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PROPOSED MODIFICATION TO THE CURRENT STAGING OF LUNG CANCER
M.
Costa Angeli, E.Tisi,
D. Ballabio, C. Arrigoni, E. Cassina, E. Corno, T. Di Sibio, C. Benenti.
Department
of Thoracic Surgery – San Gerardo Hospital- Monza - Italy
From
a revision of lung term survivals following surgical therapy in lung cancer,
obtained during a 21 year period in the department of Thoracic Surgery, S.
Gerardo Hospital, Monza, we noticed that 5 year survival rates are homogeneous
only within stages I and II. On the contrary, in stage IIIA survivals are
significantly high in substagesT3N0 and T3N1, with a significant drop in the
N2 substages. We propose a new staging system that groups in stage II all
patients with no lymph nodal involvement (N0) but with neoplasm invading
surrounding tissues (T3). We suggest that current stage II should be included
in stage IIIA, together with substage T3N1, grouping therefore all patients
with local lymph nodal involvement. The N2 statuses could be included in stage
IIIB, representing the operability limit. Patients from substages N3 and T4
should be included in stage IIIC. Stage IV should be unchanged, compared to
the current classification.
We
revised the long term results of lung cancer surgical therapy in the
department of Thoracic Surgery, S. Gerardo Hospital, Monza. Stage assessment,
defined as homogeneous grouping of patients with similar pathology and
treatment, should predict identical prognosis. However, we observed a
significant inhomogeneity in terms of survival within some of the stages. We
analysed data obtained during a time span of 21 years (1972 through 1993) and
we split this period into two parts: 1972 through 1980, and 1985 through 1993,
due to differences in the pre-operative staging system (CT was not available
in the 1972-1980 period). We consider the 1981-1984 period as a time of
transition in the staging method. Until 1985, we experienced difficulties in
the analysis of our data, due to the relative inhomogeneity of the results,
that were obtained by uncompleted pre-surgical staging. However, the
unexpected results obtained were meaningful and convinced us to extend our
observations to a subsequent period. In the first period (1972 - 1980) we followed 355 patients; in the second period (1985 - 1993), we followed 418 patients.
The results obtained in the two
periods were comparable. The introduction of chest CT in the pre-operative
staging allowed to evaluate the local spreading of the neoplasm and the mediastinic lymph nodal involvement. However, the analysis of the
relationships of the cancer with the neighbouring anatomical structures showed
little reliability. Mediastinoscopy was used only to histologically confirm
radiological lymph nodal involvement when N2 staging was necessary to exclude
surgical treatment. Starting from 1982, the pre-surgical staging included head CT, abdomen echo scan, and bone nuclear scan, thus detecting occult metastatic foci that caused a lower survival in the former period. Although overall survival rates were different between the two periods examined, the distribution of rates among the single staging groups remained constant. Post surgical 5 year survival rates were homogeneous within stages I and II but not in stage IIIA. In this stage, the survival was relatively high in the substages T3N0 and T3N1, while there was a significant drop in the N2 substages (N0: 46% > N2: 2-4%) The clinical importance of the N Status in the determination of outcome is unquestionable, We therefore reasoned that stage grouping should be redefined giving more emphasis to the N status and down sizing the T status, with the aim of increasing the reliability of survival prediction. We propose a new Staging system that should render more homogeneous the TNM grouping and that could be used to define diagnosis, therapy and expected outcome. Patients with no nodal involvement (N0) but with a neoplasm invading adjacent structures (T3) should be assigned to stage II. We suggest that current stage II patients should be grouped in a new IIIA stage, together with the T3N1 substage. Therefore, all patients with local lymph nodal involvement should be grouped together. N2 status patients could be included in stage IIIB, representing the actual operability limit, except otherwise indicated by the need of neoadjuvant therapy. Patients from substages N3 and T4 should be grouped in stage IIIC. Patients with non resectable IIIC stage neoplasm could benefit of neoadjuvant radio/chemotherapy followed by surgical exeresis. Stage IV would be unmodified, compared to current classification shows the 5 year survival rates in the single subgroups according to our proposed staging system. We can notice that survival decreases progressively going from lower to higher stage. In Fig. 3, survival data are grouped according to the currently used staging method and do not show the same linear decrease.
In 1997, Mountain proposed a modification to the current staging system. In our opinion, this modified staging does not optimally fulfil the criteria of outcome homogeneity, as an excessive prognostic importance is still ascribed to the T factor, compared to the N status. (stage IIB : T2N1M0 = T3N0M0 and stage IIIA : T3N1M0 = TN2M0).
The complexive differences of our proposed staging method and of the previous
systems are summarised in Tab.3
and Fig. 4.
Reference:
1)
- Mountain CF: Revisions in the International System for Staging Cancer. Chest
111(6):1717-1717,1997.
2)
- Lung. In: American Joint Committee on Cancer: Manual for Staging of Cancer.
Philadelphia:JB Lippincott Company, 4th ed., 1992, pp 115-122. 3) - Mountain CF: A new international Staging System for Lung Cancer. – Chest 89;22S–233S,1986
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