Η συμβολή του 99mTc-depreotide (Neospect R) στη σταδιοποίηση του βρογχογενούς καρκίνου του πνεύμονα

Abstract

Lung cancer is one of the most leading causes of death worldwide. More than 99% of malignant lung tumors arise from the respiratory epithelium and are termed bronchogenic carcinoma which can be divided into 2 subgroups: small cell lung cancer (SCLC) and non-small cell lung cancer (NSCLC). SCLC accounts for 20-25% of all lung cancers and is primarily diagnosed in smokers or former smokers. NSCLC accounts for 75-80 % of all lung cancers and is divided into 3 subtypes: squamous cell carcinoma (also called epidermoid carcinoma), large cell carcinoma and adenocarcinoma. The diagnosis of lung cancer follows some algorithms based on several examinations which include invasive methods(i.e. mediastinoscopy, video assisted thoracoscopic surgery bronchoscopy, transthoracic, transbronchial or transoesophageal needle biopsy) and non invasive imaging techniques (i.e. Chest Radiograph, Computed Tomography, MRI, Nuclear Medicine procedures), cytological and tumor test markers and is finally confirmed with biopsy. Staging is achieved through all the aforementioned techniques and can be divided into presurgical and invasing staging. Accurate staging is very important in order to discriminate patients with resectable from unresectable mass. According to lung cancer mapping, for stages Ι-ΙΙΙΑ throracotomy is the therapy of choice, although Stage ΙΙΙΑ is not merely a red line but a relatively heterogeneous group of patients with metastatic disease to the ipsilateral mediastinal (N2) lymph nodes and also includes T3N1 patients. Presentations of disease range from apparently resectable tumors with occult microscopic nodal metastases to unresectable, bulky multistation nodal disease. In order to achieve better survival rates according to adequate therapy a new revised staging system has been established, giving emphasis on subdivision of T and M stages. So, in the new system, old stages have been transferred “upward” or “downward”. Computed tomography (either classical or helical) still remains a very useful tool in the lung cancer staging, although its sensitivity and positive predictive value are not excellent and frequently misses nodal N2 involvement which is of great value in the therapeutic planning. For that reason we thought to evaluate the usefulness of 99mTc-depreotide scintigraphy in non-small cell lung cancer staging especially when CT findings would be doubtful. Depreotide is a somatostatin analog with a long in-vivo half time, showing great affinity for somatostatin receptors in cancer cell membranes (SSTR2,3,5). In our study 69 patients (60 men, 9 women) with suspicious or proven clinical or radiological findings for lung cancer have been examined with 99mTc-depreotide (through 2003-2009), and our findings were correlated with those of CT and histological report. The results revealed 44 cases of NSCLC, 18 of SCLC, 1 neuroendocrine tumor, 1 metastatic and 5 cases with no malignancy (pneumonia or bronchomalacia). 30 out 44 patients with NSCLC, were grouped as resectable cases (Stages IA-IIIA) and the rest of them as non resectable cases with metastasis (Stages IIIB-IV). 18 patients had extended SCLC disease. Both CT and scintigraphy showed almost equally high sensitivity (> 93%) and positive predictive value (> 95%) whereas specificity and negative predictive values were moderate. For patients with resectable NSCLC, CT failed to diagnose 4 cases and scintigraphy 2. (4 FN results for CT and 2 for 99mTc-depreotide respectively). In all other study cancer groups (either NSCLC of non-resectable stage either SCLC of extended disease) both methods showed no false negative results, except 1 FN result for 99mTc-depreotide in SCLC. 3 False positive results for CT and 2 for 99mTc- depreotide were registered in case of non malignancy. According to our study, 99mTc-depreotide was not proven superior to CT in NSCLC staging, as it failed to elucidate occult lesions (especially mediastinal lymph nodes or nodes of the contralateral side) in case of 4 false negative CT results. Thus, it could not change the NSCLC staging. Even if our results seem disappointed and modern tendency for presurgical lung cancer staging is the use of PET/CT fusion acquisition, few works with same number of patients revealed some superiority of scintigraphy over CT supporting the alternative or additional use of scintigraphy especially in cases of doubtful CT findings and for persons who for healthy reasons cannot tolerate an invasive staging technique. As there are few PET centers and of great cost, 99mTc-depreotide scintigraphy for lung cancer staging seems a logical alternative in some cases.