Official reprint from UpToDate®
www.uptodate.com ©2016 UpToDate®

General principles of radiation therapy for head and neck cancer

Wendy Hara, MD
Shlomo A Koyfman, MD
Section Editors
Bruce E Brockstein, MD
David M Brizel, MD
Marshall R Posner, MD
Deputy Editor
Michael E Ross, MD


Radiation therapy (RT) is an important and potentially curative modality for head and neck cancers. For many primary sites within the head and neck, RT yields better functional outcomes than surgery and thus is often preferred for localized disease. For locoregionally advanced lesions, RT is often used in combination with chemotherapy as a definitive organ function-preserving approach or after surgery as an adjuvant.

The general principles of RT for head and neck squamous cell carcinoma will be reviewed here. The approach to dose and schedule for definitive radiation therapy of head and neck cancer is discussed separately. (See "Definitive radiation therapy alone for advanced (stage III and IV) head and neck cancer: Dose and fractionation schedule".)


Ionizing radiation produces its biologic effects by imparting energy to tissues. Free radicals are generated, which cause single strand and double strand DNA breaks and loss of cellular reproductive ability.

Some cells die relatively rapidly through apoptosis. However, most cells do not manifest evidence of damage until mitosis occurs, and several divisions may ensue before actual cell death (termed mitotic cell death). The cellular doubling time (typically three to five days for head and neck cancer) also influences the rapidity with which a tumor shrinks. For this reason, most tumors do not show immediate shrinkage after starting radiation therapy (RT). While radioresponsive tumors start to shrink in a few days, most head and neck cancers may take weeks or longer to shrink. Some low-grade, slowly proliferating tumors histologically appear to be viable for prolonged periods after irradiation.

The radiation dose is measured in Gray (Gy), which is defined as the absorption of 1 joule of energy per kilogram of matter (water or human tissue). One Gy is equivalent to 100 centigray (cGy) or 100 rad (the formerly used unit of measure). As the radiation beam passes through tissue, its energy is absorbed; the higher the energy of the beam (expressed as megavoltage [MV]), the deeper it penetrates. The depth of tumor in the head and neck area is relatively shallow compared with many other visceral organs. Thus the energy of the beam used for head and neck cancer treatment is usually lower.


Subscribers log in here

To continue reading this article, you must log in with your personal, hospital, or group practice subscription. For more information or to purchase a personal subscription, click below on the option that best describes you:
Literature review current through: Sep 2016. | This topic last updated: Mar 17, 2016.
The content on the UpToDate website is not intended nor recommended as a substitute for medical advice, diagnosis, or treatment. Always seek the advice of your own physician or other qualified health care professional regarding any medical questions or conditions. The use of this website is governed by the UpToDate Terms of Use ©2016 UpToDate, Inc.
  1. Boero IJ, Paravati AJ, Xu B, et al. Importance of Radiation Oncologist Experience Among Patients With Head-and-Neck Cancer Treated With Intensity-Modulated Radiation Therapy. J Clin Oncol 2016; 34:684.
  2. Lee N, Puri DR, Blanco AI, Chao KS. Intensity-modulated radiation therapy in head and neck cancers: an update. Head Neck 2007; 29:387.
  3. Nutting CM, Morden JP, Harrington KJ, et al. Parotid-sparing intensity modulated versus conventional radiotherapy in head and neck cancer (PARSPORT): a phase 3 multicentre randomised controlled trial. Lancet Oncol 2011; 12:127.
  4. Kam MK, Leung SF, Zee B, et al. Prospective randomized study of intensity-modulated radiotherapy on salivary gland function in early-stage nasopharyngeal carcinoma patients. J Clin Oncol 2007; 25:4873.
  5. Gupta T, Agarwal J, Jain S, et al. Three-dimensional conformal radiotherapy (3D-CRT) versus intensity modulated radiation therapy (IMRT) in squamous cell carcinoma of the head and neck: a randomized controlled trial. Radiother Oncol 2012; 104:343.
  6. Dirix P, Vanstraelen B, Jorissen M, et al. Intensity-modulated radiotherapy for sinonasal cancer: improved outcome compared to conventional radiotherapy. Int J Radiat Oncol Biol Phys 2010; 78:998.
  7. Lee AW, Ng WT, Chan LL, et al. Evolution of treatment for nasopharyngeal cancer--success and setback in the intensity-modulated radiotherapy era. Radiother Oncol 2014; 110:377.
  8. Pisani L, Lockman D, Jaffray D, et al. Setup error in radiotherapy: on-line correction using electronic kilovoltage and megavoltage radiographs. Int J Radiat Oncol Biol Phys 2000; 47:825.
  9. Hong TS, Tomé WA, Chappell RJ, et al. The impact of daily setup variations on head-and-neck intensity-modulated radiation therapy. Int J Radiat Oncol Biol Phys 2005; 61:779.
  10. Mageras GS, Mechalakos J. Planning in the IGRT context: closing the loop. Semin Radiat Oncol 2007; 17:268.
  11. Piermattei A, Cilla S, D'Onofrio G, et al. Large discrepancies between planned and actually delivered dose in IMRT of head and neck cancer. A case report. Tumori 2007; 93:319.
  12. Hansen EK, Bucci MK, Quivey JM, et al. Repeat CT imaging and replanning during the course of IMRT for head-and-neck cancer. Int J Radiat Oncol Biol Phys 2006; 64:355.
  13. Vásquez Osorio EM, Hoogeman MS, Al-Mamgani A, et al. Local anatomic changes in parotid and submandibular glands during radiotherapy for oropharynx cancer and correlation with dose, studied in detail with nonrigid registration. Int J Radiat Oncol Biol Phys 2008; 70:875.
  14. Nishi T, Nishimura Y, Shibata T, et al. Volume and dosimetric changes and initial clinical experience of a two-step adaptive intensity modulated radiation therapy (IMRT) scheme for head and neck cancer. Radiother Oncol 2013; 106:85.
  15. Salama JK, Haddad RI, Kies MS, et al. Clinical practice guidance for radiotherapy planning after induction chemotherapy in locoregionally advanced head-and-neck cancer. Int J Radiat Oncol Biol Phys 2009; 75:725.
  16. Owen D, Iqbal F, Pollock BE, et al. Long-term follow-up of stereotactic radiosurgery for head and neck malignancies. Head Neck 2015; 37:1557.
  17. Vargo JA, Heron DE, Ferris RL, et al. Examining tumor control and toxicity after stereotactic body radiotherapy in locally recurrent previously irradiated head and neck cancers: implications of treatment duration and tumor volume. Head Neck 2014; 36:1349.
  18. Holliday EB, Frank SJ. Proton radiation therapy for head and neck cancer: a review of the clinical experience to date. Int J Radiat Oncol Biol Phys 2014; 89:292.
  19. Wang CC. Improved local control of nasopharyngeal carcinoma after intracavitary brachytherapy boost. Am J Clin Oncol 1991; 14:5.
  20. Mazeron JJ, Belkacemi Y, Simon JM, et al. Place of Iridium 192 implantation in definitive irradiation of faucial arch squamous cell carcinomas. Int J Radiat Oncol Biol Phys 1993; 27:251.
  21. Nag S, Cano ER, Demanes DJ, et al. The American Brachytherapy Society recommendations for high-dose-rate brachytherapy for head-and-neck carcinoma. Int J Radiat Oncol Biol Phys 2001; 50:1190.
  22. Scala LM, Hu K, Urken ML, et al. Intraoperative high-dose-rate radiotherapy in the management of locoregionally recurrent head and neck cancer. Head Neck 2013; 35:485.