International Journal of Radiation Oncology*Biology*Physics
Clinical InvestigationDiffusion-Weighted Magnetic Resonance Imaging Early After Chemoradiotherapy to Monitor Treatment Response in Head-and-Neck Squamous Cell Carcinoma
Introduction
Head and neck squamous cell carcinoma (HNSCC) is the fifth most common cancer worldwide, accounting for approximately 3% to 4% of all malignancies 1, 2. The most important treatment modalities for HNSCC consist of surgery, radiotherapy (RT), and systemic therapy. Progressive use of the separate treatment modalities mainly aims to improve locoregional control (LRC) with a maximal reduction of therapy-induced damage to the surrounding tissue and maximal preservation of organ functionality 3, 4. The choice of treatment modality is largely influenced by primary tumor site, clinical stage, functional and oncologic outcome, and operability (5). After curative chemoradiotherapy (CRT), salvage surgery is generally difficult and potentially associated with poor outcome and high morbidity (6). As early detection of persistent or recurrent disease may, at least in part, determine success of salvage therapy, diagnostic surveillance should aim to detect potential persistent locoregional disease in an early stage (7).
For lymphadenopathy assessment, computed tomography (CT) 4 weeks post-CRT has shown high negative predictive value (NPV) up to 95%, although with low positive predictive value (PPV) of 35% 8, 9, 10, 11. For primary lesions, post-CRT surveillance with anatomical imaging is preferred at 4 months, showing value for detection of persistent laryngeal and hypopharyngeal cancer 12, 13. Fluoro-deoxy-glucose positron emission tomography (FDG-PET) can provide additional value for the detection of post-CRT tumor recurrence to anatomical imaging (14). However, susceptibility to inflammatory changes and low spatial resolution may decrease accuracy during the first 4 months post-CRT (15).
Diffusion-weighted imaging (DWI) quantified by the apparent diffusion coefficient (ADC) allows for differentiation of post-CRT inflammation and necrosis from recurrent HNSCC at the time of clinical presentation 16, 17. Historadiological correlation has shown an inverse correlation between the ADC and lesion cellularity (18).
The aim of this study was to evaluate the value of DWI for the assessment of treatment response 3 weeks after the end of CRT for HNSCC in comparison to anatomical imaging by MRI at 3 weeks post-CRT and the routinely implemented CT at 3 months post-treatment, in correlation to 2 years clinical follow-up or histopathology.
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Study design
Thirty-one patients (mean age, 54 years old; range, 39–67 years) with histologically proven HNSCC were enrolled in this prospective study. One patient was excluded because of distant metastases pretreatment; another patient due to claustrophobia. The tumor localization and stage of the remaining 29 patients are summarized in Table 1. Treatment consisted of concomitant CRT in 26 patients and radiotherapy alone in 3 patients. RT was delivered to a total dose of 72 Gy by means of a hybrid
Treatment outcome
At 2 years post-CRT, complete LRC was achieved in 15 of 29 patients (51%). Six of 29 patients (21%) developed an isolated local recurrence (at a median of 129 days post-CRT; range, 27–189 days) for which salvage surgery was performed. Six of 29 patients (21%) developed a regional recurrence without primary tumor recurrence (at a median of 224 days post-CRT; range, 91–364 days), 3 of whom were eligible for neck dissection at the time of diagnosis. Two of 29 patients (7%) developed a simultaneous
Discussion
In correlation with 2 years’ patient follow-up, the ΔADC3w allowed for early response assessment of HNSCC 3 weeks after the completion of CRT, with higher accuracy than anatomical imaging. Primary tumors and lymphadenopathies without significant increase in ΔADC3w (primary tumors, less than 25%; adenopathies, less than 20%) were not cured by CRT. Our findings corroborate the results of studies investigating DWI for early response assessment during and early after CRT of HNSSC 23, 24, 25. An
Conclusions
DWI is useful for early post-CRT assessment of HNSCC. Its accuracy for the detection of persistent HNSCC is higher than that of morphological imaging assessment at 3 weeks and 3 months post-CRT. The high NPV of DWI may help avoiding invasive diagnostic procedures or unnecessary salvage surgery while the ability for early identification of treatment failure by DWI may facilitate the timely selection of patients for salvage surgery. Further studies in a larger patient population, prospectively
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This work was supported in part by the Prof. em. A. L. Baert, Siemens Medical Solutions research grant.
Conflict of interest: none.