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Purpose Radiation therapy (RT) improves control of Hodgkin lymphoma (HL), but patients who undergo RT are at risk for late effects, including cardiovascular disease and second cancers, because of radiation doses to organs at risk (OARs). Proton therapy (PT) can reduce OAR doses compared with conventional photon RT. However, access to PT is currently limited, so referrals must be appropriately selective. We aimed to identify subgroups of patients with HL who could benefit the most dosimetrically from RT with PT based on the prechemotherapy disease characteristics. Methods and materials Normal tissue radiation doses were calculated for 21 patients with HL who were treated with deep-inspiration breath-hold pencil-beam scanning (PBS) PT and compared with doses from 3-dimensional conformal (3D-CRT) and partial arc volumetric modulated (PartArc) photon RT. Prechemotherapy disease characteristics associated with significant dosimetric benefits from PBS compared with photon RT were identified. Results Treatment with PBS was well tolerated and provided with good local control. PBS provided dosimetric advantages for patients whose clinical treatment volume extended below the seventh thoracic level and for female patients with axillary disease. In addition, an increasing dosimetric benefit for some OARs was observed for increasing target volume. PBS significantly reduced the mean dose to the heart, breast, lungs, spinal cord, and esophagus. Dose homogeneity and conformity within the target volume were also superior with PBS, but some high-dose measures and hot spots were increased with PBS compared with partial arc volumetric modulated photon RT. Conclusions PBS gives good target coverage and local control while providing reductions in radiation dose to OARs for individuals who receive RT for HL compared with advanced photon RT. Our findings highlight groups of patients who would be expected to gain more dosimetric benefit from PBS. These findings facilitate the selection of patients who should be considered a priority for PT.

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The prognostic value of positron emission tomography (PET) in early therapy response assessment, after completion of chemotherapy and 3 months after the end of treatment in advanced Hodgkin lymphoma (HL) remains to be defined. We report the results of 69 patients with first presentation of advanced HL. [18F]-fluoro-2-deoxy-d-glucose (FDG)-PET scan was performed after four cycles (PET-4), on completion of chemotherapy after 6/8 cycles (PET-6/8) and 3 months after the completion of chemotherapy (PET 3-months). Median follow-up was 55 months. The negative predictive value (NPV) for PET-4, PET-6/8 and PET 3-months was 98%, 95% and 97%, respectively. The 4-year progression-free survival (PFS) for PET-4 negative (n = 51) and PET-4 positive (n = 18) patients was 96% and 78%, respectively (p = 0.016). The 4-year PFS for PET-6/8 negative (n = 59) and PET-6/8 positive (n = 9) patients was 95% and 78%, respectively (p = 0.046). Patients with a large mediastinal mass constituted nearly all of the PET-4 positive (16/18) and PET-6/8 positive (8/9) patients. After radiotherapy of PET-6/8 positive patients, PET 3-months was negative in 64 (97%) and positive in two (3%) patients. PET 3-months after the end of chemotherapy was of limited value when the interim PET-4 was negative. Interim PET after four cycles of bleomycin, etoposide, adriamycin, cyclophosphamide, vincristine, procarbazine and prednisone (BEACOPP) is a strong prognostic marker for PFS in advanced HL.