br In our series no T and T diseases
In our series, no T1 and T2 diseases invaded parotid gland directly, and only one patient with T2 tumor had potential parotid gland lymph node metastasis at the time of initial diagnosis. Fortunately, the recurrence tumor was successfully salvaged by superficial parotidectomy without facial nerve paralysis. In the present study, the rates of potential parotid gland lymph node metastasis in T1 and T2 were 0% (0/14) and 5% (1/19) respectively. That is significantly lower than the previous reports. The possible explanation of this discrepancy is the accuracy of the preoperative assessment of extent of disease.
Fig. 1. Patient survival curves (with Kaplan–Meier estimates of overall survival rate, disease specific survival rate, and local control rate for T1 patients (solid line) and T2 patients (dotted line)).
As mentioned above, the extents of the diseases were precisely assessed by RNase Inhibitor and thin-sliced CT scan, MRI, and FDG-PET in our series. The patients in the previous reports may include underdiagnosed advanced diseases. Taken together, present results suggest that prophylactic superficial parotidect-omy is not mandatory in T1 disease and in T2 disease without tumor in anterior or inferior canal wall. However, precise preoperative assessment and careful follow-up are mandatory using diagnostic imaging including high-resolution CT scan, MRI and FDG-PET.
A necessity of prophylactic neck dissection in T1 and T2 patients is also controversial. Gidley et al.  suggested selective neck dissection (level II-III) for T1 or T2 patients. Prasad et al.  proposed that they examined frozen section of level II lymph node, then dissected neck lymph node only when histology of frozen section showed positive metastatic cancer. However, in the present study, no neck LN metastasis was observed in any of the 37 patients not only at the time of initial diagnosis but also during the all the follow-up period. Thus, we believe that prophylactic neck dissection is not necessary for T1 and T2 patients , as long as precisely extent of tumor is assessed by imaging as mentioned above.
As for PORT, UK guidelines recommend post-operative (C)RT for most of T2–T4 with the exception of T1 and selected T2 without particularly peri-neural infiltration and with clear margins. In accordance with UK guidelines, many authors recommended PORT in T2 patients [2,3,16], especially in case with close or positive surgical margins, peri-neural invasion, or vascular invasion. Oya et al.  reported meta-analysis of PORT for early stage patients. Survival analysis of all patients showed no differences between the surgery-only and PORT groups. However, PORT exhibited a better prognosis than surgery alone in T1 patients. They indicated that PORT can be the standard therapy for T1 and T2 patients. In the present series, we recommended PORT only for the patients with positive surgical margins in T1 and T2. As a result, 4 patients had positive surgical margins and 3 of them underwent PORT and have been alive without recurrence during the observation period. In the present study, local recurrence occurred in only one patient treated by sleeve resection, who was successfully salvaged by LTBR. Indeed, complete resection without positive surgical margins is essential for the treatment of the patients with T1 and T2. However, PORT should be considered for patients with positive surgical margins. In our case series, we have not recommended PORT to the patients with peri-neural invasion, vascular invasion, or bone invasion, but almost all patients with these elements have not had local recurrence except for only one patient who was salvaged by operation.
This study has some limitation due to the retrospective nature. Firstly, sample size is very small for a meaningful decision. However, the rarity of EAC cancer makes sieve plates difficult to perform well-designed analysis at a single institution. The retrospective chart review is an important method for gathering clinical data on outcomes, aiding clinical decision-making. Secondly, selection criteria for parotidectomy is not completely constant case by case.