Staging of the involvement of anterior commissure is controversial. Steiner has further classified T1a, T1b and T2a, as with or without anterior commissure involvement . There is no international consensus on the management of tumours involving the anterior commissure. Certain countries have issued guidelines for the management of tumours involving the anterior commissure. Dutch national guidelines recommend performing laser surgery only on T1a lesions when a sufficient margin can be obtained within the affected fold. They further recommend this using either a subligamental or subepithelial resection that does not extend into the anterior commissure. Lesions that require resection of the anterior commissure have in the past largely been regarded as unsuitable for laser surgery because of poor voice quality . According to the consensus statement on management in the United Kingdom, patients should be given the choice of TLM for tumours involving the anterior commissure, but advised of the greater chance of adverse voice outcome when the anterior commissure is treated surgically . Steiner and colleagues reported that laser surgery is effective despite anterior commissure involvement .
Disadvantages of laser surgery include: the need for general anaesthesia, difficult access to anterior commissure, and possibly poor voice outcome due to resection of anterior commissure. By comparison the disadvantages of radiotherapy include: longer treatment schedule, increased expense, risk of chondronecrosis, development of radiation induced tumours, delay in diagnosing recurrence due to oedema, and total laryngectomy is often required as a salvage operation .
According to some studies, anterior commissure involvement adversely affects local control, laryngeal preservation and survival [13–15]. Other studies have not found this effect to be significant [16, 17]. Mlynarek compared patients with early glottic cancer after radiotherapy and microsurgery and found that in both groups 50% of patients with involvement of anterior commissure had recurrences .
Opinion is divided regarding the effectiveness of radiotherapy for local control of tumours involving the anterior commissure. Five-year control rates for tumours with involvement of the anterior commissure varied from 56% to 80% and without anterior commissure involvement from 82% to 90% [13, 14, 19, 20]. In contrast a study by Mendenhall showed no difference in local control rate . Sjogren studied 36 patients with anterior commissure involvement who had radiotherapy as their primary treatment. Five patients developed local recurrence and 1 patient developed distant metastasis. Three patients underwent total laryngectomy as salvage. Their local control and laryngeal preservation rates were 88% and 91% respectively .
Steiner and colleagues studied 89 T1 glottic cancer patients with anterior commissure involvement and reported 21 local recurrences. Their 5 year local control, laryngeal preservation rate, ultimate local control and overall survival were 71%, 95%, 98% and 88% respectively . In a larger series by Motta (169 patients with anterior commissure involvement) actuarial survival, adjusted actuarial survival and ultimate local control were 84%, 96% and 83% respectively . Gallo studied 22 patients with anterior commissure involvement and local control and overall survival were 91% and 95% respectively . In the paper by Bocciolini 5 out of 10 patients developed local recurrence and their laryngeal preservation rate was 80%.
In our study there was an apparent difference in the local control and laryngeal preservation rates between the laser and radiation arms as seen from the Kaplan Meier plots. These observed differences would be clinically significant, but are not statistically significant in the present study (p = 0.38 for local control and 0.077 for laryngeal preservation using the Log Rank test). In the present study, the lack of significance likely represents our small sample size rather than no true effect. Disease free survival and overall survival shows no significant differences between modalities (p = 0.82 and 0.6 respectively using the Log Rank test).
Cohen in 2006 performed a meta-analysis from 1966 to 2005 comparing voice outcomes with radiation compared with laser for the treatment of early glottic cancer. This series included 6 studies with 208 patient (6 T1b and 202 T1a) treated with laser and 91 patients (6T1b and 85 T1a) treated with radiation. This showed comparable levels of voice handicap with both interventions. This study reported that the resections involving the superficial vocalis muscle (mean VHI, 6.23) had improved VHI scores compared to those involving the contralateral vocal fold (mean VHI, 15.7) and concluded that further study is needed to clarify voice outcomes in lesions involving anterior commissure . Our study shows no obvious difference in the post-operative VHI-10 score between the two arms.
To our knowledge there are no studies in the literature directly comparing the oncologic and voice outcomes for the treatment of glottic cancer with anterior commissure involvement after treatment with laser and radiation. Access to the anterior commissure is one of the determining factors when assessing the feasibility for laser resection. We generally use Kleinsasser laryngoscope to expose the larynx. In our experience we were able to successfully complete the procedure in all the patients listed for laser resection in the T1b cohort.
Limitations of the study
Due to lack of randomization study design the possibility of selection bias is unavoidable. Given that all tumours were a narrowly defined T-stage and demographic information was similar between groups, we do not believe that this bias is so significant that it negates our ability to make meaningful comparisons between groups.
A further weakness of the study was the lack universal VHI-10 data. Finally, lack of intra-operative staging in the radiation arm could have potentially under staged some cancers. Interestingly none of the patients in the laser arm were up staged intra-operatively.