gms | German Medical Science

48th Meeting of the Particle Therapy Co-Operative Group

Particle Therapy Co-Operative Group (PTCOG)

28.09. - 03.10.2009, Heidelberg

Proton radiotherapy: is “batched” field delivery botched field delivery?

Meeting Abstract

Suche in Medline nach

  • M. Engelsman - Radiation Oncology, Massachusetts General Hospital and Harvard Medical School, Boston, USA
  • T. DeLaney - Radiation Oncology, Massachusetts General Hospital and Harvard Medical School, Boston, USA
  • T. Hong - Radiation Oncology, Massachusetts General Hospital and Harvard Medical School, Boston, USA

PTCOG 48. Meeting of the Particle Therapy Co-Operative Group. Heidelberg, 28.09.-03.10.2009. Düsseldorf: German Medical Science GMS Publishing House; 2009. Doc09ptcog056

DOI: 10.3205/09ptcog056, URN: urn:nbn:de:0183-09ptcog0564

Veröffentlicht: 24. September 2009

© 2009 Engelsman et al.
Dieser Artikel ist ein Open Access-Artikel und steht unter den Creative Commons Lizenzbedingungen (http://creativecommons.org/licenses/by-nc-nd/3.0/deed.de). Er darf vervielfältigt, verbreitet und öffentlich zugänglich gemacht werden, vorausgesetzt dass Autor und Quelle genannt werden.


Gliederung

Text

Purpose: It is common practice in proton radiotherapy to deliver only a subset of all fields in the treatment plan on any given treatment day (“batched” field delivery). This results in variation in the daily dose to normal tissues which may have a detrimental biological effect. We analyze this effect for a small group of representative patients for each of four cancers commonly treated with proton radiotherapy; prostate, chordoma of the skull base and cervical spine, pancreas and lung.

Methods and materials: The cumulative normalized total dose (NTD) was determined for normal tissues of each patient using the exact fractionation schedule documented in our record and verify system (FSclin). This was compared to hypothetical fractionation schedules delivering all fields every day (FSall) or only a single field each day (FSsingle).

Results: In general the increase in biologically corrected dose to the normal tissues because of batched field delivery is non-negligible but small and often most visible in those regions of the dose-volume histogram (DVH) that are not clinically significant. For prostate treatments, FSall would reduce the NTD of the femoral heads by 9 Gy, from 29 Gy to 20 Gy. Both values are well below the tolerance level of 52 Gy. For the chordoma group, the largest effect is a 3 Gy reduction in cochlear dose, from 26 Gy to 23 Gy. The lung cancer patients show negligible variation for the NTD of the heart and the lungs, even when delivering only a single field (out of three fields) every day. For the pancreas tumors, variations in the DVH of the normal tissues outside of the high dose region are most obvious in 5-15 Gy dose range. Use of FSsingle always resulted in the highest dose to the normal tissues. For all patient groups, except the femoral head for prostate treatments, typically the difference between FSall and FSclin, and between FSclin and FSsingle was limited to within a few Gy.

Conclusion: Batched field delivery is already widely applied in many proton radiotherapy institutes. It allows the application of proton radiotherapy to many more patients at the cost of an acceptable increase in normal tissue doses to each patient. For accurate determination of dose-effect relations, it is beneficial to consider the effect of batched field delivery prior to submission of DVHs to internal or external data centers.