Surgery Alone without Adjuvant Radiation Therapy for High- or Intermediate-Grade Salivary Gland Cancer

Introduction: Postoperative radiation therapy (RT) is recommended for completely resected T1-2 salivary gland cancer (SGC), if the tumor pathology is adenoid cystic carcinoma, intermediate, or high-grade tumors. In this case series, we reviewed cases of intermediate- or high-grade SGC, managed with curative surgery alone without adjuvant RT, and compared those outcomes with pathology- and tumor stage-matched SGC, treated with surgery and postoperative RT. Methods: We retrieved cases of intermediate- or high-grade tumors arising from the major salivary glands treated with surgery alone without adjuvant RT (N = 29) from the institutional SGC database. The main reasons for no adjuvant RT and treatment outcomes were reviewed in detail. In addition, we established the tumor pathology (grade)- and tumor stage (T1-2N0M0)-matched cases treated with surgery and postoperative RT as comparison groups (N = 59), to investigate relative treatment outcomes. Results: The overall treatment outcome was 82.7% disease-specific survival (DSS) at a median follow-up of 41 months, with a 10.3% incidence of systemic metastasis in intermediate- or high-grade SGCs treated with surgery alone. The primary reasons for not receiving adjuvant RT were no recommendation by the surgeon (37.9%) and patient refusal of RT (27.6%). Comparisons of the surgery alone and surgery with postoperative RT in tumor pathology (grade)- and tumor stage-matched groups revealed similar treatment outcomes; 100% DSS at 35-50 months in the surgery alone group and 90-100% DSS at 37-60 months in the surgery and postoperative RT group. Meanwhile, patients with advanced SGCs (T3-4 or N+) treated with surgery alone had a DSS of 50.0% at a median follow-up of 63 months, and systemic metastasis was the main cause of treatment failure (37.5%). Conclusion: Our findings suggest that surgery alone may yield favorable outcomes for a specific subset of early-stage, intermediate- to high-grade SGCs without any adverse pathological features. Further studies are warranted to validate this approach.