Main Session
Sep 29
PQA 07 - Head and Neck Cancer, Lung Cancer/Thoracic Malignancies, and Nursing and Supportive Care

3623 - Adjuvant Radiotherapy is Associated with Improved Risk-Adjusted Outcomes in Resected Salivary Gland Cancers

03:45pm - 05:00pm ET
Poster Hall - Exhibit Hall A
Screen: 15
POSTER

Presenter(s)

Jeffrey Shogan, DO - University of Pittsburgh Medical Center, Pittsburgh, PA

J. Shogan1, C. T. Wilke2, H. D. Skinner1, D. A. Clump II3, D. E. Heron4, J. Ohr5, D. P. Zandberg6, Z. Rahman5, S. Kim7, J. T. Johnson7, S. Sridharan8, M. W. Kubik8, U. Duvvuri9, D. Bell10, R. Seethala11, and Y. M. Mowery1; 1Department of Radiation Oncology, UPMC Hillman Cancer Center, Pittsburgh, PA, 2Department of Radiation Oncology, University of Pittsburgh Medical Center, Pittsburgh, PA, 3Department of Radiation Oncology, West Virginia University School of Medicine, WVU Cancer Institute, Morgantown, WV, 4American College of Radiation Oncology (ACRO), Bethesda, MD, 5Department of Hematology and Oncology, UPMC Hillman Cancer Center, Pittsburgh, PA, 6UPMC Hillman Cancer Center, Pittsburgh, PA, 7Department of Otolaryngology–Head and Neck Surgery, University of Pittsburgh School of Medicine, Pittsburgh, PA, 8Department of Otolaryngology, Division of Head and Neck Surgery, UPMC, Pittsburgh, PA, 9Department of Otolaryngology, NYU Grossman School of Medicine, New York, NY, 10University of Pittsburgh, Department of Pathology, Pittsburgh, PA, 11Department of Pathology, University of Pittsburgh Medical Center, Pittsburgh, PA

Purpose/Objective(s):

Salivary gland cancers (SGC) are heterogeneous malignancies primarily treated with surgery. Adjuvant radiotherapy (RT) is often recommended for adverse features, yet its impact on outcomes remains debated due to treatment selection bias. We hypothesized that adjuvant RT improves recurrence-free survival (RFS).

Materials/Methods:

We performed a single-institution retrospective review of pts with SGC treated with surgery ± RT from 2005–2022. Predictors of RT use were assessed by multivariate logistic regression. RFS and overall survival (OS) were measured from surgery. Survival was analyzed using Kaplan–Meier (KM) & Cox regression. To mitigate selection bias, propensity scores (PS) were generated using factors predictive of RT use on multivariate regression with an expanded PS model including additional factors.

Results:

Among 286 pts (134 surgery alone; 152 surgery + RT) with median follow-up of 104 mo, 80 (28%) recurred & 94 (33%) died. Locoregional recurrence occurred in 38 (13%), usually isolated (n=33, 12%) & predominantly after surgery alone. Distant recurrence occurred in 47 (16%), most often isolated (n=42, 15%) & more frequently in the RT cohort. On unadjusted KM, the RT cohort had worse OS & RFS, reflecting higher baseline risk (table). High-risk histology (per ASCO 2021 guidelines), positive margins, & nodal positivity independently predicted RT use. In multivariate Cox models including these factors, RT was associated with improved RFS (HR 0.43, 95% CI 0.21–0.88; p=0.021) with a trend toward improved OS (HR 0.61, 95% CI 0.32–1.13; p=0.116). In PS-adjusted models, RT remained associated with improved RFS (HR 0.38, 95%CI 0.19–0.74; p=0.005) and trended toward improved OS (HR 0.56, 95% CI 0.31–1.01; p=0.054). In expanded PS models adding age, T category, lymphovascular invasion (LVI), & perineural invasion (PNI), RT was associated with improved RFS (HR 0.37, 95% CI 0.15-0.88; p=0.025) & OS (HR 0.32, 95% CI 0.13-0.80; p=0.014).

Conclusion:

Resected SGC carries substantial recurrence risk, with distant failure predominating. Despite enrichment of adverse features in the RT cohort, adjuvant RT was independently associated with improved RFS and OS after adjustment, driven by improved locoregional control. These findings support RT for selected patients & highlight the unmet need for improved systemic strategies.

 Surgery alone

 Surgery + RT

 MVA p value
Age (median, IQR)

 62.0 (49.8-71.0)

 60.6 (50.5-69.8)

Histologic risk

High

Low

 13%

87%

 63%

37%

 <0.001
Histologic Subtypes*

Mucoepidermoid

Salivary duct

Epithelial-myoepithelial

Acinic cell

Adenoid cystic

Other

 24%

7%

27%

17%

2%

23%

 16%

30%

7%

10%

18%

19%

T Category

T1-2

T3-4b

 88%

12%

 66%

34%

 0.22
N Category

N0

N+

 94%

6%

 61%

39%

 0.005
Margins

+

-

Unk

 11%

83%

6%

 54%

38%

9%

 <0.001
PNI

+

-

Unk

 13%

80%

7%

 59%

35%

7%

 0.11
LVI

+

-

Unk

 7%

81%

12%

 38%

43%

19%

 0.68
*Carcinoma-ex pleomorphic adenoma classified per malignant component