Breast-conserving therapy yields better 10-year outcomes than mastectomy for early-stage patients

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Published: 10 Dec 2015
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Dr Sabine Siesling - Netherlands Comprehensive Cancer Organisation, Utrecht, Netherlands

Dr Siesling talks to ecancertv at SABCS 2015, about the results of a large population-based study that compared the 10-year overall survival (OS) and disease-free survival (DFS) after breast-conserving therapy plus radiotherapy with mastectomy without radiation therapy in Dutch women with early stage breast cancer.

The study considered data on 37,207 women diagnosed with primary invasive early (T1-2N0-1M0) breast cancer over a 4-year period staring in 2000. Of these 58% had received breast-conserving surgery with radiotherapy and 42% had undergone mastectomy.

The respective 10-year OS were 76.8% and 59.7%. Although DFS was similar, patients who had breast-conserving treatment were less likely to experience distant metastases or regional recurrence.

Dr Siesling observes that the additional radiotherapy may be responsible for the better OS seen in the breast-conserving arm, although residual factors could explain part of the difference in recurrences.

ecancer's filming at SABCS 2015 has been kindly supported by Novartis through the ECMS Foundation. ecancer is editorially independent and there is no influence over content.

You’ve been presenting a paper on ten year survival and this is among patients who were treated for their breast cancer either with breast conserving therapy or with mastectomy. What were you trying to look at and what issue you were trying to investigate here?

We wanted to see whether there was a difference in survival, in overall survival or in distant metastasis free survival, between the two groups.

But it has always been quite well balanced, hasn’t it? It was never completely clear-cut but certainly it was non-inferiority for lumpectomy.

No, as a result of randomised clinical trials it was equivalent, they were both equal survival. What we saw in some observational studies with less follow-up that there were differences and there was better survival in breast conserving therapy.

You’ve done a population based study and a big one, what exactly did you do?

We selected patients with breast conserving therapy and mastectomy and that’s patients who were treated in the period 2000 until 2004. There were 37,000 patients and we compared them in overall survival and distant metastasis free survival.

No-one could complain about the size of the sample. What did you find?

We found a difference in survival and breast conserving therapy had more and better survival than patients who had an amputation.

But there has to be selection bias in that, doesn’t there?

Yes, that’s in observational studies the largest problem. What we did is we corrected our analysis with as much as possible data we had, so we corrected for age because patients with breast conserving therapy were younger than patients who had mastectomy. We corrected for other adjuvant therapies so, for instance, chemotherapy or endocrine therapy.

Have you ironed out the differences between better prognosis patients getting lumpectomy and worse prognosis patients getting mastectomy?

I think we cannot really totally correct for everything because there might be some residual confounding. But we did it as much as possible and I think we really saw a real difference.

Within that you have, in fact, got a hazard ratio which is extremely significant in favour of lumpectomy. Why should that be?

Yes. What we think is that the radiotherapy after the breast conserving surgery kills the last bit of cancer cells and that makes the difference. So we are going to evolve and have more research on that.

So another endorsement to radiotherapy as a very significant modality of treatment.

Yes, and it was mainly seen in very small tumours like less than 2cm without lymph node invasion.

What should doctors understand from all of this in terms of clinical usefulness?

They really should discuss these results as well with their patients so that the patients together with the clinician can decide on which treatment fits best for them.

Can you paint me a picture of how you would decide, if you’re going to advise an individual patient what sorts of factors would you look at?

Factors like family and relatives and the situation at home is very important. For instance, if you do the breast conserving surgery you have to have radiotherapy and that lasts for a couple of weeks and you have to go to hospital every day. So that’s really a burden to patients so that could be not fitting in the situation in which the woman is.

A burden though, but when there’s an advantage in staying alive it might well be a burden that many people would take on.

Yes, and therefore I think the patients and clinicians should be very well informed of the possible effects of either choice.

So what is the take home message for cancer doctors?

Cancer doctors should really inform their patients well and should inform themselves based on several studies on this topic.

But conservative therapy is highly effective?

Yes.