The role of 18FDG-PET in gastric cancer
Cite this article as: Graziosi L, Evoli LP, Cavazzoni E, Donini A. The role of 18FDG-PET in gastric cancer. Transl Gastrointest Cancer 2012;1(2):186-188. DOI: 10.3978/ j.issn.2224-4778.2012.07.11
Perspective

The role of 18FDG-PET in gastric cancer

Luigina Graziosi, Luca Pio Evoli, Emanuel Cavazzoni, Annibale Donini

University of Perugia, Section of General and Emergency Surgery, “Santa Maria della Misericordia Hospital”, Via Dottori, 06132, Perugia, Italy

Corresponding to:
Luigina Graziosi, MD. University of Perugia, Section of General and Emergency Surgery, “Santa Maria della Misericordia Hospital”, Via Dottori, 06132, Perugia, Italy.
Email: luiginagraziosi@yahoo.it.
Submitted Jun 29, 2012. Accepted for publication Jul 30, 2012.
DOI: 10.3978/j.issn.2224-4778.2012.07.11

Imaging with 18F-fluoro-2-deoxyglucose PET (18FDGPET) is based on the increased glucose uptake of neoplastic cells, which over-express the main cell-membrane glucose transporter GLUT-1 resulting in higher uptake of 18FDG as well. More than visual analysis an often-used semiquantitative method to assess tumor 18FDG uptake is the standard value (SUV), which is the measurement of 18FDG up-take in a tumor volume normalized on the basis of a distribution volume.

18FDG-PET has been widely used to evaluate various types of malignant tumors, including lung, oesophageal, and colorectal cancer and lymphomas (1). However, the role of 18FDG PET in gastric cancer is debatable. Although 18FDG-PET is clinically useful in detecting recurrent gastric cancer after surgical resection (2,3), the role of 18F-FDG PET in preoperative workup is limited due to its low sensitivity for primary tumour and lymph node (LN) metastasis (4,5). Furthermore, because only a few studies with a small number of patients have been performed, the role of 18F-FDG PET in predicting prognosis of patients with gastric cancer is still contentious.

The primary site detection rate of 18FDG-PET is about 50% in early gastric cancer and 92% in advanced gastric cancer. Sensitivity for detecting the primary tumour varies between 47 and 96% due to the different characteristics of enrolled patients (5-12) of the studies considered. The variable and sometimes intense physiological 18FDG uptake in the normal gastric wall and differences of 18FDG uptake in cancer lesions according to hystopathological subtypes of gastric cancer are the most significant contributing factors for the low detection rate of gastric primary tumours.

Normal gastric wall devoid of malignant lesions can displays an SUV exceeding 2.5 and benign gastric mucosal inflammation can show focal intense 18FDG accumulation, which restricts detection of gastric cancer lesions (13-15). 18FDG uptake in mucinous carcinoma can be positively correlated with tumour cellularity, but negatively correlated with the amount of mucin within the tumor mass, which accounts for low detectability of 18FDG-PET for undifferentiated and mucinous tumors (16). Furthermore, an infiltrative growth pattern, high content of mucus and low concentration of cancer cells lead to low 18FDG uptake in poorly differentiated cancer and signet-ring cell cancer, in spite of their aggressiveness. Detection rate is higher when tumors are larger than 3.5 cm and have deeper depth of invasion, and at a later stage. In many multivariate analyses, tumor size, spread of tumor cells beyond the muscle layer (≥ T2), and lymph node metastasis were statistically significant factors in primary site detection rate.

The sensitivity, specificity, and positive predictive value of 18FDG-PET to lymph node metastasis are 60%, 85%, and 80%, respectively; sensitivity being lower compared to CT while specificity and positive predictive value are higher. PET is less sensitive than CT in the detection of lymph node metastasis located near to gastric wall in the regional stations, mainly due to its poor spatial resolution, which makes it unhelpful in discriminatine between lymph nodes and the primary tumor (17). Detection of lymph node metastases in the 12, 13, 14, 15, 16 stations can change the extent of lymph node dissection or may preclude unnecessary surgery. Metastases at these anatomical sites would theoretically be easier to identify at PET because they are located away from the primary lesions. In other words, the relatively low spatial resolution of PET does not adversely affect the detection of these metastases because they are remote from the primary tumor or from areas of intense FDG uptake. Sensitivity, specificity, and positive predictive value to distant metastasis are, respectively, 65%, 99%, and 88%, similar to CT. The major advantage of 18FDG-PET over anatomic imaging modalities is its capacity to detect distant solid organ metastases. Metastases to the liver, lungs, adrenal glands, and ovaries can be readily identified at FDG PET (18). 18FDG PET has a little value in diagnosing peritoneal carcinomatosis, again hampered by its low sensitivity (mean 32%) but relatively high specificity ( mean 88.5%). Some authors have reported that peritoneal lesions show an extensive fibrosis around relatively few malignant cells, wich could explain the low sensitivity of this imaging modalità, the small size of peritoneal nodules (<5 mm) could represent another reason for the low detection rate (19). The study of Lee et al. (20) demonstrated that 18FDG uptake in gastric cancer is an independent and significant prognostic factor for predicting cancer recurrence after curative surgical resection. Patients with negative 18FDG uptake in gastric cancer showed a significantly recurrences rate after surgical resection than patients with positive 18FFDG uptake. Furthermor, recurrence-free survival was significantly different between patients with positive and negative 18F-FDG uptake. Therefore, although the detectability of 18FDG-PET/CT for gastric cancer is low, preoperative 18F-FDG-PET/CT could provide effective information on the prognosis after surgical resection in patients with gastric cancer expecially in tubular and undifferenziated types. In addition, 18FDGPET has actually a significant role in monitorino the response to neoadjuvant chemotherapy, showing chemoresponders at early stage. It is anticipated that the use of new metabolic tracers, such as coline or methionine will improve the sensitivity of PET-CT in staging gastric cancer.

Acknowledgements

Disclosure: The authors declare no conflict of interest.

References

  1. Kostakoglu L, Agress H Jr, Goldsmith SJ. Clinical role of FDG PET in evaluation of cancer patients. Radiographics 2003;23:315-40; quiz 533.
  2. Bilici A, Ustaalioglu BB, Seker M, et al. The role of 18F-FDG PET/CT in the assessment of suspected recurrent gastric cancer after initial surgical resection: can the results of FDG PET/CT influence patients’ treatment decision making? Eur J Nucl Med Mol Imaging 2011;38:64-73.
  3. De Potter T, Flamen P, Van Cutsem E, et al. Wholebody PET with FDG for the diagnosis of recurrent gastric cancer. Eur J Nucl Med Mol Imaging 2002;29:525-9.
  4. Dassen AE, Lips DJ, Hoekstra CJ, et al. FDG-PET has no definite role in preoperative imaging in gastric cancer. Eur J Surg Oncol 2009;35:449-55.
  5. Kim SK, Kang KW, Lee JS, et al. Assessment of lymph node metastases using 18F-FDG PET in patients with advanced gastric cancer. Eur J Nucl Med Mol Imaging 2006;33:148-55.
  6. Stahl A, Ott K, Weber WA, et al. FDG PET imaging of locally advanced gastric carcinomas: correlation with endoscopic and histopathological findings. Eur J Nucl Med Mol Imaging 2003;30:288-95.
  7. Mochiki E, Kuwano H, Katoh H, et al. Evaluation of 18F-2- deoxy-2-fluoro-D-glucose positron emission tomography for gastric cancer.World J Surg 2004;28:247-53.
  8. Yun M, Lim JS, Noh SH, et al. Lymph node staging of gastric cancer using (18)F-FDG PET: a comparison study with CT. J Nucl Med 2005;46:1582-8.
  9. Oh HH, Lee SE, Choi IS, et al. The peak-standardized uptake value (P-SUV) by preoperative positron emission tomography-computed tomography (PET-CT) is a useful indicator of lymph node metastasis in gastric cancer. J Surg Oncol 2011;104:530-3.
  10. Hur H, Kim SH, Kim W, et al. The efficacy of preoperative PET/CT for prediction of curability in surgery for locally advanced gastric carcinoma. World J Surg Oncol 2010;8:86.
  11. Yamada A, Oguchi K, Fukushima M, et al. Evaluation of 2-deoxy-2-[18F]fluoro-D-glucose positron emission tomography in gastric carcinoma: relation to histological subtypes, depth of tumor invasion, and glucose transporter-1 expression. Ann Nucl Med 2006;20:597-604.
  12. Mukai K, Ishida Y, Okajima K, et al. Usefulness of preoperative FDG-PET for detection of gastric cancer. Gastric Cancer 2006;9:192-6.
  13. Stahl A, Ott K, Weber WA, et al. FDG PET imaging of locally advanced gastric carcinomas: correlation with endoscopic and histopathological findings. Eur J Nucl Med Mol Imaging 2003;30:288-95.
  14. Koga H, Sasaki M, Kuwabara Y, et al. An analysis of the physiological FDG uptake pattern in the stomach. Ann Nucl Med 2003;17:733-8.
  15. Takahashi H, Ukawa K, Ohkawa N, et al. Significance of (18)F-2-deoxy-2-fluoro-glucose accumulation in the stomach on positron emission tomography. Ann Nucl Med 2009;23:391-7.
  16. Berger KL, Nicholson SA, Dehdashti F, et al. FDG PET evaluation of mucinous neoplasms: correlation of FDG uptake with histopathologic features. AJR Am J Roentgenol 2000;174:1005-8.
  17. McAteer D, Wallis F, Couper G, et al. Evaluation of 18F-FDG positron emission tomography in gastric and oesophageal carcinoma. Br J Radiol 1999;72:525-9.
  18. Kinkel K, Lu Y, Both M, et al. Detection of hepatic metastases from cancers of the gastrointestinal tract by using noninvasive imaging methods (US, CT, MR imaging, PET): a meta-analysis. Radiology 2002;224:748-56.
  19. Turlakow A, Yeung HW, Salmon AS, et al. Peritoneal carcinomatosis: role of (18)F-FDG PET. J Nucl Med 2003;44:1407-12.
  20. Lee JW, Lee SM, Lee MS, et al. Role of (18)F-FDG PET/ CT in the prediction of gastric cancer recurrence after curative surgical resection. Eur J Nucl Med Mol Imaging 2012. [Epub ahead of print].