Prospective Longitudinal Assessment of Quality of Life After Stereotactic Ablative Radiotherapy for Oligometastases: Analysis of the Population-based SABR-5 Phase II Trial

AIMS

To evaluate longitudinal patient-reported quality of life (QoL) in patients treated with stereotactic ablative radiotherapy (SABR) for oligometastases.

MATERIALS AND METHODS

The SABR-5 trial was a population-based single-arm phase II study of SABR to up to five sites of oligometastases, conducted in six regional cancer centres in British Columbia, Canada from 2016 to 2020. Prospective QoL was measured using treatment site-specific QoL questionnaires at pre-treatment baseline and at 3, 6, 9, 12, 15, 18, 21, 24, 30 and 36 months after treatment. Patients with bone metastases were assessed with the Brief Pain Inventory (BPI). Patients with liver, adrenal and abdominopelvic lymph node metastases were assessed with the Functional Assessment of Chronic Illness Therapy-Abdominal Discomfort (FACIT-AD). Patients with lung and intrathoracic lymph node metastases were assessed with the Prospective Outcomes and Support Initiative (POSI) lung questionnaire. The two one-sided test procedure was used to assess equivalence between the worst QoL score and the baseline score of individual patients. The mean QoL at all time points was used to determine the trajectory of QoL response after SABR. The proportion of patients with 'stable', 'improved' or 'worsened' QoL was determined for all time points based on standard minimal clinically important differences (MCID; BPI worst pain = 2, BPI functional interference score [FIS] = 0.5, FACIT-AD Trial Outcome Index [TOI] = 8, POSI = 3).

RESULTS

All enrolled patients with baseline QoL assessment and at least one follow-up assessment were analysed (n = 133). On equivalence testing, the patients' worst QoL scores were clinically different from baseline scores and met MCID (BPI worst pain mean difference: 1.8, 90% confidence interval 1.19 to 2.42]; BPI FIS mean difference: 1.68, 90% confidence interval 1.15 to 2.21; FACIT-AD TOI mean difference: -8.76, 90% confidence interval -11.29 to -6.24; POSI mean difference: -4.61, 90% confidence interval -6.09 to -3.14). However, the mean FIS transiently worsened at 9, 18 and 21 months but eventually returned to stable levels. The mean FACIT and POSI scores also worsened at 36 months, albeit with a limited number of responses (n = 4 and 8, respectively). Most patients reported stable QoL at all time points (range: BPI worst pain 71-82%, BPI FIS 45-78%, FACIT-AD TOI 50-100%, POSI 25-73%). Clinically significant stability, worsening and improvement were seen in 70%/13%/18% of patients at 3 months, 53%/28%/19% at 18 months and 63%/25%/13% at 36 months.

CONCLUSIONS

Transient decreases in QoL that met MCID were seen between patients' worst QoL scores and baseline scores. However, most patients experienced stable QoL relative to pre-treatment levels on long-term follow-up. Further studies are needed to characterise patients at greatest risk for decreased QoL.

Health-Related Quality of Life after Combined External Beam and Either High Dose Rate (HDR) or Low Dose Rate (LDR) Brachytherapy: Does the Rectal Dose from the LDR Brachytherapy Make a Difference?

PURPOSE/OBJECTIVE(S)

The recently reported randomized Phase III trial comparing health related quality of life (HRQOL) after combined external beam radiation therapy (EBRT) and either HDR or LDR brachytherapy (BT) found a significant decline in the EPIC Bowel domain HRQOL score at 24- 48 months after treatment in the LDR arm of the trial. As all patients in the trial received the same EBRT dose, and HDR rectal dose was strictly controlled to be <9.5 Gy to 1cc of rectal wall (RD1cc), we investigated whether the variable rectal dose from the LDR component of treatment was related to the decline in Bowel HRQOL for these patients.

MATERIALS/METHODS

A total of 195 men with upper tier intermediate or high-risk prostate cancer were assigned by a random number generator to receive either an HDR (15 Gy, n = 108) or LDR (110Gy, n = 87) brachytherapy boost combined with 46Gy/23 fractions EBRT. All LDR patients had 1 month post implant quality assurance using CT-MRI fusion. The Expanded Prostate Cancer Composite (EPIC) questionnaire was used to evaluate HRQOL at baseline, q3 mo for 1 year, q6mo for 3 yr and then annually. A multivariate linear regression model was used to investigate the dose-response relationship between EPIC bowel domain score at 24- 48 months and RD1cc.

RESULTS

With a median follow up of 48 months, the previous analysis confirmed the expected time course of acute bowel/urinary symptoms, with LDR showing more prolonged decline in HRQOL bowel domain at 3 and 6 months, but equivalence to HDR by 12 months. HRQOL urinary domain remained equivalent from 12-60 mo. The decline in the HRQOL bowel domain observed for LDR patients from 24-48 mo was analyzed for the 79 patients with sufficient data. The mean baseline HRQOL bowel domain score was 92 and fell on average to 85 at 24-48 mo. Mean RD1cc for the LDR patients was 82Gy (SD 22 Gy), with a maximum value of 129 Gy. In this range of rectal doses, a 20Gy increase in RD1cc, was associated on average with a 1.5-point decrease in EPIC HRQOL bowel domain score (p = 0.21).

CONCLUSION

The rectal dose received by the LDR patients showed a non-significant dose-response with the EPIC Bowel domain HRQOL score. This confirms the accepted rectal dose constraints for LDR brachytherapy but does not explain the observed decline in bowel scores from 24-48 months.

Prospective Longitudinal Assessment of Quality of Life after Stereotactic Ablative Radiotherapy for Oligometastases: Analysis of the Population-Based SABR-5 Phase II Trial

PURPOSE/OBJECTIVE(S)

To evaluate longitudinal patient-reported quality of life (QoL) in patients treated with stereotactic ablative radiotherapy (SABR) for oligometastases.

MATERIALS/METHODS

The SABR-5 trial was a population-based single-arm phase II study of SABR to up to 5 sites of oligometastases, conducted in 6 regional cancer centers in British Columbia from 2016 to 2020. Prospective QoL was measured using treatment site-specific QoL questionnaires at pre-treatment baseline and 3, 6, 9, 12, 15, 18, 21, 24, 30, and 36 months after treatment. Patients with bone metastases were assessed with the Brief Pain Inventory (BPI). Patients with liver, adrenal, and abdominopelvic lymph node metastases were assessed with the Functional Assessment of Chronic Illness Therapy-Abdominal Discomfort (FACIT-AD). Patients with lung and intrathoracic lymph node metastases were assessed with the Prospective Outcomes and Support Initiative (POSI) lung questionnaire. The two one-sided test procedure was used to assess equivalence between the worst QoL score and baseline score of individual patients. Mean QoL at all time points was used to determine the trajectory of QoL response after SABR. The proportion of patients with "stable," "improved," or "worsened" QoL was determined for all time points based on standard minimal clinically important differences (MCID; BPI worst pain = 2, BPI Functional Interference Score [FIS] = 0.5, FACIT-AD Trial Outcome Index [TOI] = 8, POSI = 3).

RESULTS

All enrolled patients with baseline QoL assessment and at least 1 follow-up assessment were analyzed (n = 135). On equivalence testing, patients' worst QoL scores were clinically different from baseline scores and met MCID (BPI worst pain mean difference: 1.8, 90% CI [1.19 to 2.42]; BPI FIS mean difference: 1.68, 90% CI [1.15 to 2.21]; FACIT-AD TOI mean difference: -8.76, 90% CI [-11.29 to -6.24]; POSI mean difference: -4.61, 90% CI [-6.09 to -3.14]). However, the mean FIS transiently worsened at 9, 18 and 21 months but eventually returned to stable levels. The mean FACIT and POSI scores also worsened at 36 months, albeit with a limited number of responses (n = 4 and 8, respectively). The majority of patients reported stable QoL at all time points (range: BPI worst pain 71-82%, BPI FIS 45-78%, FACIT-AD TOI 50-100%, POSI 25-73%). Clinically significant stability, worsening, and improvement were seen in 70%/13%/18% of patients at 3 months, 53%/28%/19% at 18 months and 63%/25%/13% at 36 months.

CONCLUSION

SABR in the oligometastatic setting can lead to transient decreases in QoL. However, most patients experienced stable QoL relative to pre-treatment levels on long-term follow-up. Further studies are needed to characterize patients at greatest risk for decreased QoL.

Progression-free survival and local control following stereotactic ablative radiotherapy for up to 5 oligometastases: an analysis from the population-based phase II SABR-5 trial

PURPOSE

Despite increasing utilization of stereotactic ablative therapy (SABR) for oligometastatic cancer, prospective outcomes are lacking. The purpose of this study was to determine progression-free survival (PFS), local control (LC) and prognostic factors from the population-based phase II XXX trial.

METHODS AND MATERIALS

The XXX trial was a single arm phase II study with the primary endpoint of toxicity, conducted at the 6 regional cancer centres across XXX, during which time SABR for oligometastases was only offered on trial. Patients with up to 5 oligometastases (total or not controlled by prior treatment, and including induced oligometastatic disease) underwent SABR to all lesions. Patients were 18 years of age or older, ECOG 0-2 and had life expectancy ≥ 6 months. The secondary outcomes of PFS and LC are presented here.

RESULTS

Between November 2016 and July 2020, 381 patients underwent SABR on trial. Median follow-up was 27 months (IQR 18-36). Median PFS was 15 months (95% CI 12-18). LC at 1 and 3 years were 93% (95% CI 91 - 95) and 87% (95% CI 84 - 90), respectively. On multivariable analysis, increasing tumor diameter (HR=1.09, p<0.001), declining performance status (HR=2.13, p<0.001), disease-free interval < 18 months (HR=1.52, p=0.003), four or more metastases at SABR (HR=1.48, p=0.048), initiation or change in systemic treatment (HR=0.50, p<0.001) and oligoprogression (HR=1.56, p=0.008) were significant independent predictors of PFS. Tumor diameter (SHR=1.28, p<0.001), colorectal histology (SHR=4.33, p=0.002) and "other" histology (SHR=3.90, p<0.001) were associated with worse local control.

CONCLUSIONS

In this population-based cohort including patients with genuine oligometastatic, oligoprogressive, and induced oligometastatic disease, the median PFS was 15 months and LC at 3 years was 87%. This supports ongoing efforts to randomize patients on phase III trials, even outside the original 1-5 metachronous oligometastatic paradigm.