130P - Radiation induced lymphopenia (RAILs on time saves nine): In carcinoma esophagus

Background

In carcinoma esophagus patients where large volumes of lymphocyte producing organs and organs with circulating lymphocytes are exposed to radiation field, Radiation induced lymphopenia (RIL) is quite profound. Absolute Lymphocyte Count (ALC) has been postulated to have a crucial impact on treatment outcomes.In this study, dosimetric analysis on the organs at risk (OARs) for lymphopenia and its effect on pathological complete response (PCR) was assessed.

Methods

Carcinoma Esophagus patients who underwent neoadjuvant chemo-radiotherapy(NACT-RT) and definitive surgery from December 2018 to March 2021 were studied retrospectively. Data collected included baseline and weekly ALC, PCR on histopathology, mean dose (Dmean) and volume based dosimetry of the OARs for lymphopenia (thoracic vertebrae, bilateral lungs, liver, heart and spleen) and the effective dose to the circulating lymphocytes (EDIC), calculated using the formulae 0.12 (Dmean lung) + 0.08 (Dmean heart) + [0.45+ 0.35x 0.85(no of fractions/45ˆ1/2] Dmean body. PCR rates were correlated with ALC using Spearman’s correlation. Dosimetric parameters and EDIC was correlated with ALC using Pearson’s correlation test (p value<0.05).

Results

33 patient’s data who were eligible for the study was analysed. On Pearson’s correlation test the thoracic vertebrae Dmean (p-0.008) and V15 (p-0.012), liver Dmean (p-0.034) and V20 (p-0.038), heart Dmean (p-0.013) and V15 (p-0.022), spleen Dmean (p-0.040) were found to have significant correlation with ALC nadir. The mean EDIC was 6.21 (SD±5). No significant correlation between EDIC and ALC nadir was identified. 5% of patients did not achieve PCR at surgery. Spearman’s correlation test did not show a significant correlation between PCR and ALC nadir.

Conclusions

RIL has been demonstrated to have a negative impact on treatment outcomes. In our study, we discovered that dosimetric parameters of Dmean and volume based analysis of the OARs for lymphopenia were strongly correlated with ALC Nadir. Statistically significant correlation between ALC nadir and PCR rates was not seen. A larger multicentric study with a large number of patients, however, may be required to statistically prove our hypothesis.

Clinical trial identification

Editorial acknowledgement

Legal entity responsible for the study

The authors.

Funding

Has not received any funding.

Disclosure

All authors have declared no conflicts of interest.