Pseudoprogression (PsP)

KEY FACTS

TERMINOLOGY

• Treatment-related increase in contrast enhancement

mimics tumor progression

• Classically described after treatment with chemoradiation

(temozolomide with radiation therapy)

• Typically occurs within 3-6 months after conclusion of

radiation therapy (XRT)

IMAGING

• New enhancing lesion + ↑ FLAIR hyperintensity in treated

malignant glioma at 3-4 months after XRT completion

• T2/FLAIR: Increased hyperintensity with mass effect

• DWI: Higher ADC values in PsP compared with tumor

• DSC MR

○ Lower mean rCBV values in PsP compared with tumor

• DCE MR

○ Mean K trans (volume transfer constant) is lower in PsP

compared with true progression

• MRS: No significant elevation of choline in PsP

• Best imaging: Contrast-enhanced MR, DWI, ± MRS, MRP

• Follow-up studies may be necessary to make accurate

diagnosis of PsP

• Knowing clinical history and timing of therapy is key to

accurate brain tumor imaging

TOP DIFFERENTIAL DIAGNOSES

• Recurrent malignant glioma

• Radiation necrosis

CLINICAL ISSUES

• Current standard of care for malignant gliomas is surgical

resection followed by concurrent XRT and chemotherapy

with temozolomide (Temodar)

○ PsP occurs in ~ 35-50% of patients

• PsP is self-limited, enhancing lesions resolve without new

treatment

• PsP has been associated with improved survival

• Important to recognize that not all new enhancement in

patient with treated glioblastoma is progressive tumor

(Left) Axial T1 C+ MR in a 48-

year-old man treated with

radiation therapy and

Temodar for 3 months for his

malignant glioma shows new

enhancement ﬊ in the frontal

lobes bilaterally. His initial

postoperative MR study

showed no enhancement. He

was clinically doing well.

(Right) Axial T1 C+ MR in the

same patient 4 weeks later

shows a marked decrease in

the enhancement ﬊ without

a change in therapy. Imaging

findings are related to

pseudoprogression, not true

progression, likely related to

an inflammatory response.

(Left) Axial T1 C+ MR in a 62-

year-old woman with a

multifocal glioblastoma

treated with Temodar and

radiation therapy shows new

enhancement ﬊ in the

hemispheres on her 4-month

scan, concerning for

progressive tumor. (Right)

Axial T1 C+ MR in the same

patient 8 weeks later with no

therapy change shows a

marked decrease in the

enhancing lesions ﬊. The new

enhancement was related to

pseudoprogression, which is

associated with an increased

survival.

Cysts, and Disorders

Brain: Pathology-Based Diagnoses: Neoplasms,

155