Consolidative involved-node proton therapy for Stage IA-IIIB mediastinal Hodgkin lymphoma: preliminary dosimetric outcomes from a Phase II study.
OBJECTIVE
To compare the dose reduction to organs at risk (OARs) with proton therapy (PT) versus three-dimensional conformal radiotherapy (3D-CRT) and intensity-modulated radiotherapy (IMRT) in patients with mediastinal Hodgkin lymphoma (HL) enrolled on a Phase II study of involved-node radiotherapy (INRT).


METHODS
Between June 2009 and October 2010, 10 patients were enrolled on a University of Florida institutional review board-approved protocol for de novo "classical" Stage IA-IIIB HL with mediastinal (bulky or nonbulky) involvement after chemotherapy. INRT was planned per European Organization for Research and Treatment of Cancer guidelines. Three separate optimized plans were developed for each patient: 3D-CRT, IMRT, and PT. The primary end point was a 50% reduction in the body V4 with PT compared with 3D-CRT or IMRT.


RESULTS
The median relative reduction with PT in the primary end point, body V4, was 51% compared with 3D-CRT (p = 0.0098) and 59% compared with IMRT (p = 0.0020), thus all patients were offered treatment with PT. PT provided the lowest mean dose to the heart, lungs, and breasts for all 10 patients compared with either 3D-CRT or IMRT. The median difference in the OAR mean dose reduction with PT compared with 3D-CRT were 10.4 Gy/CGE for heart; 5.5 Gy/CGE for lung; 0.9 Gy/CGE for breast; 8.3 Gy/CGE for esophagus; and 4.1 Gy/CGE for thyroid. The median differences for mean OAR dose reduction for PT compared with IMRT were 4.3 Gy/CGE for heart, 3.1 Gy/CGE for lung, 1.4 Gy/CGE for breast, 2.8 Gy/CGE for esophagus, and 2.7 Gy/CGE for thyroid.


CONCLUSIONS
All 10 patients benefitted from dose reductions to OARs with PT compared with either 3D-CRT or IMRT. It is anticipated that these reductions in dose to OAR will translate into lower rates of late complications, but long-term follow-up on this Phase II INRT study is needed.
University of Florida Proton Therapy Institute, Jacksonville, FL, USA. bhoppe@floridaproton.org
Bradford S
BS
Hoppe
Stella
S
Flampouri
Zhong
Z
Su
Christopher G
CG
Morris
Naeem
N
Latif
Nam H
NH
Dang
James
J
Lynch
Zuofeng
Z
Li
Nancy P
NP
Mendenhall
D000293:Adolescent; D000328:Adult; D001940:Breast / Q000528:radiation effects; D004947:Esophagus / Q000528:radiation effects; D005260:Female; D006321:Heart / Q000528:radiation effects; D006689:Hodgkin Disease / Q000473:pathology / Q000532:radiotherapy*; D006801:Humans; D008168:Lung / Q000528:radiation effects; D008297:Male; D008479:Mediastinal Neoplasms / Q000473:pathology / Q000532:radiotherapy*; D058958:Organs at Risk / Q000528:radiation effects*; D011446:Prospective Studies; D061766:Proton Therapy; D011832:Radiation Injuries / Q000517:prevention & control*; D011879:Radiotherapy Dosage; D011880:Radiotherapy Planning, Computer-Assisted / Q000379:methods; D020266:Radiotherapy, Conformal / Q000009:adverse effects / Q000379:methods; D050397:Radiotherapy, Intensity-Modulated / Q000009:adverse effects / Q000379:methods; D013961:Thyroid Gland / Q000528:radiation effects; D047368:Tumor Burden; D055815:Young Adult; D011522:Protons
D011522:Protons