The data show that "major de-escalation" of radiotherapy in elective regions is "feasible while maintaining locoregional tumor control," researchers report in JAMA Oncology.
Beginning in March 2017, Memorial Sloan Kettering Cancer Center in New York adopted a de-escalation strategy for patients with HPV-positive OPC undergoing CCRT, comprised of a lower radiotherapy dose to elective nodal and subclinical regions, while sparing selected negative neck, retropharyngeal, level Ib and level V nodal basins.
In their retrospective study, Dr. C. Jillian Tsai and colleagues assessed the impact of these changes in 276 patients with locally advanced HPV-positive OPC consecutively treated with CCRT from 2017 to 2019.
All patients received reduced radiotherapy volume and dose of 30 Gy to the elective treatment regions over 15 fractions, followed by a cone down of 40 Gy in 20 fractions to gross disease for a total dose of 70 Gy.
At a median follow-up of 26 months, only eight patients (3%) had a locoregional recurrence; one recurrence was in the 30-Gy dose region, which turned out to be a node not previously identified as gross disease. The other seven recurrences occurred within a region that received a total dose of 70 Gy.
The de-escalation strategy was associated with 24-month locoregional control rate of 97%, progression-free survival rate of 88 %, distant metastasis-free survival rate of 95% and an overall-survival rate of 95.1%, report Dr. Tsai and colleagues.
The de-escalation strategy was associated with several favorable toxicity metrics, including feeding-tube placement, which was required by 17 patients (6%), and quality-of-life outcomes.
"Long-term follow-up data will help affirm the efficacy of this strategy as a care option for treating HPV-associated OPC with primary CCRT," the researchers say.
The authors of a linked editorial say the data are "encouraging but are still hypothesis-generating; the concept of substantially reducing elective dosing should be further integrated into prospective trial design."
Dr. Philip Schaner of Dartmouth-Hitchcock Medical Center, in Hanover, New Hampshire, and Dr. Raci Chandra of Oregon Health & Science University, in Portland, add, "It is still unclear how to select the best option from among the many strategies investigating additional modes of de-escalation, such as the use of tailored induction and other systemic therapies for cytoreduction, of biomarkers (eg, circulating tumor DNA), and of imaging (eg, fluoromisonidazole for hypoxia), as well as of adaptive and particle therapy."
"More data are needed to determine which patients may safely undergo de-escalation using these different strategies and which patients would benefit from varying degrees of deintensification," they caution.
SOURCE: https://bit.ly/35dovVE and https://bit.ly/3AvJYEZ JAMA Oncology, online January 20, 2022.
By Reuters Staff
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