Impact of Frozen Section Pathology Examination of Surgical Margins in Sublobar Pulmonary Resections for Clinical Stage IA NSCLC

B. A. Ortiz¹, S. K. Engrav¹, M. C. Aubry¹, J. M. Boland¹, A. C. Roden¹, E. Yi¹, F. A. Abdallah², R. Shen³, S. Cassivi⁴, S. Saddoughi¹, D. Wigle¹, J. Reisenauer¹, L. F. Tapias^1
1Mayo Clinic, Rochester, Minnesota ²Abdallah, Rochester, Minnesota ³Mayo Clinic, Dept. of Surgery, Division of General Thoracic Surgery, Rochester, Minnesota ⁴Mayo Clinic, Division of Thoracic Surgery, Rochester, Minnesota

Purpose: Sublobar resections are a valid surgical treatment for many patients with clinical stage IA NSCLC. However, incomplete resections are associated with decrease long-term survival. This study aimed to evaluate the impact of routine frozen section pathology evaluation of surgical margins during sublobar pulmonary resections for clinical stage IA NSCLC.

Methods: Patients with clinical stage IA NSCLC who underwent curative-intent lung resections during 2018-2023 were reviewed. Patients who proceeded to the operating room with a preoperative intention to undergo a sublobar resection (wedge resection or segmentectomy) were included. Pathology reports were reviewed, and frozen section intraoperative reports were compared to final pathology reports. Operative notes were reviewed to determine changes in surgical plan based on intraoperative findings from frozen section evaluation of margins.

Results: There were 1008 patients that underwent surgery for clinical stage IA NSCLC during the study period, of which 673 (66.8%) had a preoperative plan to undergo sublobar resection. Median preoperative tumor size was 1.5 cm (interquartile range: 1.2-2.0 cm). There were 7 (1.0%) patients with a positive margin identified at some point as part of the operation (intraoperatively or postoperatively). Frozen section evaluation successfully identified 6/7 (85.7%) cases intraoperatively, all corresponding to the parenchymal margin. In 4/6 (66.7%) cases, the surgeon was able to alter the procedure to achieve a negative margin on final pathology. Two cases of planned wedge resection were converted to lobectomy. In 2 cases of planned segmentectomy, additional parenchymal margin and conversion to lobectomy was observed in 1 case each. In the other 2 cases, an additional margin was obtained after wedge resection, but continued to return positive; a larger resection was not pursued due to limited pulmonary function. A positive margin was only found on final pathology postoperatively in 1 case. The final rate of non-R0 resection was 3/673 (0.4%). Therefore, frozen section evaluation of resection margins assisted in decreasing the potential rate of non-R0 resection from 1.0% to 0.4% (approximate 60% reduction).

Conclusion: Frozen section pathology is a valuable tool to assess resection margins during sublobar resection of clinical stage IA NSCLC. Intraoperative margin analysis can identify most cases with positive margins allowing the surgeon to alter the planned procedure, if appropriate, thus minimizing non-R0 resections when attempting sublobar lung resections.

Identify the source of the funding for this research project: None