Head and Neck Cancer

PV QA 2 - Poster Viewing Q&A 2

MO_32_2747 - Heterogeneity of Treatment Effect: Radiation Therapy for Graves Orbitopathy and Compressive Optic Neuropathy

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

Heterogeneity of Treatment Effect: Radiation Therapy for Graves Orbitopathy and Compressive Optic Neuropathy
T. Nanda1, K. Dunbar1, A. Campbell2, R. Bathras1, C. C. Wu3, J. Purswani4, T. J. C. Wang3, and M. Kazim1; 1Harkness Eye Institute, New York, NY, 2John Hopkins Wilmer Eye Institute, Baltimore, MD, 3Department of Radiation Oncology, Columbia University Medical Center, New York, NY, 4New York University School of Medicine, New York, NY

Purpose/Objective(s): The efficacy of radiotherapy (RT) in thyroid eye disease (TED) is well known, with a mono-therapeutic response rate of 66%. In cases with compressive optic neuropathy (CON), up to 95% of patients show clinical improvement. The majority of these studies assume an average treatment effect across a varied patient population. Few studies have conducted clinically relevant subgroup analyses to determine heterogeneity of treatment effect; in order to identify patients in whom the magnitude of benefit may differ based on known pre-treatment modifiers. The objective of this study was to conduct a retrospective subset analysis for patients receiving RT for TED-CON measured across mean deviation on 24-2 Humphreys visual field (VF), LogMAR visual acuity (VA), and Hardy-Rand-Rittler color plates (CP).

Materials/Methods: 62 patients, 117 orbits with TED-CON who received RT were retrospectively analyzed pre and post RT treatment (20Gy in 10fx). CON was confirmed by decreased VA with either an afferent pupillary defect, VF defect, or CP deficit. Patients were divided into quintiles based on pre-treatment VF, with more negative values indicating larger VF defects. The first follow up was gathered, approx. 1.5-3 months post-RT. Statistical analysis was conducted via one-way ANOVA.

Results: Overall improvement on VFs was +16.6%, +22.5% in CP, +31.6% in VA, 71.84 days post-RT for all 117 orbits. Results by quintile are represented in Table 1. The five quintiles constituted respective ranges on pre-RT VFs of; Q1 (-25.94 to -7.11), Q2 (-6.97 to -3.93), Q3 (-3.9 to -2.53), Q4 (-2.46 to -1.12), and Q5 (-1.11 to +7.47). There was no significant difference amongst quintiles in pre-RT steroids, post-RT steroids, and follow up duration (p=0.421, 0.635, and 0.991).

Conclusion: Q5 showed a 75% decrease in VFs post treatment. A closer examination of the Q4/Q5 quintile showed no improvement in VFs with pre-RT values of -1.0 to -0.5. From -0.5 to >0.00, outcomes actually worsened post-RT. This did not translate, however, to CP and VA, which continued to show post-RT improvement. VA showed fairly equivalent improvement across all quintiles, un-associated with the worsening VFs in Q4/Q5. CP showed the most improvement in the worst patients, Q1, vs. Q4/Q5, in which CP improvement was minimal (5.6-9%). Consistent with anecdotal experience, our subset analysis shows heterogeneity of treatment effect amongst patients treated for TED-CON with RT. Further evaluation and extended follow up of patients with minimal deficits on pre-RT VFs is warranted to determine if RT confers benefit.
Quintile VF CP VA Follow Up (days) Steroids (mg)
Q1 Mean -10.81 3.77 0.253 0.0 23.2
% change +35.9 +55.5 +30.7 71.84 9.9
Q2 Mean -5.59 3.69 0.25 0.0 20.9
% change +25.4 +29.0 +22.4 72.83 11.5
Q3 Mean -3.15 3.46 0.28 0.0 33.9
% change +38.2 +38.2 +33.6 71.40 12.2
Q4 Mean 1.87 4.65 0.266 0.0 31.3
% change +3.2 +5.6 +36.8 70.43 9.9
Q5 Mean 0.41 4.46 0.131 0.0 20.8
% change -75.7 +9.0 +32.0 73.68 7.4

Author Disclosure: T. Nanda: None. K. Dunbar: None. A. Campbell: None. R. Bathras: None. C. Wu: None. T.J. Wang: Honoraria; Elekta, Wolthers Kluwer. Consultant; Abbvie, Merck, Doximity, Elekta. Advisory Board; American Cancer Society North Jersey, AstraZeneca. Travel Expenses; Abbvie, AstraZeneca, Elekta. Stock Options; Doximity. M. Kazim: President; International Thyroid Eye Disease Society.

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