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. 2025 Jun;23(2):236-245.
doi: 10.1111/vco.13050. Epub 2025 Mar 15.

Half-Body Radiation Therapy Results in a Prolonged Progression-Free Interval in Canine High-Grade Lymphoma After First Remission

Yen-Hao Erik Lai  1   2 , Sarah Lyles  3 , Mark Mitchell  1 , Jayme Looper  1
Affiliations

Half-Body Radiation Therapy Results in a Prolonged Progression-Free Interval in Canine High-Grade Lymphoma After First Remission

Yen-Hao Erik Lai et al. Vet Comp Oncol. 2025 Jun.

Abstract

An optimal protocol of adding wide-field irradiation to multi-agent chemotherapy for dogs with lymphoma has not been established. The aim of this retrospective case-control study was to evaluate the efficacy of a protocol combining chemotherapy and half-body irradiation (HBI) for dogs with high-grade lymphoma. Dogs in the treatment group received cranial HBI 2 weeks after completing the second cycle of the multi-agent chemotherapy protocol. The radiation therapy protocol consisted of 4 Gy/fraction once per day for 2 consecutive days for the cranial half body, followed by the same protocol for the caudal half 2 weeks later. The control group only received multi-agent chemotherapy. All patients were required to have cytological confirmation of high-grade lymphoma and achieve complete remission after two cycles of multi-agent chemotherapy. Fourteen patients receiving HBI and 11 patients in the control group were included. The median progression-free interval (PFI) in the HBI group (1143 days) was significantly longer than that in the control group (316 days, p = 0.004). In the HBI group, dogs with T cell lymphoma had statistically shorter PFI (292 days) than dogs with B cell lymphoma (2127 days, p = 0.0013). The median survival time in the HBI group (1924 days) was significantly longer than that in the chemotherapy-only group (566 days, p = 0.0077). The predictive factors for longer PFI and ST were found in the patients who received HBI and chemotherapy (p = 0.0062 and 0.0252, respectively). For chemotherapy-responding patients that completed a multi-agent protocol, HBI significantly prolonged the time to tumour relapse compared with the chemotherapy-only group.

Keywords: canine lymphoma treatment; case–control study; chemotherapy responders; combination therapy; lymphoma radiation; novel half body radiation therapy protocol.

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Conflict of interest statement

The authors declare no conflicts of interest.

Figures

FIGURE 1
FIGURE 1
Neutrophil count (A) and platelet count (B) after cranial half body radiation. The curve represented the mean with the error bar depicting SD. The individual dots represent neutrophil or platelet count from a dog. The dashed line indicated the level of grade 2 neutropenia (1500/ μL) and grade 3 thrombocytopenia (50 k/μL).
FIGURE 2
FIGURE 2
Kaplan–Meier curves of progression‐free interval (PFI) and overall survival time (ST). (A) The median PFI in HBI compared is significantly longer than that of the control group. (B) Within the HBI group, dogs with T cell lymphoma had a significantly shorter median PFI than dogs with B cell lymphoma. (C) The median ST in HBI is significantly longer than that of the control group. (D) The median ST was statistically longer in B cell lymphoma than in T cell lymphoma within the HBI group. The tick marks represent censored data. p values represent univariate log rank values.
See this image and copyright information in PMC

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