European Multidisciplinary Conference in Thoracic Oncology (EMCTO) 2013

Diagnosis and treatment in rare cases of thymoma

Dr Walter Klepetko - Vienna Medical University, Austria

Walter, you are normally at the Medical University of Vienna dealing with all sorts of cases of thoracic oncology, you’ve got quite a workload there. But one of the interesting cases is thymoma because you have tumours which are a little bit rare and that’s what you’ve chosen to talk about here at the Conference on Thoracic Oncology, here in Lugano. So tell me, what is special about thymoma and what do you have that’s new to say?

That’s correct. Thymoma is quite a rare disease compared to non-small cell lung cancer and the problem of these specific tumours is that they present in a very heterogeneous form. They are different, very different, histologies and even the pathological differentiation is quite challenging so it really needs an expert pathological team to precisely define the subtype of thymoma.

How do you normally find that they’re there?

Thymomas usually are detected just by incidence when you identify a mass in the anterior mediastinum or the other way around is that there are some symptoms with that. In the early stages there could be the association with myasthenia gravis; in advanced stages there can be some functional disorders by obstructing of the vena cava or making any other discomfort in the chest.

You’ve been addressing controversies in surgical treatment of thymoma. What are the controversies then?

The problem of the treatment in thymomas, I mentioned it before, is that the tumour is rare and heterogeneous which automatically implies that we are unable to provide large prospective randomised studies at the moment which would be able to guide our treatment decisions. So most of our decisions that we take nowadays are, at least in part, based on best evidence, best available evidence, but not randomised trials.

What are the parameters you need to look at?

You have to look at the histological subtype of the thymoma; you have to look at the extent of the disease, the stage, there are certain staging systems, the most frequent is the Masaoka-Koba system which is well established and accepted. Then you have to define the treatment algorithm which is adequate for the patient, which in the early stages is always surgical resection. There are issues which type of resection, which approach, which surgery should be applied to the patients. And in the advanced stages of thymoma there is neoadjuvant chemotherapy or chemo-radiotherapy comes into the game and all the adjuvant treatments as well.

Now you’ve said that there is a paucity of randomised studies because of the rarity of this very fascinating tumour. But from your work in Vienna, what sorts of things have you been able to discern about best guidelines for managing this tumour?

Our managing guidelines in the early stages, which means stage 1 and 2, a tumour which is encapsulated or just going through the capsule but not invading adjacent organs, is always the surgical resection which is always performed in a complete radical mediastinal dissection with resecting all the fat tissue as well because there is the likelihood of some distant spread of thymoma tissue in the other fat tissue of the mediastinum.

And when do you use neoadjuvant therapy?

Neoadjuvant, as mentioned before, gets its place as soon as there is higher tumour stage which means stage 3 invasion of the chest organs. In this situation you would like to downstage the tumour if possible with neoadjuvant chemo-radiotherapy. But all the histology has an impact on the choice for neoadjuvant chemotherapy, yes or no. So if it’s a more advanced histology, more malignant histology of course, you would early on use neoadjuvant therapy.

And are you in a position to judge from the histology how aggressive the tumour is?

Yes. There is good evidence that thymomas increase in aggressiveness as much as they increase more from their lymphatic type more to the epithelial type. So the more they are epithelially-wise differentiated, the more aggressive they become and the most aggressive type of thymoma is the thymic carcinoma, really, which certainly has to be considered a highly malignant tumour.

And what about adjuvant therapy?

Adjuvant therapy is always used when you start the resection and ultimately after resection you detect some local invasion of some adjacent structures or you have to upgrade the staging, the pre-surgical staging, to a higher grade after surgery and you would like to offer the patient better outcome chances with administering adjuvant therapy.

So what are the different controversies, then, that you need to address as a clinician managing your patients?

The real controversies are, first of all, early stages – how complete resection is really necessary for those tumours. Do you have to do this mediastinal fat tissue dissection as well because there are also some negative issues with that – it’s a more aggressive operation with a higher likelihood for some comorbidities. This is not established by randomised trials. There are a variety of different surgical approaches – through the neck, by VATS surgery, unilateral VATS surgery, bilateral robotic approaches or, I have to say, all types of median sternotomy is used in several institutions as well. So there is not a standardisation of the surgical approach.

So with video-assisted surgery and also robotic surgery, are they making inroads into the standard technique?

Yes, they are making but we are still lacking proof that this should be the standard of care. And if you go to the higher stages there are quite aggressive operations which allow us nowadays even to resect pleural spread of the tumour by performing a complete pleurectomy or, the most invasive operation, performing an extrapleural pleuropneumonectomy where all the lung, diaphragm and pleura is removed.

Now typically what are the outcomes with all of these different stages of the disease with the different treatments you’ve been describing?

It’s difficult to give a short answer to this question. I would say if you have a type AB or A or B1 thymoma in a stage 1 or 2 you have a fairly good outcome with a ten year survival rate of about 85-90%, I would say. If it comes to B2, B3 or C type thymomas which are the more aggressive ones, and we’re talking about stage 3 or 4, the five year survival can come down as low as 10-15% at most. So it’s quite a variety depending on the type of tumour and the stage as well.

So potentially quite a disturbing tumour to have?

Yes.

So what is the main point that at this meeting you’d like to get over to doctors about managing this tumour optimally?

The main point about managing thymomas optimally is that these tumours have to be seen by a really specialised team which really is specialised in thymoma work. It’s not a routine resection which should be done by an ordinary surgeon who doesn’t see thymomas frequently, it needs a dedicated surgeon, it needs a dedicated oncologist and pathologist and you have to set up a real thymoma interest group in your institution to deal with a disease like that.

And at your institution in Vienna typically how many cases do you get each year?

Every year we see about thirty to forty cases and we are not only seeing them by ourselves, we are sharing this information with a referral centre in Germany as well. So we have a second opinion on histology, which is very helpful as well. So this brings us really to international standards.

So has therapy improved? You’re describing a comprehensive list of measures which seem to have a lot of potential. What’s the summary message that you’d give coming out of all of this?

I think the summary message is that if you offer the patient the nowadays available therapy strategies that we have, which unfortunately are not based on randomised trials but on the evidence that is collected in these interested institutions, I think the outcome of these patients can be improved as compared to the past. But definitely thymomas should be treated only by really focussed interest groups.

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