Main Session
Sep
28
PQA 04 - Breast Cancer, Patient Reported Outcomes/QoL/Survivorship, Functional Radiation Medicine, Hematologic Malignancies, Palliative Care, and International/Global Oncology
2831 - Does Intensity Modulated Proton Therapy Reduce Clinical Hypothyroidism after Supraclavicular Irradiation for Breast Cancer?
Presenter(s)
Nikolai Strusberg, MD - Baptist Health Herbert Wertheim Cancer Institute, Miami, FL
N. Strusberg1,2, R. Herrera1,2, D. Wang1,2, K. Mamanna3, M. Voskanyan4, R. Patel4, L. Hodgson2,5, M. A. Fagundes2,6, M. A. M. Rodrigues2,6, A. Wroe2,7, A. Gutierrez2,6, R. P. Tolakanahalli2,6, C. Tohtz2,6, and J. E. Panoff1,2; 1Department of Radiation Oncology, Miami Cancer Institute, Miami, FL, 2Department of Oncological Sciences, Herbert Wertheim College of Medicine, Florida International University, Miami, FL, 3Florida International University, Miami, FL, 4Herbert Wertheim College of Medicine, Florida International University, Miami, FL, 5Department of Biostatistics, Miami Cancer Institute, Miami, FL, 6Department of Radiation Oncology, Miami Cancer Institute, Baptist Health South Florida, Miami, FL, 7Miami Cancer Institute, Miami, FL
Purpose/Objective(s):
Hypothyroidism (HT) is an endocrine disorder characterized by a variety of symptoms affecting quality of life and may lead to multi-organ failure. HT has been found to be associated in breast cancer (BC) patients that received photon radiation (PhT) to the supraclavicular fossa (SC). There is a paucity of data evaluating clinical HT (CHT) in patients who received proton therapy (PT) to the SC. We sought to compare CHT rates in BC patients who had the SC treated with PT versus IMRT based PhT. We hypothesized that the PT cohort would have statistically significant less CHT than the PhT cohort due to PT dosimetric sparing to the contralateral thyroid.Materials/Methods:
An IRB approved retrospective study was conducted on BC patients who had the SC treated between January 2017- December 2024 at our institution. Patients with baseline thyroid dysfunction were excluded. CHT was the primary outcome variable and was defined by AAEC/ATA criteria. Thyroid dose-volumetric parameters were compared between the two cohorts. A multivariable (MVA) logistic regression model was fitted to estimate the adjusted association between RT technique and post RT CHT. Covariates were selected based on clinical relevance. Adjusted odds ratios (ORs) with 95% confidence intervals (CIs) were reported. Freedom from CHT was estimated using the Kaplan–Meier method.Results:
750 patients were identified, 249 were included (PhT n=129; PT n=120) in the analysis. Median follow up was 41.4 months. All PT patients were treated with a pencil beam scanning delivery technique and all PhT patients were treated with IMRT. The majority of PT was conventionally fractionated (58.0%), whereas PhT was largely hypo-fractionated (77.9%). Patient demographics including age, race, ethnicity, menopausal status, molecular subtype, stage, diabetes, and autoimmune disease were balanced between groups. There were more left sided patients in the proton cohort (p<0.001). Systemic therapy was balanced between groups except for pre-radiation Immunotherapy (p=.02) and post radiation endocrine therapy (p=.01). PT patients had smaller baseline mean thyroid volumes, median 7.5 cc vs 10.9 cc (p<0.001). All dosimetric parameters (mean thyroid dose, V5,10,20,30,40) were significantly higher with PhT (all p<.001) and all were associated with CHT (all p<.017). PhT was associated with a higher rate of CHT in MVA (OR 2.94; 95% CI, 1.12-8.41, p=.03). Additionally, white race had more CHT but there were few non-white patients (OR 4.99; 95% CI, 1.32-32.89, p=.04).Conclusion:
This is the largest series to date in the literature comparing CHT in BC patients who had the SC treated with PT versus PhT. Patients who received PT had a lower incidence of CHT compared with IMRT PhT. This was associated with reduced thyroid dose across all dosimetric parameters. Prospective analysis of PT thyroid sparing is imperative.