6092 Background: Although laterally extended endopelvic resection (LEER) has been introduced to control the pelvic sidewall tumors, there is a lack of evidence about its efficacy and safety despite high skillful procedure, compared with the other treatments. Thus, we performed a prospective cohort study with historical comparison for four years. Methods: One gynecologic oncologist performed LEER consecutively for patients with the pelvic sidewall tumors between March 2014 and July 2018. We compared clinicopathologic characteristics and survival between patients who received primary LEER and with those treated with other treatments. Results: We enrolled 37 patients treated with LEER. Among them, 22 (59.5%) and 15 (40.5%) had recurrent and primary disease. Among perioperative outcomes, there was more estimated blood loss, and hospitalization was longer in recurrent disease and previous surgery (p < 0.05). In recurrent disease, previous progression-free survival < 8 months was related to poor recurrence-free survival after LEER (median, 5.4 vs. 10.2 months; p < 0.05). When LEER was applied for the first recurrence of cervical cancer, recurrence-free survival and overall survival after treatment seemed to be longer in LEER (n = 9) than in palliative chemotherapy (n = 27) without statistical significance (median, 12.2 vs. 4.7 months and 23.2 vs. 12.4 months; p = 0.13 and p = 0.63). In 15 patients with primary locally advanced cervical cancer, LEER after partial response to neoadjuvant chemotherapy showed longer progression-free survival than LEER after stable or progressive disease to neoadjuvant chemotherapy and primary radiotherapy (p = 0.012). After LEER, grade 3 and 4 complications developed in 15 (23.1%) and 2 (3.1%) patients. Conclusions: Compared with palliative chemotherapy, LEER followed by palliative chemotherapy may improve progression-free survival in patients with recurrent cervical cancer located in the pelvic sidewall. If possible, it is more effective to apply LEER without preceding palliative chemotherapy for recurrent cervical cancer located in the pelvic sidewall.