Functional Imaging to Differentiate Pulmonary Carcinoids
========================================================

* Tarun Jindal
* Arvind Kumar
* Rakesh Kumar
* Roman Dutta

**TO THE EDITOR:** We read with great interest the article by Kayani et al. (1). They evaluated 11 cases of typical carcinoids, 2 of atypical carcinoids, 1 of small cell neuroendocrine tumor, 1 of large cell neuroendocrine tumor, 2 of diffuse idiopathic pulmonary neuroendocrine hyperplasia, and 1 of adenocarcinoma with neuroendocrine differentiation using 18F-FDG PET/CT and 68Ga-DOTATATE PET/CT. They reported that, compared with typical carcinoids, atypical and other less differentiated carcinoids revealed significantly higher uptake on 18F-FDG PET/CT scans (*P* = 0.005) and significantly lower uptake on 68Ga-DOTATATE PET/CT scans (*P* = 0.002).

We observed an interesting finding by evaluating the ratios of maximum standardized uptake value (SUVmax) on 68Ga-DOTATATE PET/CT to SUVmax on 18F-FDG PET/CT scans. The ratios range from 1.2 to 19.5 in typical carcinoids (median SUVmax, 7.3) but from 0.1 to 1.1 in other less differentiated carcinoids (median SUVmax, 0.16). This difference in the ratios of typical versus atypical and other less differentiated carcinoids is statistically significant. The *P* value is 0.002 (Mann–Whitney test for nonparametric data, 2-tailed). Thus, the ratio of SUVmax on 68Ga-DOTATOC PET/CT and 18F-FDG PET/CT may also be of help in predicting the histopathologic variety of the carcinoid tumor and may have an equally high accuracy. A larger study is indicated to validate this observation and to objectively determine a cutoff value for the possible differentiation.

*   © 2010 by Society of Nuclear Medicine

## REFERENCE

1.  1.Kayani I, Conry BG, Groves AM, et al. A comparison of 68Ga-DOTATATE and 18F-FDG PET/CT in pulmonary neuroendocrine tumors. J Nucl Med. 2009;50:1927–1932.
    
    [Abstract/FREE Full Text](http://jnm.snmjournals.org/lookup/ijlink/YTozOntzOjQ6InBhdGgiO3M6MTQ6Ii9sb29rdXAvaWpsaW5rIjtzOjU6InF1ZXJ5IjthOjQ6e3M6ODoibGlua1R5cGUiO3M6NDoiQUJTVCI7czoxMToiam91cm5hbENvZGUiO3M6Njoiam51bWVkIjtzOjU6InJlc2lkIjtzOjEwOiI1MC8xMi8xOTI3IjtzOjQ6ImF0b20iO3M6MjQ6Ii9qbnVtZWQvNTEvOS8xNDg4LjEuYXRvbSI7fXM6ODoiZnJhZ21lbnQiO3M6MDoiIjt9)