Magnetic resonance imaging following endoscopic nasopharyngectomy with a potassium-titanyl-phosphate (KTP) laser for early locally recurrent nasopharyngeal carcinoma.

INTRODUCTION: This study aims to investigate the spectrum of magnetic resonance imaging (MRI) features following endoscopic potassium-titanyl-phosphate (KTP) laser nasopharyngectomy.
METHODS: From January 2005 to December 2010, a total of 35 patients underwent KTP laser nasopharyngectomy for early recurrent NPC (rT1 or rT2) at our institute. Those who were lost to follow-up (N = 2) were excluded. Among the remaining patients, ten were proved to have locally recurrent disease and the other 23 not locally recurrent within 2 years of postoperative follow-up. Their serial MRIs were evaluated.
RESULTS: Postoperative nasopharyngeal mucosal changes were present in all of the subjects on first follow-up MRI, ranged from focal mucosal thinning (19/33, 57.6 %), focal mucosal thickening (8/33, 24.2 %) to mixed thinning and thickening (6/33, 18.2 %). Nasopharyngeal submucosal soft tissue volume loss was found in 23 (23/33, 69.7 %), and parapharyngeal soft tissue necrosis was found in 3 (3/33, 9.1 %). Postoperative bone marrow change involved the clivus in 31 (31/33, 93.9 %) and the petrous or pterygoid in 17 (17/33, 51.5 %). There were no significant differences between the two groups in the changes of mucosa, adjacent soft tissue, and skull base on the first MRI. The evaluation of serial MRIs disclosed that the patients in the recurrent group were more likely to develop new or enlarging mucosal masses (p = 0.01) and enlarging skull base changes (p = 0.0001).
CONCLUSIONS: KTP laser nasopharyngectomy induces mucosal and skull base changes that could be misinterpreted as tumor progression on early postoperative MRI scans. Sequential imaging is required to distinguish between postoperative changes and progressive disease.