Value of real-time tissue elastography for squamous cell carcinoma of the tongue

Objectives: Real-time tissue elastography is an ultrasound tomography technique that can objectively display tissue elasticity. The aim of this study was to evaluate the strain ratio of tongue carcinoma and the normal tongue and to investigate how clinico-pathological factors influenced the strain ratio. We also investigated differences in the strain ratio between tumor and non-tumor tissue after preoperative chemo-radiotherapy. Materials and methods: Patients with tongue carcinoma were categorized into two groups: 38 patients who underwent surgery alone and who underwent preoperative elastography (group 1), and 12 patients who underwent elastography before and after preoperative chemo-radiotherapy (group 2). Results: The mean strain ratios in group 1 were 0.16 ± 0.13 in tumor tissue and 0.82 ± 0.35 in normal tissue. Statistical analysis revealed that the strain ratio of tumor significantly correlated with tumor thickness. In group 2, the mean strain ratio of tumor tissue, scar tissue, and normal tissue were 0.19 ± 0.18, 0.51 ± 0.28, and 0.77 ± 0.58, respectively. The mean strain ratio of scar tissue was 0.51 and had lower elasticity than tumor tissue and higher elasticity than normal tissue. Conclusions: It was useful to characterize the tissue distortion using the strain ratio. Additional studies to establish a cutoff value for tumor tissue might help expand the indications for limited surgery. Correspondence to: Hiroyuki Harada, Professor, Oral and Maxillofacial Surgery, Department of Oral Health Sciences, Graduate School of Medical and Dental Sciences, Tokyo Medical and Dental University, 1-5-45 Yushima, Bunkyo-ku, Tokyo 113-8549, Japan, Tel: +81-3-5803-5508, Fax: +81-3-5803-0199, E-mail: hiro-harada.osur@tmd.ac. jp Received: October 27, 2016; Accepted: November 04, 2016; Published: November 07, 2016 Introduction Preservation of function is important to preserve quality of life for patients undergoing treatment for oral cancer. The tongue is an essential organ for speech, food bolus formation and deglutition. Alternatively, this site is a good candidate for organ preservation techniques with the goal of preserving speech and swallowing function. Fortunately, preoperative chemo-radiotherapy has enabled many patients to avoid surgery and to improve cancer control with few side effects for patients with large unresectable cancers. These combined (chemo-radiotherapy) modality treatments lead to higher cure rates while maintaining the patient’s quality of life [1,2]. Indeed, advances in anticancer agent and radiotherapy have resulted in a potent antitumor effect in many patients. However, some patients treated with this strategy develop induration in the center of their tumor that histologically varies from viable tumor to scar tissue. If a determination could be made as to whether the remaining induration is tumor or scar tissue, it may be possible to establish criteria for limited resection versus no surgery [3-5]. Many diseases cause changes in the mechanical properties of tissues. The tissue flexibility is decreased by pathologic tissue changes, such as inflammation and tumor growth. Indeed cancer growth results in an increase in tissue stiffness, even during the early stages of cancer. Real-time tissue elastography is an ultrasound tomography modality that can objectively display tissue elasticity [6]. Basic principles including calculated method of strain ratio had been well described in the literature accompanied with a new guideline [7]. The strain distributions in tissues in response to external compression are closely related to the distribution of tissue elasticity. These strain images can give a clear illustration of underlying tissue stiffness and provides useful clinical information. Erastography is currently under investigation for diagnosing malignant breast tumor, thyroid tumor and cervical lymph node metastases [8,9]. However, there are no reports of its use in the evaluation of primary oral cancers. This method relies of the phenomenon in which compression of living tissue results in marked distortion of flexible tissues without affecting the shape of stiff tissues. When applying different levels of compression or relaxation, the elasticity imaging algorithm measures the displacement and strain by analyzing the RF (radiofrequency) signal in real time with subsequent conversion to a color-coded image. Using this method, the elasticity and strain ratio of squamous cell carcinoma of the tongue was measured, and the elasticity and strain ratio of the scar portion was quantified in cases in which preoperative therapy was performed [10]. Materials and methods Eligibility criteria The study was conducted between August 2011 and April 2015 in the Department of Oral and Maxillofacial Surgery of the Tokyo Medical and Dental University, Japan. All study protocols were approved by the institutional ethics committee (Approval number 729). All patients Aktar D (2016) Value of real-time tissue elastography for squamous cell carcinoma of the tongue Volume 2(6): 371-375 Dent Oral Craniofac Res, 2016 doi: 10.15761/DOCR.1000181 provided written informed consent before entry into this study. The subjects comprised 50 patients (38 men, 12 women; mean age, 59.1 years; age range, 30-86 years) who were treated for squamous cell carcinoma of tongue. Patients were categorized into two groups. Group 1 included 38 patients. These patients underwent surgery alone and elastography before glossectomy. Patients in group 1 underwent surgery for partial glossectomy (n=14) or for hemi-glossectomy (n=24). Group 2 included 12 patients who underwent elastography before and after preoperative chemo-radiotherapy. Patients in group 2 underwent surgery for hemiglossectomy (n=7) or for subtotal glossectomy (n=5). Preoperative therapies were chemoradiotherapy in 5 patients and chemotherapy in 7 patients. Preoperative chemoradiotherapy consisted of a total dose of S-1 at 65 mg/m2 per day for 5 consecutive days over 4 consecutive weeks with concomitant radiotherapy (40 Gy, provided at a fractional dose of 2 Gy for 5 days/week) in 4 patients. Preoperative chemotherapy consisted of a regimen of CDDP 80 mg/m2 (day 1) and 5-FU 800 mg/ m2 per day (days 1-5) plus a regimen of CDDP 60 mg/m2 and docetaxel 60 mg/m2 (day 1) and 5-FU 600 mg/m2 per day (days 1-5) for each one course plus 40 Gy of radiotherapy in one patient. Preoperative chemotherapy consisted of a regimen of CDDP 80 mg/m2 (day 1) and 5-FU 800 mg/m2 per day (days 1-5) for one course in 2 patient and for 2 courses in 2 patients. Preoperative chemotherapy consisted of a regimen of CDDP 60 mg/m2 and docetaxel 60 mg/m2 (day 1) and 5-FU 600 mg/m2 per day (days 1-5) for one course in one patient and for 2 courses in 2 patients. The median interval between end of preoperative treatment was 22.5 days (range, 13-35 days). T classification (group 1/ group 2) was T1: 6/0, T2: 26/4, T3: 6/8, and the N classification was N0: 30/3, N1: 4/1, N2b: 4/3 and N2c: 0/5. Histological classification of malignancy In group 1, the histological classification of malignancy was evaluated according to the multifactorial system proposed by Anneroth (Table 1) [11]. The histologic malignant score was determined using blocks of tissue that showed the maximum cross-sectional area. The number of mitoses was assessed by evaluating five random fields (magnification x400).