Stereotactic Body Radiotherapy Shows Potential in Oligometastatic Cancer

Kendra Harris, MD, MSc

Interim Chair

Department of Radiation Oncology

Tulane University School of Medicine

An increasing amount of evidence shows that a proportion of patients with cancer found to have low-volume metastases at diagnosis see meaningful benefit from aggressive local therapy. Equally important, there have been no meaningful reductions in reported quality of life among patients receiving intensive local therapy, and a small percentage of patients appear to be cured with this strategy.

Stereotactic body radiotherapy (SBRT) is a relatively new approach to aggressive local management. SBRT is a specialized type of radiation delivery that precisely focuses high doses of radiation on tumor cells while sparing normal tissue and often delivering treatment over a much shorter time— often 1 to 5 days. Advances in radiotherapy delivery and imaging allow for safe administration of much higher doses of radiation per day than were previously and safely possible. Although SBRT cannot be used in every circumstance, this approach has cured patients with lung cancer with a single site of metastasis (eg, to the brain, to the adrenal glands), and growing evidence suggests that a similar approach in many other cancers may enable patients to delay their intensified next line of treatment. The data are exciting and still maturing (Table^1-3).

Table. Clinical Trials Assessing Aggressive Local Therapy WITH SBRT^1-3

At the 2018 American Society for Radiation Oncology annual meeting, initial data from the SABR-COMET trial were presented. This randomized phase II trial enrolled patients with a wide range of tumors extending to 5 or fewer sites. Patients were randomized to standard of care (SOC) or SOC plus SBRT for all metastatic lesions. Progression-free survival in the arm that received aggressive local management was double that of the SOC arm alone: 12 months (95% CI, 6.9-30.0 months) versus 6 months (95% CI, 3.4-7.1 months; P = .001), respectively. Importantly, no meaningful excess toxicity affecting quality of life was observed among patients who received aggressive local therapy.¹ In STOMP, a published prospective randomized multicenter trial for men with prostate cancer with a low number of metastases, the use of SBRT or metastasectomy doubled the time to next line of therapy (in this case, androgen blockade) from 13 months to 21 months. Again, it was important that quality of life was similar between arms at 3 months and 1 year, meaning that aggressive local therapy was not associated with meaningful negative adverse effects.² Follow-up for this trial is ongoing.

The data for this approach in newly diagnosed lung cancer are so strong that the National Comprehensive Cancer Network has changed its guidelines. For patients with newly diagnosed lung cancers, the guidelines now direct practitioners to aggressively manage the local disease. For example, a patient with newly diagnosed lung cancer with limited metastatic lesions (clinical trials have included 3 to 5 metastases) should have those lesions aggressively managed with SBRT, surgery, or a combination of both. The cancer team is directed to proceed thereafter with lung cancer management as if the patient were not known to have had disease spread at the start.

The data being collected in breast cancer may affect tens of thousands of women across the country. Multiple additional trials are under way. One of these, NRG-BR002, is an ongoing randomized phase IIR/III trial that compares SOC plus or minus SBRT and/or surgical ablation for newly diagnosed oligometastatic breast cancer (NCT02364557).³

Such trials are game changers for patients. At Tulane University School of Medicine’s Department of Radiation Oncology, SBRT helps our patients pursue their best possible outcomes. And for the right patient, even when the promise of possible cure is not within reach, SBRT management of active localized disease can preserve quality of life by delaying systemic therapy intensification.

References

1. Palma DA, Olson RA, Harrow S, et al. Stereotactic ablative radiation therapy for the comprehensive treatment of oligometastatic tumors (SABR-COMET): results of a randomized trial. Int J Radiat Oncol Biol Phys. 2018;102(3)(suppl):S3-S4. doi: 10.1016/j.ijrobp.2018.06.105.
2. Ost P, Reynders D, Decaestecker K, et al. Surveillance or metastasis-directed therapy for oligometastatic prostate cancer recurrence: a prospective, randomized, multicenter phase II trial. J Clin Oncol. 2018;36(5):446-453. doi: 10.1200/JCO.2017.75.4853.
3. Chmura SJ, Winter KA, Salama JK, et al. NRG BR002: a phase IIR/III trial of standard of care therapy with or without stereotactic body radiotherapy (SBRT) and/or surgical ablation for newly oligometastatic breast cancer. J Clin Oncol. 2017;33(suppl 15). doi: 10.1200/jco.2015.33.15_suppl.tps1105.