Stereotactic Body Radiotherapy Boost Versus Simultaneous Integrated Boost to Pelvic Nodes Among Patients Receiving Radical Chemoradiation in Carcinoma Cervix

Experimental Arm: Stereotactic Body Radiotherapy Boost to Involved Pelvic Lymph Nodes Participants in the experimental arm will receive definitive radical chemoradiation for stage IIIC carcinoma cervix with a stereotactic body radiotherapy (SBRT) boost to the radiologically involved pelvic lymph node(s). The purpose of this intervention is to intensify the dose to gross nodal disease while maintaining acceptable doses to nearby organs at risk, including bowel, rectum, bladder, sigmoid, spinal cord, kidneys, femoral heads, duodenum, and active bone marrow. The SBRT boost is integrated with standard pelvic external beam radiotherapy and concurrent chemotherapy, followed by brachytherapy as per institutional curative protocol.

Patients in the standard arm will receive radical chemoradiation with pelvic external beam radiotherapy to 45 Gy in 25 fractions over 5 weeks, along with a simultaneous integrated boost to involved pelvic node(s) to a total dose of 55 Gy or 57.5 Gy in 25 fractions, delivered in a simultaneous integrated manner according to nodal size, location, and institutional planning constraints. Concurrent weekly cisplatin 40 mg/m² will be administered during external beam radiotherapy, subject to adequate renal function and treatment tolerance. After completion of external beam treatment, patients will receive brachytherapy as per institutional protocol, using intracavitary or interstitial technique depending on residual disease and anatomy. Treatment will be planned with appropriate image guidance, and organs at risk will be respected according to predefined dose constraints. Toxicity will be monitored during treatment and follow-up, and graded using CTCAE version 5.0.