OtherLetters to the Editor

Reply: Scintigraphic TNM Staging of Tumors: A Proposition

Angela Spanu and Giuseppe Madeddu
Journal of Nuclear Medicine August 2009, 50 (8) 1386; DOI: https://doi.org/10.2967/jnumed.109.063149

REPLY: We read with interest the letter by Regi Oommen about potential changes in postoperative pathologic TNM (pTNM) staging brought about by integrating 131I whole-body scintigraphy (WBS) with 131I SPECT/CT in patients with differentiated thyroid cancer (DTC). In particular, the author has illustrated a DTC case in which preablative 131I WBS and 131I SPECT/CT changed the pTNM stage from T1N1bMx to T1N1bM1 when scintigraphy showed distant lung metastases that had been missed on chest radiography. SPECT/CT confirmed the lung uptake.

Among the patients enrolled in our study (1), 9 underwent preablative 131I WBS and 131I SPECT/CT. SPECT/CT was concordant with WBS in 7 of 9 patients, confirming residual tissues seen on planar scanning. In the remaining 2 patients, SPECT/CT was more accurate than WBS: in one patient, SPECT/CT identified a higher number of residues; in the other, SPECT/CT detected mediastinal lymph nodes and lung metastases occult on planar scanning, as well as a higher number of bone metastases (some of which were small and in the ribs). Moreover, SPECT/CT was more accurate than WBS in several of our patients studied with diagnostic radioiodine during long-term follow-up after radioiodine ablation, identifying occult locoregional or distant lesions not evident on planar scanning and contributing to selection of the most appropriate radioiodine therapeutic dose or to a change in therapeutic approach in some cases.

Schmidt et al (2) demonstrated that SPECT/CT determines lymph node involvement at the radioablation study more accurately than does planar imaging, altering management in roughly one quarter of DTC patients by upstaging or downstaging their disease.

On the basis of the above results, we conclude, in agreement with Dr. Oommen, that in patients scheduled for preablation diagnostic 131I scanning, integration of WBS with SPECT/CT is of extreme importance because of the resulting increase in specificity and sensitivity. In particular, this new procedure has the potential to modify pTNM stage by identifying locoregional iodine-avid lymph node metastases that need to be treated surgically before radioiodine ablation, as well as by detecting distant metastases and thus guiding one to the most appropriate radioiodine therapeutic dose or to a treatment alternative to radioiodine.

A reassessment of the role of 131I-WBS in the management of DTC patients is probably necessary in light of the high performance obtainable when 131I-WBS is integrated with SPECT/CT.

Footnotes

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References

  1. 1.
    Spanu A, Solinas ME, Chessa F, Sanna D, Nuvoli S, Madeddu G. 131I SPECT/CT in the follow-up of differentiated thyroid carcinoma: incremental value versus planar imaging. J Nucl Med. 2009;50:184–190.
  2. 2.
    Schmidt D, Szikszai A, Linke R, Bautz W, Kuwert T. Impact of 131I SPECT/spiral CT on nodal staging of differentiated thyroid carcinoma at the first radioablation. J Nucl Med. 2009;50:18–23.