Dosimetric Analysis and Clinical Correlation of Brachial Plexus Toxicity in Head and Neck Cancer Patients Treated with Chemoradiotherapy by IMRT Technique

Abstract

Introduction: Radiation-induced brachial plexopathy (RIBP)
is an uncommon but potentially disabling late complication of
radiotherapy in head and neck cancer. Despite the increasing
use of intensity-modulated radiotherapy (IMRT), the brachial
plexus is not routinely contoured as an organ at risk (OAR), and
its dose–toxicity relationship remains inadequately studied. The
aim is to evaluate the dosimetric parameters of the brachial
plexus in head and neck cancer patients treated with IMRTbased
concurrent chemoradiotherapy and to correlate these
parameters with clinical, radiological, and neurophysiological
evidence of brachial plexus toxicity.
Materials and Methods: This prospective observational study
included 38 patients with stage II–IVA histologically proven
squamous cell carcinoma of the head and neck treated between
November 2019 and April 2021. Patients received definitive
radiotherapy (70 Gy/35 fractions) or adjuvant radiotherapy
(60 Gy/30 fractions), with concurrent weekly cisplatin when
indicated. The brachial plexus was retrospectively delineated
according to RTOG guidelines, and dosimetric parameters
including Dmax, Dmean, V40–V70, D50, and D80 were
analyzed. Clinical assessment was performed using
CTCAE v5.0, an 18-item brachial plexopathy questionnaire,
neurological examination, MRI, and nerve conduction velocity
(NCV) studies. The median follow-up was 39 months (range:
12–54 months).
Results: The mean maximum dose (Dmax) to the brachial
plexus was 65.15 Gy, exceeding recommended tolerance limits
in many patients. Clinically, 22 of 38 patients (57.9%) developed
symptoms suggestive of brachial plexopathy, most commonly
sensory disturbances (65.7%), proximal arm weakness (63.1%),
impaired hand function (42.1%), and limitation of daily activities
(42.1%). Over 20 patients underwent MRI and NCV evaluation;
among them, 14 (70%) demonstrated clinical evidence of
brachial plexopathy, while 10 (50%) showed concordant clinical,
MRI, and NCV abnormalities. MRI findings included nerve
root thickening, T1/T2 hyperintensity, edema, and contrast
enhancement. Significant deterioration in NCV parameters was
observed in the median, radial, axillary, musculocutaneous,
and left ulnar nerves. Patients receiving 70 and 60 Gy had
comparable brachial plexus Dmax values (66.9 vs. 66.5 Gy),
with RIBP observed in 41 and 52.3% of patients, respectively.
Conclusion: The brachial plexus frequently receives doses
exceeding recommended tolerance during IMRT for head and
neck cancer when no specific dose constraints are applied.
A substantial proportion of patients developed clinical,
radiological, and neurophysiological features of RIBP during
follow-up. Routine contouring of the brachial plexus as an OAR,
implementation of dose constraints (maximum dose ≤60–66 Gy),
and long-term surveillance are recommended to minimize
the risk of radiation-induced brachial plexopathy and improve
functional outcomes.