ESTRO 36 Abstract Book

S625 ESTRO 36 2017 _______________________________________________________________________________________________

To report 5-year outcomes and toxicity in early breast cancer pts treated with whole breast hypofractionated adjuvant radiotherapy(HRT) and concomitant trastuzumab after breast conservation surgery(BCS). Material and Methods From February 2009 to October2011, 442 pts with breast cancer pTis-T2 pN0-N1(up to 3 positive lymph nodes) underwent forward planned intensity modulated HRT to a TD=40 Gy/15 fr at out institution, and reached 5 year median follow up; 31/442 pts presented c-erb B2 overexpression and were treated with HRT and concomitant trastuzumab. Acute toxicity during HRT was evaluated using the RTOG scale, while late side effects were assessed using SOMA-LENT score. Results Patients’ median age was 60,5(28-75)years; tumor breast side: 20 left and 11 right. Histology: DCI: 24 pts; DCI+DCIs: 6 pts; DCI+ LCIs:1 patient; apocrine carcinoma: 1 patient. With a median follow-up of 63,8 (42,5-79,2) mts 3/31 pts (9,7%) presented a local relapse, 2/31 pts ( 6,5%) a lymph nodal relapse and 4/31 pts (12,9%) a distant relapse, confirming the higher propensity for loco-regional and distant relapse of c-erb B2 positive tumors. All pts were alive at the last follow up. Acute toxicity was G0 in 7 pts (22,6%), G1 in 20 pts(64,5%) and G2 in 4 pts(12,9%) with no G3 toxicity. Late G1 edema and hyperpigmentation persisting up to 18 mts after HRT was observed in 7 pts (22,6%). Two persistent late toxicities were registered only in pts treated with FEC chemotherapy before HRT: one G2 fibrosis, starting 36 months after the end of HRT, with breast volume of 1812 cc (cut-off observed in our series: 866 cc), and one G3 teleangiectasy with breast volume of 596 cc. Two cardiac toxicities were registered, both in left sided breast cancers, one in a patient treated with AC x3 cycles+TXT x 12 weeks +trastuzumab x 12 mts, another in a patient treated with FECx5 cycles+ trastuzumab x 12 mts, which presented a mediastinal relapse, treated with salvage chemotherapy. The same patient presented BPCO exacerbations, again after the salvage chemotherapy. While chemotherapy and breast volume were important predictors for acute toxicity, the association of trastuzumab was not statistically significant for both acute and late toxicity at the multivariate analysis. Conclusion HRT after BCS demonstrated good outcomes and low toxicity. The association of hypofractionated radiotherapy with trastuzumab does not increase acute and late toxicity. EP-1160 T4s for T4 small Breast cancer: a new TNM classification subgroup proposal W.S. Zrafi 1 , S. Tebra 1 , H. Ouaz 1 , N. Bouaouina 1 1 Farhat Hached University Hospital, Radiation oncology departement, Sousse, Tunisia Purpose or Objective T4 breast cancer are tumors of any size with direct extension to the chest wall and, or the skin, including inflammatory breast cancer. Non inflammatory T4 breast cancer are a considerably heterogeneous group of tumors with a subgroup of small-sized tumors. Our aim is to evaluate the prognosis of small sized (under 3 cm) non inflammatory T4 breast cancer, comparing them with larger T4 tumors and inflammatory breast cancer. Material and Methods We had undertaken a retrospective study of T4 tumors treated by radiotherapy in the departments of radiation oncology in the Farhat Hached University Hospital and Medical Centre Ibn Khaldoun Results 250 patients classified as T4 tumors by our Committee for Gynecologic Oncology were treated in our departments between January 1995 and December 2013.

From these 250 patients, 79 were classified as T4d breast tumors and 171 non inflammatory breast cancer. From these, 11 cases the primary tumor size is unknown, 20 patients had small tumors under 3 cm at presentation, and 140 patients had tumors of 3cm in size or larger. Seventeen were classified as T4a, 127 as T4b and 27 as T4c. 148 patients had underwent neoadjuvant chemotherapy, mastectomy, and adjuvant radiotherapy. The median age was 50 years (ranging from 23 to 78). The median size at presentation was 5 cm. the median follow- up period was 42 months (ranging from 0 to 231). The 5 years Disease free survival was 89% for small tumors versus 59% for non-inflammatory larger tumors and 48% for inflammatory breast cancer. With statistically significant difference p = 0.037 (fig 1). The overall survival was 89% versus 70% for non- inflammatory larger tumors and 62% for inflammatory breast (p = 0.28). These finding support the fact that small T4 tumors had a different behavior and better prognosis than other locally advanced tumors, thus it should be considered as a distinct entity. Indeed we propose that these tumors should be classified T4”s” ('s” as small). Although the actual T4 TNM subgrouping is lacking of discriminative power, actually we did not find a significant difference comparing the DFS (p = 0.34) or OS (p = 0.7) according to the T4 TNM subgrouping (fig 2).

Fig 1: Disease free survival of the T4 s subgroup compared with larger T4 non inflammatory breast cancer and T4d