UT Southwestern Medical Center, Dallas, TX
Akshat Patel , Rohit R Badia , Armon Amini , Christopher Kung , Samuel B. Kusin , Sarah Neufeld , Samantha Mannala , Aurelie Garant , Raquibul Hannan , Robert D. Timmerman , Michael J. Zelefsky , Michael Ryan Folkert , Neil Bipinchandra Desai
Background: SBRT for localized prostate cancer (PCa) is the focus of several ongoing and reported high-impact trials, which often focus on physician-reported toxicity (P-Tox) when comparing regimens. Patient-reported quality of life (PR-QoL) may differ and provide a more sensitive comparative metric of treatment burden, especially with fewer provider interactions during SBRT than during protracted RT courses. We evaluated the concordance of prospective genitourinary (GU) and gastrointestinal (GI) P-Tox and PR-QOL in men receiving SBRT for PCa. Methods: Data from two concurrently-enrolled prospective trials of SBRT in high-risk (Phase I Safety Endpoint, NCT01896271) and low-intermediate risk (Phase II GI Toxicity Endpoint, NCT02353832) PCa were used. Matching standardized schedules of collected PR-QoL [Expanded Prostate Cancer Index Composite (EPIC)] and P-Tox (CTCAE v5.0) were analyzed over the first 18 months of follow up, where symptoms are most pronounced. We assessed concordance of Grade≥2 GU/GI physician reported toxicity with PR-QoL declines exceeding anchor based minimal clinically important difference (MCID) thresholds (-6 urinary and -5 bowel summary scores, respectively) for each patient at each time point. Patients without baseline PR-QoL data were excluded in full, while time points with missing PR-QoL or P-Tox were excluded individually without imputation. Concordance was evaluated by Cohen’s kappa statistic. Results: From 101 patients, there were 256 (64%) follow up observations through 18 months with both PR-QoL and P-Tox at the time point and baseline. Concordance of PR-QoL and P-Tox was low at all time points for both GU and GI toxicity domains (mean kappa 0.093; Table). MCID was more often reported by patients than Grade≥2 toxicity by physicians (38% vs 17% for GU and 44% vs 10% for GI). There was little overlap of PR-QoL and P-Tox reporting: Grade≥2 P-Tox reported in 17% of observations with MCID in PR-QoL, while MCID in PR-QoL reported in 54% of observations of Grade ≥2 P-Tox. Mean concordance was similarly low when analyzing sub-groups of trial, investigator, and an alternative 2xMCID threshold. Conclusions: P-Tox and PR-QoL differed dramatically in two prospective studies of SBRT despite toxicity primary endpoints. This may reflect subjective and varying intervention thresholds driving P-Tox reporting, rather than actual patient burden. These data strongly support use of PR-QoL rather than P-Tox for SBRT comparative study endpoints and guidelines in this rapidly evolving space.
Time from RT (mo) | N | MCID PR-QoL, N (%) | P-Tox Grade≥2, N (%) | Concordant N | Kappa | |
---|---|---|---|---|---|---|
GU | 1.5 | 75 | 33 (44%) | 11 (15%) | 7 | 0.126 |
3 | 69 | 14 (20%) | 10 (14%) | 5 | 0.298 | |
12 | 57 | 26 (46%) | 12 (21%) | 7 | 0.113 | |
18 | 52 | 24 (46%) | 10 (19%) | 3 | -0.130 | |
GI | 1.5 | 76 | 28 (37%) | 8 (11%) | 6 | 0.203 |
3 | 70 | 18 (26%) | 2 (3%) | 0 | -0.054 | |
12 | 55 | 18 (33%) | 5 (9%) | 3 | 0.138 | |
18 | 53 | 23 (43%) | 1 (2%) | 1 | 0.049 |
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