Clinical Utility of the Modified Segmental Boost Technique for Treatment of the Pelvis and Inguinal Nodes
Received 1 October 2008; received in revised form 19 February 2009; accepted 27 February 2009. published online 13 July 2009.
Purpose
Low-lying pelvic malignancies often require simultaneous radiation to pelvis and inguinal nodes. We previously reported improved homogeneity with the modified segmental boost technique (MSBT) compared to that with traditional methods, using phantom models. Here we report our institutional clinical experience with MSBT.
Methods and Materials
MSBT patients from May 2001 to March 2007 were evaluated. Parameters analyzed included isocenter/multileaf collimation shifts, time per fraction (four fields), monitor units (MU)/fraction, femoral doses, maximal dose relative to body mass index, and inguinal node depth. In addition, a dosimetric comparison of the MSBT versus intensity modulated radiation therapy (IMRT) was conducted.
Results
Of the 37 MSBT patients identified, 32 were evaluable. Port film adjustments were required in 6% of films. Median values for each analyzed parameter were as follows: MU/fraction, 298 (range, 226–348); delivery time, 4 minutes; inguinal depth, 4.5 cm; volume receiving 45 Gy (V45), 7%; V27.5, 87%; body mass index, 25 (range, 16.0–33.8). Inguinal dose was 100% in all cases; in-field inhomogeneity ranged from 111% to 118%. IMRT resulted in significantly decreased dose to normal tissue but required more time for treatment planning and a higher number of MUs (1,184 vs. 313 MU).
Conclusions
In our clinical experience, the mono-isocentric MSBT provides a high degree of accuracy, improved homogeneity compared with traditional techniques, ease of simulation, treatment planning, treatment delivery, and acceptable femoral doses for pelvic/inguinal radiation fields requiring 45 to 50.4 Gy. In addition, the MSBT delivers a relatively uniform dose distribution throughout the treatment volume, despite varying body habitus. Clinical scenarios for the use of MSBT vs. intensity-modulated radiation therapy are discussed. To our knowledge, this is the first study reporting the utility of MSBT in the clinical setting.
∗Yale University School of Medicine, Department of Therapeutic Radiology, New Haven, Connecticut
†Yale New Haven Hospital, New Haven, Connecticut and William W. Backus Hospital, Norwich, Connecticut
Reprint requests to: Meena S. Moran, M.D., Yale University School of Medicine, 333 Cedar Street, P.O. Box 208040, New Haven, CT 06520-8040. Tel: (203) 785-6384; Fax: (203) 785-4622
ABSTRACT