Tongue squamous cell carcinomas are one of the most common oral cancers yet one of the most difficult to successfully treat. Getting an accurate measure of the depth of the tumor is critical to determining a patient’s prognosis and currently CT, MRI, and ultrasound are used to determine the depth and location of the tumor.
“Several studies have reported a significant relationship between radiological depth of invasion measured on MRI and pathological depth of invasion in the tongue squamous cell carcinoma. To the best of our knowledge, this is the first study on MRI divided into ‘before biopsy’ and ‘after incision biopsy,’ ” Hiroyuki Harada, DDS, PhD, of Tokyo Medical and Dental University, and colleagues wrote.
The issue of depth of invasion is so critical to determining metastasis to neck lymph nodes that in 2017 it was added to the AJCC Cancer Staging Manual.
This retrospective Japanese study included 128 patients with tongue carcinoma who underwent glossectomy between 2006 and 2019. The researchers evaluated which radiologic depth of invasion measurement – MRI before or after biopsy and ultrasound – was the most agreeable to clinical depth of invasion.
All the participants had undergone ultrasound, while 18 had undergone MRI before biopsy and 110 had undergone MRI after biopsy. The coefficients of determination were 0.664, 0.891, and 0.422 respectively, suggesting that calculating radiologic depth of invasion using MRI before biopsy was the most reliable radiologic method. MRI before biopsy slightly overestimated clinical depth of tumor invasion, MRI after biopsy severely overestimated the clinical measurement, and ultrasound slightly underestimated the clinical depth of tumor invasion.
Ultrasound is often preferred because of its easy use, yet measuring ulcerous lesions is difficult with ultrasound. But with MRI, there is no upper limit of measured value, but tongue movement during the procedure can make getting accurate images during the procedure difficult.
“The advantage of the MRI is that the image is acquired in the tongue’s resting position and that there is no upper limit of the measured value. The disadvantages include difficult detection of superficial tumors, influence of metal artifacts, and movement of the tongue,” the authors wrote. “Biopsy may lead to edema or hemorrhage and subsequent overestimation of tumor size and invasion depth in MRI.”
A small Canadian study published in 2016 in the Journal of Otolaryngology–Head & Neck Surgery, found a strong correlation between clinical, pathological, and MRI measurements of depth of invasion in oral tongue SCC. Meanwhile, a 2017 U.K. study published in the British Journal of Oral and Maxillofacial Surgery found that the accuracy of clinical staging in oral SCC did not differ whether the biopsy was taken before or after MRI. While a good radiologic-pathological tumor thickness correlation has been reported in 2018 in the American Journal of Neuroradiology, tongue carcinoma often shows exophytic or ulcerous lesions, which are difficult to measure with MRI, CT, or ultrasound.
The authors suggested that further studies are needed to determine the effects on MRI of postbiopsy tongue inflammation. Limitations of the study included the small number of cases with MRI before biopsy.
The authors declared no conflicts of interest.