 b and c]. In contrast, NS images of the PET images of the same period demonstrated interval decrease in lesional FDG uptake visually and semi-quantitatively with NS, consistent with partial treatment response [Figure 1e and f].
Brain magnetic resonance images, T1-weighted contrast-enhanced, at 1 month (a) and 7 months (b) after stereotactic radiosurgery showed the area of the right frontal brain lesion (cross-hair). Normalized subtraction result of A and B, overlaid with the magnetic resonance image (c), showed marked decrease in the signal intensity and size of the ring enhancement. Corresponding positron emission tomography images at 1 month (d) and 7 months (e) after stereotactic radiosurgery showed the area of the right frontal lesion (cross-hair). Normalized subtraction result overlaid with positron emission tomography image (f) demonstrated small areas of mild interval decreased uptake (purple) within the brain lesion and other areas with no interval change. Given the residual fludeoxyglucose avidity compared to the surrounding and contralateral brain parenchyma, residual tumor was suspected. Interval increased (orange-red) uptake in brain tissue surrounding the tumor lesion reflected metabolic recovery and improving vasogenic edema (F, arrow).
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F2
Brain MRIs at 7 months demonstrated a significant decrease in lesion size and contrast enhancement compared with the scan performed at 1 month after SRS [Figure 2 a, b, and c]. In contrast, the PET scan of the same periods showed small areas of mildly decreased FDG uptake [Figure 2 d, e, and f], but the lesion remained FDG avid suggestive of residual tumor.
Brain magnetic resonance images, T1-weighted contrast-enhanced, at 7 months (a) and 17 months (b) after stereotactic radiosurgery focused on the right frontal lesion (cross-hair). Normalized subtraction result, overlaid with the magnetic resonance image (c), demonstrated interval increase (orange-red) in signal intensity and size of the contrast enhancing lesion. Corresponding positron emission tomography images at 7 months (d) and 17 months (e) after stereotactic radiosurgery focused on the right frontal lesion (cross-hair). Normalized subtraction result, overlaid with the positron emission tomography image (f), showed interval increased (orange-red) fludeoxyglucose uptake within the tumor bed suspicious for tumor recurrence. Interval decreased (purple) uptake in brain areas surrounding the tumor (F, arrow) represented metabolic dysfunction due to vasogenic edema associated with tumor recurrence. Subsequent proton magnetic resonance spectroscopy was also suspicious for recurrent tumor, so a tissue sampling was foregone. The patient was retreated again with Still Birth Rate in a single dose of 21 Gy. Although the patient remained free of neurologic symptoms, the lesion size progressed on follow-up magnetic resonance imaging scans. A biopsy was positive for residual metastasis, and subsequent surgical resection of the lesion revealed metastatic tumor and an additional area of increased secondary to radiation treatment effect.
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F3
Brain MRIs at 17 months showed an enlarging lesion with increased signal intensity compared with the scan at 7 months [Figure 3 a, b, and c], which raised the suspicion for recurrent tumor. Similarly, FDG PET scan of the same periods demonstrated interval increase in lesional uptake suggestive of recurrent disease [Figure 3 d, e, and f].