Impact of Clinical Factors and RT-induced Lymphopenia on Risk of
Disease Recurrence
Sixteen of 54 (30%) patients developed a recurrence at an average of
30.2 months after diagnosis. As expected, patients with M+ disease had a
significantly increased risk of disease recurrence (log-rank p=0.0004;
Cox p=0.001). Table 2 demonstrates the impact of clinical
factors and RT-induced lymphopenia on the risk of disease recurrence.
There was a higher risk of disease recurrence (lower RFS) in patients
with grade 3 or lymphopenia during weeks 4 (log-rank p=0.015; Cox
p=0.03) and 5 (log-rank p=0.0009; Cox p=0.004) of RT (Fig. 3 ).
When considering the RFS of patients with ALC above or below the median
during weeks 4 and 5 of RT, there was a significant difference during
week 5 (log-rank p=0.0026; Cox p=0.002) (Fig. 4B ) but not
during week 4 (log-rank p=0.123; Cox p=0.22) (Fig. 4A ). These
results all held true when adjusted for risk group (Table 2 ).
No correlation was found between risk of tumor recurrence and early
lymphopenia (RT weeks 0-3) either when measured as CTCAE grade or as
median ALC. Additionally, there was not a statistically significant
difference between RFS in patients treated with proton compared to
photon RT (Cox p=0.09) (Supplemental Fig. 1 ) or based on sex
(Cox p=0.810).