The lymphatic pathways of non-small cell lung cancer and their implication in curative irradiation treatment

Using the pre-therapy CT scans of 266 node positive non-small cell lung cancer patients, we analysed the lymphatic pathways and the incidence of lymph node metastases in regional lymph nodes (as described by CT criteria corresponding to the modified mapping scheme of the American Thoracic Society), in order to develop the target volume for curative irradiation treatment. Among the 105 patients with node positive left sided primaries, the incidence of involvement of the ipsilateral supraclavicular lymph nodes was 9.5%, and the incidence of involvement of the contralateral lymph nodes was 3.8%. The incidence of involvement of the contralateral hilar lymph nodes was 4.8%. Among the 161 patients with nodal positive right sided primaries, the incidence of involvement of the ipsilateral supraclavicular lymph nodes was 8.7% and the incidence of involvement of the contralateral lymph nodes was 1.8%. For this group of patients, the incidence of involvement of the contralateral hilar lymph nodes was 3.7%. All patients with involvement of the contralateral hilar lymph nodes died within 2.5 years of diagnosis. In the cases where there was involvement of the supraclavicular lymph nodes, the patients died within 1.6 years. Involvement of the ipsilateral and/or contralateral supraclavicular lymph nodes, and/or the contralateral hilar lymph nodes, is defined as N3 disease, and is included in Stage IIIb. No curative surgery is indicated for these patients. Why therefore should this group of patients be treated with curative intent by irradiation of the primary, ipsilateral and contralateral hilar lymph nodes, as well as mediastinal, ipsilateral and contralateral supraclavicular lymph nodes? The curative radiation treatment volume for lung cancer has to include the primary tumor and the ipsilateral hilar, and the low and high mediastinal lymph nodes, as is indicated for Stage I, II and IIIa disease.