We are going to present the ten years median follow-up of data, the phase III trials on accelerated partial breast irradiation delivered using an IMRT technique, so an intensity modulated radiotherapy technique, as compared to whole breast irradiation. We already presented this study five years ago, the five year updated follow-up, and this is the ten year update. The main outcome is the ipsilateral breast tumour recurrence for patients but we also present the adverse events and the cosmetic outcome of the study.
Could you outline the trial design?
This is a very small trial but it’s a single centre trial and all patients were treated in a homogeneous way. So all patients were treated using the step-and-shoot IMRT technique, a very easy technique, easy also to delineate the target, that is another issue in accelerated partial breast irradiation concerns and issues. Using five fractions every other day, 30Gy in five fractions of 6Gy per fraction as compared to a conventionally fractionated whole breast irradiation, so patients receive 50Gy in 25 fractions and a tumour bed boost of 10Gy in five additional fractions. So that’s the main method.
The quality assurance is really easy. We contour organs at risk – heart, homolateral lung, contralateral lung, homolateral breast, contralateral breast – with very, very easy thresholds that we adopted and they worked very well. This will be related also to results, obviously.
What are the results so far?
Basically we confirmed the main results that we already presented for the five year update trial, even at a median follow-up of ten years. So it’s a cumulative incidence at ten years that we are going to report. There is basically no significant difference between arms. The ipsilateral breast tumour recurrence rate is very, very low, less than 1% difference at a median follow up of ten years. So basically in adequate selected patients an approach based on accelerated partial breast irradiation could lead to an equivalent result in terms of disease control.
At the same time we present also the adverse events. Concerning skin toxicity all the results were in favour of the accelerated partial breast irradiation arm, both at in acute and at the late adverse events
Finally we report also about cosmesis, both reported by patients and by physicians. In both cases, again, we observed significant results in favour of the accelerated partial breast irradiation arm. Basically using this technique we obtain satisfactory results in terms of cosmetic and late adverse events and it’s very clear the difference, even if you check the patient reported outcome. There is 15% of patients that reported a fair cosmetic result as compared to less than 1%. So we are very satisfied about these results and this technique.
What could the clinical impact be?
The clinical impact is very important, very clear. Basically this is another piece of the puzzle because we have got already outstanding published phase III trials, larger phase III trials, that suggest that accelerated partial breast irradiation could be a good chance as compared to whole breast. This is another piece of the puzzle. So we really can obtain an equivalent control, less acute events, less late events, a better cosmetic profile, reducing the volume irradiated for patients, the overall treatment time. This is a schedule in five fractions every other day so basically it’s ten days of schedule. But really it reduces the waiting list, it reduces the burden for the patients so this is the main relevant adding from these studies. And also the quality of life for the patients, obviously, that is the primary endpoint in these patients with very, very low risk of recurrence.
How should a clinician decide what technique to use?
We have two points to discuss. The first one is an adequate selection of patients. This is nothing about technique. So we have the recommendation from both the European and the American Society for Radiation Oncology so now we exactly know who is the patient, the best patient, for accelerated partial breast irradiation. We have always to consider to offer partial breast irradiation to a postmenopausal woman with early breast cancer, PT1, N0, adequate surgical margins, non-lobular, they are very good candidates to receive partial breast irradiation.
Concerning the technique, something about toxicity, something about adverse events. There are still some concerns in some schedules that use twice daily regimens, for example the RAPID trial, but this concern is very well studied, probably depends on the recovery time between fractions and the irradiated volume of the healthy tissue of the homolateral breast. So this is a once daily regimen, it’s very good results and probably the best choice to deliver partial breast irradiation.
What are the next steps?
Now we have to focus on the quality of life of patients. So probably now we know that the patients are very well selected we obtain an equivalent control, now we have to focus just on the de-escalation of treatment based on the better quality of life profile for our patients. This will be the future in these patients.
Are there any limitations in using accelerated partial breast radiation?
Basically if you perform a good quality assurance when you perform radiotherapy probably there are no limitations. There will be some cases in which you are not respecting organs at risk thresholds so probably an accelerated partial breast irradiation is not the best approach. In that case you can consider hyperfractionated whole breast irradiation or other solutions. Otherwise it’s the best solution.