Submandibular salivary gland transfer for the prevention of radiation-induced xerostomia in patients with nasopharyngeal carcinoma: 5-Year outcomes

Submandibular gland transfer for the prevention of radiation-induced xerostomia in oropharyngeal cancer: Dosimetric impact in the intensity modulated radiotherapy era

BACKGROUND

Submandibular gland (SMG) transfer decreased radiation-associated xerostomia in the 2/3-dimensional radiotherapy era. We evaluated the dosimetric implications of SMG transfer on modern intensity modulated radiotherapy (IMRT) plans.

METHODS

Eighteen oropharynx cancer patients underwent SMG transfer followed by IMRT; reoptimized plans using the baseline SMG location were generated. Mean salivary gland, oral cavity, and larynx doses were compared between clinical plans and reoptimized plans.

RESULTS

No statistically significant difference in mean SMG dose (27.53 Gy vs. 29.61 Gy) or total salivary gland dose (26.12 Gy vs. 26.41 Gy) was observed with or without SMG transfer (all p > 0.05). Mean oral cavity and larynx doses were not statistically different. Neither tumor site, target volume crossing midline, stage, nor salivary gland volumes were associated with mean doses.

CONCLUSIONS

Salivary gland doses were similar with or without SMG transfer. IMRT likely decreases the benefit of SMG transfer on the risk of radiation-associated xerostomia.

Mechanism, Prevention, and Treatment of Radiation-Induced Salivary Gland Injury Related to Oxidative Stress

Radiation therapy is a common treatment for head and neck cancers. However, because of the presence of nerve structures (brain stem, spinal cord, and brachial plexus), salivary glands (SGs), mucous membranes, and swallowing muscles in the head and neck regions, radiotherapy inevitably causes damage to these normal tissues. Among them, SG injury is a serious adverse event, and its clinical manifestations include changes in taste, difficulty chewing and swallowing, oral infections, and dental caries. These clinical symptoms seriously reduce a patient’s quality of life. Therefore, it is important to clarify the mechanism of SG injury caused by radiotherapy. Although the mechanism of radiation-induced SG injury has not yet been determined, recent studies have shown that the mechanisms of calcium signaling, microvascular injury, cellular senescence, and apoptosis are closely related to oxidative stress. In this article, we review the mechanism by which radiotherapy causes oxidative stress and damages the SGs. In addition, we discuss effective methods to prevent and treat radiation-induced SG damage.

Long-term outcomes of interventions for radiation-induced xerostomia: A review

Xerostomia, or dry mouth, is a significant problem affecting quality of life in patients treated with radiation therapy for head and neck cancer. Strategies for reduction of xerostomia burden vary widely, with options including: sialagogue medications, saliva substitutes, acupuncture, vitamins, hyperbaric oxygen, submandibular gland transfer, and acupuncture or associated treatments. In this review, we sought to evaluate long-term outcomes of patients treated with various interventions for radiation-induced xerostomia. A literature search was performed using the terms "xerostomia" and "radiation" or "radiotherapy"; all prospective clinical trials were evaluated, and only studies that reported 1 year follow up were included. The search results yielded 2193 studies, 1977 of which were in English. Of those, 304 were clinical trials or clinical studies. After abstract review, 23 trials were included in the review evaluating the following treatment modalities: pilocarpine (three); cevimeline (one); amifostine (eleven); submandibular gland transfer (five); acupuncture like transcutaneous electrical nerve stimulation (ALTENS) (one); hyperbaric oxygen (one); and acupuncture (one). Pilocarpine, cevimeline, and amifostine have been shown in some studies to improve xerostomia outcomes, at the cost of toxicity. ALTENS has similar efficacy with fewer side effects. Submandibular gland transfer is effective but requires an elective surgery, and thus may not always be appropriate or practical. The use of intensity-modulated radiation therapy, in addition to dose de-escalation in select patients, may result in fewer patients with late xerostomia, reducing the need for additional interventions.

Submandibular Gland Transfer for the Prevention of Postradiation Xerostomia in Patients with Head and Neck Cancer: A Systematic Review and Meta-Analysis

<b><i>Background:</i></b> Submandibular gland transfer has been widely used to prevent postradiation xerostomia in head-and-neck cancers. However, there are still some controversies. <b><i>Methods:</i></b> Six databases were searched, data extraction was performed and the risk of bias was assessed by 2 reviewers independently. The meta-analysis was performed using Review Manager, version 5.2. <b><i>Results:</i></b> A total of 7 trials (12 articles) and 369 participants were included. <b><i>Conclusions:</i></b> The present clinical evidence suggests that submandibular gland transfer might be highly effective to prevent postradiation xerostomia in head-and-neck cancers without serious adverse events. However, more randomized controlled trials are still needed to confirm this conclusion.

A phase II study of submandibular gland transfer prior to radiation for prevention of radiation-induced xerostomia in head-and-neck cancer (RTOG 0244)

PURPOSE

We report the results of a phase II study to determine the reproducibility of a submandibular salivary gland transfer (SGT) surgical technique for prevention of radiation (XRT)-induced xerostomia in a multi-institutional setting and to assess severity of xerostomia.

METHODS AND MATERIALS

Eligible patients had surgery for primary, neck dissection, and SGT, followed by XRT, during which the transferred salivary gland was shielded. Intensity modulated radiation therapy, amifostine, and pilocarpine were not allowed, but postoperative chemotherapy was allowed. Each operation was reviewed by 2 reviewers and radiation by 1 reviewer. If 13 or more (of 43) were "not per protocol," then the technique would be considered not reproducible as per study design. The secondary endpoint was the rate of acute xerostomia, grade 2 or higher, and a rate of ≤ 51% was acceptable.

RESULTS

Forty-four of the total 49 patients were analyzable: male (81.8%), oropharynx (63.6%), stage IV (61.4%), median age 56.5 years. SGT was "per protocol" or within acceptable variation in 34 patients (77.3%) and XRT in 79.5%. Nine patients (20.9%) developed grade 2 acute xerostomia; 2 had grade 0-1 xerostomia (4.7%) but started on amifostine/pilocarpine. Treatment for these 11 patients (25.6%) was considered a failure for the xerostomia endpoint. Thirteen patients died; median follow-up for 31 surviving patients was 2.9 years. Two-year overall and disease-free survival rates were 76.4% and 71.7%, respectively.

CONCLUSIONS

The technique of submandibular SGT is reproducible in a multicenter setting. Seventy-four percent of patients were prevented from XRT-induced acute xerostomia.

A novel aldehyde dehydrogenase-3 activator leads to adult salivary stem cell enrichment in vivo

PURPOSE

To assess aldehyde dehydrogenase (ALDH) expression in adult human and murine submandibular gland (SMG) stem cells and to determine the effect of ALDH3 activation in SMG stem cell enrichment.

EXPERIMENTAL DESIGN

Adult human and murine SMG stem cells were selected by cell surface markers (CD34 for human and c-Kit for mouse) and characterized for various other stem cell surface markers by flow cytometry and ALDH isozymes expression by quantitative reverse transcriptase PCR. Sphere formation and bromodeoxyuridine (BrdUrd) incorporation assays were used on selected cells to confirm their renewal capacity and three-dimensional (3D) collagen matrix culture was applied to observe differentiation. To determine whether ALDH3 activation would increase stem cell yield, adult mice were infused with a novel ALDH3 activator (Alda-89) or with vehicle followed by quantification of c-Kit(+)/CD90(+) SMG stem cells and BrdUrd(+) salispheres.

RESULTS

More than 99% of CD34(+) huSMG stem cells stained positive for c-Kit, CD90 and 70% colocalized with CD44, Nestin. Similarly, 73.8% c-Kit(+) mSMG stem cells colocalized with Sca-1, whereas 80.7% with CD90. Functionally, these cells formed BrdUrd(+) salispheres, which differentiated into acinar- and ductal-like structures when cultured in 3D collagen. Both adult human and murine SMG stem cells showed higher expression of ALDH3 than in their non-stem cells and 84% of these cells have measurable ALDH1 activity. Alda-89 infusion in adult mice significantly increased c-Kit(+)/CD90(+) SMG population and BrdUrd(+) sphere formation compared with control.

CONCLUSION

This is the first study to characterize expression of different ALDH isozymes in SMG stem cells. In vivo activation of ALDH3 can increase SMG stem cell yield, thus providing a novel means for SMG stem cell enrichment for future stem cell therapy.