Adjuvant radiotherapy for patients with parotid acinic cell carcinoma “does not confer a therapeutic advantage in low-grade and early-stage tumors if resection is complete,” but the benefit for patients with higher-grade or higher-stage disease is uncertain because there were few of these patients included in the retrospective database review, the reviewers reported in the Archives of Otolaryngology Head and Neck Surgery.1
The authors noted that acinic cell carcinoma is a rare parotid gland tumor accounting for approximately 10% of salivary gland tumors. “Given this tumor’s rare incidence, treatment paradigms used for other tumors have been applied to [acinic cell carcinoma]. These recommendations include the use of radiotherapy because parotid cancers overall demonstrate a potential survival advantage with adjuvant radiotherapy, despite studies of this particular tumor showing a lack of radiosensitivity,” the investigators stated.
Using the NCI’s Surveillance, Epidemiology, and End Results (SEER) Program, the researchers identified all cases of acinic cell carcinoma of the parotid gland from 1998 to 2007. This totaled 1,241 patients, including 969 patients that had sufficient data for inclusion. “To our knowledge, this retrospective study of 20 years of SEER data is the largest analysis of this type of tumor,” the investigators reported.
Key Results
Comparing surgery alone to surgery plus radiotherapy, the researchers found “no statistical difference in overall survival” when stratifying for stage. There were, however, few stage IV tumors (occurring among 21 patients receiving surgery only and 58 patients receiving surgery plus radiation). When data were stratified by tumor grade, surgery alone demonstrated a survival advantage over surgery plus radiotherapy for grade 1 tumors, the researchers reported, “but this survival difference disappeared when further stratifying for tumor stage.” There was no statistical difference in overall survival between the surgery alone and surgery plus radiotherapy for patients with grade 2 and 3 tumors. “However, there were only 35 grade 3 tumors with sufficient data for survival analysis,” the investigators noted.
Study Implications
“Owing to the more aggressive course of these stage III, stage IV, and grade 3 tumors, and the lack of enough patients who were treated with and without [radiotherapy] to distinguish a difference, we cannot definitively determine whether adjuvant external beam [radiotherapy] for these uncommon high-stage or high-grade variants holds clinical utility,” the authors wrote. However, they continued, this study shows that adjuvant radiotherapy offers no survival advantage in acinic cell carcinoma for tumor stage I/II and tumor grade 1/2, despite widespread use of this approach. “These results should be considered during patient counseling and treatment planning and may spare these patients unnecessary radiation,” the authors wrote.
“Considering the potentially serious complications of parotid [radiotherapy], … recognizing tumors that lack sensitivity to [radiotherapy] may reduce the need for ineffective adjuvant therapy,” the researchers commented. “Reducing the number of treatment modalities would reduce patient inconvenience, risk of posttherapy complications, and treatment cost.” ■
Reference
1. Andreoli MT, Andreoli SM, Shrime MG, et al: Radiotherapy in parotid acinic cell carcinoma: Does it have an impact on survival? Arch Otolaryngol Head Neck Surg 138:463-466, 2012.
