Background: Potential benefits of concurrent chemo-radiation include: shorter duration of treatment, smaller interval between surgery and adjuvant therapies, and synergistic effects. We have previously shown that PBI with concurrent dose dense doxorubicin and cyclophosphamide (ddAC) is well tolerated (Zellars JCO 2009). We performed a follow-up feasibility trial of PBI delivered concurrently with other various chemotherapy regimens. Methods: Women with T1-2, N0-1 breast cancer s/p lumpectomy with ≥2 mm margins were eligible. Chemotherapy regimen was at the discretion of the medical oncologist (Table). PBI (40.5 Gy in 15 daily 2.7 Gy fractions) was delivered within the first 2 cycles of chemotherapy. Primary endpoints were hematologic and non-hematologic toxicities graded according to Common Terminology Criteria for Adverse Events manual (v. 3.0). Results: Thirty-four patients enrolled with median f/u of 19.2 mos. (4.0 - 38.6). Mean tumor size was 1.8 cm (+/- 0.7 cm), 71% pN0, 68% HR +, 18% Her2 +. All patients completed concurrent chemo-radiation. Three patients had a 3-8 day delay in chemotherapy (1 grade 2 thrombocytopenia; 1 Grade 2 liver enzymes; 1 T desensitization). There was 1 local (DCIS) and no regional/distant recurrences or deaths. Toxicity: 2 grade 4 neutropenia (ddAC, TCarboH); 1 grade 3 neutropenia (post-AC paclitaxel); 1 Grade 3 hyponatremia and DVT (TC); 1 syncope (TAC). None had > grade 2 radiation dermatitis. Conclusions: PBI and concurrent chemotherapy is associated with minimal toxicity and appears to be well tolerated. These results deserve further investigation. Funded by The Breast Cancer Research Foundation.

Regimen	Patients N=34	Dose/schedule	Schedule	No. of cycles
Standard AC then P	2	A 60 mg/m2 C 600 mg/m2 P 80 mg/m2	Q 3 wks Q wk	4 12
Dose dense AC then P	12	A 60 mg/m2 C 600 mg/m2 G-CSF P 80 mg/m2	Q 2 wks Q wk	4 12
TAC	1	T 75 mg/m2 A 50 mg/m2 C 500 mg/m2	Q 3 wks	6
TC*	16	T 75 mg/m2 C 600 mg/m2	Q 3 wks	4-6
TCarboH	3	T 75 mg/m2 Carbo AUC6 C#1 H 8mg/kg, then 6mg/kg	Q 3 wks	6

Abbreviations: C, cyclophosphamide; P, paclitaxel; T, docetaxel (Taxotere); A, doxorubicin (Adriamycin); Carbo, carboplatin; H, trastuzumab (Herceptin); G-CSF, granulocyte colony stimulating factor.

*One patient had 6 cycles of TC, all others had 4 cycles.