Targeted radiotherapy trialled

Behind the Headlines

Friday December 18 2009

Lymphoma cancer cells

A “radioactive bullet cancer treatment” will offer hope to cancer sufferers according to The Daily Telegraph.

The story comes from research into a form of targeted radiotherapy combining radioactive substances with antibodies that will latch onto cancerous cells. In a preliminary trial 15 patients with treatment-resistant lymphoma were given the radioactive antibodies, with seven showing a positive response. Although the purpose of this small study was to establish safe and appropriate doses to use in future research, it is not clear whether this treatment will be a safe or effective alternative to conventional treatments.

While this research will be of interest to many, it is early stage research only. Conclusive effectiveness and safety data from future research are required to determine whether this therapy has potential to treat lymphomas that have not responded to other treatments.

 

Where did the story come from?

This research was conducted by Gairin Dancey and colleagues of Cancer Research UK and other London-based universities and institutions. The study was published in Cancer Therapy, the peer-reviewed medical journal. Financial support included a grant from Cancer Research UK.

The Daily Telegraph has generally reported this research well, making it clear that this is only a small pilot study involving 15 people and that more research is needed.

 

What kind of research was this?

This was a small non-randomised phase I trial investigating a new treatment for lymphoma (T-cell and Hodgkin’s lymphoma) in certain patients who had not responded to treatment because their cancer was drug resistant.

The treatment under investigation was a form of radioimmunotherapy. This is a relatively new technique that uses the immune system to deliver radiotherapy.

Conventional radiotherapy works on the principle that radiation can damage and kill cancerous cells, but, unfortunately, this radiation can also damage the body’s healthy cells. Radioimmunotherapy is based on the idea that radiation can be delivered in a targeted way. It does this by attaching a radioactive substance to a molecule that attaches itself to receptors found only on the surface of some cancerous cells.

In this case, radioactive iodine was attached to the CHT-25 antibody that targets the CD25 cell receptor. The treatment is designed for use in people who have CD25-receptor-positive lymphomas and who have not responded to other treatments.This pilot was extremely small, involving only 15 patients. All patients in the trial were treated with radioimmunotherapy, with no groups receiving other treatments to provide a comparison. Future randomised control trials will be needed in the form of phase II and III trials involving larger population groups. Only when these trials provide effectiveness and safety data will it be known whether this experimental treatment has the potential to be used in the clinical treatment of lymphomas that have not responded to other therapies.

 

What did the research involve?

The study enrolled 15 adults aged 18 or over who had CD25-positive lymphoma (12 with Hodgkin’s lymphoma, one with angioimmunoblastic T-cell lymphoma and two with adult T-cell leukaemia/lymphoma). Those selected for the trial had to have at least a three-month life expectancy and no other serious medical illnesses. Any prior chemotherapy or radiotherapy had to have been completed at least four weeks before infusion of the radioactive CHT-25 antibody. Doses were increased as required.

The main purpose of the study was to determine dosage and safety levels for the therapy. The specific aspects assessed were:

  • Dose-limiting toxicity: the maximum dose before serious haematologic toxicity (blood problems) or adverse effects of treatment were observed in any person
  • Maximum tolerated dose: the dose at which toxic or adverse effects started to occur in at least half of the people treated
  • Pharmacokinetic actions of the treatment: what happens to a substance when it enters the body, where it travels and how it breaks down or leaves the body.

Secondary objectives were to assess tumour response (monitored radiologically) and immune response.

 

What were the basic results?

None of the 15 people treated experienced a severe reaction when the intravenous infusion of the antibody was given. At the maximum tolerated dose the major adverse effects were suppression of white blood cells and blood platelets used in clotting. The lowest platelet and white cell counts occurred at 38 and 53 days, respectively, after the start of treatment.

One patient treated with a dose more than double the maximum tolerated dose developed prolonged, serious low levels of white blood cells and platelets and died of pneumonia. Aside from blood-related adverse effects, other toxic effects to the body were mild. Radiological scans showed that the antibodies were being taken up by tumour cells only, with no excess uptake by normal organs.

Of nine patients who received at least the maximum tolerated dose, six responded to treatment, with three complete responses and three partial responses. Of six patients who received considerably less than the maximum tolerated dose, one had a complete response to treatment.

 

How did the researchers interpret the results?

The researchers concluded that CHT-25 is well tolerated, with treatment at the maximum tolerated dose showing clinical activity in patients who have not responded to conventional therapies. They say there is justification for phase II studies to determine efficacy and toxicity in a wider range of patients.

 

Conclusion

This study investigated the use of a radioactive antibody to treat patients with a CHT-25 receptor-positive lymphoma who have not responded to conventional treatments. The primary aim of this study in 15 people was to find appropriate dosage levels for treatment. As such it involved no comparison groups. All results should be interpreted in the correct context as early stage research only.

Although seven of the patients responded to treatment, some toxic effects of treatment did occur, mostly related to a drop in white blood cell count and blood platelets. Also, at this early stage of research all patients in the study were treated with radioimmunotherapy only, meaning its safety and effectiveness were not compared to other treatments. In order to assess this, a randomised control trial is needed as part of phase II and III trials involving larger population groups.

Only when more conclusive effectiveness and safety data have been obtained will it be clear whether this treatment has potential for use against treatment-resistant lymphomas.

Analysis by Bazian

Edited by NHS Choices

Links to the headlines

'Radioactive bullet' cancer treatment offers hope to cancer sufferers. The Daily Telegraph, December 16 2009

Links to the science

Dancey G, Violet J, Malaroda A et al. A Phase I Clinical Trial of CHT-25 a 131I-Labeled Chimeric Anti-CD25 Antibody Showing Efficacy in Patients with Refractory Lymphoma. Clinical Cancer Research December 2009 15; 7701

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