European Multidisciplinary Conference in Thoracic Oncology (EMCTO) 2013

Treating peripheral lung tumours with SABR

Dr Suresh Senan - VU University Medical Center, Amsterdam, the Netherlands

Suresh, you’ve been reviewing the literature on a relatively new technique. It’s not new in one aspect of lung cancer but it is new in centrally located tumours in fairly early lung cancer. Can you tell me what it is that you’ve been doing?

What is well established is that SABR for peripheral lung tumours is a very effective local treatment which has been shown to improve population survival. But for central tumours, some experience in North America suggests that it’s dangerous to do it in three fractions.

So you’re zapping the tumour but there is a danger, isn’t there, that you could damage other tissues?

It’s very high precision treatment but you could damage normal tissue when it’s in close proximity to major blood vessels or large airways. So what we have been doing in Europe and many other countries is to do the same precision treatment but in five to eight fractions of radiation. We did a systematic review of the literature to assess outcomes in about 500 patients with such treatments.

You’ve been reviewing studies of centrally located tumours treated with radiation. Can you tell me what happened?

The systematic review suggested that when one uses a more gentle dose fractionation scheme with lower doses each time and spread over a number of fractions, as opposed to three times for peripheral lung tumours, the chance of a local control or cure is more than 85%. If one tailored the doses to the normal organs the chances of serious damage was less than 9% so making it an attractive option for unfit patients who may not be able to come for many visits.

And in non-small cell lung cancer getting a tumour early does have a potential for cure, doesn’t it? A great potential.

But the tumours which are located centrally are often larger than those tumours which are located far away. The second point is if a patient is unfit for the standard therapies which are surgery or chemoradiotherapy because of a central tumour then central SABR becomes a treatment option. So we know now that it’s safe if you limit the normal tissue doses and that was the main conclusion of the systematic review.

So what is the data so far for the efficacy of this technique?

The pooled data, and it is very heterogeneous – varying techniques, varying quality of reporting – suggests that in about 15% it tends to come back in the treatment area but in about 85% it provides durable local control which means a cure.

Diagnosis is an issue, though, isn’t it? Is diagnosis difficult for this situation?

It remains a challenge. There are some countries where SABR is only performed after histological diagnosis and the other countries like the Netherlands where they have experience with CT scans and PET scans and when you look at the likelihood of it not being cancer then the same patient goes to surgery. It’s only about 6% or so. So we have patients evaluated by the same tumour boards going on to surgery, so if you look at the performance of the tumour boards in anticipating the risk of the cancer you can extrapolate what it would have been in a patient without a tissue diagnosis. So it’s an indirect proof but it’s not absolute proof, you’re right.

Do you see this, then, as a direct competitor for surgery?

Not for central tumours exactly because the standard treatments remain surgery and, if the patient is unfit, it’s chemo-radiotherapy because many of these central tumours by definition are not early stage. They’re T2, T3s with high risk of occult lymph node metastases. But we know that in the past about a quarter of patients with lung cancer were simply not treated, even if they had early stage, simply because patients were not fit; they’re growing older, they have more comorbidity. So this offers a treatment option for a group of patients who are not very fit.

Overall though, how much of a difference do you think this could make in remission rates and cure?

Potentially very significant because the average age of patients getting cancer is more than 70 and with the aging population we’re going to see increasingly frail people who cannot tolerate surgery or aggressive chemo-radiotherapy. This offers a good option to them. We’re also waiting for prospective studies in North America which are evaluating histology proven patients and trying to do it in five fractions. So that could in future even be more attractive for patients, they would not have to come eight times as my centre practices but in five times. So we have to get more reliable data on the likelihood of normal tissue toxicity but, on balance, the systematic review suggests that it’s low if one does this mini-fractions, risk-adapted scheme.

Does it look as though this is as effective in the centrally located tumours as it is evidently in peripheral tumours that has already been established.

It’s hard to say because the follow-up for patients with central tumours has been much shorter than those with peripheral tumours. For peripheral tumours we’ve shown that population survival has been better but it remains to be seen whether the entire population survival would be better because the patients with a central tumour who were not fit for all the standard therapies often have a high risk of competing mortality.

So what would you say is the take home message for doctors coming out of this research?

That there is another treatment option for your patients if they are unfit, they have a central tumour, they’re unfit for surgery, they’re unfit for standard radiotherapy, that a short course of radiotherapy of between five to eight fractions offers a very high chance of durable control or cure without excessive toxicity.

Suresh, thank you very much for joining us here on ecancer.tv.