Early glottic squamous cell carcinoma (SCC) has an excellent local control rate (LCR) independently of the treatment choice. In particular, for T1 category, LCR is reported to range from 86 to 95% for transoral laser microsurgery (TLM) and from 85 to 94% for radiotherapy (RT) (1–4). In T2 lesions, RT shows a slightly worse LCR, ranging from 67 to 76%, with respect to TLM (76–89%) (1–8). However, a large meta-analysis of 11 studies, involving 1,135 patients, failed to identify any difference in LCR of patients with early glottic SCC receiving TLM or RT, even though overall costs were lower with TLM (7). Despite the above reported similar LCR, present evidence suggests that RT may perform worse than TLM in terms of disease-free survival (9); moreover, the radiation therapy approach seems to entail a higher risk for subsequent total laryngectomy in comparison with TLM (10).

On the other hand, the choice of TLM implies the assessment of a series of patient-dependent and technique-related factors, to obtain the most favorable therapeutic outcome (11–14). One of the most influencing factors in TLM is definitively represented by surgical margins status after surgery. This issue is complicated by the lack of a homogeneous definition of negative, close, and positive margins. In fact, most authors define a margin as “negative” when the tumor-margin distance is >1 mm, “close” when the distance is <1 mm, and “positive” in presence of tumor at the surgical edge. However, management of patients with close and positive margins is still controversial (15–18). Specific indications for surgical re-treatment (by TLM or open-neck approaches) or complementary RT and the impact of such adjuvant treatments on recurrence-free survival (RFS) and disease-specific survival (DSS) are not yet clearly defined.

In light of this, we retrospectively analyzed a large homogeneous cohort of patients affected by early glottic SCC treated by TLM, focusing our attention on the impact of close and positive surgical margins on RFS and DSS, and on the possibility to reduce their rates by using new biologic endoscopy tools such as narrow band imaging (NBI).

We retrospectively analyzed data from a series of 634 untreated patients (560 males, 74 females; mean age, 64.1 ± 10.4 years; age range, 30–88) affected by Tis–T2 glottic SCC who underwent TLM from January 2000 to March 2014 at the Departments of Otorhinolaryngology—Head and Neck Surgery, University of Genoa and Brescia, Italy (Table 1). All patients signed a written informed consent, which was reviewed and approved by the local Ethics Committees and including the use of anonymized patient data for research purposes.

The tumors were intraoperatively assessed by both 0° and 70° rigid telescopes (Olympus Medical System Corporation, Tokyo, Japan and Karl Storz, Tuttlingen, Germany), increasing the accuracy of neoplastic superficial spreading evaluation (19). In all patients since January 2008, preoperative videolaryngoscopy was combined with high definition television (HDTV)-NBI (Olympus Medical System Corporation, Tokyo, Japan) (20). In selected cases, CT or MR was carried out to evaluate anterior commissure, visceral spaces, and laryngeal framework involvement.

Adequate laryngeal exposure in microlaryngoscopy was obtained by different laryngoscopes comprising Sataloff (Microfrance^®iXomed, Saint Aubin Le Monial, France), Dedo, and Dedo-Ossoff (Pilling, Philadelphia, PA, USA). The lasers used were the Sharplan 1055 S (Sharplan, Tel Aviv, Israel) from 2000 to 2004, and the UltraPulse/Surgitouch CO₂ laser (Lumenis, Yokneam, Israel) from 2004 to 2014.

Patients were treated by six different types of cordectomies according to the European Laryngological Society classification (Table 1), using “en bloc” or “multi bloc” approaches, in relation to the tumor site, size, category, depth of infiltration, and laryngeal exposure (21–23). Frozen sections were not routinely performed. Extra-surgical margins, when deemed necessary, were taken from the surgical bed after resection of larger lesions and sent separately for definitive histopathologic examination.

On the basis of histopathological reports, the entire cohort was divided in two groups: Group A included 507 (102 pTis, 316 pT1a, and 89 pT1b) subjects and Group B 127 (all pT2) patients (Table 1), staged according to the seventh TNM classification by the American Joint Committee on Cancer (17).

We defined surgical margins as follows: negative (distance tumor-margin >1 mm), close (distance tumor-margin between 0 and 1 mm), and positive (presence of at least carcinoma in situ at the surgical margin). In case of extra-surgical margins taken at the end of procedure, these were considered as the definitive surgical margins.

Median follow-up for the entire cohort of patients was 60 months (range, 12–176): those staged as pTis–pT1b with negative margins were followed by videolaryngoscopy every 2 months in the first year, every 3 months in the second, every 4 months in the third, every 6 months in the fourth, and once a year afterward. In patients staged as pT2, MR or CT was added every 6 months for the first 2 years of follow-up even if the endoscopy was negative.

In case of close margins and/or single positive superficial margin, a monthly follow-up and, where indicated, periodic imaging were performed. In case of positive multiple superficial or deep margins, intraoperative recording was reviewed and, after multidisciplinary discussion, an adjuvant treatment (transoral re-resection, open partial laryngectomy, or adjuvant RT) was proposed to the patient. Whenever this option was refused by the patient or deemed too risky for his/her general conditions, a strict watch-and-see policy was followed.

Among all patients, 288 (45.4%) had positive margins. In particular, 146 (23%) had positive single superficial margins, 94 (14.8%) positive multiple superficial margins, and 48 (7.5%) positive deep margins. One hundred fourteen patients (18%) had close margins, among which 79 (12.5%) CS and 35 (5.5%) CD margins (Table 1).

Transoral laser microsurgery is a surgical approach that has emerged as a viable alternative to open-neck approaches and RT as it allows sound oncological results, while preserving organ function and ensuing high salvage rates in case of persistent/recurrent or secondary laryngeal tumors (1–8). Moreover, its favorable cost-effectiveness ratio profile could be helpful in containing ever-growing healthcare costs (7). This type of surgery is mostly applied in early-stage disease and is characterized by a very narrow-margin approach, which makes the process of performing a safe and clean resection challenging. Moreover, the use of laser invariably leads to tissue dehydration and consequent margin shrinkage, which further reduces the ability to obtain widely negative surgical margins at histopathological examination (23). These two aspects force the surgeon to put significant effort in balancing between the best oncological and functional outcomes in each patient.

Actually, one of the most important prognostic factors in TLM remains the status of surgical margins (11, 14, 16). In the present series, we confirmed the feasibility and oncological soundness of this technique, as demonstrated by the high RFS and DSS rates, which favorably compare to those reported in the literature (1, 5, 6). Moreover, it should always be kept in mind that, in TLM for early glottic SCC, RFS does not necessarily have a significant impact on DSS, LCR, or OP, due to the high percentage of recurrences that are salvageable by further conservative treatment options (1). In fact, our data show that even when surgery is executed in the best-case scenario and the surgical margins are completely clean, recurrence is still possible and may affect up to one-tenth of all patients during follow-up. This figure shows a slight variation according to tumor category, which is, however, of minor significance. Use of HDTV-NBI further improved this outcome, as only one in 20 patients with negative margins suffered from disease recurrence after introduction of this bio-endoscopic tool in our routine practice. No patient with negative margins died of disease, thus confirming their good prognostic role.

The same line of thinking can be applied to close surgical margins, as no such patient died of disease. However, the surgeon may expect a higher recurrence rate with respect to fully negative borders, especially in the presence of CD margins, which significantly affected the recurrence rate in our series.

Single superficial margin infiltration had an overall impact on RFS, which was not significantly divergent from CS margins; it has to be noted, however, that, in the setting of T2, risk of recurrence tends to be significant, as 4 in 10 patients were found with recurrence during the course of their follow-up. Again, surveillance in these patients allowed thwarting any disease-related death and DSS was not statistically different from negative and close margins. Moreover, use of HDTV-NBI was especially beneficial in T2 patients, reducing the number of single superficial margin positivity.

It may be surmised that, even though CS and single superficial margins appear to be hallmarks of imperfect disease control, strict follow-up may be sufficient in avoiding the most severe outcomes. Further prospective studies could be aimed to test the validity of such approach against the routine application of adjuvant RT and/or repeated TLM. Our data, however, confirm that CD margins do have an impact on RFS and should not be overlooked.

Actually, even though fatal outcome is a rare occurrence in early glottic SCC (1), the vast majority of events clustered in patients with multiple superficial positive margins. This subpopulation, along with patients with deep margin infiltration, was also burdened by the highest recurrence rate. Moreover, in case of deep margin infiltration, we observed an increased need for total laryngectomy. Our results do not indicate a significant improvement in RFS with the application of adjuvant treatment. However, this analysis was limited by the reduced sample size and by patient selection bias; therefore, to draw any definite conclusions, large controlled prospective trials are needed.

This study has several limitations. First, it is retrospective in nature, analyzing pathologic data gathered at two different institutions over a relatively long time period. Moreover, follow-up was variable, as some patients, treated in the early 2000s, stopped attending visits after a long remission period, while others were recruited at relatively recent dates.

Overall, this study offers a possible key of interpretation of margin results in the framework of clinical decision during long-term follow-up. In particular, it suggests caution in presence of positivity of deep or multiple superficial margins, as these findings are hallmarks of possible disease persistence, especially in higher T categories. Patients with close margins, however, as well as those with single superficial margins, could undergo rigorous follow-up, as their recurrence rate is slightly higher.

Our data confirm that TLM for early-stage glottic SCC offers sound results in terms of DSS and RFS, as well as a high rate of OP. Survival-related parameters can be effectively stratified by margin status, even though larger studies are needed to definitively assess the opportunity, type, and outcomes of additional treatments in case of positive margins.

The manuscript does not contain any individual person’s data.

The datasets analyzed during the current study are available from the corresponding author on reasonable request.

All patients signed a written informed consent, which was reviewed and approved by the local Ethics Committees and including the use of anonymized patient data for research purposes.

IF designed the study; FrancescoM, IF, FilippoM, MF, and AP collected and organized the clinical data. FF performed the statistical analysis. IF, FF, GiampieroP, CP, and GiorgioP drafted and reviewed the manuscript. All the authors read and approved the final manuscript.

The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.