Staging as a Guide for Treatment Selection
The staging system serves as a guide to therapeutic options; however, neither the present classification nor any other could be absolute in this regard. In terms of conventional treatment,
surgery is the primary treatment option for all patients with non-small cell lung cancer with stages IA, IB, IIA and IIB disease who are physiologically able to undergo thoracic operation and the required sacrifice of lung tissue. Selected patients with stage IIIA tumors are also candidates for surgery, usually in combination with neoadjuvant and adjuvant treatment. The potential for complete resection of all known tumor is a key element and limiting factor. Controversy exists over the options for surgery in patients with evidence of ipsilateral mediastinal and subcarinal lymph node metastasis. In general, evidence of lymph node metastasis to lymph nodes in the thoracic inlet, of multiple levels of metastasis and of extranodal invasion indicates further occult disease and contraindicates surgery. For patients with nonsurgical stage IIIA tumors and those in the stage IIIB category, the T and N categories serve as guides for structuring treatment plans, most often radiotherapy, chemotherapy or combined therapy. Treatment for stage IV disease is usually palliative radiotherapy or chemotherapy. The structure of new investigational approaches and the evaluation of results depends on reproducible classification of the extent of disease in these patients.

When clinical and surgical estimates of disease extent are compared, errors in clinical staging usually relate to an underestimate of the T and N categories. Therefore, if the extent of disease is questionable, it is appropriate to classify to the higher designation.

Staging for Small Cell Lung Cancer
In patients with small cell carcinoma, the anatomic extent of disease is a major factor in the proportion of patients that achieve the complete response required for long term survival. Consistent and reproducible TNM and stage classifications are useful for this cell type as well as for non-small cell lung cancer²⁴. For example, the selection of patients for treatment programs involving adjuvant surgery depends on the initial TNM and stage classifications or the retreatment evaluations following induction therapy.

Review of the literature confirms that it is common for the terms "limited" and "extensive" disease to be inconsistently applied to small cell lung cancer. The use of these designations defeats the purpose and utility of consistent, reproducible classification, which is now, and will continue to be useful in the mileau of evolving cancer knowledge. The structure of new treatment plans depends on the results achieved for specific groups of patients that are best described in terms of the TNM and stage categories.