Low Grade, Indolent Lymphomas of the Head and Neck: Comparative Toxicity of Standard Versus Very Low Dose Radiation Therapy

National Comprehensive Cancer Network guidelines recommend radiation therapy (RT) for localized indolent non‐Hodgkin lymphomas (iNHL). Many referring physicians avoid RT to the head and neck (HN) due to fears of toxicity. Very low‐dose radiation (4 Gy) for select patients produces sustained local control and recently gained popularity. We compared early and late toxicities of standard 24–30 Gy to 4 Gy in patients with HN iNHL. We retrospectively analyzed 266 consecutive patients with HN iNHL receiving RT from 1994 to 2017. Patient characteristics, outcomes, and toxicities were collected from medical records. Early (≤2 months post‐RT) and late (>2 months post‐RT) toxicities were graded per Common Terminology Criteria for Adverse Events version 4. Grades 1–2 were defined as “low‐grade” and 3–4 “high‐grade.” Toxicity incidence was compared between 4 and >4 Gy, grouped by treated site (orbit, nonorbital head, neck, skin) and early versus late. Median follow‐up was 23 months (2–145) and 68 months (2–256) for 4Gy and >4 Gy cohorts, respectively. Median dose for the >4 Gy cohort was 30 Gy (10.5–54 Gy). Early and late toxicity incidences were lower in the 4 Gy cohort compared to >4 Gy across all RT‐sites: early toxicity, orbit, 42% versus 96%; nonorbital head, 24% versus 96%; neck, 22% versus 94%; skin, 31% versus 87%; late toxicity, orbit, 20% versus 71%; nonorbital head, 6% versus 66%; neck, 6% versus 57%; skin, 0% versus 46% (4 Gy vs. >4 Gy, respectively). Toxicities among both cohorts were largely low‐grade. High‐grade early and late toxicities did not occur in the 4 Gy cohort. There was 1 high‐grade early toxicity (Grade 3 dry mouth) and 17 high‐grade late toxicities (Grade 3 cataracts) in the >4 Gy cohort. RT to HN for iNHL is associated with minimal short‐ and long‐term toxicity and excellent local control among 4 Gy and >4 Gy treatments. In this setting, “toxicity” concerns should not deter oncologists from potentially curative RT. In select patients where toxicity remains a concern, very low dose 4 Gy could be considered.