Radiation exposure of the heart, lung and skin by radiation therapy for breast cancer: a dosimetric comparison between partial breast irradiation using multicatheter brachytherapy and whole breast teletherapy.

Background And Purpose: Accelerated partial breast irradiation by means of multicatheter brachytherapy shows great promise in the modern treatment of early breast cancer combining high efficacy in preventing tumour recurrence with low levels of toxicity. The present work attempts a dosimetric comparison between this treatment modality and conventional whole breast external beam radiotherapy by looking at differences in risk organ exposure to radiation.

Patients And Methods: The planning CT data sets of 16 consecutive patients with left-sided breast cancer who received external beam radiotherapy to the whole breast followed by a boost to the tumour bed using multicatheter interstitial brachytherapy after breast conserving surgery were used to create two independent physical treatment plans - one for an external radiotherapy, one for sole partial breast brachytherapy in each case assuming a total reference dose of 50Gy for each patient. Dose-volume parameters D(0.1cc), D(0.5cc), D(1cc,)D(2cc), D(5cc,)D(10cc), D(25cc), D(50cc), V(100), V(90), V(50), V(10), V(5) for the ipsilateral lung, the heart and the adjacent skin were calculated and compared between the two treatment modalities.

Results: All organs at risk showed a substantially lower radiation exposure in the brachytherapy plan. This was most pronounced for the heart with values differing by a factor of four. Although somewhat less marked this was also true for the ipsilateral lung and the adjacent skin with exposure ratios of three and two, respectively.

Conclusions: With the use of multicatheter interstitial brachytherapy substantial reductions in the radiation exposure of risk organs can be achieved in comparison to whole breast external beam radiotherapy. These are likely to translate into profound clinical benefits.