Level-specific analysis
Table 3 examines the frequency of nodal metastases in each neck
level in specimens that were cN0 and cN+ve, respectively, at the
corresponding level. ‘Occult’ nodes for each level were from here
defined as those found on pathological staging in levels that had been
cN0 at the corresponding level. It therefore demonstrates the
concordance of ND specimens with preoperative clinical and radiological
examination.
Two hundred individual neck level specimens were analysed (see Table 2)
from the sixty-one patients. Seventy-seven neck level specimens had been
ascribed cN+ve status at the corresponding level, of which 83.1%
(64/77) had pathological evidence of metastatic disease. One hundred and
twenty-three neck level specimens were cN0 in the corresponding level,
of which occult disease was found in 13.0% (16/123). This occult
disease was found in 58.3% (7/12) of cN0 level IIs, 13.3% (6/45) of
cN0 level IIIs, 5.5% (3/61) of cN0 level IVs, and 0/5 cN0 level Vs.
Overall, sixteen of sixty-one patients had pathological nodes in levels
not established clinically. All four level I NDs were performed on necks
cN+ve for level I, of which three were pN+ve in level I; two of the
seven level V NDs were performed on necks cN+ve for level V, of which
one was pN+ve in level V.
Table 4 presents the negative predictive values (NPV) and positive
predictive values (PPV) for cN0 and cN+ve status, respectively, for each
level. With regard to the distribution of lymph node metastasis at
adjacent neck levels, it was found that patients who were cN+ve at level
II had a PPV of 30.9% (95% CI 27.4% - 34.6%) for also being pN+ve at
level III, and those who were cN0 at level II had a NPV of 87.5% (95%
CI 48.1% - 98.2%) for being pN0 at level III. Patients who were cN+ve
at level III had a PPV of 11.1% (95% CI 4.8% - 23.6%) for also being
pN+ve in level IV, and a NPV of 97.8% (95% CI 89.8% - 99.6%) for the
absence of pathological level IV nodes (data not shown).