Main Session

Sep 27

PQA 02 - Pediatric Cancer, Sarcoma and Cutaneous Tumors, Medical Education & Professional Development, and Health Services Research

2336 - Smaller Radial Margins in Superficial Radiotherapy Patients Using Reflectance Confocal Microscopy

04:00pm - 05:00pm ET

Poster Hall - Exhibit Hall A

Screen: 15

POSTER

Presenter(s)

Sreenija Yarlagadda, MD - University of Mississippi Medical Center, Jackson, MS

L. Gonzalez¹, S. Yarlagadda¹, and N. S. Kalman^1,2; ¹Department of Radiation Oncology, Miami Cancer Institute, Baptist Health South Florida, Miami, FL, ²Department of Oncological Sciences, Florida International University, Herbert Wertheim College of Medicine, Miami, FL

Purpose/Objective(s):

Superficial radiotherapy (SRT) is an established treatment for skin cancer. Integrated ultrasonography can be used to evaluate lesion depth, but radial treatment margins can be difficult to assess visually. Reflectance confocal microscopy (RCM) lesion mapping can help delineate lesion borders and has been used to assist in surgical planning. We evaluated its use in reducing radial treatment margins in patients treated with SRT.

Materials/Methods:

We conducted a retrospective analysis of skin cancer patients who received SRT and evaluated the difference in treatment margin and outcomes between patients who underwent RCM mapping pre-treatment versus those who did not. Descriptive statistics were used to summarize the disease and treatment-related variables. Group comparisons were performed using an independent-samples t-test. Equality of variances was assessed using Levene’s test; when unequal variances were detected, Welch’s t-test was applied. A two-sided p value < 0.05 was considered statistically significant. Kaplan-Meir survival analysis was used to compute local failure free survival (LFFS).

Results:

The cohort included 98 lesions in 62 patients. Mean patient age was 77 years (range [R]: 53-102 years), majority were male (63%), and basal cell carcinoma was the most common type (48 [77.4%]), followed by squamous cell carcinoma (11 [17.7%]) and Kaposi sarcoma (3 [4.8%]). Nose was the most common site (48 [49%]), followed by other sites on face (22 [22.4%]) and extremity (16 [16.3%]). 83 were primary lesions, while 15 were recurrent; 67 were cT1, 8 were cT2. Most common dose schedule was 40 Gy in 8 fractions (68.4%). 53 lesions had RCM mapping, while 45 lesions did not. The median lesion size in standard margin group was 1 cm (R: 0.30-3.5 cm) compared to 1.5 cm (R: 0.5-3.5 cm) in the RCM group (p=0.001). The median radial margin size in the standard group was 7.5 mm (R: 5-15 mm) compared to 5 mm (R: 2.5-10 mm) in RCM group (p=0.001). No significant difference in RT field size was observed between the groups (p = 0.99), likely due to larger lesions in RCM group. Overall, 3 lesions had local failure in 2 patients, both of whom had Kaposi sarcoma. Overall mean LFFS was 27.5 months; this was 27.9 months (95% CI: 23.4-33.4 months) in the RCM group and 20.9 months (95% CI: 18.8-22.9 months) in the standard group (p=0.55).

Conclusion:

RCM enabled reduced radial margins in patients receiving SRT without reduction in local control. These findings will be confirmed with larger patient numbers and longer follow up.