A 38-year-old woman from Delhi presents with vaginal bleeding and pelvic pain. Cervical biopsy confirms stage IIB squamous cell carcinoma of the cervix (4.5 cm lesion with parametrial invasion). Staging workup including chest X-ray, abdominal ultrasound, and pelvic MRI shows no distant metastases. She has no contraindications to chemotherapy or radiation. What is the most appropriate primary treatment for this patient?