A 68-year-old woman was diagnosed with left renal pelvic cancer by enhanced CT after presenting with gross hematuria. The CT image showed an enhancing mass in the area. Urine cytology revealed class III cells and cystoscopy suggested no apparent tumor in the bladder. She underwent total nephroureterectomy and regional LN dissection with no major perioperative complications. The lesion in the surgical pathology specimen was identified as high-grade UC (pT2 with lymphovascular invasion) but there was no metastasis to the surrounding LNs (0/7). Eight months after the surgery, follow-up cystoscopy revealed recurrence within the bladder, which was confirmed as UC upon biopsy analysis. At this time, imaging studies (CT and positron emission tomography/CT) detected local recurrence (surrounding the original kidney) and paraaortic LN enlargement consistent with metastasis. Chemotherapy (cisplatin + gemcitabine) was administered as the first-line systemic therapy immediately after the diagnosis was made. Two months later, CT showed an increase in the size of the paraaortic LN consistent with PD, and the treatment was switched to ICI therapy with pembrolizumab. However, subsequent CT scans revealed not only paraaortic LN enlargement but also left subclavian LN and right renal hilum LN enlargement at 3 and 4 months after the initiation of pembrolizumab, respectively, which also satisfied the criteria for PD. Pembrolizumab was discontinued, and after discussing the risks and benefits of each third-line chemotherapy regimen with the patient, we decided to start GD which resulted in continuous overall tumor growth. At this time, the patient complained of unbearable left back pain, which was considered to be caused by local recurrence invading the surrounding muscles. RT (30 Gy in 10 fractions) was administered to the lesion considered to be the source of the pain; this resulted in dramatic symptom relief. CT 2 months after the initiation of RT showed reduction of the irradiated lesion from 51 to 8 mm as well as reduction of some non-irradiated LNs, such as two paraaortic LNs (#1: 30–24 mm, #2: 28–13 mm) and the right renal hilar LN (16–7 mm). In summary, partial response was achieved even in non-irradiated lesions after RT. CT performed 21 months post-operation showed that the irradiated lesion had disappeared (from 8 to 0 mm) and that two of the non-irradiated lesions remained stable without a decrease in size (paraaortic LN #2: from 13–10 mm and right renal hilum LN: from 7–5 mm). However, one of the aortic LNs (#1) increased in size (from 24 to 50 mm). Therefore, additional RT doses were administered to the aortic LN #1 and tumor shrinkage was observed (from 50 to 30 mm), while the other lesions remained stable.