Should Sentinel Lymph Node Biopsy Status Guide Adjuvant Radiation Therapy in Patients With Merkel Cell Carcinoma?

Tessnim R Ahmad; Harish N Vasudevan; Ann A Lazar; Jason W Chan; Jonathan R George; Michael D Alvarado; Siegrid S Yu; Adil Daud; Sue S Yom

doi:10.1016/j.adro.2021.100764

Should Sentinel Lymph Node Biopsy Status Guide Adjuvant Radiation Therapy in Patients With Merkel Cell Carcinoma?

Adv Radiat Oncol. 2021 Jul 31;6(6):100764. doi: 10.1016/j.adro.2021.100764. eCollection 2021 Nov-Dec.

Authors

Tessnim R Ahmad¹, Harish N Vasudevan², Ann A Lazar³, Jason W Chan², Jonathan R George⁴, Michael D Alvarado⁵, Siegrid S Yu⁶, Adil Daud⁷, Sue S Yom²

Affiliations

¹ Department of Ophthalmology, University of California San Francisco, San Francisco, California.
² Department of Radiation Oncology, University of California San Francisco, San Francisco, California.
³ Department of Preventative and Restorative Dental Sciences, University of California San Francisco, San Francisco, California.
⁴ Department of Otolaryngology - Head and Neck Surgery, University of California San Francisco, San Francisco, California.
⁵ Department of Surgery, University of California San Francisco, San Francisco, California.
⁶ Department of Dermatology, University of California San Francisco, San Francisco, California.
⁷ Department of Medicine, University of California San Francisco, San Francisco, California.

Abstract

Purpose: Radiation of the draining lymph node basin remains controversial for Merkel cell carcinoma, particularly in the era of sentinel lymph node biopsy (SLNB).

Methods and materials: Based on a 20-year experience using SLNB-guided adjuvant radiation therapy (RT), we conducted a retrospective review of clinically node-negative patients testing 2 hypotheses: (1) whether nodal RT could be safely omitted in SLNB-negative Merkel cell carcinoma and (2) whether the excised primary site should always be radiated. Clinically node-positive patients were excluded.

Results: Among 57 clinically node-negative patients who underwent SLNB and wide local excision (WLE), 42 (74%) had a negative SLNB, and 15 (26%) had a positive SLNB. At a median follow-up of 43 months (range, 5-182), SLNB-negative patients irradiated to the primary site had improved 4-year disease-specific survival (100% vs 65%, P = .008), local recurrence-free survival (100% vs 76%, P = .009), and distant recurrence-free survival (100% vs 75%, P = .008), but not overall survival (87.5% vs 57.7%, P = .164) compared with SLNB-positive patients receiving comprehensive RT. Among SLNB-negative patients treated with WLE only, 67% (6/9) had a disease relapse, half of which were local relapses (33%).

Conclusions: In this single-institution retrospective review, after negative SLNB and WLE, RT given only to the primary site provided 100% disease control without a need for nodal RT. Among SLNB-negative patients who had WLE, omission of postoperative primary-site RT was associated with 67% cancer relapse, of which half was local.