ESTRO 2024 - Abstract Book

S1878

Clinical - Mixed sites, palliation

ESTRO 2024

Median age is 68.5 (50-88). Median follow-up 4 (0-22) months. Median dose to PTV, internal volume 1, and internal volume 2, in the inhomogeneous dose session were 3 (2.25-5), 9 (4-9), and 12 (6-12) Gy, respectively.

42.1% patients (n=8) had complete radiologic response, 26.3% (n=5) partial response, 15.8% (n=3) achieved radiologic stability (2 of them with only one month of follow up), and in 15.8% (n=3) of patients, response could not be assessed (two of them had intercurrent deaths a few days after the end of radiotherapy). Median percentage of volume reduction (in the patients that could be assessed) was 90% (0-100). Ten patients (52.6%) experienced complete response in the symptoms referred at the start of radiotherapy, and 8 (36.8%) partial response. Two patients (10.50%) could not be assessed (these were the patients who died intercurrently). The inhomogeneous treatment was excellently tolerated in all patients.

Conclusion:

SFRT is a useful alternative in patients with bulky disease, that permits higher doses to be delivered inside the tumour, without compromising nearby OARs, and to target radioresistant areas, allowing for better clinical and radiologic responses, that could not be achieved otherwise. Our gradient-based technique is useful in tumours that are not as voluminous as the ones targeted with traditional SFRT, with similar response rates, adapting the concept and benefit of inhomogeneous radiotherapy treatment in cases that would not necessarily benefit from geometrical spherical high dose volume placement.

It is necessary to have a longer follow-up in these patients, to be able to analyze possible late toxicities, and lasting responses in the treated areas.

Keywords: Spatially fractionated radiotherapy, bulky tumours

References: