Reducing radiation therapy dose to bilateral submandibular lymph nodes improves salivary function

For head and neck cancer patients undergoing radiation therapy, a reduction in the amount of radiation treatment volume to the submandibular (level IB) lymph nodes resulted in better patient-reported salivary function, according to new research. The findings were presented at the 2014 Multidisciplinary Head and Neck Cancer Symposium in Scottsdale, Arizona. The study results also found significant reductions in radiation dose to the salivary organs, and good local regional control.

Researchers evaluated 125 patients with node-positive oropharyngeal cancer who received chemoradiation at Memorial Sloan-Kettering Cancer Center in New York, New York, between May 2010 and December 2011. The average patient age was 57 years. A total of 51% of patients had base of tongue lesions; 41% had tonsil cancer; and 6% were classified as other. The breakdown of patients' cancer stage/classification was: 74% T1-2 and 26% T3-4. All patients had cancer with lymph node involvement, including 16% N1; 8% N2A; 48% N2B; and 28% N2C.

Patients were categorized into two groups: those with sparing, or a reduction of radiation treatment volume to the region, of bilateral level IB nodes and those who underwent treatment without sparing. A prospective questionnaire regarding xerostomia (dry mouth) to assess late xerostomia was given to patients in both groups at each patient follow-up visit; clinical assessment (observer-rated) xerostomia scores were also recorded.

The participants who received treatment involving sparing experienced significant improvement in patient-reported xerostomia summary scores (P=.021) and observer-rated xerostomia scores (P=.006) over the group in which there was no sparing. The 2-year local regional control rate for the spared group was 97.5% and for the group treated was 93.8%, indicating a low rate of cancer recurrence at the original tumor site.

In addition, study results showed reductions in the mean radiation doses to the mouth and neck regions of patients in the spared group over the group with no sparing, including the ipsilateral submandibular gland (63.9 Gy vs 70.5 Gy; P<.001); the contralateral submandibular gland (45.0 Gy vs 56.2 Gy, P<0.001); and the oral cavity (35.9 Gy vs 45.2 Gy; P<.001).

"Radiation therapy plays an important role in the treatment of head and neck cancers," said Moses Tam, lead author of the study and an MD candidate in his final year at New York University School of Medicine. "Poor salivary function is the most common side effect of radiation treatment to the head and neck region. Our data show that it is safe to spare the tumor-free level IB lymph nodes in oropharyngeal cancer from radiation treatment. Sparing this lymph node level will reduce radiation dose to several nearby salivary organs and therefore cause less damage to a patient's posttreatment salivary function."

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