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Does inadequate Point-A dose warrant treatment plan modifications in CT-image-based cervix high dose-rate brachytherapy planning? A dosimetric perspective

Published online by Cambridge University Press:  07 June 2013

R. Yaparpalvi ,
K. J. Mehta ,
S. Mutyala ,
H. C. Kuo ,
L. Hong  and
S. Kalnicki
R. Yaparpalvi*
Affiliation:
Department of Radiation Oncology, Montefiore Medical Center and The Albert Einstein College of Medicine, Bronx, NY, USA
K. J. Mehta
Affiliation:
Department of Radiation Oncology, Montefiore Medical Center and The Albert Einstein College of Medicine, Bronx, NY, USA
S. Mutyala
Affiliation:
Department of Radiation Oncology, Scott & White Healthcare, Texas A&M Health Science Center, Temple, TX, USA
H. C. Kuo
Affiliation:
Department of Radiation Oncology, Montefiore Medical Center and The Albert Einstein College of Medicine, Bronx, NY, USA
L. Hong
Affiliation:
Department of Radiation Oncology, Montefiore Medical Center and The Albert Einstein College of Medicine, Bronx, NY, USA
S. Kalnicki
Affiliation:
Department of Radiation Oncology, Montefiore Medical Center and The Albert Einstein College of Medicine, Bronx, NY, USA
*
Correspondence to: Ravindra Yaparpalvi, Department of Radiation Oncology, Montefiore Medical Center, 111 East 210th Street, Bronx, New York 10467, USA. Tel: +718-920-7750. Fax: +718-882-6914. E-mail: ryaparpa@montefiore.org
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Abstract

Background and purpose

To investigate whether inadequate dose to Point-A necessitates treatment plan changes in a time of computed tomography (CT)-image-guided brachytherapy treatment planning for cervix cancer.

Materials and methods

A total of 125 tandem and ovoid insertions from 25 cervix patients treated were reviewed. CT-image-based treatment planning was carried out for each insertion. Point-A is identified and the dose documented; however, dose optimisation in each plan was based on covering target while limiting critical organ doses (PlanTarget). No attempts were made to equate prescription and Point-A dose. For each insertion, a second hypothetical treatment plan was generated by prescribing dose to Point-A (PlanPoint-A). Plans were inter-compared using dose–volume histogram analyses.

Results

A total of 250 treatment plans were analysed. For the study population, the median cumulative dose at Point-A was 80 Gy (range 70–95) for PlanTarget compared with 84·25 Gy for PlanPoint-A. Bladder and rectal doses were higher for PlanPoint-A compared with PlanTarget (p < 0·0001). Target D90 did not correlate with Point-A dose (p = 0·60).

Conclusions

Depending on applicator geometry, tumour size and patient anatomy, Point-A dose may vary in magnitude compared with prescription dose. Treatment plan modifications purely based on inadequate Point-A dose are unnecessary, as these may result in higher organ-at-risk doses and not necessarily improve target coverage.

Keywords

cervixdose prescriptionHDRpointvolume
Type
Original Articles
Information
Journal of Radiotherapy in Practice , Volume 12 , Issue 4 , December 2013 , pp. 318 - 325
Copyright
Copyright © Cambridge University Press 2013 

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