In NSCLC treatment and prognosis are entirely dependent on accurate staging. Stage I tumours are small and readily resectable with good prognosis. The standard treatment is surgery though radical radiotherapy is an option in those who are unfit for a surgical procedure. Stage II tumours have local lymph node metastases. They are readily resectable but because of the node metastases they have a reduced prognosis. Stage III tumours are locally advanced and cure is uncommon with surgery alone. They fall into two general categories: either invading structures which compromise surgical resection, or metastatic to mediastinal lymph nodes. Unlike Stage IV tumours (disseminated) they may be encapsulated in a therapeutic radiation field. Recent advances in neo-adjuvant chemotherapy and radiotherapy have changed the approach to these tumours and the prognosis has been improved especially where a good response to induction therapy has allowed complete surgical resection.

The staging of NSCLC is based on the TNM classification. A modification was made in 1987 by Mountains et al to differentiate those stage III tumours which could be excised with en-bloc nodal dissection (stage IIIa) as opposed to those which could not be excised en-bloc (Stage IIIb). Updated analyses of survival databases identified a number of anomalies and further revision became necessary. The Revised International System for Staging Lung Cancer was adopted in 1997 by the American Joint Committee on Cancer and the Union Internationale Contre le Cancer. The major changes were the division of Stage I into A and B depending on the T stage of the tumour and the reallocation of T3 N0 tumours to Stage IIB in line with their better prognosis than those tumours which have N2 node metastases.

CT scan has become the main tool for assessment of the site and size of tumour, chest wall invasion, mediastinal lymphadenopathy and metastases to liver, adrenal and dorsal spine. MRI may clarify chest wall or mediastinal invasion.

Histological confirmation of mediastinal nodes is made at mediastinoscopy or mediastinotomy via left anterior thoracotomy. These are invasive procedures but may avoid unnecessary thoracotomy. Percutaneous, trans-bronchial, thoracoscopic and trans-oesophageal (with ultrasound guidance) biopsies are also possible for some node stations.