The Main Event
« Standardized planning, standardized treatment | Main | Accuray’s theatrical flourish »
Plenary session: it’s all about outcome
15.15 PDT Monday: A couple of leading-edge cancer studies stood out from the background noise here today and mapped perfectly against the conference theme of “treating cancer while preserving quality of life”. First up, the use of 4D CT to standardize the reporting of radiation dose volumes can lead to a more accurate radiation dose to the lungs when treating lung cancers - lowering the risk of lung injury in the process. That’s the conclusion of a paper presented at the plenary session this afternoon by Yixiu Kang, a radiation physicist at M D Anderson Cancer Center in Houston, TX.
Basically, 4D CT allows clinicians to measure how much a tumour moves when a patient breathes - and in turn to compensate for this motion. Trouble is, radiation doses are measured by the volume of a person’s lungs and lung volumes change during each phase of the breathing cycle. As a result, there is a substantial difference in the reporting of the amount of normal lung tissue exposed to radiation during treatment.
Kang and colleagues therefore set out to a) investigate various lung-volume definitions and their inter-relationships; b) evaluate the impact on lung dose-volume histograms (DVHs); and c) propose a population-based model for converting one lung-volume definition to another for prospective or retrospective dose reporting.
The authors believe theirs is the first study to evaluate the degree of differences that 4D CT has on dose volumes and to propose a method to standardize them for more effective radiation treatment. “We believe standardized reporting can lead to better interpretation of existing data and more accurate reporting of future studies,” noted lead author Kara Bucci, a radiation oncologist at M D Anderson. “This will lead to improved risk assessment in planning individualized patient care.”
The retrospective study involved 40 stage III/IV non-small-cell lung-cancer patients who received a 4D CT and a fast, free-breathing helical CT scan. The authors conclude: “We found large variations in reported DVH values when different lung-volume definitions were used. However, population-based relationships among different lung volumes can be used to convert DVHs into a more standardized dose-volume definition.”
Next up at the plenary session, Rene-Olivier Mirimanoff, a radiation oncologist at the Centre Hospitalier Universitaire Vaudois in Lausanne, Switzerland, answered his own question - “Is long-term survival in glioblastoma possible?” - in the affirmative.
In fact, Mirimanoff went on to explain that more than four times as many patients with a rapidly fatal type of brain cancer, glioblastoma multiforme (GBM), who are treated with a combination of the chemotherapy drug temozolomide (TMZ) and radiation therapy can live for four years after diagnosis, compared to those who receive only radiation treatment.
Previously, GBM patients typically only lived between six to 12 months after diagnosis, and there were almost no survivors beyond two years. This type of cancer accounts for 20-25% of all primary brain tumours.
Early results of the Phase III trial published in the New England Journal of Medicine in 2005 showed for the first time that twice as many GBM patients who were treated with TMZ and radiation therapy survived two years after diagnosis, compared to those who received radiation alone. The trial involved 573 patients who were randomized to receive TMZ during and after radiation therapy or radiation alone. The combination treatment immediately became the standard treatment for GBM patients worldwide.
Subsequently, the researchers extended the study to find out if patients with GBM who had this treatment plan could live more than two years. The latest results, presented today, show that 12.9% of patients who added TMZ during and after radiation treatment lived for four years compared to 3.8% of those who received radiation alone and survived the same amount of time.
Findings also show that the main group of patients who survived for four years after diagnosis was less than 50 years old and in otherwise good health without any prior major medical condition. Over one-quarter (28%) of these patients who were treated with TMZ and radiation lived for four years, versus only 7% of patients who received only radiation therapy.
The researchers conclude: “The survival advantage conferred by the addition of TMZ to RT in GBM remains highly significant with a longer follow-up, and we expect a modest but significant proportion of patients to be long-term survivors.”
Further reading
Y Kang et al. 2007 Which lung volumes to use for radiotherapy planning of lung cancer: inspiration, expiration, averaged, or free-breathing? Proc. 49th Annual ASTRO Meeting: Int. J. Radiat. Oncol. Biol. Phys. 69 3 S1.
R Mirimanoff et al. 2007 Is long-term survival in glioblastoma possible? Updated results of the EORTC/NCIC Phase III randomized trial on radiotherapy and concomitant and adjuvant temozolomide (TMZ). Proc. 49th Annual ASTRO Meeting: Int. J. Radiat. Oncol. Biol. Phys. 69 3 S2.
