SN mapping for cervical cancer is gradually becoming more widespread in Japan [17] and is described as a standard procedure in overseas guidelines [18]. This study investigated the effect of SNNS on the long-term prognosis of patients with cervical cancer. In this study, no lymph node recurrence was observed in patients with SNNS, and the prognosis was good, with RFS and OS rates of 96.4% and 96.6%, respectively. Therefore, SNNS for cervical cancer is safe and effective without increasing recurrence.

In this study, SNNS was performed for cervical cancer cases of less than 3 cm, and 56% of cases were operated on by laparotomy, partly due to the worldwide decrease in minimally invasive surgeries such as laparoscopy and robotics, according to the results of the LACC study [19]. However, the most significant reason for this is that in Japan, laparoscopic radical hysterectomy is restricted to tumors smaller than 2 cm, and robotic surgery is not yet covered by insurance.

In our previous study [20], the SN detection rate (at least one SN identified) in 70 patients who underwent SNNS was 100%. In the SENTICOL study [15], SNs were detected in 136 (97.8%) of the 139 patients (95% confidence interval, 93.8–99.6%), and SNs were found on both sides in 104 (76.5%) patients. Contrarily, Aoki et al. [21]. identified SN using ICG in laparoscopic surgery for cervical cancer, and the per-patient and side-specific SN detection rates were 98.7% (76/77 patients) and 93.5% (144/154), respectively. In the present study, the detection rate of SNs (at least one SN identified) was 100%, and the bilateral SN identification rate was 94% (130/138). Consistent with previous reports, the SN identification rate in cervical cancer appears to be high. In this study, SN metastasis was observed in four cases, with two cases of macrometastasis and two cases of micrometastasis. Regarding micrometastasis, there is a possibility of poor prognosis, and a prospective clinical trial is currently underway, with clear evidence for SNNS still awaited [22, 23].

Previous studies have reported that the incidence of LEL with PLA in patients with cervical cancer is between 16.6% and 42% [5, 7,8,9,10,11]. In contrast, the LEL occurrence rate in patients who underwent SNNS for cervical cancer was reported to be 0–5.6% [20, 24, 25]. In the present study, the incidence of LEL in patients in whom PLA could be omitted with SNNS was 0.7%, suggesting that SNNS may improve patient QOL, which is similar to results from previous reports. In contrast, Yahata et al. reported a low incidence of pelvic lymphocele at 0.6% in their study, which focused on SNNS cases of cervical cancer [25]. Here, we also found that only 2.2% of patients without PLA had a pelvic lymphocele, suggesting that SNNS can reduce lymphatic-related complications.

Lennox et al. [26] reported that recurrence occurred in four patients with SNNS, and the five-year RFS was 93%. Favre et al. [27] reported that the four-year disease-free survival (DFS) and OS rates of 105 patients with SNNS were 89.5% and 95.2%, respectively. In this study, four cases (3%) experienced recurrence over a median follow-up period of 57.5 months. The 5-year RFS rate and OS rate were 97% and 97.3%, respectively.

Our study had a longer median follow-up than these reports did, and the RFS and OS were more favorable.

In contrast, Balaya et al. [28] reported that there were 10 recurrences (11.5%) in 87 patients with SNNS, and the DFS was 85.1% (median follow-up, 47 months). Minimally invasive surgery was performed in 95.4% of the patients, and approximately 10% of the cases were high-risk with tumor diameters greater than 2 cm in diameter, which may have contributed to a worse prognosis. Yahata et al. [24] reported on the long-term follow-up of 181 SNNS cases, observing four instances of recurrence. The 5-year progression-free survival and OS rates were noted as 98.8% and 99.4%, respectively. These results indicate that SNNS is safe with respect to long-term prognosis, which is similar to the outcomes of our study.

This study had several limitations. First, this was a retrospective study, which inherently carries a risk of selection bias. Second, although this study analyzed the long-term prognosis of 138 cases of cervical cancer SNNS, the number of cases remains limited. Future research with a larger study population is required to validate our findings.

In conclusion, our data demonstrated that SNNS is an effective and safe procedure for patients with early-stage cervical cancer. A large prospective trial on SNNS to evaluate the prognosis of early-stage cervical cancer is warranted.