Top Line: Does SBRT improve progression free survival in patients with oligoprogressive cancer?
The Study: The CURB trial, first presented at ASTRO 2021, was a randomized phase 2 trial of SBRT for oligoprogressive NSCLC and breast cancer. Eligible patients (n=106) had either NSCLC or breast cancer (34% had TNBC) with progression of 1-5 lesions on standard first-line systemic therapy. They were randomized to receive standard of care systemic therapy with or without SBRT to all sites of oligoprogression. The most common target sites were non-spine bone (31%), lung (26%), lymph nodes (15%), and spine (14%). Over half of these (52%) were treated with 27-30Gy in 3 fractions with 19% receiving 30-50 Gy in 5 fractions. Overall, median PFS was significantly higher with SBRT (7.2 v 3.2 months), however this was driven by the NSCLC cohort where mPFS was increased from 2.2 months to 10 months with SBRT. In contrast, there was no improvement in the breast cancer cohort (4.4 v 4.2 months). In this context, it is important to note that none of the 111 lesions treated with SBRT progressed. In other words, we’re not seeing a problem with the efficacy of SBRT. We’re seeing differences in the behavior of oligometastatic breast and lung cancer. Among breast cancer patients, >60% of patients progressed at new sites regardless of whether they received SBRT. In contrast, most (68%) NSCLC patients in the standard arm progressed at existing sites, and this was slashed to 26% in the SBRT arm. With NSCLC, what we see at the time of oligoprogression is a truer picture of the disease state than with breast cancer. The latter continues to elude us as the majority of patients with supposed oligometastatic disease progress at new, previously occult sites of disease. What we see with breast cancer isn’t all there is.
TBL: In the CURB trial, SBRT provides excellent control of oligometastatic lesions. For NSCLC, this translates to a significant improvement in PFS, but for breast cancer, SBRT was not beneficial as most patients progress at new sites. | Tsai, Lancet 2023
The Study: The CURB trial, first presented at ASTRO 2021, was a randomized phase 2 trial of SBRT for oligoprogressive NSCLC and breast cancer. Eligible patients (n=106) had either NSCLC or breast cancer (34% had TNBC) with progression of 1-5 lesions on standard first-line systemic therapy. They were randomized to receive standard of care systemic therapy with or without SBRT to all sites of oligoprogression. The most common target sites were non-spine bone (31%), lung (26%), lymph nodes (15%), and spine (14%). Over half of these (52%) were treated with 27-30Gy in 3 fractions with 19% receiving 30-50 Gy in 5 fractions. Overall, median PFS was significantly higher with SBRT (7.2 v 3.2 months), however this was driven by the NSCLC cohort where mPFS was increased from 2.2 months to 10 months with SBRT. In contrast, there was no improvement in the breast cancer cohort (4.4 v 4.2 months). In this context, it is important to note that none of the 111 lesions treated with SBRT progressed. In other words, we’re not seeing a problem with the efficacy of SBRT. We’re seeing differences in the behavior of oligometastatic breast and lung cancer. Among breast cancer patients, >60% of patients progressed at new sites regardless of whether they received SBRT. In contrast, most (68%) NSCLC patients in the standard arm progressed at existing sites, and this was slashed to 26% in the SBRT arm. With NSCLC, what we see at the time of oligoprogression is a truer picture of the disease state than with breast cancer. The latter continues to elude us as the majority of patients with supposed oligometastatic disease progress at new, previously occult sites of disease. What we see with breast cancer isn’t all there is.
TBL: In the CURB trial, SBRT provides excellent control of oligometastatic lesions. For NSCLC, this translates to a significant improvement in PFS, but for breast cancer, SBRT was not beneficial as most patients progress at new sites. | Tsai, Lancet 2023