OPTIMIZATION OF DOSIMETRIC PLANNING PARAMETERS FOR RADIOTHERAPY OF HEAD AND NECK TUMORS

The study was conducted at the Center of Nuclear Medicine and Oncology of the Abai Region (Semey, Kazakhstan) and was aimed at the quantitative evaluation and optimization of dose planning parameters in patients with head and neck tumors. A retrospective analysis included seven patients (N = 7) treated in 2024, for whom radiotherapy plans were generated using intensity-modulated radiation therapy (Intensity-Modulated Radiation Therapy, IMRT) and volumetric modulated arc therapy (Volumetric Modulated Arc Therapy, VMAT) on a TrueBeam linear accelerator within the Eclipse treatment planning system. The objective of the study was a comparative physical-dosimetric assessment of plan quality with analysis of key dosimetric metrics and logistical efficiency of dose delivery. The analysis demonstrated comparable coverage of the planning target volume (PTV) for both techniques, while clinically significant differences were observed in dose distribution to organs at risk. The use of VMAT resulted in a reduction of the mean dose to the parotid glands by 4,65 Gy compared with IMRT (19,60±7,97 Gy vs. 24,26±3,75 Gy), achieving values below the critical threshold of 25 Gy and contributing to preservation of glandular function. The mean dose to the spinal cord was also lower with VMAT (37,96±4,16 Gy vs. 41,37±1,94 Gy), thereby enhancing radiation safety of treatment. Logistical analysis revealed a clear advantage of VMAT, characterized by more than a 60% reduction in monitor units and dose delivery time compared with IMRT, which contributes to decreased radiation exposure of organs at risk and supports the feasibility of VMAT as a preferred technique in routine clinical practice.

1. Ouyang Z., Shen Z.L., Murray E. [et al.] Evaluation of auto planning in IMRT and VMAT for head and neck cancer // J. Appl. Clin. Med. Phys. – 2019. – Vol. 20, No. 7. – P. 39–47.

2. Szalkowski G., Xu X., Das S., Yap P.-T., Lian J. Automatic treatment planning for radiotherapy: a cross-modality and protocol study // Adv. Radiat. Oncol. – 2024. – Vol. 9, No. 12. – Art. 101649.

3. Nanda S., Parida S., Ahirwar M.K. A dosimetric comparison of volumetric modulated arc therapy and IMRT for cochlea sparing radiation therapy in locally advanced nasopharyngeal cancer // J. Med. Phys. – 2023. – Vol. 48, No. 3. – P. 248–251.

4. Hamatani N., Sumida I., Seo Y., Isohashi F., Tamari K., Ogawa K. Three-dimensional dose prediction and validation with the radiobiological gamma index based on a relative seriality model for head and neck IMRT // J. Radiat. Res. – 2017. – Vol. 58, No. 5. – P. 701–709.

5. Rawal T., Sharma N., Gajraj V.K., Meena R., Thanvi S., Singh G., Jakhar S.L., Kumar H.S. Comparative dosimetric analysis of IMRT and VMAT in head and neck cancers // Asian Pac. J. Cancer Care. – 2024. – Vol. 9, No. 1. – P. 77–80.

6. Bera S., Choudhury D., Roy S., Mukhopadhyay P., Sarkar S. Development of prediction model for mean parotid dose of HNC undergoing radiotherapy: a single institutional study // J. Med. Phys. – 2023. – Vol. 48, No. 3. – P. 274– 280.

7. Nowicka Z., Tomasik B., Papis-Ubych A. [et al.] Radiation-induced hypothyroidism in patients with oropharyngeal cancer treated with IMRT: independent and external validation of five NTCP models // Cancers (Basel). – 2020. – Vol. 12, No. 9. – Art. 2716.

8. Rawal T., Sharma N., Gajraj V.K. [et al.] Comparative dosimetric analysis of IMRT and VMAT in head and neck cancers // Int. J. Radiat. Oncol. Biol. Phys. – 2024. – P. 19–22.

9. Bhide S.A., Nutting C.M. Advances in radiotherapy for head and neck cancer // Oral Oncol. – 2020. – Vol. 111. – Art. 104915.

10. Fokdal L., Grau C., Høyer M., Bentzen S. M. Impact of adaptive radiotherapy in head and neck cancer: a review // Acta Oncol. – 2021. – Vol. 60, No. 8. – P. 1013–1022.

11. Xu J., Lin S., Huang M. Clinical implementation of radiobiological γ-index for head and neck IMRT QA // Phys. Med. Biol. – 2022. – Vol. 67, No. 10. – Art. 105012.

12. Kunkler I. H., Robinson M., McIntyre J. Review of VMAT in head and neck cancer: dosimetric and clinical outcomes // Br. J. Radiol. – 2023. – Vol. 96. – Art. 1143.

13. International Atomic Energy Agency. Accuracy Requirements and Uncertainties in Radiotherapy. Human Health Series No. 31. Vienna: IAEA, 2016.

14. International Atomic Energy Agency. Radiation Protection and Safety in Medical Uses of Ionizing Radiation. Safety Standards Series No. SSG-46. Vienna: IAEA, 2018.

15. International Atomic Energy Agency. Institutions for Radiotherapy: Recommendations for the Development of a General Plan and Conceptual Design. STI/PUB/1645. Vienna: IAEA, 2015.