MRI in head and neck cancer following chemoradiotherapy: what is the optimal delay to demonstrate maximal response?

Abstract

Objectives: To investigate the optimal timing for post-chemoradiotherapy (CRT) reference magnetic resonance imaging (MRI) in head and neck cancer, so as to demonstrate a maximal treatment response. To assess whether this differs in human papillomavirus-related oropharyngeal cancer (HPV-OPC) and whether the MRI timing impacts on the ability to predict treatment success.

Methods: Following ethical approval and informed consent, 45 patients (40 male, mean age 59.7 ± 7.9 years, 33 HPV-OPC) with stage 3 and 4 HNSCC underwent pre-treatment, 6- and 12-week post-CRT MRIs in this prospective cohort study. Primary tumour (n = 39) size, T2w morphology and diffusion weight imaging (DWI) scores, together with nodal (n = 42) size and necrotic/cystic change, were recorded. Interval imaging changes were analysed for all patients and according to HPV-OPC status. MRI descriptors and their interval changes were also compared with 2-year progression-free survival (PFS).

Results: All MRI descriptors significantly changed between pre-treatment and 6-week post-treatment MRI studies (p < .001). Primary tumour and nodal volume decreased between 6- and 12-week studies; however, interval changes in linear dimensions were only evident for HPV-OPC lymph nodes. Nodal necrosis scores also evolved after 6 weeks but other descriptors were stable. The 6-week nodal necrosis score and the 6- and 12-week nodal volume were predictive of 2-year PFS.

Conclusion: Apart from HPV-OPC patients with nodal disease, the 6-week post-CRT MRI demonstrates maximal reduction in the linear dimensions of head and neck cancer; however, a later reference study should be considered if volumetric analysis is applied.

Key points: • This study provides guidance on when early post-treatment imaging should be performed in head and neck cancer following chemoradiotherapy, in order to aid subsequent detection of recurrent tumour. • Lymph nodes in HPV-related oropharyngeal cancer patients clearly reduced in size from 6 to 12 weeks post-treatment. However, other lymph node disease and all primary tumours showed only a minor reduction in size beyond 6 weeks, and this required a detailed volumetric analysis for demonstration. • Timing of the reference MRI following chemoradiotherapy for head and neck cancer depends on whether the patient has HPV-related oropharyngeal cancer and whether there is nodal disease. MRI as early as 6 weeks post-treatment may be performed unless volumetric analysis is routinely performed.

Keywords: Chemoradiotherapy; Diffusion magnetic resonance imaging; Human papillomavirus; Squamous cell carcinoma of head and neck; Treatment outcome.

Fig. 1

Measurable right base of tongue carcinoma and largest right level 2 lymph node to demonstrate dimensions evaluated. a Axial fat-saturated post-gadolinium T1w image demonstrates the long axial primary tumour measurement (white line), and both the long and short axial largest lymph node measurements (black lines) are depicted. There is necrotic/cystic change recorded in the largest lymph node. b DWI b = 800 axial image is used to aid the delineation of tumour. The highest DWI signal of the tumour (black open arrow) was recorded as 2 (isointense to cord) and that of the lymph node (white open arrow) was recorded as 3 (moderately hyperintense to cord)

Fig. 2

Left palatine tonsillar carcinoma to illustrate T2w morphology and DWI scoring. a–c T2w axial images on a pre-treatment, b 6-week post-treatment and c 12-week post-treatment MRI. The T2 morphology scores (lesions indicated by open white arrows) were 2 on pre-treatment, 0 on 6-week post-treatment and 0 on 12-week post-treatment MRIs. d–f DWI b = 800 axial images on (d) pre-treatment, (e) 6-week post-treatment and (f) 12-week post-treatment MRIs. The DWI scores (lesion indicated by open white arrows) were 3 on pre-treatment, 1 on 6-week post-treatment and 1 on 12-week post-treatment MRIs

Fig. 3

Bilateral base of tongue carcinoma more marked on the left to illustrate T2w morphology and DWI scoring. a–c T2w axial images on (a) pre-treatment, (b) 6-week post-treatment and (c) 12-week post-treatment MRI. The T2 morphology scores (lesions indicated by open white arrows) were 2 on pre-treatment, 1 on 6-week post-treatment and 1 on 12-week post-treatment MRIs. d–f DWI b = 800 axial images on d pre-treatment, e 6-week post-treatment and f 12-week post-treatment MRIs. The DWI scores (lesions indicated by open white arrows) were 4 on pre-treatment, 1 on 6-week post-treatment and 0 on 12-week post-treatment MRIs

Fig. 4

Participant flow-chart

Fig. 5

Right piriform carcinoma which recurred at 2-year follow-up. a–c T2w axial images on (a) pre-treatment, (b) 6-week post-treatment and (c) 12-week post-treatment MRI. The T2 morphology scores (lesions indicated by open white arrows) were 2 on pre-treatment, 1 on 6-week post-treatment and 1 on 12-week post-treatment MRIs. d 18-FDG PET-CT at 12 weeks post-treatment did not reveal any focal uptake but e subsequent 18-FDG PET -CT demonstrates focal uptake with a time to recurrence of 215 days