Variable metabolic activity of primary and metastatic site at different organs in lung cancer as measured by corrected SUV of FDG uptake: A new observation

Abstract

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Objectives: The most important prognostic indicator in lung cancer is the extent of disease. FDG PET is the standard of care in initial staging, monitoring the response to therapy and detection of recurrent lung cancer. One of the most limiting factors for the accurate quantification of metabolic parameters with PET is the partial volume effect. Our aim was to establish the accurate biologic tumor behavior in primary and metastatic lesions in various organs in the body in patients with lung cancer, using partial volume correction technique.

Methods: 22 patients with biopsy proven lung cancer diagnosis, who underwent FDG PET scans and CT scans, were involved in this study (15 women 7 men; age range 43-83 years, mean age 64±11). The time interval between the PET and CT were 48±45 days. Maximum SUV values in the primary and metastatic lesions for all the patients were calculated. The sites of the primary and metastatic lesion were determined. The lesions were categorized into 5 different groups according to the region of the lesion. Partial volume correction using the CT sizes of lesions were applied to measure the accurate SUV values (Lubberink M et al JNM. 2002; 43:1391-7). The partial volume corrected mean SUVmax for each lesion sites was calculated and compared using one way ANOVA method.

Results: A total of 69 primary and metastatic lesions were detected The SUVmax for the 25 mediastinal and hilar lymph nodes after partial volume correction ranged between 7.1-17.8, with a mean and SD of 10.0±3.1. For the 10 right lung lesions the range was 5.6-16.4, with a mean of 11.9±3.5. For the 11 left lung lesions the range was 4.6-19.6, with a mean of 10.5±5.2. For the 16 bone bone marrow lesions SUVmax ranged 5.1-40, with a mean of 18.3±13. For the 7 liver, spleen and bowel lesions the range was 4.6-29.9, with a mean of 13.6±9.1. There were statistically significant difference in the mean SUVmax values between the lung lesions, bone marrow lesions and liver-spleen-bowel lesions (p=0.02). There was no statistically significant difference between left and right lungs and mediastinal-hilar lesions.

Conclusions: This study shows the highest FDG uptake in the bone marrow lesions and distant organs (liver, spleen and bowel). The lowest uptake was found in the mediastinal and hilar lymph nodes. These findings indicate that metabolic activities of the lesions vary considerably depending on the location of the metastatic sites. These findings may have implications with regard to local and systemic treatment of these lesions. Resistance to treatment in certain sites such as bone marrow may be related to metabolic aggressiveness of these lesions.