Baseline patient’s characteristics
In our cohort (n = 39) we identified 31 males (79%) and eight females (21%) (Table 1). The median age was 72 years-old (range 54–88 years old) and most subjects (95%) had Eastern Cooperative Oncology Group (ECOG) performance status (PS) 0–1. The primary tumour location was in the urinary bladder in 25 patients (64%) whereas in 14 subjects (36%) the primary tumour was in the upper urinary tract (UTUC). Thirty-four patients (87%) had been initially treated with curative intention prior the SBRT whereas five were diagnosed with de novo non-operable locally advanced or metastatic disease. Only 36% had received palliative systemic treatment before SBRT.
Table 1
Baseline patient characteristics
Patient variable | n = 39 |
Sex, n (%) Male Female | 31 (79) 8 (21) |
Age, yr median (range) | 72 (54–88) |
Age interval, years (%) 54–67 68–75 76–88 | 12 (31) 13 (33) 14 (36) |
ECOG performance status, n (%) 0 1 2 | 21 (54) 16 (41) 2 (5) |
Primary tumour location, n (%) Upper tract tumour Bladder | 14 (36) 25 (64) |
Primary curative treatments, n (%) Curative cystectomy or nephrectomya Radiotherapy Peri-operative chemotherapyb | 34 (87) 30 (77) 4 (10) 10 (26) |
Primary metastatic disease, n (%) | 5 (13) |
Palliative systemic treatment pre-SBRT, n (%) | 14 (36) |
aAdditional three patients underwent palliative cystectomy or nephrectomy. bNeo-adjuvant chemotherapy, n = 9, adjuvant chemotherapy, n = 1. ECOG Eastern Cooperative Oncology Group. |
Treatment characteristics regarding SBRT
In total 51 metastatic lesions were treated with SBRT in 39 patients (Table 2). The most common metastatic sites of the first SBRT were lungs (45%) and lymph nodes (22%). Most patients had only one radiological metastasis at first SBRT (74%) but 26% of cases received SBRT against more than one lesion simultaneously. The indication of SBRT was primarily OMD in most individuals (69%). The median time between the diagnosis of muscle invasive urothelial cancer and the first SBRT was 23 months (range between 5 and 70 months). Summarized information about SBRT dosimetry including number of fractions, mean doses, and BED 10 against CTV and PTV is described in Table 2 with extended dosimetry data available in Supplementary Table 1. Sixty-three percent of patients received palliative systemic treatment due to disease progression after SBRT and 32% were treated with further radiation, including three patients receiving sequential SBRT (Table 2).
Table 2
Treatment characteristics regarding SBRT
Variable | n = 39 |
Intention of first SBRTa, n (%) Oligometastatic disease (OMD) Oligoprogressive disease (OPD) | 27 (69) 12 (31) |
Metastatic site of first SBRTa, b, n (%) Local recurrence Lgll Bone Liver Lung Otherc | 2 (4) 11(22) 6 (12) 4 (8) 23 (45) 5 (10) |
Nr of metastases treated at first SBRTa, b, n (%) 1 2 3 4 | 29 (74) 9 (23) 0 1 (3) |
SBRT dosimetry data Fractions, nr median (range) Dose CTV mean, Gy median (range) Dose PTV mean, Gy median (range) Dose CTV mean BED10, Gy median (range) Dose PTV mean BED10, Gy median (range) | 5 (2–10) 64 (35–75) 57 (31–68) 168 (65–210) 146 (55–183) |
Palliative systemic treatment post-SBRT, n (%) | 24 (62) |
Palliative radiotherapy post-SBRTd, n (%) | 12 (31) |
No systemic palliative treatment post-SBRT and OS > 36 monthse, n (%) | 6 (15) |
aFirst SRT treatment, three patients received consecutive SRT treatment bTotal nr of treated lesions was 51, in 39 patients cAdrenal gland, n = 3, subcutaneous, n = 2 dConventional radiotherapy or consecutive SRT eOne patient with consecutive SBRT SBRT stereotactic body radiation, CTV clinical planning target volume, Gy Grey, PTV planning target volume, BED biological equivalent dose. |
Local control rate, survival, and tolerability
The median follow-up was 25.6 months (range 2.9–118.6). The LCR at 2 years was 85% (Fig. 1A) and only 6 of the SBRT irradiated lesions progressed locally. The pre-planned SBRT fractions were given to all patients except for one case where the SBRT was interrupted prematurely due to treatment related pain in the chest wall. There were no significant differences in LCR or local PFS regarding CTV and/or PTV-doses (Supplementary Table 2).
The median systemic PFS and OS were 4.1 and 26.2 months, respectively (Fig. 1B and 1C). Patients with two or more metastatic lesions treated with SBRT simultaneously had a significantly shorter median systemic PFS of 1.8 month compared to patients with only one lesion treated, 9.8 months (HR 4.12, 95% CI: 1.81–9.38, p = 0.001) (Fig. 2A). There was a numerical difference in OS between these groups, with a median OS of 20.1 months versus 28.1, respectively however not statistically significant (HR 2.08, 95% CI: 0.91–4.76, p = 0.084) (Fig. 2B).
Univariate analyses were performed to investigate whether sex, age, ECOG PS, primary tumour location, primary curative treatment vs primary metastatic disease, palliative systemic treatment pre-SBRT, location of SBRT-irradiated metastases, or number of metastases receiving SBRT were associated with PFS and OS. Palliative systemic treatment given pre-SBRT, and the number of metastases treated with SBRT were associated with survival outcome (Supplementary Table 3).
Subgroups of patients with benefit of SBRT
Patients who did not receive any subsequent treatment after SBRT, neither systemic nor radiation treatment, had a significantly longer PFS of 8.3 months versus 4.0 months for patients who received treatment post-SBRT (HR 0.40, 95% CI: 0.16–0.98, p = 0.046) (Fig. 3A). For OS the KM-curves separate but were not statistically significant performing survival analyses (HR 0.66, 95% CI: 0.27–1.60, p = 0.353) (Fig. 3B).
An interesting subgroup of patients (n = 6, 15%) achieved long OS and never required systemic therapy after SBRT, whereof all of them had only one metastatic lesion. The OS for these individuals ranged between 43.8 and 113.3 months at study cut-off, and the only death in this sub-group was not cancer related (OS 93.8 months). Noteworthy, one of these patients received sequential SBRT due to disease progression to in total four different targets, inclusive in the brain, at different time points. This patient had a short systemic PFS of 2,7 months but was still alive at study cut-off with an OS of 118.6 months. All other patients never presented with recurrent disease.