Main Session
Sep 28
PQA 04 - Breast Cancer, Patient Reported Outcomes/QoL/Survivorship, Functional Radiation Medicine, Hematologic Malignancies, Palliative Care, and International/Global Oncology

2866 - Mechanism-Based Recurrence Phenotyping after Trigeminal Radiosurgery

03:00pm - 04:00pm ET
Poster Hall - Exhibit Hall A
Screen: 12
POSTER

Presenter(s)

Vangipuram Shankar, MD, MBBS Headshot
Vangipuram Shankar, MD, MBBS - Apollo Proton Cancer Centre, Chennai , Tamil Nadu

V. Shankar1, S. Ghosh2, H. S. Vangipuram3, D. Arjundas4, V. R. Anand5, and S. Cholayil6; 1Division of Radiosurgery, Apollo Cancer Centers, Chennai, India, 2Dept. of Neurosurgery, Apollo Proton Cancer Center, Chennai, India, 3Department of Undergradute Education, All India Institute of Medical Sciences, Ansari Nagar, New Delhi, India, 4Chief Neurologist, Mercury Hospital, Chennai, India, 5Sai Neuro Hospital, Chennai, India, 6Apollo Cancer Centers, Chennai, India

Purpose/Objective(s): Stereotactic radiosurgery (SRS) provides meaningful initial pain relief in most patients with primary trigeminal neuralgia (TN), yet long-term recurrence remains common and repeat SRS carries increased risk of sensory morbidity. We evaluated a mechanism-based recurrence phenotyping framework to classify patterns of failure and assess associations with retreatment outcomes, facial sensory toxicity, and phenotype-specific clinical trajectories.

Materials/Methods: We retrospectively reviewed 478 consecutive adults treated with SRS for TN treated between 2006-2024. After applying stringent inclusion criteria — age =18 years, primary TN, and complete follow-up — 418 patients were evaluable; secondary TN was excluded. Median follow-up was 8 years.

Patients with recurrence underwent structured phenotyping across five domains: relapse timing, pain quality, trigger specificity, sensory examination/background pain, and psychological distress. Psychological assessment incorporated PHQ-9, GAD-7, and Insomnia Severity Index (ISI). Recurrences were categorized into three dominant phenotypes: axonal escape, central sensitization rebound, and psychological overlay. Phenotypes were not mutually exclusive; patients were assigned a dominant mechanism guiding retreatment.

The primary endpoint was meaningful pain improvement after retreatment. Secondary endpoints included facial sensory morbidity and time to recurrence. Kaplan–Meier methods estimated recurrence-free survival. Associations between phenotype, retreatment response, and toxicity were evaluated using ?²/Kruskal–Wallis testing and multivariable logistic regression.

Results: At median 8-year follow-up, 146 of 418 patients (35%) recurred. Among failures, 30% demonstrated axonal escape, 30% central sensitization rebound, and 40% psychological overlay.

Axonal escape patients most frequently achieved meaningful improvement following mechanistically adjusted repeat SRS. Central sensitization rebound was associated with longer disease duration, greater background pain, and reduced retreatment responsiveness. Psychological overlay patients showed elevated PHQ-9/GAD-7/ISI scores, discordance between objective paroxysmal improvement and reported pain, and limited benefit from further radiosurgery. Facial sensory morbidity was more common with uniform retreatment, whereas phenotype-guided management supported more selective SRS use.

Conclusion: In adults with primary TN, recurrence after SRS reflects heterogeneous and overlapping peripheral, central, and affective mechanisms identifiable through structured clinical and psychological phenotyping. Mechanism-based recurrence phenotyping offers a precision framework to guide repeat radiosurgery, prioritize neuromodulatory or multidisciplinary care, and potentially reduce unnecessary dose escalation and sensory morbidity. Prospective validation is warranted.