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Tang et al. Mini-invasive Surg 2024;8:24 https://dx.doi.org/10.20517/2574-1225.2024.04 Page 5 of 13

[21]
of the orbit, and the dura mater at the lateral portions of the anterior skull base . When deciding on
surgical treatment, understanding these anatomical limitations can help surgeons weigh the utility of EES
and the ability to achieve a negative-margin resection. Although these limitations exist, EES is constantly
evolving with improvements in both surgical skill and surgical technology and equipment that can further
expand the degree of exposure and resection available through this approach.

OUTCOMES OF ENDOSCOPIC ENDONASAL SURGERY FOR SINONASAL MALIGNANT
TUMORS WITH SKULL BASE INVOLVEMENT
Comparative studies have supported EES for resection of SNMTs, demonstrating EES can have better
postoperative quality of life while maintaining similar oncological outcomes when compared to open
[22]
approaches . Rawal et al. demonstrated that EES achieved optimal survival outcomes after reporting a
5-year overall survival (OS) rate of 72.3% which was comparable to or better than previous reports of open
craniofacial surgery . Moreover, the absence of facial incisions and osteotomies, less postoperative pain,
[23]
shorter hospitalization stays, and reduced perioperative mortality represent major advantages of EES .
[24]
When comparing EES to conventional open surgical approaches, multiple studies have reported similar
oncologic outcomes with improved morbidity and complications with EES. An early study by Snyderman
et al. suggested that the oncological outcomes for SNMTs with skull base involvement treated with EES
[25]
were comparable to outcomes from open approaches . In a series of 120 patients, Hanna et al. found that
disease recurrence and survival did not differ significantly between an exclusive EES and a mixed
cranioendoscopic approach. The group reported an overall 11% complication rate, with a 3% rate of
postoperative cerebrospinal fluid leakage that was not statistically different between groups . A more
[26]
recent study by Schur et al. compared anatomically matched cohorts of patients with stage T4 sinonasal
malignancies with skull base involvement and found a lower risk of complications after EES than after open
[27]
surgical approaches . Additionally, no significant differences in OS and progression-free survival were
found, although patients treated with EES trended towards lower rates of disease progression and higher
OS.

LONG-TERM OUTCOMES OF EES
Long-term survival is significantly different depending on tumor histology. For example, ONB has an
excellent survival rate, with studies measuring 5-year OS ranging from 82.3%-92.9% [28-30] . Anscheutz et al.
also report long-term OS rates of 87.5% for ACC and 65.3% for SCC . The most frequent sites for SNMT
[31]
recurrence are at either local or regional sites . In addition, there is also limited data comparing long-term
[31]
complications for endoscopic and open resections. However, Hagemann et al. did report in a long-term
[32]
study that endoscopic resection was associated with improved OS and disease-specific survival .
Reports on long-term complications for SNMTs are limited as these outcomes vary greatly based on tumor
[33]
stage and histology. A study by Levin et al. reports an overall complication rate of 53% . Shah et al.
discussed complications of EES for SNMTs with skull base involvement . Arnold et al. found that many of
[34]
the patients who required reoperation (21%) were for postoperative sinusitis (18%). Importantly, studies
have found that EES leads to lower long-term complication rates than open approaches [35-37] .

ENDOSCOPIC ENDONASAL SURGERY FOR SELECTED PATHOLOGIES
Although histological confirmation is not always available prior to treatment, differences in SNMT
histology may impact outcomes and selection of surgical approaches. Diagnosis and staging of SNMTs is
imperative for treatment selection in patients and biopsy is typically indicated prior to any skull base