Stereotactic Ablative Radiotherapy for Oligo-Progressive Cancers: Results of the Randomized Phase II STOP Trial

PURPOSE/OBJECTIVE(S)

In the metastatic setting, there is uncertain benefit to localized eradication of one or more lesions that are progressing despite systemic therapy. This randomized phase II trial examined if patients with ≤5 sites of oligoprogression benefited from the addition of stereotactic ablative radiotherapy (SABR) to standard of care (SOC) systemic therapy.

MATERIALS/METHODS

Eligibility criteria included age ≥18 years, ECOG performance status 0-2, and oligoprogressive disease, defined as 1-5 lesions actively progressing while on systemic therapy. Patients were required to have at least 3 months of disease stability/response on systemic therapy prior to oligoprogression. After stratifying by type of systemic therapy (cytotoxic vs. non-cytotoxic), patients were randomized 2:1 to SABR to all progressing lesions plus SOC (SABR arm) vs. SOC alone (SOC arm). The trial began exclusive to non-small cell lung cancer but did not meet accrual goals and was expanded in 2019 to include all non-hematologic malignancies. The primary endpoint was progression-free survival (PFS). Secondary endpoints included overall survival (OS), lesional control, quality of life (QOL), toxicity, and duration of current systemic agent post-SABR.

RESULTS

Between February 2017 and June 2021, 90 patients with 125 oligoprogressive metastases were enrolled across 8 Canadian institutions, with 59 patients randomized to SABR and 31 to SOC. Median age was 67 years (IQR: 61-73 years) and 39 (43%) were female. The most common primary sites were lung (44% of patients), genitourinary (23%) and breast (13%), with the most common oligo-progressive locations being lung (43%), bone (19%), lymph nodes (14%), and liver (13%). In the SABR arm, the most common fractionations were 35 Gy/5 (38% of lesions) and 50 Gy/5 (18%). Protocol adherence in the SOC arm was suboptimal: 3 patients (10%) withdrew immediately after randomization, and 7 additional patients (23%) received high-dose or ablative therapies. Median follow-up was 31 months. There was no difference in PFS between arms (median PFS 8.4 months in the SABR arm vs. 4.3 months in the SOC arm; however, the curves cross and 2-year PFS was 9% vs. 24% respectively, p = 0.91). Median OS was 31.2 months vs. 27.4 months, respectively (p = 0.22). Lesional control with SABR was 71% vs. 39% with SOC (p = 0.002). Median duration of post-randomization first-line systemic therapy was 10.3 months vs. 7.6 months, respectively (p = 0.71). Treatment was well-tolerated with 2 (3.4%) grade 3 treatment-related toxicities in the SABR arm and no grade 4/5 related events in either arm. QOL did not differ between arms.

CONCLUSION

Despite being a well-tolerated treatment providing superior lesional control, SABR for oligoprogression did not improve PFS or OS. Results may have been impacted by withdrawals and desire for ablative treatments on the SOC arm, and this lack of equipoise may make accrual to phase III trials difficult, although larger studies in select sub-populations are desired. (NCT02756793).

Assessment of Precision Irradiation in Early Non-Small Cell Lung Cancer and Interstitial Lung Disease (ASPIRE-ILD): Primary Analysis of a Phase II Trial

PURPOSE/OBJECTIVE(S)

The use of stereotactic ablative radiotherapy (SABR) in patients with fibrotic interstitial lung disease (ILD) has been associated with an increased risk of toxicity, but patients with ILD and lung cancer may have no other options for curative-intent treatment. The goal of the ASPIRE-ILD trial was to assess the benefits and toxicities of SABR in patients with fibrotic ILD.

MATERIALS/METHODS

We enrolled patients with fibrotic ILD and a diagnosis of T1-2N0 NSCLC who were not candidates for surgery. All patients were centrally reviewed prior to enrollment to confirm the presence and subtype of ILD. After stratification by the ILD-GAP score (a measure of ILD severity and prognosis), patients were treated with SABR to a dose of 50 Gy in 5 fractions EOD (BED = 100 Gy10), with a built-in de-escalation protocol in case of unacceptable toxicity. The primary endpoint was overall survival (OS), powered to distinguish 1-year OS >70% vs. an unacceptable rate of ≤50%. Secondary endpoints included toxicity (CTC-AE version 4.0), progression-free survival (PFS), local control (LC), patient-reported outcomes (FACT-L quality of life and cough severity), and changes in pulmonary function tests (PFTs). The study pre-specified that SABR would be considered worthwhile if median OS was >1 year, with a grade 3-4 toxicity risk <35% and a grade 5 toxicity risk <15%. Target accrual was 39 treated patients.

RESULTS

Thirty-nine patients were enrolled and treated with SABR between March 2019 and January 2022, all to a dose of 50 Gy in 5 fractions, at 5 institutions in Canada and 1 in Scotland. Median age was 78 years (interquartile range: 67-83), 59% were male, and 92% had a history of smoking (median 43 pack-years). At baseline, 70% reported dyspnea, median FEV1 was 80% predicted and median DLCO was 49% predicted. ILD-GAP scores were as follows: ≤2 (i.e., best ILD status): n = 14; 3-5: n = 23; ≥6 (i.e., worst ILD status): n = 2. Median follow-up was 19 months. OS at 1-year was 78.9% (p<0.001 by binomial test vs. the unacceptable rate). Median OS was 25 months, median PFS was 19 months, and 2-year LC was 92%. AE rates (possibly, probably or definitely related) were as follows (highest grade per patient): grade 1-2: n = 12 (31%); grade 3: n = 4 (10%); grade 4; n = 0; grade 5 n = 3 (7.7%, all due to respiratory deterioration). AE rates did not differ by ILD-GAP category or ILD subtype. FACT-L scores trended downward over time (p = 0.07), and cough severity scale scores worsened over time (p = 0.02). Comparing last-available PFTs with baseline, DLCO declined (median: -4%; p = 0.046), FVC trended downward (median: -2.5%; p = 0.11), and FEV1 remained stable (median change: 0%).

CONCLUSION

The use of SABR in patients with ILD met the pre-specified acceptability thresholds for both toxicity and efficacy, supporting the use of SABR for curative-intent treatment after a careful discussion of risks and benefits. Further studies exploring pharmacologic options to reduce toxicity may be beneficial in this population. ().