Stereotactic ablative body radiotherapy benefits shown in early NSCLC
medwireNews: Patients with inoperable peripherally located stage 1 non-small-cell lung cancer (NSCLC) achieve better local control and overall survival with stereotactic ablative body radiotherapy (SABR) than with standard radiotherapy, phase III study data show.
The improved outcomes occurred without an increase in major toxicity and “suggest that SABR should be the treatment of choice for this patient group,” David Ball (Peter MacCallum Cancer Centre, Melbourne, Victoria, Australia) and co-investigators remark in The Lancet Oncology.
During a median follow-up of 2.6 years, 14% of 66 patients randomly assigned to receive SABR (54 Gy in three 18 Gy fractions, or 48 Gy in four 12 Gy fractions if the tumor was <2 cm from the chest wall) experienced local disease progression according to RECIST criteria.
This compared with a local progression rate of 31% among 35 patients randomly assigned to receive standard radiotherapy (66 Gy in 33 daily 2 Gy fractions or 50 Gy in 20 daily 2.5 Gy fractions, depending on institutional preference) who were followed up for a median of 2.1 years.
And the researchers calculated that the risk for local progression was a significant 68% lower among the patients who received SABR versus standard radiotherapy.
The multicenter CHISEL trial, conducted in Australia and New Zealand, also showed that the patients in the SABR group had a significant 47% lower risk for death than those in the standard radiotherapy group, with 2-year overall survival rates of 77% and 59%, respectively, and corresponding median overall survival durations of 5 and 3 years.
Ball and team note that “[t]reatment was generally well tolerated in both groups,” and there were no significant quality of life differences reported.
There were also no treatment-related deaths, and just one grade 4 adverse event (dyspnea), which occurred in a patient who received SABR.
More patients in the SABR group experienced treatment-related grade 3 adverse events than in the standard radiotherapy group (seven vs two) but the authors point out that the cumulative time at risk was longer for SABR than for standard radiotherapy (153 vs 66 years).
In an accompanying comment, Faiez AlShafa and David Palma, both from the London Health Sciences Centre in Ontario, Canada, say that the CHISEL trial “establishes SABR as the standard radiotherapy approach in patients with stage 1 NSCLC who are not undergoing surgery.”
However, they add that “many unanswered questions remain.”
These include what the minimum technological requirements for SABR are, to aid implementation in developing countries, and also how SABR might work in combination with immunotherapy because the technique is known to trigger innate immunity.
AlShafa and Palma say: “Perhaps the immune-stimulatory effects of SABR in conjunction with immunotherapy will bring advances in the treatment of early-stage NSCLC; this combined treatment will be tested in upcoming randomised controlled trials.”
They also ask “whether SABR should be an alternative to surgical resection in patients who are operable.”
Indeed, “[p]ooled data from two incomplete randomised controlled trials, published in The Lancet Oncology, suggested that SABR might be more effective and be associated with fewer adverse events than surgery, but firm conclusions await larger trials,” the commentators remark.
By Laura Cowen
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