Prognostic significance of platelet and microvessel counts in operable non-small cell lung cancer
Introduction
Angiogenesis is the formation of new blood vessels from the endothelium of the existing vasculature and is a requirement for solid tumour growth beyond 1–2 mm in diameter [1]. Currently the best predictor of outcome in non-small cell lung cancer (NSCLC) is the T, N, M stage [2]. Recent research suggests that microvessel density may be an important independent prognostic indicator in this disease [3], [4], [5], [6] although some studies have not found microvessel counts to be predictive for survival [7], [8].
Thrombocytosis is associated with a worse prognosis in solid tumours including primary lung cancer [9], [10]. Angiogenic factors including vascular endothelial growth factor (VEGF) are transported by platelets [11] and released when platelets are activated [12]. Platelet count has been shown to be associated with serum VEGF concentration in solid tumours [11], [13], [14]. VEGF is the most potent and specific growth factor for endothelial cells and plays an important role in angiogenesis [15]. VEGF also increases vascular permeability allowing leakage of plasma proteins, fibrin and platelets into the extracellular matrix [15]. Recently it has been proposed that platelets contribute to tumour-induced angiogenesis by locally releasing angiogenic growth factors such as VEGF [13], [16].
This study was aimed at evaluating the relationship between microvessel and pre-operative platelet counts in NSCLC and to see if these factors had an impact on survival.
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Study population
This is a retrospective study of 181 patients with stage I–IIIa NSCLC who underwent surgical resection in Glenfield Hospital, Leicester, UK between 1991 and 1996 with a post-operative survival >60 days. No patient received neoadjuvant or adjuvant chemotherapy. Radiotherapy was given to 14 patients post-operatively for a positive resection margin. The follow-up ranged from 24 to 108 months (median 39.8 months). A total of 98 (54.1%) subjects died from a recurrence of their lung primary. Some 128
Clinicopathological findings
The clinicopathological findings are listed in Table 1. The stage of the tumour was prognostic (P=0.0001). Tumour spread to nodes was associated with poor prognosis (P=0.0007) and increasing nodal status was more significant (P<0.0001). The trend to worse survival with increasing T status did not reach significance (P=0.15). No other clinicopathological finding, including age, sex, grade or histological sub-type was associated with outcome.
Platelet count
The pre-operative platelet count was identified in 175
Discussion
The growth of a tumour beyond 1–2 mm in diameter requires the development of new blood vessels [1]. These vessels play an important role in tumorigenesis supplying nutrients and oxygen, disposing of metabolic waste products and allowing metastatic spread. The study showed that tumours with a high vessel count were associated with a worse survival. This is in agreement with several other studies showing an inverse relationship between vascularity and patient survival in NSCLC [3], [4], [5], [6].
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Tumour and Angiogenesis Research Group.