KEY POINTS
- This retrospective health-system cohort included 2,002 patients treated with palliative RT between 2012 and 2024. The three institutional regimens were 8 Gy in 1 fraction, 20 Gy in 5 fractions, and 30 Gy in 10 fractions; patients receiving brain RT were excluded.
- Baseline lymphopenia was already present in 877 patients (43.8%). After palliative RT, 1,580 patients (79%) were lymphopenic, including 743 with grade 3–4 lymphopenia; among 1,125 patients without baseline lymphopenia, 748 developed it after RT.
- Lymphocyte depletion increased with treatment length. Median absolute lymphocyte count change was −0.27 after 8 Gy/1, −0.49 after 20 Gy/5, and −0.66 after 30 Gy/10 (p<0.01).
- After multivariable adjustment, 20 Gy/5 was associated with 1.85-fold higher odds of developing lymphopenia versus 8 Gy/1 (95% CI 1.41–2.44), while 30 Gy/10 was associated with 3.12-fold higher odds (95% CI 2.19–4.43).
- The pattern was not explained simply by lower baseline counts: median pretreatment ALC actually increased across the three regimens (1.04, 1.10, and 1.30, respectively), whereas post-treatment values fell to 0.70, 0.60, and 0.50.
- Treatment site did not significantly alter lymphocyte decline when bone/spine irradiation was compared with other sites (p=0.09). Concurrent systemic therapy was independently associated with greater odds of lymphopenia (OR 1.45).
CLINICAL TAKEAWAY
Shorter palliative RT schedules may be relatively lymphocyte-sparing, adding another potential argument for avoiding unnecessarily prolonged treatment courses. However, regimen selection was non-randomized and strongly influenced by clinical factors, so these data should not by themselves drive fractionation decisions.
SOURCE
International Journal of Radiation Oncology, Biology, Physics