Adjuvant Radiotherapy for Major Salivary Gland Malignancies: Impact on Locoregional Control and Survival Outcomes

BACKGROUND/AIM

This study aimed to assess the effect of adjuvant radiotherapy on locoregional control, disease-free survival, and overall survival rates in patients with major salivary gland malignancies. The study also aimed to provide findings to guide clinicians in selecting appropriate candidates for adjuvant radiotherapy and optimizing treatment strategies for this challenging disease.

PATIENTS AND METHODS

A retrospective single-center analysis was conducted, reviewing the medical records of patients diagnosed with major salivary gland malignancies between November 2008 and May 2023. Inclusion criteria were histologically confirmed malignancy, surgical resection of the primary tumor, adjuvant radiotherapy, and availability of clinical and follow-up data. Survival analyses were performed using the Kaplan-Meier method, and Cox proportional hazards regression models were used to assess survival outcomes.

RESULTS

The study included 37 patients with major salivary gland malignancies. The most common site was the parotid gland, and the predominant histopathological diagnosis was salivary duct carcinoma. Adjuvant radiotherapy was generally well-tolerated, with the most common acute toxicities being grade 1-2 mucositis and dermatitis. The 5-year overall survival and progression-free survival rates were 93.8% and 62.9%, respectively. Locoregional control rate at five years was 89.1%. Recurrence occurred in 12 patients, with most cases observed within two years from the start of adjuvant radiotherapy. Distant metastasis was observed in nine patients.

CONCLUSION

This retrospective analysis highlights the positive impact of adjuvant radiotherapy on locoregional control and survival outcomes in major salivary gland malignancies. The findings contribute to the existing body of evidence, aiding clinicians in treatment decision-making and potentially informing future prospective studies and treatment guidelines for this challenging disease.

PSMA-Directed Imaging and Therapy of Salivary Gland Tumors: A Single-Center Retrospective Study

We analyzed the diagnostic performance of prostate-specific membrane antigen (PSMA) PET/CT and the dosimetry, efficacy, and safety of 177Lu-PSMA-617 radioligand therapy (RLT) in salivary gland malignancies (SGMs). Methods: We identified 28 SGM patients with PSMA PET/CT from our database. CT and PSMA PET/CT images were evaluated separately by 3 masked readers in joint reading sessions. Pathologic findings were grouped into 6 TNM regions, and lesion-based disease extent was classified as no disease (n = 1, 4%), unifocal (n = 2, 7%), oligometastatic (n = 9, 32%), multifocal (n = 3, 11%), or disseminated (n = 13, 47%). For each region, the SUVmax of the lesion with the highest uptake was measured and the visual PSMA expression score was evaluated on a per-patient basis using PROMISE criteria. The association between PSMA expression and clinical and histopathologic markers was tested using the Student t test. Five patients underwent PSMA RLT with intratherapeutic dosimetry. Response was assessed using RECIST 1.1, and adverse events were graded according to version 5.0 of the Common Terminology Criteria for Adverse Events. Results: Compared with CT, PSMA PET/CT demonstrated additional metastatic lesions in 11 of 28 (39%) patients, leading to upstaging of TNM and lesion-based disease extent in 3 (11%) and 6 (21%) patients, respectively. PSMA PET/CT detected CT-occult local tumor, regional lymph nodes, nonregional lymph nodes, and bone metastases in 1 (4%), 4 (14%), 2 (7%), and 4 (14%) patients, respectively; no additional lesions were detected in the other predefined regions. PSMA expression level was higher than liver in 6 patients (25%). A significantly higher SUVmax was observed in male than female patients (15.8 vs. 8.5, P = 0.007) and in bone than lung lesions (14.2 vs. 6.4, P = 0.006). PSMA RLT was discontinued after 1 cycle in 3 of 5 patients because of insufficient tumor doses. No adverse events of grade 4 or higher occurred. Conclusion: In SGMs, PSMA PET/CT demonstrated a superior detection rate and led to upstaging in about one third of patients when compared with CT. The male sex and the presence of bone metastases were associated with significantly higher PSMA expression. PSMA RLT was well tolerated, but most patients did not have more than 1 cycle because of insufficient tumor doses.

The Therapeutic Landscape of Salivary Gland Malignancies-Where Are We Now?

Salivary gland malignancies (SGMs) account for less than 5% of new diagnoses in head and neck tumors. If feasible, surgery is the preferred treatment modality. Nevertheless, some malignancies have a tendency of recurrence, with possible distant metastasis. Alternative treatment strategies, such as primary radiation or chemotherapeutics, often present low response rates. As a result, there is an unmet need for novel therapeutic approaches. Nowadays, target-based therapies (e.g., small inhibitors and immunotherapy) are used by the medical oncologist for possible treatment of advanced SGMs. Based on recent published trials, some novel treatments may provide additional disease control for some patients. However, sample sizes are small, the general findings are unsatisfactory, and a lot of uncertainties remain to be elucidated. Nevertheless, research shows that patients do not benefit from blind administration of systemic treatments and therefore a more personalized approach is highly needed. The aim of this review paper is to summarize the most recent advances in the biological understanding and molecular pathways of salivary gland cancers, the association of these pathways with the current treatments used and their implications for more personalized targeted-based therapies.

Malignant tumours of the parotid gland: management of the neck (including the clinically negative neck) and a literature review

Major salivary gland malignancies are rare, constituting 1%-3% of head-neck tumours. The surgical management of the clinically negative neck (cN0) does not have a univocal consensus yet. We have carried out a retrospective study on 119 cases of malignant parotid tumours that were surgically treated between January 1999 and January 2014. Our aim was to analyse preoperative findings (cytotype, cTNM) and to correlate these with postoperative results (grading, histotype, occult neck metastasis) in patients with parotid tumours to obtain an appropriate indication for neck management. In cN0 patients with a T1, T2 low-grade cancer a wait-and-see approach is preferred. Instead, in cNO patients with high-grade or low-grade T3, T4 tumours an elective neck dissection (END) is always planned. Levels II, III and IV, at least, must be dissected. The decision to dissect level V or I depends on the location of the primary tumour. In the cN0 group 19 of 58 (32.7%) patients who underwent an END had occult metastases. In clinically positive neck (cN+) patients a Modified Radical Neck Dissection (MRND), at least, must be performed. The criteria to add adjuvant radiotherapy (PORT) include deep lobe parotid tumours, advanced lesions (T3-T4), microscopic (R2) or macroscopic (R1) residual disease after surgery, high grade tumours, perineural diffusion, lymph node metastasis, capsular rupture, and local recurrence after previous surgery. Kaplan-Meier analyses have shown a reduction in the overall survival (OS) from 100% to 91% and in disease-free survival (DFS) from 100% to 95.5% for the NO-PORT and PORT group, respectively. In our study, the cN0 pN+ patients had a higher degree of DFS compared to the cN+.