The institutional review board of Sun Yat-sen University Cancer Center has approved this retrospective study in compliance with the Helsinki Declaration.
Patients with NPC coexisting with hypertrophic adenoids were identified in the pathology databases at Sun Yat-sen University Cancer Center between January 2007 and January 2011. The selection criteria were as follows: 1) MRI was performed before and after treatment; 2) patients had a nasopharyngeal adenoid hypertrophy greater than 10 mm (measured at the greatest anteroposterior diameter on axial T1-weighted contrast-enhanced images before treatment); and 3) the diagnosis of hypertrophic adenoids was confirmed in biopsy specimens.
T staging and subtype classification of NPC
NPC T staging was performed according to the newly released 7th edition of the Union for International Cancer Control (UICC) staging system. The World Health Organization (WHO) recognizes three subtypes of NPC: type 1, squamous cell carcinoma; type 2, non-keratinizing carcinoma; and type 3, undifferentiated carcinoma.
The treatment for childhood and adolescent patients with NPC followed the guidelines that were established for adults. For patients who received neoadjuvant chemotherapy followed by chemoradiotherapy or radiotherapy, follow-up MRI studies were performed approximately 10 days after neoadjuvant chemotherapy completion and 3 and 6 months after chemoradiotherapy or radiotherapy completion. For patients who received chemoradiotherapy or radiotherapy without neoadjuvant chemotherapy, follow-up MRI studies were performed at 3 and 6 months after treatment completion.
MRI examinations were performed by using a 1.5 T MRI scanner (Signa CV/i, GE Healthcare, Milwaukee, WI, USA) or a 3 T MRI scanner (Trio Tim, Siemens Medical Systems, Erlangen, Germany) with a head and neck combined coil. T2-weighted images in the axial planes and T1-weighted images in the axial, sagittal, and coronal planes were obtained before the injection of contrast material. After the intravenous injection of gadopentetate dimeglumine at a dose of 0.1 mmol per kg body weight, T1-weighted axial, sagittal, and coronal sequences with fat saturation were performed sequentially using parameters similar to those for pre-injection imaging. The section thicknesses and intersection gaps in the axial plane were 4 mm and 1 mm, respectively.
Two radiologists (with 10 and 5 years of experience, respectively, in head and neck imaging) evaluated the images of nasopharyngeal lesions using a Picture Archiving and Communication System (Centricity Radiology RA1000, GE Medical Systems Integrated Imaging Solutions, Mount Prospect, IL, USA). Consensus interpretations were accepted in cases with discrepancies.
For the purpose of this study, the roof and the posterior superior nasopharyngeal wall were defined on axial MRI sections as being above and level, respectively, with the distal ends of the torus tubarius .
The MRI features of hypertrophic adenoids were recorded, including location, striped appearance, size, the interface between hypertrophic adenoids and NPC, symmetry/asymmetry, cyst formation, and the presence of hypertrophic adenoids that extend into the pharyngeal recesses. A normal striped appearance consists of alternating dark and bright vertical stripes of hypo- and hyper-enhanced tissues [5,7]. This striped appearance was also recorded after treatment as some of the stripes may appear only after treatment because of tumor involvement. The greatest anteroposterior diameter of hypertrophic adenoids was measured based on the visualization of stripes before treatment; if the stripes only appeared after treatment, then the greatest anteroposterior diameter was measured after treatment. The interface between hypertrophic adenoids and NPC was classified as well-defined or ill-defined. Cyst formation was defined by the presence of an area that is hypo-intense on T1-weighted MR images obtained before and after enhancement and that is markedly hyper-intense on T2-weighted MR images. When hypertrophic adenoids are markedly large, they may extend into the pharyngeal recesses (hypo-enhanced band similar to the dark stripes in the hypertrophic adenoids) . The presence of hypertrophic adenoid extension into the pharyngeal recesses was recorded.
Familiarity with the MRI appearances of hypertrophic adenoids (if still in existence) after treatment is necessary to reduce overtreatment and unnecessary biopsies. Therefore, the characteristics of hypertrophic adenoids after treatment were also reviewed.
The intact stripe closest to the interface was used as a safe margin between the tumor tissue and the uninvolved adenoids to improve GTV delineation. Before treatment, when the tumor tissue could be distinguished from the adenoids, the GTVs, both including and excluding the uninvolved adenoids, were calculated at the post-processing MRI workstation (GE SUN ADW 4.4) using a volume rendering application. Additionally, the percentage change at which the uninvolved adenoids could be excluded from the GTV was also calculated. The location of this safe stripe was roughly classified as being in 1 of 3 sites. Site 1 was near the pharyngeal recess ipsilateral to the site of primary tumor (supposing that the NPC was located at the pharyngeal recess or nasopharyngeal lateral wall). In this case, all hypertrophic adenoids were present and remained uninvolved. Site 2 was between site 1 and the midline of the nasopharynx. In this case, approximately half of the hypertrophic adenoid volumes were left. Site 3 was between the midline of the nasopharynx and the pharyngeal recess contralateral to the site of primary tumor. In this case, only a few hypertrophic adenoids were present. When the NPC originated in the posterior superior nasopharyngeal wall and/or the roof where hypertrophic adenoids normally reside, no safe margin existed between the two tissues. This case was classified as site 3. The frequencies of these three sites were recorded.
According to the new Response Evaluation Criteria in Solid Tumors Guideline (version 1.1) from 2009 , the response criteria were defined as follows: complete response (CR), no evidence of disease; partial response (PR), a ≥ 30% decrease in the sum of the greatest dimensions of the target lesions and no evidence of new lesions or progression of any lesion; progressive disease (PD), a ≥ 20% increase in the sum of the greatest diameters of the target lesions or the appearance of new lesions; and stable disease (SD), small changes that did not meet the criteria for PR or PD. In addition to these criteria, a near-CR was added and defined as an extremely good PR with little visual disease left .