Practice Patterns in Management of Low‐ to Intermediate‐Grade Salivary Gland Carcinoma: A Multi‐Institutional Study

ABSTRACT

Objectives

To characterize practice patterns and outcomes in the management of low‐ and intermediate‐grade salivary gland carcinoma prior to the existence of treatment guidelines.

Methods

Analysis of a registry of patients who underwent parotid and submandibular gland resections for low‐and intermediate‐grade carcinomas between 2010 and 2019.

Results

Of all 786 patients included in the study, 726 (92%) had preoperative imaging and 653 (83%) had preoperative biopsy. Of the 729 patients with parotid gland cancer, the majority underwent superficial (n = 384, 53%) or total (n = 254, 35%) parotidectomy. In patients with facial nerve preservation, total parotidectomy was associated with a significant increase in transient facial weakness (72/177 (41%) vs. 82/311 (26%), RR 0.65, 95% CI 0.50–0.84, p < 0.05) and permanent facial nerve weakness (23/176 (13%) vs. 16/301 (5%), RR 0.41, 95% CI 0.22–0.75, p < 0.05) compared to superficial parotidectomy. Adjuvant radiation therapy (RT) was delivered to 285 (36%) patients. The proportion of patients receiving adjuvant RT declined significantly over the time period from 2015 to 2019 compared to 2010 to 2014 at 162/504 (32%) and 123/282 (44%), respectively (RR 0.74, 95% CI 0.61–0.89, p < 0.05). When comparing the time periods from 2015 to 2019 and 2010 to 2014, there was no significant difference in local control rates (RR 0.52, 95% CI 0.26–1.04, p = 0.06) or regional control rates (RR 0.75, 95% CI 0.26–2.13, p = 0.58).

Conclusions

Management of low‐ and intermediate‐grade salivary cancer from 2010 to 2019 was variable, which is expected given the rarity and heterogeneity of the disease and the lack of treatment guidelines prior to 2021. Most patients with parotid malignancies underwent superficial or total parotidectomy. The extent of parotidectomy had an impact on facial nerve function outcomes. Delivery of adjuvant radiation trended down with time. The data presented here will support dissemination of the guidelines and provide data that could inform future trials.

Level of Evidence

2b.

1. Introduction

Salivary gland malignancies are a relatively rare and diverse group of tumors comprising 5% of all head and neck cancers [1]. The wide range of histopathologic entities and biologic behavior of salivary gland cancers has resulted in challenges identifying and standardizing optimal management. While surgery is a mainstay of treatment, historically there have been limited data to guide preoperative evaluation, extent of surgery, and adjuvant therapy [2].

To address this gap, the American Society of Clinical Oncology (ASCO) published evidence‐based recommendations for the management of salivary gland malignancies in 2021 [2]. However, given the prior lack of available guidelines, the management related to salivary gland carcinomas until this point has been variable. Several single institution studies report different usage of preoperative imaging modalities, extent of parotidectomy, and rates of neck dissection [3, 4, 5]. Adjuvant radiation (RT) is commonly recommended for high‐risk features [6, 7], however, there is controversy with respect to low‐ and intermediate‐grade tumors with close margins [2, 8]. Additionally, there is considerable variation in RT delivery practices with respect to dose and volume, and with regards to the addition of chemotherapy [9].

To further explore practice patterns and outcomes in low‐ to intermediate‐grade salivary gland malignancies, a comprehensive multi‐institutional registry of patients who underwent parotid and submandibular gland resections between 2010 and 2019 was created for analysis. The objectives of this study are to characterize the historic practice patterns and secondarily report on their outcomes. These observational data will provide a baseline for future evaluations of dissemination and uptake of the ASCO guideline and may identify gaps in practice allowing for focused educational outreach to enhance adherence to the guidelines. The data may also show treatment outcomes to support future prospective studies of low‐ to intermediate‐grade salivary gland malignancies.

2. Materials and Methods

This retrospective analysis was reviewed and approved by the institutional review boards from each participating study site. Waiver of informed consent was requested and obtained at all centers, as no direct patient identifiers were collected. Coded, de‐identified data sets were collected in each institution's REDCap (Research Electronic Data Capture) software. REDCap is a secure, web‐based software platform designed to support data capture for research studies [10, 11]. Data were then shared for analysis with the primary author's institution through data use agreements.

2.1. Study Population

The study population comprised patients who underwent parotid and submandibular gland resections for low‐ and intermediate‐grade carcinomas between 2010 and 2019. Participating sites included 40 centers in 5 countries: United States (30), Canada (5), Austria (1), Switzerland (1), and Brazil (3). Exclusion criteria were patients who were (1) 17 years of age or younger, (2) pathology indicating adenoid cystic carcinoma or high‐grade carcinomas: squamous cell carcinoma, salivary ductal carcinoma, poorly differentiated carcinoma, (3) Tis, T0, or T4 stage, (4) lymph node metastases on presentation or subsequently found on histopathologic review, (5) preoperative facial or hypoglossal paralysis or lingual nerve numbness, (6) distant metastases at presentation, (7) prior head and neck radiation, (8) prior ipsilateral salivary gland surgery (unless referred for revision definitive oncologic parotidectomy—situations such as when patients had an initial partial parotidectomy for an expected benign tumor with final pathology demonstrating a low‐grade malignancy with narrow or positive margins for which the surgeon then performed a definitive re‐resection), and (9) patients for whom operative or pathology reports were not available or follow‐up status was not reported.

2.2. Data Collection

A standardized data collection form was developed, piloted, refined, and then distributed to all participating institutions for data capture from the medical records of participating institutions. These data included age, sex, smoking status, preoperative imaging/biopsy, tumor histopathology, gland type (parotid or submandibular), T‐classification, perineural invasion (PNI), lymphovascular invasion (LVI), margin status, facial nerve status at first postoperative visit and last follow‐up, extent of surgery, postoperative radiation/chemotherapy, local recurrence, regional recurrence, and distant metastasis recurrence. Race/ethnicity data were not collected. Further details are available in an earlier publication using this data set for a separate analysis [12].

2.3. Definitions

Salivary gland carcinoma stage was determined following the 8th edition of the American Joint Committee on Cancer Staging Manual [13]. Carcinomas with initial staging prior to the 8th edition were restaged in concordance with the updated manual. Histologic grades were categorized according to the 2017 classification for head and neck salivary gland cancers established by the World Health Organization [2]. The following 18 low‐ and intermediate‐grade tumors were included in this study: acinic cell carcinoma, low‐ and intermediate‐grade mucoepidermoid carcinoma, basal cell adenocarcinoma, (mammary analog) secretory carcinoma, low‐grade intraductal carcinoma, carcinoma ex pleomorphic adenoma (intracapsular/minimally invasive or with low‐grade histology), clear cell carcinoma, myoepithelial carcinoma, sialoblastoma, low‐grade cystadenocarcinoma, sebaceous adenocarcinoma, mucinous adenocarcinoma, polymorphous low‐ and intermediate‐grade adenocarcinomas, epithelial‐myoepithelial cancers, and low‐ and intermediate‐grade adenocarcinoma not otherwise specified. A category was made for intermediate‐grade carcinoma comprising intermediate‐grade mucoepidermoid carcinomas, intermediate‐grade polymorphous adenocarcinomas, and intermediate‐grade adenocarcinomas not otherwise specified. The remainder were categorized as the low‐grade carcinoma group because histologic grading is not applicable in many salivary tumors and rather is based on intrinsic biologic behavior [14]. Preoperative biopsy results were classified according to the Milan system for reporting Salivary gland cytopathology published in 2018 [15]. Biopsy reports prior to 2018 or that did not have a designated Milan category were placed into the most appropriate Milan category based on the diagnosis/description. Surgical margins from pathology reports were classified as R0 (negative margin), R1 (microscopically positive margin), or R2 (macroscopically positive margin). R0 was further subclassified into clear margins: > 1 mm; or close margins: ≤ 1 mm. Extent of parotidectomy included enucleation, extracapsular dissection, partial superficial parotidectomy, superficial parotidectomy, and total parotidectomy.

2.4. Outcomes

The primary study outcome was to characterize historical workup and treatment practices compared to the subsequently released guidelines. The secondary outcome was to characterize treatment outcomes with respect to margin status, locoregional control, and facial nerve function.

2.5. Statistical Analysis

Descriptive statistics were reported for patient and disease characteristics. The proportion of cases whose management matched the subsequently developed guideline statement was calculated and compared for the time periods 2015–2019 versus 2010–2014 using chi‐square tests. Additional comparisons examined facial nerve weakness by extent of parotidectomy. For effect sizes, we calculated relative risks (RRs) with 95% confidence intervals (CIs). Analyses were conducted using SAS 9.4 (Cary, NC: SAS Institute Inc.).

3. Results

Females made up 503/786 (64%) of included patients with low‐ and intermediate‐grade salivary gland carcinomas, and among all patients, the median age was 56 years (IQR 43–66 years). Tumors were located in the submandibular gland in 57 (7%) and 729 (93%) in the parotid, with 677 (86%) being low‐grade and 109 (14%) intermediate‐grade.

3.1. Preoperative Evaluation

Preoperative imaging was performed in 726/786 (92%) patients, with the most common imaging modality being computed tomography (CT) (64%) followed by magnetic resonance imaging (MRI) (34%) and ultrasound (29%). Patients may have had more than one imaging modality, and the imaging may have been performed for another indication that yielded an incidental salivary finding. There was no difference in the proportion of patients undergoing imaging in the time periods from 2010 to 2014 and 2015 to 2019 (RR 1.02, 95% CI 0.97–1.06, p = 0.43) (Table 1). A total of 653/786 (83%) patients had preoperative biopsy, with the majority being fine needle aspiration (FNA) in 618/653 (95%). There was no difference in the proportion of patients undergoing preoperative biopsy in the time periods from 2010 to 2014 and 2015 to 2019 (RR 1.05, 95% CI 0.98–1.13, p = 0.12) (Table 1).

TABLE 1.

Preoperative evaluation and extent of surgery trends for low‐ to intermediate‐grade salivary gland carcinoma over time.

	No./total (%)	2010–2014	2015–2019	RR	95% CI	p
		No./total (%)	No./total (%)
Imaging
Preoperative imaging	726/786 (92%)	258/282 (91%)	468/504 (93%)	1.02	0.97–1.06	0.43
Biopsy
FNA or core	653/786 (83%)	227/282 (81%)	426/504 (85%)	1.05	0.98–1.13	0.12
Surgery
Parotidectomy extent	N = 726	N = 263	N = 466			0.26
Enucleation	2 (< 1%)	1 (< 1%)	1 (< 1%)	0.56	0.04–8.99
Extracapsular dissection	10 (1%)	3 (1%)	7 (1%)	1.32	0.34–5.05
Partial superficial parotidectomy	64 (9%)	31 (12%)	33 (7%)	0.60	0.38–0.96
Superficial parotidectomy	384 (53%)	133 (51%)	251 (54%)	1.07	0.92–1.23
Total parotidectomy	254 (35%)	88 (33%)	166 (36%)	1.06	0.86–1.31
Other	11 (1%)	4 (2%)	7 (2%)	0.99	0.29–3.34
Not recorded	4 (1%)	3 (1%)	1 (< 1%)	0.19	0.02–1.80
Neck dissection	288/786 (37%)	110/282 (39%)	178/504 (35%)	0.91	0.75–1.09	0.30
Neck dissection—parotid	262/729 (36%)	106/263 (40%)	156/466 (33%)	0.83	0.68–1.01	0.07
Neck dissection—submandibular	26/57 (46%)	4/19 (21%)	22/38 (58%)	2.75	1.10–6.85	0.008

Preoperative diagnosis of malignancy was determined in 259/653 (40%), suspicious for malignancy in 65/653 (10%), salivary gland neoplasm of uncertain malignant potential (SUMP) in 116/653 (17%), and atypia of undetermined significance in 28/653 (4%). False negative diagnosis of non‐neoplastic or benign neoplasm categories occurred in 24/653 (4%) and 91/653 (13%), respectively, of patients who underwent biopsy. Non‐diagnostic and “other” were reported in 58/653 (9%) and 36/653 (5%), respectively.

3.2. Extent of Surgery

Of the 729 patients with parotid gland cancer, surgical treatments included superficial parotidectomy (n = 384, 53%), total parotidectomy (n = 254, 35%), partial superficial parotidectomy (n = 64, 9%), and extracapsular dissection (n = 10, 1%). One or more branches of the facial nerve were reported to be sacrificed in 96 (13%) parotidectomy cases. A total of 288/786 (37%) patients underwent neck dissection with level I performed in 76 (26%), level II in 247 (85%), level III in 166 (58%), level IV in 77 (27%), level V in 27 (9%), and not reported in 9 (3%). Of 729 parotid patients, 262/729 (36%) underwent neck dissection with level I performed in 60 (23%), level II in 226 (86%), level III in 149 (57%), level IV in 67 (26%), level V in 25 (10%), and not reported in 8 (3%). Of 57 submandibular patients, 26/57 (46%) underwent neck dissection with level I performed in 16 (62%), level II in 21 (81%), level III in 17 (65%), level IV in 10 (38%), level V in 2 (8%), and not reported in 1 (4%). There was no difference in the extent of parotidectomy between the time periods from 2010 to 2014 and 2015 to 2019, but there were changes in trends of elective neck dissection depending on cancer site (Table 1).

3.3. Adjuvant Treatment

Adjuvant radiation therapy (RT) was delivered in 285/786 (36%) patients. The proportion of patients receiving adjuvant RT declined significantly over the time period of 2015–2019 compared to 2010–2014 at 32% (162/504) and 44% (123/282), respectively (RR 0.74, 95% CI 0.61–0.89, p < 0.05) (Table 3). The most common indications reported for adjuvant RT were a close or positive margin (76%), PNI (17%), LVI (8%), and intraoperative tumor spillage (4%). Other reasons reported for RT included extra‐glandular extension and intermediate‐grade histology. In patients who had any of the following risk factors: T3 classification, PNI, LVI, or positive margins (R1/R2), 186/302 (62%) received adjuvant treatment. In patients who had close margins (≤ 1 mm), 85/328 (26%) received adjuvant treatment. The proportion of patients with any of the above risk factors receiving adjuvant RT was no different when comparing time periods of 2015–2019 and 2010–2014 (Table 2). In the 109 patients with intermediate‐grade tumors, 67/109 (61%) underwent adjuvant RT. Patients with intermediate‐grade tumors receiving adjuvant RT decreased significantly when comparing the time period of 2015–2019 to 2010–2014 with 32/62 (52%) versus 35/47 (74%) receiving RT, respectively (RR 0.69, 95% CI 0.52–0.93, p < 0.05) (Table 2). A total of 8 (1%) patients received adjuvant chemotherapy in our study, with 7 of those receiving it concomitantly with adjuvant RT. Of the 235 patients in whom adjuvant RT start dates were recorded, 166 (71%) had initiation of treatment within 8 weeks of surgery.

TABLE 3.

Facial nerve paresis or paralysis with reference to extent of parotidectomy at first post operative visit (A) and on final evaluation (B).

A. facial nerve status first post‐operative visit	Total no.	Any weakness no. (%)	RR (95% CI)
Overall	606	181 (30%)
Parotidectomy extent
Total parotidectomy	177	72 (41%)	Reference
Superficial parotidectomy	311	82 (26%)	0.65 (0.50–0.84)
Partial superficial parotidectomy	54	12 (22%)	0.55 (0.32–0.93)
Extracapsular dissection	9	3 (33%)	0.82 (0.32–2.10)
Enucleation	2	0 (0%)	0 (NA)
Other	5	2 (40%)	0.98 (0.33–2.92)
Not recorded	48	10 (21%)	0.51 (0.29–0.91)
p = 0.01

B. Facial nerve status on last follow up	Total no.	Any weakness no. (%)	RR (95% CI)
Overall	593	51 (9%)
Parotidectomy extent
Total parotidectomy	176	23 (13%)	Reference
Superficial parotidectomy	301	16 (5%)	0.41 (0.22–0.75)
Partial superficial parotidectomy	52	5 (10%)	0.74 (0.29–1.84)
Extracapsular dissection	9	2 (22%)	1.7 (0.47–6.12)
Enucleation	2	0 (0%)	0 (NA)
Other	4	0 (0%)	0 (NA)
Not recorded	49	5 (10%)	0.78 (0.31–1.95)
p = 0.07

TABLE 2.

Proportion of patients receiving adjuvant radiation therapy for low‐ to intermediate‐grade salivary gland carcinomas by indication and over time.

Radiotherapy	No./total (%)	2010–2014	2015–2019	RR	95% CI	p
		No./total (%)	No./total (%)
Received RT	285/786 (36%)	123/282 (44%)	162/504 (32%)	0.74	0.61–0.89	0.001
T3 or PNI or LNI or positive margins that received RT	186/302 (62%)	77/126 (61%)	109/176 (62%)	1.01	0.85–1.21	0.89
Close margins that received RT	85/328 (26%)	30/98 (31%)	55/230 (24%)	0.78	0.54–1.14	0.21
Intermediate tumors that received RT	67/109 (61%)	35/47 (74%)	32/62 (52%)	0.69	0.52–0.93	0.02

3.4. Margin and Facial Nerve Outcomes

The rate of positive margins was 152 (19%) for microscopic (R1) and 22 (3%) for macroscopic (R2) disease for a total margin positivity rate of 174/786 (22%). In patients who had facial nerve function status recorded and did not undergo facial nerve sacrifice, total parotidectomy was associated with a significant increase in transient facial weakness relative to superficial parotidectomy, occurring in 72/177 (41%) versus 82/311 (26%) (RR 0.41, 95% CI 0.22–0.75, p < 0.05). Similarly, permanent facial nerve weakness was more common in the total parotidectomy group, occurring in 23/176 (13%) versus 16/301 (5%) in the superficial parotidectomy group (RR 0.65, 95% CI 0.50–0.84, p < 0.05) (Table 3).

3.5. Locoregional Recurrence

A total of 31 (4%) patients experienced local recurrence, and 14 (2%) experienced regional recurrence. When comparing the time periods from 2015 to 2019 and 2010 to 2014, there was no significant difference in local control rates (RR 0.52, 95% CI 0.26–1.04, p = 0.06) or regional control rates (RR 0.75, 95% CI 0.26–2.13, p = 0.58).

4. Discussion

The ASCO published evidence‐based recommendations for the management of salivary gland malignancies in 2021. Our multi‐institutional study of practice patterns in low‐ to intermediate‐grade parotid and submandibular cancers from 2010 to 2019 shows the extent of variation in preoperative evaluation, extent of surgery, and adjuvant therapy compared to the subsequently released guidelines, providing a useful point‐in‐time analysis of practice patterns on which to base future evaluations of guideline dissemination efforts (Table 4).

TABLE 4.

Practice patterns in management of low‐ to intermediate‐grade salivary gland cancers in reference to the subsequently released ASCO guidelines.

Statement	Action	Strength	No. (%) in present study	Comments
Preoperative evaluation
Imaging	Providers should perform imaging (neck ultrasound, computed tomography [CT] with intravenous contrast, and/or magnetic resonance imaging [MRI] of the neck and primary site) in patients with a suspicion of a salivary gland cancer	Evidence quality: intermediate; strength of recommendation: strong	726/786 (92%) had imaging	Imaging may have been performed for another indication that yielded the salivary finding incidentally
Biopsy	Providers should perform a tissue biopsy (either fine needle aspiration biopsy [FNAB] or core needle biopsy [CNB]) to support distinction of salivary gland cancers from nonmalignant salivary lesions	Evidence quality: high; strength of recommendation: strong	653/786 (83%) had biopsy
Surgery
	Surgeons may perform partial superficial parotidectomy (PSP) for appropriately located superficial T1 or T2 low‐grade salivary gland cancers	Evidence quality: low; strength of recommendation: weak	64/726 (9%) had PSP	Rationale for parotidectomy extent cannot be evaluated. Rate may be underestimated due to coding discrepancies
	Surgeons should perform facial nerve preservation in patients with intact preoperative facial nerve function when a dissection plane can be created between the tumor and the nerve	Evidence quality: intermediate; strength of recommendation: strong	Cannot determine	Unknown if a dissection plane was present in patients with facial nerve sacrifice
	Surgeons should perform resection of involved facial nerve branches in patients with impaired facial nerve movement preoperatively or when branches are found to be encased or grossly involved by a confirmed malignancy	Evidence quality: intermediate; strength of recommendation: moderate	Cannot determine	Unknown if facial nerves that were sacrificed were found to be encased or grossly involved
Adjuvant radiation
	Postoperative RT should be offered to patients with tumors with the following features: high‐grade tumors, positive margins; perineural invasion; lymph node metastases; lymphatic or vascular invasion; and T3–T4 tumors	Evidence quality: intermediate; strength of recommendation: strong	186/302 (62%) received RT	Unknown how many patients were offered RT but declined
	Postoperative RT may be offered to patients with tumors with close margins or intermediate‐grade tumors	Evidence quality: insufficient; strength of recommendation: weak	Close margins = 85/328 (26%), intermediate tumors = 67/109 (61%) received RT	Unknown how many patients were offered RT
	Radiation should be initiated within 8 weeks of surgery	Evidence quality: insufficient; strength of recommendation: moderate	166/235 (71%) received RT within 8 weeks
Systemic therapy
	In the setting of patients undergoing adjuvant radiotherapy, the addition of concurrent chemotherapy may not be routinely offered outside of a clinical trial	Evidence quality: low; strength of recommendation: moderate	8/786 (1%) received systemic therapy	Unknown how many patients were treated on a clinical trial

4.1. Preoperative Evaluation

In patients with suspicion of salivary gland cancer, the ASCO guideline recommends imaging (neck ultrasound, CT with intravenous contrast, and/or MRI of the neck and primary site) and tissue biopsy (FNA or core) [2]. Among our 786 patients, preoperative imaging was performed in 726 (92%), with the most common imaging modality being CT (64%) followed by MRI (34%) and ultrasound (29%). Of note, patients may have had more than one imaging modality, and the imaging may have been performed for another indication that yielded the salivary finding incidentally. The reason for the imaging modality selected was not collected in our study, but it is suspected that variations in imaging choice may reflect ease of access, such as the availability of point of care ultrasound.

Of the 786 patients, 133 (17%) patients did not have preoperative biopsy, which potentially represents an area for education in light of the ASCO guideline recommendations. FNA and core biopsy have been shown to be low risk and can support the distinction of salivary gland cancers from nonmalignant salivary lesions [16, 17]. It is worth noting, however, that the preoperative diagnosis of malignancy or suspicious for malignancy was only determined in 50% of patients who underwent biopsy in this study. SUMP was reported in 17% of patients, which carries approximately a 35% risk of malignancy, and definitive diagnosis typically requires excision. However, with the uncertainty of a benign versus malignant entity, it can be difficult to determine the best approach in terms of the extent of surgery. These limitations of FNA are important to note and discuss with patients. The false negative diagnosis of non‐neoplastic or benign neoplasm categories occurred in 17% of patients, which is consistent with other reports in the literature [18, 19]. Therefore, in cases of non‐neoplastic or benign FNA results, it may be worthwhile to follow patients longitudinally to evaluate for concerning growth or changes that would prompt adjustments in management.

4.2. Extent of Surgery

The extent of surgery in salivary gland cancers is dictated by the location, size, and grade of the tumor. Per the ASCO guidelines, surgeons may perform partial superficial parotidectomy for appropriately located superficial T1 or T2 low‐grade salivary gland cancers [2]. In this cohort study, partial superficial parotidectomy was reported only in 9%. While this may be an underestimate related to coding discrepancies, the majority of patients were documented to receive superficial (53%) or total (35%) parotidectomy. More extensive surgeries performed may be due to uncertainty of the diagnosis preoperatively and an attempt to ensure negative and/or wider margins. However, there is increasing data that patients with narrow margins including ≤ 1 mm will likely achieve excellent locoregional control, and therefore more limited surgery may be adequate [12].

Operative elective neck management of salivary cancers is recommended in T3 and T4 tumors and high‐grade malignancies per ASCO guidelines [2]. In these cases, elective ipsilateral selective neck dissection should be performed with levels dependent on the primary site, which for parotid malignancies may include levels 2–4 [2]. A total of 288 (37%) patients in our study underwent neck dissection, with level I performed in 76 (26%), level II in 247 (85%), level III in 166 (58%), level IV in 77 (27%), level V in 27 (9%), and not reported in 9 (3%). The varying rate and levels of neck dissection may be due to uncertainty of metastatic potential, for example, in cases where preoperative biopsy was inconclusive or showed SUMP.

4.3. Facial Nerve Management and Outcomes

Facial nerve preservation is recommended in patients with intact preoperative facial nerve function when a dissection plane can be created between the tumor and the nerve [2]. In this cohort study, one or more branches of the facial nerve were reported to be resected despite normal function preoperatively in 96 (13%) of parotidectomy cases. Due to the retrospective nature of the study, the specific reason for facial nerve resection in each of these cases is unknown. In patients who did not undergo facial nerve sacrifice and had facial nerve function status recorded, there was a significant increase in both transient and permanent facial nerve weakness with total parotidectomy. This is consistent with multiple other studies reporting increased facial nerve injury correlating with increased extent of parotidectomy [20, 21]. Data on intraoperative facial nerve monitoring was not collected, so its role on outcome cannot be assessed in this study.

4.4. Adjuvant Therapy

Patients who have T3 classification, PNI, LVI, or positive margins (R1/R2) are to be offered adjuvant RT per the ASCO guidelines [2]. In our study, 186/302 (62%) who had any of those risk factors underwent adjuvant RT. It is unknown what proportion of those patients were offered RT but declined. Per the ASCO guidelines, postoperative RT may be offered to patients with tumors with close margins or intermediate‐grade tumors [2]. In the 109 patients with intermediate‐grade tumors, 67/109 (61%) underwent adjuvant RT although this trended down between 2010 to 2014 and 2015 to 2019. In patients who had close margins (≤ 1 mm), 85/328 (26%) received adjuvant treatment. The low proportion of patients with close margins receiving adjuvant therapy may reflect the growing body of evidence that patients with low‐ or intermediate‐grade tumors and narrow margins including ≤ 1 mm will likely achieve excellent locoregional control with surgery alone [12, 22, 23]. Overall, the proportion of patients receiving adjuvant RT decreased when comparing 2015 to 2019 and 2010 to 2014 without an apparent decrease in locoregional control.

The addition of concurrent chemotherapy may not be routinely offered outside a clinical trial per ASCO guidelines [2]. Only 8 (1%) patients received chemotherapy in our study, although it is unknown whether these patients were part of a clinical trial. The majority of patients who had RT had it initiated within 8 weeks of surgery (71%), as recommended by the ASCO guidelines [2].

Limitations of this study include those inherent to retrospective design including the potential for selection bias. The majority of participating institutions were large academic medical centers and therefore may not be representative of smaller community hospitals. Specific reasons for management decisions such as the selection of preoperative imaging modality and the extent of surgery cannot be determined and so should be used cautiously, if at all, to make decisions about the extent of treatment due to the risk of confounding by indication. Nonetheless, this study provides insights into management patterns from a large multi‐national, multi‐institutional database of patients that informs knowledge gaps in the treatment of low‐ to intermediate‐grade salivary gland cancers.

5. Conclusion

The management related to low‐ and intermediate‐grade salivary gland cancer demonstrates variance, which may reflect a prior history of a lack of treatment guidelines. While the majority of these patients have preoperative imaging, the modality varies. Most patients with parotid malignancies underwent superficial or total parotidectomy, although more limited surgeries including extracapsular dissection and partial superficial parotidectomy were also performed, with the extent of parotidectomy having an impact on facial nerve function outcomes. Similarly, neck dissection rate and levels dissected were variable. Delivery of adjuvant radiation was reduced between earlier and later time periods. The data presented here provide a baseline for future evaluations of dissemination and uptake of the ASCO guideline and provide data that could inform future clinical trials in the management of low‐ to intermediate‐grade major salivary gland carcinomas.

Conflicts of Interest

The authors declare no conflicts of interest.

Sajisevi M., Nguyen K., Callas P., et al., “Practice Patterns in Management of Low‐ to Intermediate‐Grade Salivary Gland Carcinoma: A Multi‐Institutional Study,” Laryngoscope Investigative Otolaryngology 10, no. 5 (2025): e70246, 10.1002/lio2.70246.