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Stereotactic ablative radiation therapy safely improves survival in oligometastatic cancer
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Stereotactic ablative radiotherapy safely extended long-term survival for some patients with oligometastatic cancer, according to results from a prospective phase 2 trial published in International Journal of Radiation Oncology Biology Physics.
The highly precise local therapy resulted in few acute or late grade 3 toxicities.
“Despite many advances in cancer care over the last 20 to 30 years, some patients still go on to develop metastatic or stage IV disease. Generally speaking, radiation therapy in that setting has been used only to make the patient comfortable,” Dwight E. Heron, MD, director of radiation services at UPMC Hillman Cancer Center and professor of radiation oncology, otolaryngology and head and neck surgery at University of Pittsburgh School of Medicine, said in a press release. “It has also been the case, however, that a small number of patients with stage IV disease could have surgery to remove their metastases and live a long time. And so, our question was, could we use highly focused radiation to destroy these tumors and have the same effect as surgery? The initial answer from this large prospective trial is yes.”
Heron and colleagues conducted an international, multicenter trial that included 147 patients (median age, 66.4 years; interquartile range [IQR], 59.9-74.6; 51% women) with biopsy-confirmed oligometastatic or recurrent cancer.
Participants had as many as five metastases, with most having one (70.7%) or two (19%).
The most prevalent primary tumors included lung (21.8%; non-small cell, n = 29; small cell, n = 3); colorectal adenocarcinoma (21.1%); head and neck (10.9%; squamous cell carcinoma, n = 11); breast carcinoma (8.8%) and prostate adenocarcinoma (7.5%).
The most common tumor sites included lung (52.3%), lymph nodes (16.5%), bone (14.7%) and liver (6.9%). All patients had ECOG scores between 0 and 1 and life expectancy exceeding 6 months.
Patients underwent stereotactic radiotherapy at metastatic sites according to guidance from American College of Radiology and American Society for Radiation Oncology. In total, 218 lesions were treated.
Clinicians determined the radiotherapy dose and fractionation based on the size and location of the lesion, as well as the dose limitations of the organs at risk. Follow-up occurred within 6 weeks of radiotherapy completion, at 3-month intervals for 3 years, and at 6-month intervals thereafter.
Researchers assessed patient-reported quality of life through a Functional Assessment and Cancer Therapy-General questionnaire distributed at baseline and at each follow-up. Feasibility of radiotherapy for patients with oligometastatic cancers served as the study’s primary endpoint. Secondary endpoints included 5-year OS, 5-year local PFS, quality of life and toxicity.
With median follow-up of 41.3 months (IQR, 14.6-59), results showed median OS of 42.3 months (95% CI, 27.4-not reached), with 5-year OS of 43%, 5-year local PFS of 74% and 5-year distant PFS of 17%.
Primary tumor type appeared associated with OS (P = .002) and distant PFS (P = .008). Those with primary breast, prostate and colorectal tumors survived longer than those with primary lung or head and neck tumors.
Fewer than 10 percent of patients experienced short-term toxicity, including 7.5% with acute grade 2 or higher events and 2% with acute grade 3 or higher events. Only 1.4% of patients had long-term toxicity, including one case of grade 3 ureter obstruction and one case of grade 4 small-bowel obstruction.
Patients reported no significant quality of life changes at completion of therapy or at 6 weeks or 3 months after treatment. At 6 months and 12 months, however, they reported statistically significant improvement in quality of life.
“Many of the cancer treatments we deliver, even though they have a therapeutic benefit, also are associated with some toxicity, and that may impact patients’ quality of life. In this study, for patients with stage 4 disease, we have a treatment paradigm that can result in long-term survival while maintaining overall quality of life,” Heron said. “We had a sense this was the case from retrospective data, but the addition of prospective data is very convincing.”
The trial supports an increasing body of evidence in favor of stereotactic radiotherapy for oligometastatic cancers. The therapy also showed potential to lengthen survival among patients with stage IV disease in two randomized, phase 2 trials presented at the most recent ASTRO Annual Meeting. Larger randomized trials may further validate the use of this treatment for patients with oligometastatic cancers.
“In combination with immunotherapy, stereotactic radiation therapy may set a new bar for achieving better outcomes, lowering side effects and improving our patients’ quality of life,” Heron said. – by Jennifer Byrne
Disclosures: The researchers report no relevant disclosures.
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