Radiation Induced Lumbar Plexopathy (RILP) in Patients of Cancer Cervix Treated by IMRT Technique: A Study of Dosimetry and Clinical Correlation

Abstract

To assess the Dosimetric parameters of lumbo sacral plexus in carcinoma cervix patients treated with concurrent chemo-radiation by Intensity modulated radiotherapy (IMRT) technique & to clinically correlate these Dosimetric parameters with the lumbo sacral plexus toxicity. Total twenty-four patients were included in this study between December 2020 to December 2021. They were all treated by Intensity modulated radiotherapy (IMRT) technique. Radiotherapy dose delivered was 50Gy in 25 fractions at 2Gy/#, it was followed by 3 applications of intracavitary brachytherapy of 7Gy/ fraction each. The lumbo-sacral plexus was delineated according to guidelines given by Sun and Xi et al. No dose constraint was prescribed to the lumbo-sacral plexus prior to the treatment. Magnetic resonance imaging (MRI) of bilateral lumbo-sacral plexus test was done prior to the treatment and 12 months' post treatment. Dose received by the lumbo-sacral plexus was calculated DVH parameters was evaluated. The lumbo-sacral plexus toxicity was assessed by the 10-point questionnaire pre-treatment & post treatment and was compared. Assessment of toxicity was done by RTOG (Radiation Therapy Oncology Group) scoring criteria. Out of the 24 patients treated, 7 patients had gross nodes which were treated with a boost dose of 60 Gy. Out of these patients 9 patients (37.5%) developed signs and symptoms of radiation induced lumbar plexopathy (RILP). Among these patients, the most common symptom was weakness in the lower limbs followed by impaired leg movement and activities interfering daily activities such as walking, squatting and getting up from the chair. Other positive findings included stiffness, lower limb pain, lower back ache radiating the lateral aspect of the thigh and numbness of the lower limbs. Total prescribed dose to 95% of the planned target volume ranged from 49.2Gy - 61.9 Gy (median - 57 Gy). The mean volume of the LS plexus was 128 cc (range, 92- 143 cc). The mean of the D-max of LS plexus was 56.2 Gy (range, 43.2 Gy- 61.9 Gy). The V30 Gy was received by 84 % of LS plexus, whereas V40, V50, V60 was received by 64 %, 13 % and 4%. The most common significant findings on MRI post treatment were unilateral thickening of the nerve roots followed by hyperintensity in T2 weighted image and STIR sequencing. Mild contrast uptake and edema were present in the nerve roots. Radiation induced lumbar plexopathy (RILP) is one of the late complications after chemoradiotherapy in patients of carcinoma cervix, which is often misdiagnosed or missed on follow up. Therefore, lumbar plexus must be contoured in all pelvic malignancies which are treated by chemoradiotherapy with IMRT technique as it prevents dose dumping in that region. Further studies with longer follow up are needed.