Patient-Reported Quality Of Life Following Stereotactic Body Radiation Therapy For Primary Kidney Cancer: Results From A Prospective Cohort Study

There is growing interest in using stereotactic body radiation therapy (SBRT) for the treatment of primary medically inoperable kidney cancer. Previous retrospective studies have shown excellent disease control with minimal toxicity. However, a paucity of data exists on the effect of SBRT on patient-reported quality of life (QOL) following treatment. Here we describe the first report of QOL post kidney SBRT. Twenty-five consecutive patients were treated with kidney SBRT on a multi-institutional prospective cohort trial (NCT03108703). Patients were treated with 5-fraction SBRT ranging from 30-40 Gy in total dose. Prospective QOL assessment was carried out using the European Organization for Research and Cancer Treatment Quality of Life Core Questionnaire-15 Palliative (EORTC QLQ C-15 PAL), the Functional Assessment of Cancer Therapy-Kidney Symptom Index (FACT-FKSI-19), and the EuroQol-5D (EQ-5D) tools at baseline, 1 month, and 3 months post treatment. All raw scores were converted using validated scoring algorithms and means (±standard deviation) were compared at each time point using paired t-tests. A total of 21 patients completed all questionnaires at baseline (84%), with 17 patients having completed them at 1 month (68%), and 12 patients at 3 months (48%). When patients did respond, all questionnaires were fully completed. No difference was observed in global QOL comparing baseline to both 1 and 3 months either with the QLQ C-15 PAL (74.5±29.3 vs 71.6±29.1, p=0.46; 77.8±21.7 vs 72.2±19.2, p=0.27, respectively), FACT-NKSI total score (59.8±11.4 vs 62.8±10.7, p=0.13; 60.5±14.2 vs 60.9±14.5, p=0.88), and EQ-5D health state index (0.80±0.11 vs 0.85±0.11, p=0.07; 0.82±0.13 vs 0.79±0.21, p=0.55). Comparable results were observed with the EQ-5D visual analogue scale over time. Using a minimally clinical importance difference (MCID) threshold of 10 points on the EORTC QLQ scale, there was no significant worsening in individual symptom or functional scores over time; conversely, there were improvements reaching the threshold in both nausea (mean improvement of 9.7) and appetite (mean improvement of 11.1) between baseline and 3-months, but these did not reach statistical significance (p=0.21, 0.17). No statistically significant declines were observed across all symptom and functional domains. Using an MCID of 10 for the QLQ C-15 PAL, 4 for the FACT-NKSI, and 0.08 for the EQ-5D index, global QOL was stable or better at 3 months in 66% (8/12), 66% (8/12), and 75% (9/12) of evaluable patients. Patient reported QOL appears to be well preserved following kidney SBRT. Owing to the small sample size and poor compliance, further prospective and long-term assessment is required to confirm these findings. Future analyses include correlation of QOL with outcomes, clinical factors, and dosimetry metrics.