Hematologic Cancer

PV QA 2 - Poster Viewing Q&A 2

MO_41_2459 - Low Grade, Indolent Lymphomas of the Head and Neck: Comparative Toxicity of Standard Versus Very Low Dose Radiation Therapy

Monday, October 22
10:45 AM - 12:15 PM
Location: Innovation Hub, Exhibit Hall 3

Low Grade, Indolent Lymphomas of the Head and Neck: Comparative Toxicity of Standard Versus Very Low Dose Radiation Therapy
M. R. Chelius1, K. Chau2, J. C. Yang2, and J. Yahalom2; 1Dartmouth's Geisel School of Medicine, Hanover, NH, 2Memorial Sloan Kettering Cancer Center, New York, NY

Purpose/Objective(s): NCCN guidelines recommend radiation therapy (RT) for the treatment of localized indolent non-Hodgkin lymphomas (NHL). Yet many referring physicians avoid recommending RT to the head and neck (HN) due to fears of RT-related toxicities despite the limited fields and doses currently used. Further, in recent years, very low doses of radiation (4Gy) that effectively produce local control in select patients have gained popularity. We compared early and late toxicity profiles of standard 24-30Gy to very low dose 4Gy in patients with indolent NHL of the HN.

Materials/Methods: We retrospectively analyzed 239 patients with indolent NHL of the HN who received RT from 1994-2017. Baseline patient characteristics, outcomes, and toxicity data were collected from medical records. Early (≤2 months post-RT) and late (>2 months post-RT) toxicities were graded as low grade (1-2) or high grade (3-4) according to CTCAEv4 criteria. Incidence of any toxicity was compared between the 4Gy and >4Gy cohorts, grouped by RT-site treated (orbit, non-orbit head, neck, skin) and by early vs late.

Results: Median follow-up was 1.8 years and 5.3 years for 4Gy and >4Gy cohorts, respectively. Median dose for the >4Gy cohort was 30Gy (5.4-50Gy). There was a lower incidence of both early and late toxicities of any grade in the 4Gy cohort compared to >4Gy across all RT-sites (Table 1). There were no early grade 2 toxicities in the 4Gy group, and incidences in the >4Gy group were as follows: orbit, 14%; non-orbit head, 48%; neck, 38%; skin, 0%. One early high grade toxicity occurred in the >4Gy cohort (dry mouth). Late grade 2 toxicities were infrequent among both the 4Gy and >4Gy groups: orbit (10% vs 7%), non-orbit head (6% vs 8%), neck (0% vs 13%), and skin (0% vs 0%). There were 17 late high grade toxicities (cataracts requiring surgery) in the >4Gy group; however, no information was available to differentiate whether these were age- or RT-related cataracts. There were no grade 4 toxicities in either treatment group. Seventy-three percent of patients in the 4Gy cohort, and 89% in the >4Gy cohort, achieved a complete response at the site of RT. There were 5 in-field failures after initial CR in the 4Gy cohort, and 8 in the >4Gy group.

Conclusion: RT to the HN region for indolent NHL is associated with minimal short- and long-term toxicity and excellent local disease control among both 4Gy and >4Gy treatment groups. Thus, toxicity should not be cited as a reason to forgo standard dose RT in the treatment of indolent NHLs of the HN. Further, in select patients for whom early or late toxicity is a concern, very low dose RT may be considered. Table 1.
Site Early toxicity Late toxicity
4 Gy (n) (%) >4 Gy (n) (%) 4 Gy (n) (%) >4 Gy (n) (%)
Orbit 5 (12) (42) 68 (70) (97) 2 (10) (20) 48 (68) (71)
Non-orbit head 4 (17) (24) 50 (52) (96) 1 (17) (6) 34 (51) (67)
Neck 4 (18) (22) 76 (81) (94) 1 (18) (6) 45 (79) (57)
Skin 5 (16) (31) 13 (15) (87) 0 (15) (0) 6 (13) (46)

Author Disclosure: M.R. Chelius: None. K. Chau: None. J.C. Yang: Senior Committee Member; ARRO. J. Yahalom: Chairman; ILROG.

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