|Year : 2020 | Volume
| Issue : 1 | Page : 34-38
The use of tumor-to-tongue thickness ratio to predict the need for microvascular flap reconstruction following glossectomy in carcinoma tongue
Adharsh Anand1, Deepak Balasubramanian1, Sandhya C Jayasankaran2, K Milind2, Samskruthi Murthy1, Narayana Subramaniam1, Renjitha Bhaskaran3, Jimmy Mathew4, Mohit Sharma4, Krishnakumar Thankappan1, Subramania Iyer5
1 Department of Head and Neck Oncology, Amrita Institute of Medical Sciences, Amrita Vishwa Vidyapeetham, Kochi, Kerala, India
2 Department of Radiodiagnosis and Imaging, Amrita Institute of Medical Sciences, Amrita Vishwa Vidyapeetham, Kochi, Kerala, India
3 Department of Biostatistics, Amrita Institute of Medical Sciences, Amrita Vishwa Vidyapeetham, Kochi, Kerala, India
4 Department of Plastic and Reconstructive Surgery, Amrita Institute of Medical Sciences, Amrita Vishwa Vidyapeetham, Kochi, Kerala, India
5 Department of Head and Neck Oncology and Plastic and Reconstructive Surgery, Amrita Institute of Medical Sciences, Amrita Vishwa Vidyapeetham, Kochi, Kerala, India
|Date of Submission||27-Jan-2020|
|Date of Decision||13-May-2020|
|Date of Acceptance||25-May-2020|
|Date of Web Publication||18-Jun-2020|
Department of Head and Neck Oncology, Amrita Institute of Medical Sciences, Amrita Vishwa Vidyapeetham, Kochi, Kerala
Source of Support: None, Conflict of Interest: None
Background: Microvascular flap reconstruction (MFR) of medium–large tongue defects following ablative surgery is the standard of care. The decision for MFR is often made prior to surgery or intraoperatively depending on the extent of the defect and the volume of remnant tongue. However, there exists no objective technique to predict this requirement preoperatively. This knowledge is crucial for counseling and planning. We aimed to identify an objective magnetic resonance imaging (MRI) measurement tool to predict the need for MFR of tongue tumors. Materials and Methods: This was a retrospective analysis of patients undergoing surgery (with or without reconstruction) for squamous cell carcinoma of the tongue. Patients had a preoperative MRI as part of their assessment. As per our institution protocol, the decision for the requirement of MFR was made by a consensus of two experienced reconstructive surgeons intraoperatively. This decision was correlated with the ratio of tumor volume to the total tongue volume (tv) as observed in the MRI. Results: A total of 47 patients were identified. Twenty-eight patients underwent reconstruction, while 19 did not. The ratio of tumor thickness to tongue thickness (Tt/tt) was calculated, and a cutoff of >0.395 (sensitivity 89.3% and specificity 89.5%) was found to significantly correlate with the decision for MFR (P < 0.001). The volume of a tumor to total tv ratio was calculated from the data of 22 cases, and a cutoff of >4.2 (sensitivity 83.3 and specificity 90) was found to be correlated significantly with the decision for MFR (P < 0.001). Conclusion: Tt/tt ratio is a useful tool to determine the need for MFR of tongue tumor excision defects in the preoperative setting and can help guide counseling.
Keywords: Magnetic resonance imaging, microvascular reconstruction, preoperative planning, tongue tumours
|How to cite this article:|
Anand A, Balasubramanian D, Jayasankaran SC, Milind K, Murthy S, Subramaniam N, Bhaskaran R, Mathew J, Sharma M, Thankappan K, Iyer S. The use of tumor-to-tongue thickness ratio to predict the need for microvascular flap reconstruction following glossectomy in carcinoma tongue. J Head Neck Physicians Surg 2020;8:34-8
|How to cite this URL:|
Anand A, Balasubramanian D, Jayasankaran SC, Milind K, Murthy S, Subramaniam N, Bhaskaran R, Mathew J, Sharma M, Thankappan K, Iyer S. The use of tumor-to-tongue thickness ratio to predict the need for microvascular flap reconstruction following glossectomy in carcinoma tongue. J Head Neck Physicians Surg [serial online] 2020 [cited 2020 Sep 20];8:34-8. Available from: http://www.jhnps.org/text.asp?2020/8/1/34/287157
| Introduction|| |
The tongue is a common subsite involved by squamous cell carcinomas (SCCs) of the oral cavity. The ideal treatment for these patients is surgical, namely wide excision of the tumor and neck dissection with or without adjuvant therapy depending on the final histology. Removal of part of the tongue, however, is not without morbidity. With the advent of microvascular reconstruction, tongue volume (tv) can be restored with these flaps to minimize deficits in speech and swallowing deficits and improve patient quality of life.
The consensus is that resection of less than a third of the tongue without reconstruction is unlikely to result in morbidity. This consensus, though widely accepted, is arbitrary and not validated in studies. In the context of larger tongue resections, significant morbidity exists with regard to speech and swallowing, and hence, reconstruction is routinely done. Accurate cutoffs regarding the size of the remnant tongue which could influence the need for flap reconstruction have not been described. Intraoperative decision-making by the reconstructive surgeon is the current standard of care and this is made by inspection of the residual tongue bulk and thickness. With the advent of magnetic resonance imaging (MRI), routine assessment of tongue carcinomas by MRI allows for an accurate estimate of the tumor dimensions along with the measurement of the size of the tongue. We attempted to correlate the intraoperative decision for microvascular flap reconstruction (MFR) with a ratio derived between the thickness of the tumor and the tongue which was obtained from the preoperative MRI scans.
| Materials and Methods|| |
This is a retrospective analysis of patients undergoing glossectomy between 2015 and 2016. All of the patients included had biopsy-proven SCC, preoperative contrast-enhanced MRI of the head and neck to assess for the tumor size, and the extent and presence of neck node metastasis. The disease management was discussed in a multidisciplinary tumor board. The surgery performed was standard, wide local excision of the lesion of the tongue tumor with a gross 1.5 cm margin in all directions (aiming for at least a 5 mm microscopic margin, with frozen section used when required) and ipsilateral neck dissection (levels I–IV).
All staging was performed as per the American Joint Committee on Cancer seventh edition where T1 was maximum tumor diameter <2, T2 was maximum tumor diameter 2–4 cm, T3 was maximum tumor diameter >4 cm, and T4 was tumor involving the mandible or skin. The decision to perform MFR in all cases was made by a combined decision of at least two experienced reconstructive surgeons who have a cumulative experience of over 1000 microvascular flaps for oral cancer reconstruction.
The preoperative MRI was performed on a 3 Tesla MRI Machine (GE System Discovery 750, GE Health care, Milwaukee, WI, USA). Three-dimensional T1 Gadolinium contrast sequence with 1.2 mm slice thickness axial section with no interslice gap was attained; these sections were reformatted and 0.37 mm coronal and sagittal sections were attained. The coronal sections were analyzed for the maximum tumor thickness (Tt), and the corresponding total thickness of the tongue was measured from the same section. The Tt was measured in the slice showing maximum tumor depth. A straight line was drawn joining the superior and inferior tumor-mucosa junction. Perpendicular to this line, two lines (A1 and A2) were drawn on either side up to the maximum tumor-tissue or tumor-air interface, respectively. The sum (A) of length of the two lines (A1 + A2) was the maximum Tt. In the same slice, the maximum tongue width was also measured (B), which was the length of the line joining the right and left farthest mucosal surface [Figure 1], as per the standard definition.
|Figure 1: A straight line joining the superior and the inferior tumor-mucosa interface is drawn on the coronal section with the maximum tumor depth. Two perpendicular lines are drawn from this horizontal line, one to the farthest mucosal surface of the tumor (A1) and the other to the maximum depth of the tumor (A2). The tumor thickness is the sum of length of A1 and A2. In the same section, tongue thickness is measured from the farthest right and left mucosal surface (B). Tumor-to-tongue thickness ratio is calculated as tumor thickness to tongue thickness|
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A ratio of tumor thickness to tongue thickness (Tt/tt) was obtained and this was correlated to the intraoperative decision to perform MFR. The volume of the tumor lesion and the total tongue was measured and recorded [Figure 2] by software in the MRI system where the tumor and the total tongue have to be contoured in each slice by freehand drawing and the software finally calculate the tumor and total tv. The ratio of tumor volume to total tongue volume (Tv/tv) (percentage) was also obtained and correlated with the decision to perform MFR.
|Figure 2: Freehand drawing done around the tumor border as well as the tongue in all the sections. The inbuilt software calculates the tumor volume and tongue volume. Ratio of tumor volume to tongue volume is calculated as tumor volume to total tongue volume|
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Statistical analysis was performed using IBM SPSS version 20.0 software (Armonk, New York). The arbitrary cutoff for the thickness and volume ratio and correlation to MFR was determined by the receiver operator characteristic (ROC) curve analysis, and the ratios with best sensitivity and specificity were taken. The numerical variables were then converted to categorical variables based on this cutoff, and statistical significance between the two categorical variables was identified using Chi-square test. A two-sided P value was considered and a value <0.05 was considered statistically significant.
| Results|| |
Forty-seven consecutive patients were considered for the final analysis. Their demographics and tumor and treatment characteristics are shown in [Table 1]. They were predominantly male (83%) and the mean age of the cohort was 50 (range: 21–71) years. The tumor (T) stage distribution for the cohort was comparable between T1 and T3; the percentage of patients of T1, T2, and T3 was 31.9%, 36.2%, and 31.9%, respectively. T4 patients were not included as they invariably needed MFR and were likely to cause undue influence on the analysis. The pathological nodal positivity rate was 55.3%. A majority of patients (68%) required adjuvant treatment (radiotherapy) based on the final pathology report.
The mean Tt was 1.74 (range: 0.66–3.82) cm and the mean tt was 4.04 (range: 2.74–7.22) cm [Table 2]. Twenty-eight (59.6%) patients had reconstruction with microvascular flaps, of which 50% were radial artery forearm flaps, 29% were anterolateral thigh free flaps, and the remaining were lateral arm or gastro-omental flaps. When the ratio of Tt/tt was calculated, the cutoff identified by the ROC analysis was 0.395, with a sensitivity of 89.3 and specificity of 89.5 [Figure 3]. This cutoff of >0.395 was found to have a statistically significant with MFR (P < 0.001) [Table 3].
|Figure 3: Receiver operator characteristic curve analysis to identify the cutoff of the tumor to tongue thickness ratio and tumor volume to tongue volume ratio to predict the use of microvascular flap reconstruction|
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|Table 3: Correlation of parameters with microvascular flap reconstruction|
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The volume of the tongue tumor and total tongue was available in 22 patients. The percentage of the tongue Tv/tv (Tv/tv ×100) was calculated in these patients, and the cutoff identified by the ROC analysis was 4.2 with a sensitivity of 83.3 and specificity of 90. This cutoff of >4.2 was found to be correlate significantly with MFR (P < 0.001) [Table 3]. Another MRI predictor factor for decision for free flap reconstruction was the floor of the mouth or sublingual space involvement by the tumor (P = 0.02).
| Discussion|| |
Tongue defects following glossectomy for tongue carcinoma result in functional morbidity in the form of speech and swallowing deficits. Tongue defects less than one-third of the tv are left unreconstructed with minimal long-term sequelae. Defects larger than half the tv are likely to result in impairment in tongue mobility and volume and need to be reconstructed. Defects between these two categories in size remain a source of confusion and disagreement. Although evidence has shown that MFR is clearly beneficial in patients for whom they are indicated, the implications for the patient and treating team are significant; they require several more hours of operative time, surgical expertise that may not be available in all centers, longer hospital stay, and higher treatment costs. Hence, preoperative planning for these patients would be highly beneficial.
Our study attempted to address this issue by deriving a ratio preoperatively which could predict the likelihood of requiring MFR. The parameters used are easy to identify and determine. The ratio between these parameters is relevant to decision-making; in patients who have a small tongue, even a relatively small tumor is likely to result in a defect that needs reconstruction. MRI was able to assess both the Tt and tt to determine the ratio required for decision-making.
In our study, after the assessment of preoperative MRI, patients with Tt/tt value of > 0.395 were likely to have not undergone MFR. Other critical factors were tumor and tv, both of which have been shown to be accurately measured on MRI. In our study, we performed this analysis values in 22 patients, and a Tv/tv of >4.2% was found to correlate well with MFR. Although this value seems low (4.2%), it is to be noted that the total tv considered includes the volume of the oropharyngeal tongue and not the oral tongue alone; the current MRI assessment precludes a separate evaluation of these two volumes. Current software algorithms do not allow for such delineation, and newer techniques are needed for delineation of the oral mobile tv from the lesser mobile pharyngeal tv. However, it is to be noted that for the purpose of preoperative planning based on MRI, Tv/tv can be performed easily and reliably.
The clinical judgment made intraoperatively is essentially an estimation of the excised tv to either total or remnant tv, which helps to determine the likelihood of the patient to speak and eat without aspiration with the remnant tv and compensatory measures. Until now, we were unable to determine an objective cutoff or score correlating with this clinical judgment. This information is vital to counsel patients regarding the duration of surgery, the need for intensive care following surgery, duration of hospital stay, and the cost of surgery. For surgeons who do not have microvascular surgery expertise, it is a valuable tool to either plan surgery with the help of more experienced colleagues or to refer patients to a more specialized center for surgery.
A potential pitfall of our study is that the MRI-measured parameters have been correlated with subjective decisions of senior reconstructive surgeons. However, this decision-making is the current standard of care. There exist no uniform or objective criteria to determine the need for MFR except in cases wherein the defects would result in oro-cervical communication independent of the size of the defect. The decision to reconstruct is essentially made on a patient-by-patient basis due to the number of factors and their complexity that influence it. Prospective randomized trials are unlikely to ever be approved or conducted to answer this question. It is to be noted that measuring functional outcomes between the groups are flawed because patients with larger defects and those who needed flaps were likely to have adjuvant treatment due to higher disease stage. Furthermore, given that this is a pilot study with a small sample size, validation on a larger cohort of patients is necessary. It is our observation that Tt/tt or Tv/tv can be easily, accurately, and reliably estimated on preoperative MRI (which is now ubiquitous in tongue cancer assessment), and the cutoff ratios mentioned above correlated with the decision made by experienced reconstructive surgeons. The cutoffs obtained in this study could potentially guide reconstructive surgeons who have initiated their microvascular practice or in cases where a decision could not be made preoperatively. Having a validated reference value could help the surgeon to counsel the patients with borderline defects.
| Conclusion|| |
MRI is an integral part of the preoperative evaluation of tongue cancers with a standardized, quick, and accurate assessment of thickness and volume. Objective criteria such as Tt/tt of >0.395 or a Tv/tv of >4.2% is of great potential for preoperative patient counseling and planning for reconstruction in patients undergoing glossectomy.
Financial support and sponsorship
Conflicts of interest
There are no conflicts of interest.
This material has never been published and is not currently under evaluation in any other peer reviewed publication.
The permission was taken from Institutional Ethics Committee prior to starting the project. All procedures performed in studies involving human participants were in accordance with the ethical standards of the institutional and/or national research committee and with the 1964 Helsinki declaration and its later amendments or comparable ethical standards.
Informed consent was obtained from all individual participants included in the study.
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[Figure 1], [Figure 2], [Figure 3]
[Table 1], [Table 2], [Table 3]