British Journal of Radiology (2005) 78, 672-673
© 2005 British Institute of Radiology
doi: 10.1259/bjr/12790920
BJR Review of the Year 2004
The Editor—Sir,
May we first applaud this latest innovation of the British Journal of Radiology to publish a review of the year [1]. With so many journals and so many papers, it is not difficult for the individual to miss one or more of the significant developments of the year. However, we feel obliged to point out a most misleading comment on intensity-modulated radiotherapy (IMRT) in the section on Oncology, which is all the more unfortunate because it's in such a widely read review. The comment was as follows:
"In a short, but chilling, paragraph Guerrero and Nutting [2] mention that the whole body equivalent dose is nearly 2000 mSv for IMRT and less than 250 mSv for conventional treatment. This could translate into an eightfold increase in radiation-induced cancers."
There are three points to be made:
- A reader who looks up the original review paper by Guerrero and Nutting [2] will find that this is not an estimate made by the authors themselves, but a quote from a much earlier paper by Verellen and Vanhavere [3]. This paper does not refer to IMRT as commonly used today, but to a rare technique generally referred to as Tomotherapy, since it involves a slice-by-slice arc rotation approach. Tomotherapy leads to a huge increase in monitor units (MU), over conventional treatment by a factor of almost 6 (3630 MU per 2 Gy dose compared with 585 MU per 2 Gy dose). This is quite different to the more widely used IMRT technique, involving perhaps 6 to 9 fields, which results in a more modest increase in monitor units by a factor of 2 to 3 [4, 5].
- To translate dose to cancer risk, Verellen and Vanhavere [3] used the ICRP 60 value of 5 x 10–2 Sv–1 for the risk of cancer. This is an average value for a general population of all ages [6]. It is too high for most radiotherapy patients, who are old and for whom 1 or 2 x 10–2 Sv–1 is more appropriate, and much too low for paediatric cases where 10 to 15 x 10–2 Sv–1 would be more appropriate.
- The "short chilling paragraph" referred to in the Review is, in fact, half a paragraph. In the paper by Guerrero and Nutting [3], the other half of the paragraph on IMRT quotes the much later estimate by Hall and Wuu [7] that IMRT might double the risks of second cancers from radiotherapy from 1% to 2%. Less chilling, but probably more realistic!
Yours etc.,
E J Hall
and
C-S Wuu
Center for Radiological Research, and the Department of Radiation Oncology, Columbia University Medical Center, New York, NY, USA
Received for publication March 28, 2005.
Accepted for publication April 15, 2005.
References
- Editorial. BJR Review of the Year – 2004. Br J Radiol 2005;78:181–5.[Free Full Text]
- Guerrero Urbano MT, Nutting CM. Clinical use of intensity-modulated radiotherapy: part II. Br J Radiol 2004;77:177–82.[Abstract/Free Full Text]
- Verellen D, Vanhavere F. Risk assessment of radiation-induced malignancies based on whole-body equivalent dose estimates for IMRT treatment in the head and neck region. Radiother Oncol 1999;53:199–203.[Medline]
- Williams PC, Hounsell AR. X-ray leakage considerations for IMRT. Br J Radiol 2001;74:98–102.[Free Full Text]
- Followill D, Geis P, Boyer A. Estimates of whole-body dose equivalent produced by beam intensity conformal therapy. Int J Radiat Oncol Biol Phys 1997;38:667–72.[Medline]
- International Commission on Radiological Protection: Recommendations. Report No. 60. New York: Pergamon Press, 1991.
- Hall EJ, Wuu CS. Radiation-induced second cancers: the impact of 3D-CRT and IMRT. Int J Radiat Oncol Biol Phys 2003;56:83–8.[CrossRef][Medline]
Related articles in BJR:
- Author's reply
- A J Munro
BJR 2005 78: 673.
[Full Text]
