Elsevier

Seminars in Oncology

Volume 35, Issue 3, June 2008, Pages 236-250
Seminars in Oncology

Head and neck cancer
New Developments in Radiation Therapy for Head and Neck Cancer: Intensity-Modulated Radiation Therapy and Hypoxia Targeting

https://doi.org/10.1053/j.seminoncol.2008.03.003Get rights and content

Intensity-modulated radiation therapy (IMRT) has revolutionized radiation treatment for head and neck cancers (HNCs). When compared to the traditional techniques, IMRT has the unique ability to minimize the dose delivered to normal tissues without compromising tumor coverage. As a result, side effects from high-dose radiation have decreased and patient quality of life has improved. In addition to toxicity reduction, excellent clinical outcomes have been reported for IMRT. The first part of this review will focus on clinical results of IMRT for HNC. Tumor hypoxia, or the condition of low oxygen, is a key factor for tumor progression and treatment resistance. Hypoxia develops in solid tumors due to aberrant blood vessel formation, fluctuation in blood flow, and increasing oxygen demands for tumor growth. Because hypoxic tumor cells are more resistant to ionizing radiation, hypoxia has been a focus of clinical research in radiation therapy for half a decade. Interest for targeting tumor hypoxia has waxed and waned as promising treatments emerged from the laboratory, only to fail in the clinics. However, with the development of new technologies, the prospect of targeting tumor hypoxia is more tangible. The second half of the review will focus on approaches for assessing tumor hypoxia and on the strategies for targeting this important microenvironmental factor in HNC.

Section snippets

Intensity-Modulated Radiotherapy

Intensity-modulated radiotherapy (IMRT) is a refinement of three-dimensional conformal radiotherapy (3DCRT). It uses a computerized treatment planning system along with sophisticated delivery machineries to tailor the radiation dose to the tumor target.1, 2 By subdividing a broad radiation beam into smaller pencil beams and by varying the intensities of these pencil beams, a conformal dose distribution is generated. Tumor coverage is improved, particularly in situations where the disease lies

Techniques to Measure Tumor Hypoxia and Their Clinical Significance in Head and Neck Squamous Cell Cancer

Currently, there exist several approaches for detecting tumor hypoxia in HNC. At a recent hypoxia workshop, convened by the National Cancer Institute (NCI), the consensus among the experts was that “there is not, and probably will never be, a single clear ‘gold standard’ for in vivo hypoxia measurement.”57 The workshop report also presented a comprehensive review of different approaches for measuring tumor hypoxia. Briefly, techniques for measuring tumor oxygen can be categorized into two

Conclusions

Given the available dosimetric and clinical data, IMRT is an effective treatment modality for HNC. It conforms the dose to the tumor while sparing nearby normal tissues. Toxicity from high-dose RT has decreased when compared to historical controls. Clinical reports have shown great promise in terms of tumor control. With advances in anatomic and functional imaging, along with more clinical experience, it is likely that IMRT will lead to further improvements in tumor control, survival, and

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    Supported in part by 1 R01 CA118582-01 (Q.-T.L.) and ASTRO Junior Investigator Award (N.Y.L.).

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