Dosimetric and Clinical Outcomes With Intensity Modulated Radiation Therapy After Chemotherapy for Patients With Early-Stage Diffuse Large B-cell Lymphoma of Waldeyer Ring.

Purpose: To assess the dosimetric benefit, prognosis, and toxicity of intensity modulated radiation therapy (IMRT) for early-stage, diffuse large B-cell lymphoma of Waldeyer ring (WR-DLBCL).

Methods And Materials: Sixty-one patients with early-stage WR-DLBCL who received chemotherapy followed by IMRT were retrospectively reviewed. Dosimetric parameters for the target volume and critical normal structures were evaluated, and survival was calculated. Linear regression analysis was used to assess the effect of the mean dose (Dmean) to the parotid glands on xerostomia.

Results: The median conformity index and homogeneity index of the planning target volume (PTV) were 0.83 and 0.90, respectively, demonstrating very good coverage of the target volume. The mean dose to the parotid glands was 24.9 Gy. The 5-year overall survival (OS), progression-free survival (PFS), and locoregional control (LRC) were 94.7%, 93.1%, and 98.3%, respectively. Early and late toxicities were mild, and no patient experienced late grade ≥3 toxicities. The Dmean to the parotid glands had a linear correlation with late grade ≥2 xerostomia.

Conclusions: IMRT after chemotherapy can provide excellent dose conformity and achieve favorable survival and LRC with mild toxicities in patients with early-stage WR-DLBCL. Dose constraints for the parotid glands should be limited to <24 Gy for early-stage WR-DLBCL.