This study aimed to evaluate the outcomes of local radiotherapy (LRT) in patients with histologic transformation (HT) following rituximab-containing chemotherapy.
We retrospectively analysed 92 patients with biopsy-confirmed HT undergoing rituximab-containing chemotherapy at our institution between 2003 and 2015.
Of the 36 patients with limited-stage disease at diagnosis of HT, 29 (78%) received LRT. The estimated 5-year progression-free survival (PFS) rate was significantly better in patients who underwent LRT than in those who did not (93% and 42%, respectively; P < 0.05). Multivariate analyses employing age, sex, performance status, LRT, and treatment response demonstrated that LRT was an independent prognostic factor for PFS (Hazard ratio [HR]: 11.8; 95% confidence interval [CI]: 1.28-108.1; P < 0.05). Of the 32 patients who underwent LRT for HT lesion treatment, 31 (97%) did not show disease progression within radiation fields; among them, 27 patients (84%) survived without disease progression during the follow-up period. One patient developed hypothyroidism due to LRT; the others had no acute or late-onset complications of LRT.
Our data support the recommendation of LRT for HT lesion treatment following rituximab-containing chemotherapy in select patients with localised HT, as a rational treatment approach with potentially limited toxicity.

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