A 52-year-old woman from urban Delhi presents with postmenopausal bleeding and vaginal discharge for 3 weeks. On speculum examination, a friable, bleeding cervical mass is noted. Pap smear shows malignant cells. Colposcopy-guided cervical biopsy confirms squamous cell carcinoma of the cervix. Staging workup including pelvic MRI reveals a 4 cm cervical lesion with parametrial invasion but no distant metastases (FIGO Stage IIB). The patient has no contraindications to chemotherapy or radiation. What is the most appropriate treatment?