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Reduced radiation minimized xerostomia in oropharyngeal cancer
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Reduced radiation treatment volume to the submandibular lymph nodes was associated with improved patient-reported salivary function in a cohort of patients with node-positive oropharyngeal carcinoma, according to study results presented at the Multidisciplinary Head and Neck Cancer Symposium.
Researchers evaluated 125 patients (median age, 57 years) who underwent chemoradiation therapy for node-positive oropharyngeal carcinoma at Memorial Sloan-Kettering Cancer Center between May 2010 and December 2011.
Seventy-four percent of patients had primary tumors staged T1 to T2, and 26% were staged T3 to T4. Lymph node involvement was present in all patients, including N1 in 16%, N2A in 8%, N2B in 48% and N2C in 28%. Lesions at the base of the tongue were present in 51% of patients, 41% had tonsil cancer and 6% had cancer categorized as “other.”
Patients were grouped according to those for whom bilateral level IB was spared in the radiation treatment vs. those for whom these nodes were not treated. At each follow-up visit, a questionnaire was administered to evaluate patient-reported symptoms of late xerostomia, and observer-rated clinical assessments also were made at each visit.
Researchers reported 2-year local regional control rates of 97.5% in the spared group and 93.9% in the treated group. Patients in the spared group demonstrated significant improvements in patient-reported xerostomia scores (P=.021) and observer-rated xerostomia scores (P=.006).
Researchers also reported significant reductions in mean doses to the ipsilateral submandibular gland (63.9 Gy vs. 70.5 Gy; P<.001), the contralateral submandibular gland (45 Gy vs. 56.2 Gy; P<.001) and the oral cavity (35.9 Gy vs. 45.2 Gy; P<.001) among patients in the spared cohort.
The findings demonstrate that it is safe to reduce radiation to the level IB lymph nodes to minimize xerostomia, according to researcher Moses Tam, an MD candidate 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,” Tam said in a press release. “Our data shows 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 post-treatment salivary function.”
For more information:
Tam M. Abstract #139. Presented at: the Multidisciplinary Head and Neck Cancer Symposium; Feb. 20-22, 2014; Scottsdale, Ariz.
Disclosure: The researchers report no relevant financial disclosures.
Perspective
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Zain A. Husain, MD
In this era of HPV-associated oropharyngeal cancer, with its favorable prognosis, concerns about minimizing long-term toxicity are paramount. Xerostomia has long been an intractable side effect of head and neck radiation, and considerable effort has focused on minimizing its effects by limiting parotid dose. This has provided a modest benefit, although the focus has now shifted to sparing of the submandibular glands, which provide the majority of unstimulated salivary flow.
The study by Tam and colleagues is an important step forward in this regard. It examined tumors in the oropharynx — which are most likely to be HPV-associated — and compared two cohorts of patients treated with chemoradiation, one with bilateral level 1B nodal sparing and the other with standard treatment. The study found an excellent rate of 2-year locoregional control in both arms. In addition, both patient and observer grading of xerostomia were used, and in both cases, the level 1B-sparing arm was favored.
The abstract also raises some interesting questions, which will hopefully be expounded upon in the manuscript. It will be critical to know the selection criteria for the bilateral 1B-sparing arm, especially because many have traditionally advocated coverage of the ipsilateral level 1B nodes in patients with involved nodes. Additionally, given the high doses received by the ipsilateral submandibular gland even in the “sparing” arm, one wonders if the benefit really lies in the sparing of the contralateral gland and oral cavity.
Nevertheless, this study represents an important contribution to the literature and reflects a greater trend of using IMRT to move beyond sparing of only the parotid glands.
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