Implementation and Outcome Assessment of the 2024 International Clinical Target Volume Delineation Guideline in Locoregionally Advanced Nasopharyngeal Carcinoma: A Prospective Clinical Study

Nasopharyngeal carcinoma (NPC) is a cancer that develops in the nasopharynx, an area located behind the nose and above the throat. Treating NPC is challenging because this region lies very close to important organs such as the brain, eyes, nerves, and salivary glands. Radiation therapy is the main treatment for NPC and is highly effective, but it must be planned with great precision to destroy the cancer while minimizing damage to nearby healthy tissues.

To ensure consistency and safety in radiation treatment planning, international expert groups have developed guidelines that define how radiation oncologists should outline the areas that need to be treated with radiation. The 2018 international guideline (IG-2018) has been widely used in routine practice. In recent years, however, the treatment of NPC has evolved. Many patients now receive chemotherapy before radiation therapy, known as neoadjuvant or induction chemotherapy. This often causes the tumor to shrink significantly before radiation treatment begins.

Because of this change in treatment approach, an updated international guideline (IG-2024) was released in 2025. This new guideline recommends using imaging done after chemotherapy to define the radiation target areas more accurately. It also suggests smaller safety margins and refined dose levels, with the goal of maintaining good cancer control while reducing radiation exposure to normal tissues. By doing so, the guideline aims to lower the risk of side effects such as dry mouth, hearing problems, and nerve damage, which can affect long-term quality of life.

Although IG-2024 is based on strong scientific evidence and expert consensus, its use has not yet been prospectively evaluated in real-world clinical settings in India. This is especially important in Northeast India, where NPC is more common than in most other parts of the country.

This study will be carried out at a tertiary cancer centre in Northeast India. Patients receiving standard treatment for NPC will be treated using radiation plans designed according to the IG-2024 guideline. No experimental drugs or additional procedures are involved. Patients will be followed during treatment and for at least two years afterward to assess how well the cancer is controlled and to record any treatment-related side effects.

The results of this study will help determine whether IG-2024 can be safely and effectively used in routine clinical practice in this region. Participation is voluntary, and all patient information will be kept confidential.