PQA 04 - Breast Cancer, Patient Reported Outcomes/QoL/Survivorship, Functional Radiation Medicine, Hematologic Malignancies, Palliative Care, and International/Global Oncology
Presenter(s)
H. S. Vangipuram1, V. Shankar2, S. Ghosh3, S. Cholayil4, V. Sai Shreya5, D. Arjundas6, and V. R. Anand7; 1Department of Undergradute Education, All India Institute of Medical Sciences, Ansari Nagar, New Delhi, India, 2Division of Radiosurgery, Apollo Cancer Centers, Chennai, India, 3Dept. of Neurosurgery, Apollo Proton Cancer Center, Chennai, India, 4Apollo Cancer Centers, Chennai, India, 5Dept of General Medicine, Sri Rama Chandra Medical College, Porur, Chennai, India, 6Chief Neurologist, Mercury Hospital, Chennai, India, 7Sai Neuro Hospital, Chennai, India
Purpose/Objective(s):
Single-fraction radiosurgery (SRS) for trigeminal neuralgia (TN) is widely recognized to function primarily as a neuromodulatory intervention producing durable pain relief often with variable sensory loss. However, current delivery paradigms implicitly treat neuromodulation as time-invariant, emphasizing spatial dose parameters while overlooking underlying temporal neurobiology. TN is increasingly understood as a disorder of electrophysiological instability in demyelinated trigeminal fibers, driven in part by maladaptive voltage-gated sodium channel kinetics, particularly Nav1.7 and Nav1.3. Experimental neurophysiology demonstrates that recovery from slow sodium-channel inactivation occurs over minutes to tens of minutes (approximately 10–20 minutes).
We hypothesized that intentional intra-session temporal structuring of dose delivery, while preserving instantaneous dose rate and total dose, could optimize neuromodulation by engaging ion-channel recovery dynamics, thereby improving pain stability with reduced sensory toxicity. Materials/Methods:
Ten consecutive patients with classical TN underwent temporally structured CyberKnife radiosurgery targeting the dorsal root entry zone and were prospectively followed (median follow-up, 12 months). All treatments prescribed 85 Gy using uniform DREZ target, prescription isodose selection, and OAR constraints. Total beam-on time was approximately 30 minutes, delivered in three ~10-minute segments separated by two planned 10–15-minute beam-off intervals within a single session. Outcomes were compared with a 1:1 matched historical cohort treated using uninterrupted radiosurgery. Categorical outcomes were analyzed using Fisher’s exact test, with analyses considered hypothesis-generating.
Results:
Spatial dosimetric parameters were equivalent between cohorts. At last follow-up, 8/10 patients (80%) in the temporally structured cohort achieved and maintained BNI I–II pain status, compared with 6/10 patients (60%) in controls (p=0.63). Early post-treatment pain oscillations occurred in 2/10 patients (20%) versus 5/10 patients (50%), respectively (p=0.35). Facial numbness was observed in 1/10 patients (10%) compared with 3/10 patients (30%) among controls (p=0.58). Kaplan–Meier patterns suggested improved pain stability, and planned beam-off intervals did not disrupt workflow.
Conclusion:
Intentional temporal dose structuring represents a biologically informed refinement of functional radiosurgery for trigeminal neuralgia. By preserving instantaneous dose rate and total dose while aligning delivery with ion-channel recovery dynamics, temporally structured SRS may enhance electrophysiological stabilization and reduce sensory morbidity. These findings suggest that treatment timing, independent of spatial dosimetry, is a modifiable determinant of pain durability and support prospective evaluation of temporally informed radiosurgical delivery strategies.
