Efficacy and safety of proton radiotherapy for progressive or surgically unfavorable adult pilocytic astrocytoma: a single-center experience.
In a single-center retrospective series of 14 adults with progressive or surgically unfavorable pilocytic astrocytoma, proton radiotherapy was associated with frequent radiographic regression, estimated 5-year overall survival of 100%, estimated 5-year progression-free survival of 83.3%, and predominantly low-grade toxicity, although radiation-induced contrast enhancement occurred in three patients.
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In a single-center retrospective series of 14 adults with progressive or surgically unfavorable pilocytic astrocytoma, proton radiotherapy was associated with frequent radiographic regression, estimated 5-year overall survival of 100%, estimated 5-year progression-free survival of 83.3%, and predominantly low-grade toxicity, although radiation-induced contrast enhancement occurred in three patients.
Research significance
The reported human observational evidence suggests that proton radiotherapy may provide durable local disease control with acceptable toxicity in selected adults with difficult-to-resect pilocytic astrocytoma; it is an inference—not established by this uncontrolled series—that proton dose distribution could offer a clinically meaningful late-toxicity advantage over other radiotherapy approaches or that these findings apply to pediatric patients.
Source abstract
PURPOSE: Progressive adult pilocytic astrocytoma is rare, and management of surgically unfavorable disease remains insufficiently defined. Given the favorable long-term prognosis of WHO grade 1 glioma, local tumor control must be balanced against late toxicity. This study evaluated the efficacy and safety of PRT in adults with pilocytic astrocytoma. METHODS: Fourteen adult patients with progressive or surgically unfavorable pilocytic astrocytoma treated with PRT at a single institution were retrospectively analyzed. Patient, tumor, treatment, radiographic, survival, and toxicity data were assessed. Radiographic response was evaluated using bidirectional T2-weighted measurements. Overall survival (OS), progression-free survival (PFS), and radiation-induced contrast enhancement (RICE)-free probability were estimated using Kaplan-Meier analysis. Toxicity was graded according to CTCAE. RESULTS: Median prescribed dose was 54.0 Gy(RBE). PRT was delivered as salvage treatment in 10 patients (71%) or primary therapy in 4 patients (29%). Tumors frequently involved anatomically complex regions, including the posterior fossa, ventricular and midline structures, the optic pathway, and the suprasellar compartment. At last follow-up, radiographic regression included complete response in 3, partial response in 7, and minor response in 2 of 14 patients. Estimated OS at 3 and 5 years was 100%, whereas estimated PFS was 83.3% at both time points. RICE occurred in 3 patients, with 3- and 5-year RICE-free probabilities of 76.2%. Toxicity was predominantly low grade, with no grade 4 or 5 events. CONCLUSION: PRT was associated with durable tumor control, marked radiographic regression, favorable survival, and acceptable toxicity in selected adults with progressive or surgically unfavorable pilocytic astrocytoma.