ESTRO 38 Abstract book

S699 ESTRO 38

Conclusion HLRT is safe and the clinical outcomes of our patients are comparable to the results of available randomized trials on hypofractionation for breast cancer. Further, prospective randomized trials are warranted to confirm our data and consider HLRT a standard of care. EP-1273 Increasing negative lymph node count prolong survival in breast cancer with neoadjuvant chemotherapy X. Wang 1 , P. Wang 1 1 Tianjin Medical University Cancer Hospital & Institute, Department of Radiation Oncology, Tianjin, China Purpose or Objective Adequate lymph node evaluation is recommended many malignant tumors including breast cancer. However, the role of negative lymph nodes (LNs) remains unclear in breast cancer (BC), especially in the setting of neoadjuvant chemotherapy. A retrospective analysis of BC treated with mastectomy after NAC in our institution was conducted. Material and Methods A total of 435 patients diagnosed with BC who were treated with mastectomy after NAC were included in this analysis. The median age was 49 years old (22-76 years old). The clinical stage distributions were cT1-2 in 245 patients and T3-4 in 190 patients, cN0 in 82 cases, cN1 in 309 cases, and cN2 in 44 cases. The pathological stage distributions were ypT0-2 in 385 patients, ypT3-4 in 187 patients, ypN0 99 cases, ypN1 in 99 cases, ypN2 in 108 cases, and ypN3 in 129 cases. Results With a median follow-up time of 61 months. The 5 year overall survival (5y-OS), 5 year locoregional failure free survival (5y-LRFS), 5 year distant metastasis free survival (5y-DMFS) were 74.8%, 84.1%, and 71.4%, respectively. The median number of dissected LNs is 22, and median positive LNs is 4. In multivariate analysis, negative LN count, estrogen receptor status, pathological T and N stage were independently prognostic factors associated with 5y-LRFS. A critical relationship was observed between negative LNs and 5y-LFRS, with a HR of 0.948 (95% CI: 0.917-0.981), p=0.002. Patients with negative LN counts more than 10 showed significantly superior 5y-LRFS than those with negative LN count no more than 10 (5y- LRFS were 90.6% in >10 negative LNs vs. 64.8% in ≤10 negative LNs, p=0.000). Interestingly, similar survival trends were showed in patients with N-positive diseases (5y-LRFS were 87.4% in >10 negative LNs vs. 64.0% in ≤10 negative LNs, p=0.000), but not in the N0 disease (5y-LRFS were 96.9% in >10 negative LNs vs. 100% in ≤10 negative LNs, p=0.724). And more importantly, postmastectomy radiotherapy seems to only improved 5y-LRFS in patients with ≤10 negative LNs (5y-LRFS were 69.0% vs. 27.6% with or without PMRT, p=0.002), but not patients with >10 negative LNs (5y-LRFS were 88.4% vs. 85.1% with or without PMRT, p=0.257). Conclusion This is the first study to confirm the relationship between negative lymph node count and prognosis of breast cancer in the setting of NAC. More negative lymph nodes imply longer survival, which may help to predict prognosis and make treatment recommendation. EP-1274 neoplastic brachial plexopathy in breast cancer survivors: diagnosis traps, RT-VMAT faisibility S. Delanian 1 , P. Ding 2 , H. Huet de Froberville 2 , C. Boguszewski 3 , P. Pradat 4 1 Hopital Saint-Louis- APHP, Oncologie-Radiotherapie- Radiopathologie, Paris, France ; 2 Centre Clinique Porte de Saint-Cloud- Hôpital Americain de Paris, Radiophysique, Boulogne, France ; 3 Centre Clinique Porte de Saint-Cloud- Hôpital Americain de Paris, Radiotherapie, Boulogne, France ; 4 Hopital Pitié-

Salpêtrière- APHP, Oncologie-Radiotherapie- Radiopathologie, Paris, France

Purpose or Objective Neoplastic brachial plexopathy (NBP) is a carcinomatous peripheral neuropathy in the axillary-supraclavicular region, often misdiagnosed as a radiation-induced (RI) complication, even when node areas have not been irradiated. The literature is old and limited: series of 5 to 78 cases have been reported in 11 articles over 40 years (1968-2009), while histology, imaging and RT have undergone deep mutations. Material and Methods 330 long-survivor patients treated for breast cancer have been referred to Hôpital Saint-Louis (2004 -17), for brachial RI plexopathy round the inclusion period of our therapeutic phase III trial (NCT01291433): 12 % of the patients were finally diagnosed with a neoplastic origin. NBP was established after expertise based on the following arguments: delayed then progressive development of arm lymphedema (75%), intense arm pain, quite fast progressing motor symptoms, ptosis, slight inflammatory signs on MRI and PET-scan imaging (re-interpretation), and axillary volume exclusion of the primary RT volume (dosimetric check). Fortywomen (65 ± 9y), treated 14 ±7 years before by surgery (5 N0, 14 N-, 14 ≤2N+, 7 ≥6N+) then radiotherapy (1974-2013), were diagnosed with NBP after 1 to 4 years of neurological evolution. Patients had salvage chemotherapy-hormonotherapy, and for some of them, plexus RT by conformal then V-mat technique. Results According to previous breast RT, 3 NBP prognostic groups were analyzed: 16 [R 0 ] (40%) without any node RT, 11 [R 1 ] supraclavicular RT only (without axillar), and 13 [R 2 ] axillary and supraclavicular RT. MRI and PET-scan were mis-interpretated either as very slow kinetic tumor (hormono-dependant) or inflammatory NBP. A triangular axillary fixation in the border of previous supraclavicular RT beam, SUV 2-5, was pathognomonic of R 1 NBP group (figure). The time BC-NBP was R 1 14±7; R 2 12±6; R 3 16± 7 years. Plexus RT was done using a classical fractionation in 10 R 0 patients /16; or a salvage fractionation by Vokes protocol (every two weeks), because partial irradiated volume, in 3 R 1 patients/11 (figure); and not in R2 patients. Radiotherapy allowed controlling pain and reducing motor signs of NBP.

Conclusion