clinical decisions regarding neck dissection in the treatment of oral squamous cell carcinoma ( oscc ) should be based not only on the potential completeness of the resection but also on postoperative functional and cosmetic morbidity . in recent years , selective neck dissection in patients with scc of the head and neck has been evaluated in terms of patient quality of life , which can be significantly compromised following extensive dissection . however , to our knowledge , little information has been published on determining the appropriateness of selective neck dissection and adequate dissection levels , especially in patients with scc of the oral cavity . surgical management of neck lymph nodes was classically controlled by radical neck dissection ( rnd ) , which resects all of the neck lymph nodes ( levels i  v , according to the neck dissection classification of the american academy of otolaryngology head and neck surgery ) . elective management remains controversial in patients with oscc who have no clinical evidence of node involvement in the neck . several studies have asserted the need for elective neck dissection because of the high incidence of occult metastases from oscc , even in its early stages . modified radical neck dissection ( mrnd ) is an alternative procedure that avoids dysfunction of the neck region by preserving the accessory nerve , internal jugular vein , and sternocleidomastoid muscle in rnd . supraomohyoid neck dissection ( sohnd ) , a type of selective neck dissection , has gradually become the usual procedure in elective situations , with the understanding that oscc carries a significant risk of metastasizing to cervical lymph nodes in neck levels i , ii , and iii . meanwhile , another report recommends a  watchful policy  based on the observation that regional control and overall survival were not significantly different with elective neck dissection versus observation . the conceptual basis for this approach is that lymphatic structures may be considered a defense mechanism against metastasis , so negative nodes should be preserved . accordingly , we do not perform elective neck dissections that would compromise a patient 's quality of life . however , in cases in which the primary tumor invades deep into the tongue or floor of the mouth , level i lymph nodes should be resected as a safety margin even in node - negative necks . for these cases smnd is a superselective neck dissection in only level i necks and is a minimally invasive procedure . we use a transcervical and pull - through approach for resection of the primary tumor and submandibular lymph nodes en bloc . for clinically node - positive necks , a radical neck dissection ( rnd ) or modified radical neck dissection ( mrnd ) however , selective neck dissection in such cases has been reexamined with increasing understanding of anatomic structures and lymphatic drainage [ 4 , 7 ] . several studies have demonstrated the efficacy of sohnd in the clinically n1 neck , with outcomes similar to those of rnd and mrnd [ 8 , 9 ] . however , postoperative morbidity , such as shoulder dysfunction , has been reported even with sohnd , leading surgeons to consider less - invasive procedures . at our institution therefore , we have performed smnds as the initial operation for therapeutic neck dissections in clinically n1 necks with metastasis to level i , followed by careful observation for regional recurrence and immediate salvage treatment if metastasis is detected . this study aimed to evaluate the efficacy of smnd in elective and therapeutic situations involving oscc . we reviewed the medical records of all patients with untreated oscc who underwent definitive surgery at the oral and maxillofacial surgery , kyushu university hospital , between 1989 and 2009 and performed a retrospective cohort study . five patients dropped out within 5 years and were excluded from the study ( follow - up rate : 98.7% ) . the patients who had positive surgical margins at the primary tumor site were excluded from the study because they received extensive salvage surgery or adjuvant chemoradiotherapy . of these , 229 had clinically defined n0 necks , and 68 had clinically defined n1 necks with metastasis to level i. all patients underwent radical excision of the primary tumor . ( 1 ) elective neck dissection is not , in principle , performed in clinically defined n0 necks . ( 2 ) smnd is performed in n0 necks with a transcervical and pull - through approach for resection of primary tumor and reconstructive surgery . ( 3 ) smnd is performed in n1 necks with metastasis only to level i. ( 4 ) rnd is performed in n1 necks with metastasis to level ii or beyond and in n2 necks . previously , we had performed mrnd in n0 necks needing reconstruction ( 2 above ) and rnd or mrnd in all of the clinically node - positive necks . most patients who had advanced disease ( stage iii or iv ) received neoadjuvant chemoradiotherapy . we analyzed the type of neck dissection , use of neoadjuvant or adjuvant therapy , and histopathological factors ( e.g. , tumor cell differentiation , mode of invasion , and extracapsular spread ) . the disease was staged according to the international union against cancer ( uicc ) tnm classification . classification of neck lymph nodes was done according to the neck dissection classification by the american academy of otolaryngology head and neck surgery ( aa - ohn ) . tumor cell differentiation was determined using the world health organization ( who ) classification scheme , and the mode of invasion was determined using the grading system described by anneroth et al . . tumor depth in tongue carcinoma was calculated by measuring from the presumed normal mucosal surface to the deepest point of the tumor using magnetic resonance imaging ( mri ) and ultrasonography ( us ) . the main outcomes were 5-year regional control and 5-year disease - specific survival ( dss ) according to the type of neck dissection , based on the kaplan - meier method and log - rank tests . a cox 's proportional hazard model with univariate and multivariate analysis was used to determine variables related to regional control and the dss . a chi - square test or fisher 's exact test was used to compare the characteristics of each cohort . the protocol for the research project was approved by a suitably constituted ethics committee of kyushu university . a total of 297 patients ( 172 men , 125 women ) were included in the analysis . the median followup was 72 months ( range , 12210 months ) . among 229 patients with clinically node - negative necks , 110 underwent neck dissection at the initial operation according to the protocol described above , and 119 patients underwent resection of the primary tumor only . regional recurrence was present in 16 ( 14.5% ) patients who underwent neck dissection and 21 ( 17.6% ) who did not undergo neck dissection . the 5-year regional control rate was 85.2% in patients who had neck dissections and 82.9% in those who did not ( p = 0.68 ) , and the 5-year dss rate was 88.0% and 85.5% , respectively , ( p = 0.78 ) . of 110 patients who underwent neck dissection , 77 ( 70% ) underwent smnd and 33 ( 30% ) underwent mrnd . positive nodes were identified histopathologically on the excised specimen in 5 ( 6.5% ) of the 77 patients who underwent smnd and 4 ( 12.1% ) of the 33 who underwent mrnd . among the 4 patients with positive nodes who underwent mrnd , 2 had metastases at level i , one at level iia , and one had multiple metastases at level i and iia . no patient had evidence of  skip metastasis  to level iii or iv or metastasis to level iib or v. occult metastases were present in 9 ( 8.2% ) of all 110 patients , and the remaining 101 ( 91.8% ) patients had histopathologically node - negative disease . regional recurrences were documented in 11 ( 14.3% ) patients who underwent smnd and 5 ( 15.1% ) who underwent mrnd , resulting in 5-year regional control rates of 85.2% and 83.3% , respectively , ( p = 0.89 ) ( figure 1 ) . most of the nodal metastases in patients who underwent smnd were in the ipsilateral neck ( 8 at level iia and 1 with multiple metastases at level iia and iii ) , while 2 were present at level i of the contralateral neck . most of the patients with nodal metastases experienced regional recurrence within several months to a year . only 1 patient who underwent mrnd had regional recurrence in the ipsilateral neck ( i.e. , intraglandular parotid node , outside of the neck dissection ) , while 4 had recurrence in the contralateral neck : 2 at level i , 1 at level iia , and 1 at level iia and iii . the 5-year dss rate was 86.5% with smnd and 87.0% with mrnd ( p = 0.94 ) ( figure 2 ) . on multivariate analysis ( table 3 ) , regional control was negatively associated with pathological nodal stage ( node - positive ) and extracapsular spread and positively associated with administration of neoadjuvant chemoradiotherapy . dss was negatively associated with clinical tumor stage , pathological nodal stage , extracapsular spread , and neoadjuvant chemoradiotherapy . regional control and survival were not significantly associated with type of neck dissection on either univariate or multivariate analysis .   among 68 patients who had clinically n1 necks with metastasis to level i , 32 underwent smnd and 36 underwent rnd . of the 32 patients who underwent smnd , 5 ( including the cases of complete response on preoperative chemoradiotherapy ) had histopathologically node - negative necks , and the other 27 had histopathologically positive necks , including 3 patients with multiple metastases at level i. of the 36 patients who underwent rnd , 6 had histopathologically n0 necks , 25 had pn1 ( at level i ) necks , and 5 had pn2b neck . among these 5 patients , 2 had multiple nodal metastases at level i , 2 at level i and sublevel iia , and one at level i , iia , iii . eight ( 11.8% ) of all 68 patients had occult nodal metastases , and no patients had skip metastasis to level iii or iv or metastases to level iib or iv . six ( 18.8% ) patients who underwent smnd and 6 ( 16.7% ) who underwent rnd had regional recurrence , leading to 5-year regional control rates of 81.3% and 83.0% , respectively , ( p = 0.72 ) ( figure 3 ) . of the 6 patients who underwent smnd followed by regional recurrences , 4 had recurrences in the ipsilateral neck : 3 at level iia and 1 at level iia and iii . of the 6 patients who underwent rnd followed by regional recurrences , 1 had a recurrence in the parapharyngeal space of the ipsilateral neck , while 5 had recurrences in the contralateral neck : 2 at level i , 2 at level iia , and 1 at level iia , iii . the 5-year dss rate was 81.3% after smnd and 80.0% after rnd , respectively , ( p = 0.94 ) ( figure 4 ) . on multivariate analysis , as in n0 neck , regional control and dds were negatively associated with pathological nodal stage ( pn2 ) and extracapsular spread and positively associated with administration of neoadjuvant chemoradiotherapy . the type of neck dissection did not significantly correlate with regional recurrence and dds on either univariate or multivariate analysis ( table 4 ) . postoperative limited shoulder mobility was present in 11 ( 30.6% ) of the 36 patients who underwent rnd . indications for elective neck dissection and its appropriate extent in patients with oscc remain controversial . elective neck dissection has become more widely used due to the possibility of occult metastases to cervical lymph nodes . weiss et al . reported that elective treatment of the neck is warranted if the probability of occult metastases is determined to be greater than 20% using decision analysis . the reported probability of occult metastasis has ranged widely from 8 to 48.2% , based on a variety of methods such as routine hematoxylin - eosin staining and immunohistochemical or molecular analysis [ 2 , 15 , 16 ] . although several predictors of occult metastases have been assessed ( e.g. , tumor depth , tumor cell differentiation , mode of invasion , and expression of molecular markers ) [ 1719 ] , micrometastases remain difficult to detect preoperatively . thus , elective neck dissection has been performed without an established method for assessing the probability of occult metastases . furthermore , several studies have demonstrated that regional control and overall survival are similar in elective neck dissection and observation , as well as in salvage treatment for regional recurrence [ 2022 ] . based on these various research findings and practices , one must carefully consider and discuss with the patient whether or not to perform elective neck dissection in clinically n0 necks , because such an approach could constitute overtreatment and unnecessarily compromise the patient 's quality of life . to assist in these decisions , we have used power doppler us and enhanced computed tomography ( ct ) to examine patients for metastatic lymph nodes . additionally , the incidence of occult metastases was 12.1% in our series ( table 2 ) , even in patients treated with elective radical neck dissection . this rate is below the suggested probability of occult metastases ( 20% ) described by weiss et al . . therefore , careful followup , including frequent imaging tests with us as the primary imaging modality , is needed to detect regional recurrence immediately . as mentioned insection 2,we have performed elective neck dissection only in cases of a transcervical approach with reconstructive surgery . accordingly , although we could not assess the significance of elective neck dissection in all patients , regardless of the need for reconstructive surgery , we found that regional control and dss were equivalent in patients who underwent neck dissection and those who underwent tumor resection without neck dissection , followed by observation . consequently , elective neck dissection does not contribute to improved outcome , and our  watchful  treatment strategy for the clinically n0 neck seems justified . several studies , including multi - institutional prospective randomized studies , have demonstrated that regional control and survival in the clinically negative neck were similar in patients treated with sohnd and mrnd . however , some authors have recommended extended sohnd , including level iv , due to the high incidence of skip metastasis to levels iii and iv [ 2 , 23 ] and lymphatic drainage to level ii in addition , some authors have argued that sublevel iib may be preserved in elective neck dissections , because oscc rarely metastasizes to this sublevel . as with extended sohnd , ordinary sohnd including sublevel iib may cause dysfunction of the accessory nerve , as well as phrenic neuropathy , chyle fistula , and cosmetic disturbance . in this way , even selective  elective neck dissection may be overly invasive for patients with clinically negative necks . we had performed mrnd as elective neck dissection along with resection of primary tumors in the past . at present , however , we perform smnd , which is more selective and less invasive than sohnd , based on the conclusion that elective neck dissection is unnecessary . we found that regional control and dds were equivalent after smnd and mrnd regardless of the primary site or histopathological malignancy grade ; in addition , no patients in our series had evidence of skip metastasis to level iii or iv . most regional recurrence in patients with smnd was detected at level iia in the ipsilateral neck within 1 year . although these patients may have had occult metastases outside the smnd , 7 of 11 patients with regional recurrence underwent successful salvage surgery . in addition , 101 of 110 patients with clinically n0 necks were confirmed on histopathological examination to be node negative ; therefore , the diagnostic accuracy of imaging tests for detecting metastatic nodes was considered excellent . thus , we do believe that smnd is acceptable as an elective neck dissection to accompany primary tumor resection . several studies have reported that regional control with therapeutic sohnd in clinically n1 or n2 necks was not very different from that with mrnd [ 8 , 9 ] . in a multi - institutional prospective study , the authors recommended sohnd for all patients with clinically n1 necks . on the other hand , another study demonstrated that rnd should be performed in clinically positive necks because of the risk of skip metastasis to levels iii and iv and of incomplete dissection with sohnd [ 6 , 23 ] . however , more extensive neck dissection causes more serious morbidity , as krause reported that 31% of patients with rnd had severe shoulder dysfunction ( 72% of patients had some grade of dysfunction ) . we assessed the efficacy of smnd in clinically n0 necks , as noted earlier , and had good results following salvage treatment for patients with regional recurrence . based on these findings , in recent years we have performed smnd even as a therapeutic neck dissection in clinically n1 necks with metastasis only to level i. in the current series , regional control and dds in this situation were similar for both smnd and rnd , and the outcomes were considered acceptable . the primary tumor site and histopathological malignancy grade did not significantly correlate with outcome on multivariate analysis . this further indicated that smnd was appropriate for all patients with clinically n1 necks with metastasis to level i. most regional recurrence in patients who underwent smnd , as well as in patients with n0 necks , was detected at sublevel iia in the ipsilateral neck early in followup . among 6 patients who had regional recurrence , 4 underwent successful salvage treatment . the fact that all the regional recurrences were detected in dissection levels of sohnd suggests that smnd is inferior to sohnd with regard to completeness of operation . nevertheless , we were able to avoid overly invasive surgery and prevent postoperative shoulder syndrome , the main residual disability that significantly reduces quality of life in patients without regional recurrences . hence , smnd should be planned only if the patients can be followed up by frequent and strict postoperative management . we believe that therapeutic smnd can be applied to carefully chosen patients with oscc , given the low incidence of postoperative functional or cosmetic disorders and excellent outcomes . in addition , 60 of 68 patients with clinically n1 necks were histopathologically confirmed to have n0 ( including complete responses to preoperative therapy ) or n1 necks . our strategy for the application of selective neck dissection may also be supported by accurate preoperative diagnosis and immediate salvage treatment on regional recurrence . in summary , this is the first paper evaluating the validity of new superselective neck dissection . smnd is an effective treatment for oscc with n0 necks or n1 necks with metastasis to level i , when careful followup is provided to detect regional recurrence immediately .
objective . to evaluate the efficacy of selective submandibular neck dissection ( smnd ) in patients with oral squamous cell carcinoma ( oscc ) with or without nodal metastasis 
 . patients . from a total of 384 patients with untreated oscc who underwent radical excision , we identified 229 with clinically n0 necks and 68 with clinically n1 necks in level i. main outcome measures . 
 the kaplan - meier 5-year regional control and 5-year disease specific survival ( dss ) were compared for smnd , radical neck dissection ( rnd ) , and modified radical neck dissection ( mrnd ) . 
 results . in clinically node - negative necks , 
 the regional control rates were 85.2% with smnd and 83.3% with mrnd ( p = 0.89 ) , and 5-year dss rates were 86.5% and 87.0% , respectively , ( p = 0.94 ) . in clinically n1 necks , 
 the regional control rates were 81.3% with smnd and 83.0% with rnd ( p = 0.72 ) , and the dss rates were 81.3% and 80.0% , respectively , ( p = 0.94 ) . 
 type of neck dissection was not significantly associated with regional control or dss on either univariate or multivariate analysis using cox 's proportional hazard model . 
 conclusions . 
 smnd can be effectively applied in elective and therapeutic management to patients with oscc that are clinically assessed as n0 or n1 to level i of the neck .