Management of Regional Metastases of Malignant Salivary Gland Neoplasms

[Surgery for parotid gland cancer-controversial and proven aspects]

BACKGROUND

Due to the rarity of primary parotid malignancies, there are currently only limited clinical study data on the optimal surgical therapy. Parotid malignancies encompass a broad spectrum of more than 20 different histological subtypes with varying biology, which thus represents a challenge for even experienced pathologists and head and neck surgeons with proven expertise in salivary gland surgery.

OBJECTIVE

The aim of this review article is to provide an overview of the current literature on surgical therapy of the primary tumor and the cN0 neck as well as treatment of the facial nerve, and to shed light on the various controversial aspects of this topic.

RESULTS

In salivary gland oncology there is a trend towards safe (R0) but more conservative surgery. Currently, less-invasive surgical approaches could potentially be applied in a small subgroup with carefully selected caudally located and R0-resected "low-grade tumors" in stages T1-T2 and cN0 in relatively young patients with high compliance and more in the context of structured clinical studies. Elective neck dissection in the case of cN0 status should be carried out if risk factors for occult cervical lymph node metastasis (T3-T4a, "high-grade subtypes," advanced age, lymphangitic carcinomatosis) are present. In cases of small "low-grade parotid carcinomas," narrow resection margins or even microscopic tumor residues on the facial nerve can potentially be adequately compensated with adjuvant radiation therapy. However, due to the lack of solid data, the significance of the actual effect of the radiation in this situation should be viewed with great caution.

Management of clinically negative neck in salivary gland cancers - elective neck dissection, irradiation, or surveillance?

Aim of the study

To retrospectively assess treatment outcomes among patients treated for salivary gland cancers at our institution to determine which of the three most common treatment approaches - elective neck dissection (END), elective neck irradiation (ENI), or observation - provide the best results.

Material and methods

A total of 122 patients were identified who had undergone primary surgery for SGC followed by END, ENI, or observation. The patients were classified into three groups according to the treatment approach used to manage the neck: END, ENI, or observation. The main outcome measures were disease-free survival (DFS) and overall survival (OS). We also sought to identify the risk factors potentially associated with neck metastasis and treatment failure.

Results

106 patients met all inclusion criteria. Of these 106 patients, 27 (25.7%) underwent END, 17 (16.0%) underwent ENI, and 62 (58.5%) observation. There were no statistically significant differences between the three groups in any of the following variables: advanced age (> 70); presence of locally advanced disease (T3 or T4); perineural invasion; lymphovascular invasion; and primary tumour location. Treatment failure was higher (non-significantly) in the END group (25.9%) vs. the observation (21.0%) and ENI (11.8%) groups. No differences (Kaplan-Meir curves) were observed among the three groups in terms of DFS or OS.

Conclusions

Our results show that elective neck dissection does not appear to provide any benefit to patients treated for malignant salivary gland cancer. Importantly, these findings contradict most of the currently available research. However, due to methodological differences among the available studies, our findings cannot be compared directly to other studies.

T-cell epitope strength in WAP-T mouse mammary carcinomas is an important determinant in PD1/PD-L1 immune checkpoint blockade therapy

Using the SV40 transgenic WAP-T/WAP-T_NP mouse models for mammary carcinomas, we compared the response to immune checkpoint blockade therapy in tumor mice expressing either SV40 T-antigen containing the LCMV NP-epitope (T-Ag_NP in WAP-T_NP mice), or the unmodified T-antigen (T-Ag in WAP-T mice). Specifically, we asked, whether the presence of the highly immunogenic NP-epitope in T-Ag_NP influences this response in comparison to the weakly immunogenic T-cell epitopes of T-Ag in WAP-T tumor mice. Treatment of WAP-T_NP tumor mice with either anti-PD1 or anti-PD-L1 antibodies led to tumor regression, with anti-PD-L1 treatment being more effective. However, tumors had fully re-appeared after 21 days, indicating that CTL exhaustion had been rapidly re-established. Surprisingly, the same treatment applied to WAP-T tumor mice resulted in a significantly prolonged period of tumor regression. We provide evidence that in contrast to the weak antigenic stimuli exerted by T-cell epitopes of T-Ag, the strong antigenic stimulus of the NP-epitope in T-Ag_NP has a dual effect: (i) a rapid generation of active NP-specific CTLs, accompanied (ii) by accelerated CTL exhaustion. Our data support the hypothesis that the immunogenicity of tumor antigen T-cell epitopes strongly influences the success of immune checkpoint blockade therapy.