A Phase I-II Trial Evaluating the Toxicity of Early Breast Partial Irradiation in Patients Aged at Least of 70 Years With Breast Cancer at Low Risk of Local Recurrence
Single dose intraoperative issued by electrontherapy or low energy photons (50 Kv) is 21 Gy
(5.11). However, these doses reported in the irradiated volume are not equivalent. Indeed,
with electrontherapy, it is a complete volume of mammary parenchyma that is irradiated,
whereas with low energy photon therapy (X 50 KV) is a "shell" of 5 mm thick which is treated
knowing that to 10 mm from the surface of the sphere of treatment, the gland received only
50% of the dose initially prescribed. On interstitial brachytherapy with high dose rate, it
has a dose escalation due to intrinsic volumes located within the irradiated area that will
receive a higher dose than prescribed (12). It is this variation in dose within the target
volume which can be efficiency, but also which can induce the toxicity of interstitial
brachytherapy. The linear quadratic model to calculate the biological equivalence of 2 Gy
irradiation scheme most often hypofractionned, is theoretically applicable for doses per
fraction less than 8 Gy. Nevertheless, the authors using the IPAS intra-operative
(electrons, photons) apply this method of calculation for doses of 21 Gy in one fraction.
In our study, we propose to treat these patients with a total dose of 16 Gy in one fraction.
This dose is calculated taking into account a report alpha/beta for the breast, on the order
of 3.4 Gy for late toxicity and 4.6 Gy for local control (13). Applying the linear-quadratic
model with alpha/beta for the breast of 4, 16 Gy in one fraction is calculated as
radio-biologically equivalent to 53 Gy in conventional fractionation (14,15). Biological
Equivalence of this dose is between the dose in the protocols IPAS intraoperative electron
or X-ray photons of 50 kV (21 Gy in one fraction, 87 Gy EQD2 alpha/beta 4.6) (5.8) and the
post-operative irradiation of 34-38 Gy in 10 fractions, 5 days (42 Gy EQD2 alpha/beta 4.6.
Endpoint Classification: Safety/Efficacy Study, Intervention Model: Single Group Assignment, Masking: Open Label, Primary Purpose: Treatment
Evaluate the early toxicity (less than 180 days) of IPAS mono split postoperatively in patients aged at least of 70 years with breast cancer at low risk of local recurrence (low risk group of ESTRO IPAS classification ESTRO)
Rate of acute toxicity evaluated bu a clinical examination, in consultation with the radiotherapist to 30, 90 days and 180 days. Common Toxicity Criteria classification for Adverse Events (CTCAE) in its fourth version is used.
Jean-Michel HANNOUN LEVI, Phd
Centre Antoine Lacassagne
France: Agence Nationale de Sécurité du Médicament et des produits de santé
2012/09 - SIFEBI