1202 - The Role of Adjuvant Primary Site Radiotherapy in the Treatment of Melanoma with Perineural Invasion
Presenter(s)
R. T. Patel1,2, A. T. M. Ho1,2, Y. Yi1, A. F. M. Salem3, R. Lin4, A. Devireddy1,2, N. X. Yang1,2, A. Farooqi3, A. J. Bishop3, B. A. Guadagnolo3, P. Nagarajan1, K. C. Nelson1, R. Weiser1, S. Fisher1, R. P. Goepfert1, M. I. Ross1, R. Amaria1, I. Glitza1, A. K. Yoder3, and D. Mitra3; 1The University of Texas MD Anderson Cancer Center, Houston, TX, 2McGovern Medical School at UTHealth Houston, Houston, TX, 3Department of Radiation Oncology, The University of Texas MD Anderson Cancer Center, Houston, TX, 4Department of Radiation Oncology, University of Texas MD Anderson Cancer Center, Houston, TX
Purpose/Objective(s): The prognostic significance of perineural invasion (PNI) for patients with melanoma and the role of adjuvant primary site radiotherapy (APS-RT) in the contemporary therapeutic era is not well understood. We sought to retrospectively evaluate the impact of APS-RT on outcomes for patients with melanoma PNI treated in this setting.
Materials/Methods: We identified 116 patients with localized cutaneous melanoma (no distant metastases, clinically involved nodes, in-transits, or micro/macrosatellites) and histologically confirmed PNI treated at our institution between 2016–2022. The effect of APS-RT on local control (LC), non-nodal locoregional control (including local and in transit recurrence, NNLRC), and disease-free survival (DFS) were estimated using the Kaplan–Meier method with comparison using log-rank testing.
Results: The overall cohort was 66% male (n=77), with a median age of 69 (IQR 58-76). Sixty-six patients (57%) received APS-RT and 50 (43%) did not. Patients treated with APS-RT were more likely to have head and neck primary tumors (82% vs. 36%, p<0.005). APS-RT was used to treat a greater proportion of high-risk PNI patients, defined as those involving “medium” or “large” caliber nerves (including those measured >0.1 mm) or with extensive/multifocal involvement (35% vs. 14%, p=0.01). All patients underwent wide local excision, and surgical nodal evaluation was performed for 95% of patients without APS-RT and 85% receiving APS-RT (p=0.23). 101 patients had sentinel lymph node biopsy, 1 elected for lymph node dissection, and 14 had no surgical nodal evaluation due to age, comorbidities, or other factors. Adjuvant systemic therapy was administered to more patients who did not receive APS-RT (48%, n=24 vs. 21%, n=14, p<0.005).
The median follow-up for the cohort was 45 months (IQR, 28–65). Three-year actuarial outcomes for the entire cohort were LC 96% (95% CI, 92-100%), NNLRC 93% (95% CI, 88-99%), and DFS 58% (95% CI, 49-69%). APS-RT was associated with better LC (3-year LC 100% vs. 93%, p=0.04) and NNLRC (3-year NNLRC 100% vs. 86%, p<0.005). The 3-year DFS was 50% for patients not receiving APS-RT and 66% for those who did (p=0.27). In the absence of APS-RT, the first site of recurrence was isolated local recurrence for 3 patients, isolated in-transit recurrence for 1 patient, and synchronous local and in-transit recurrence for 1 patient (4% overall). No patient receiving APS-RT experienced local and/or in-transit recurrence as an isolated first site of recurrence.Conclusion: In this contemporary cohort from a high-volume melanoma center, PNI was associated with a low absolute rate of local/in transit recurrence. However, APS-RT was associated with better local and non-nodal locoregional control. Thus, our data provides initial evidence that radiotherapy may benefit select high-risk patients in the current treatment landscape.