Reconstruction Outcomes In A Multi-Institution Prospective Phase Ii Hypofractionated Post-Mastectomy Radiation Therapy

Hypofractionation in the setting of post mastectomy radiation (PMRT) is not currently the standard of care in most countries, particularly in patients who have undergone reconstruction. Here we present the reconstruction outcomes of our multi-institutional phase II prospective trial evaluating a novel 15 day hypofractionated PMRT regimen. Between 2010 and 2014, we enrolled patients with Stage IIA-IIIC invasive breast cancer to receive 3.33 Gy daily to the chest wall (or reconstructed breast) and regional lymphatics in 11 fractions with an optional 4 fraction mastectomy scar boost. Forty-three patients had a breast reconstruction or temporary expander (TE). In this abstract, we report the outcomes of reconstruction completion, failure and revision with this novel hypofractionation regimen. Forty-three patients had plans for breast reconstruction. Median age was 48 years-old, range [31, 70]. Median follow up time was 3 years, range [1.1, 8.4]. Forty patients were alive at last follow up. Thirty-five (81.4%) patients had a TE at the time of mastectomy with plan for final reconstruction after RT. Three (7.0%) had immediate implants before RT. Of these 3, one patient had a revision after RT then the implant was removed because of local recurrence; one had two revisions and the other did not require any revisions. Two patients had a prior augmentation implant that was used for immediate reconstruction with no complications or revisions reported. Three patients had post RT reconstruction with flaps (TRAM, Latissimus flap + implant and SIEP), one of the three required an unplanned revision. Among the 35 patients who had TE, 3 were removed before RT for infection and one patient abandoned the plan for reconstruction. Of the three removed for infection, two completed an auto DIEP and one did not complete reconstruction. Of the 33 patients who had TE at the time of RT and completed reconstruction, 9 (27.3%) failed requiring TE or implant removal. Four of those 9 patients went on to have additional successful reconstructions but with multiple revisions and one had another repeat reconstruction that failed again – this patient was diabetic with uncontrolled blood sugar (on steroids). There were 3 patients that required revisions. Two patients had a local recurrence resulting in loss of implants. Thus, the total number of grade 3 or 4 complications attributed to RT was 15 (34.9%). We had 9 reconstruction failures, 4 of which were salvaged, and 6 unplanned revisions. This is comparable to reconstruction outcomes with conventional fractionation. This is the first prospective US trial to demonstrate the safe use of hypofractionated post-mastectomy radiation particularly in the setting of breast reconstruction. Although our fractionation was novel, the radiobiological equivalent dose is similar to other hypofractionation schedules. This trial was the basis for the creation of Alliance A221505 (RT CHARM), which is currently accruing patients in a phase 3 randomized design.