Abstract P6-19-04: Male breast cancer: Tumour characteristics and treatment compared with females in Australia – 99,768 breast cancers over a 10 year period

Abstract

Abstract Introduction Stage and tumour characteristics in males with early breast cancer (EBC) differ from those in females. Guidelines recommend that treatment of males with EBC should be based on evidence derived from clinical trials in females but some studies suggest men may be undertreated. We assessed tumour characteristics and adjuvant treatment in Australian males as recommended by NCCN guidelines. Methods Using data collected prospectively in the BreastSurgANZ Quality Audit - society of breast surgeons in Australia and New Zealand. Membership requires entry of tumour and treatment details of all breast cancer patients managed by individual surgeons onto an online secure database. No outcome data is collected. The collected information is bound by the National Privacy Principles of both countries. Patients diagnosed with EBC from 1 October 2006 to 30 September 2016 were analysed. The study period was chosen as it corresponds with the availability of trastuzumab and contemporary chemotherapy regimens. Comparisons between males and females were made using chi-square test, significance was considered with alpha of 0.05. Results There were a total of 99,768 episodes, comprising 585 (0.6%) males (544 invasive; 41 DCIS) and 99,183 (99.4%) females (85,596 invasive; 13,525 DCIS; 62 unk). Mean age (range) 68y (25-94) males; 61y (15-102) females. Bilateral synchronous cancer in 6 (1%) males, 3636 (3.7%) females. Histology was ductal/lobular/other in 85%/2%/13% males; 76%/12%/12% females. DCIS in 7% males, 14% females. Triple negative (2% males, 11% females), hormone receptor positive (HR+ - 94% males, 82% females), HER2 positive (7% males, 13% females). Node positive 44% males, 35% females. No breast surgery was performed in 1.9% males, 1.3% females. Where breast surgery was done, complete local excision/mastectomy in 7%/90% males, 55%/40% females. In regard to axillary procedures; 632 were done in males with sentinel node biopsy (SLN) 53%, axillary dissection (AD) 44%, unk 3%; 100,187 done in females with SLN 65%, AD 33%, unk 2%. Table 1 shows the rate of adherence to NCCN February 2018 guidelines. Table 1 Treatment recommendedFEMALE % (TR/total)MALE % (TR/total)P valueER/PR - & HER2 +, tumour > 10mm OR node positiveC+T79% 2336/2943100% 1/11.0ER/PR + & HER2 +, tumour 6-10mm AND node negativeE+C/T81% 436/539100% 1/11.0ER/PR + & HER2 +, tumour >10mm OR node positiveC+T+E62% 3377/548153% 17/320.33ER/PR + & HER2 -, node positiveC+E64% 12349/1935056% 109/1940.028Triple negative, 10mm OR node positiveC85% 5756/678971% 5/70.33C - chemotherapy, T – trastuzumab, E – Endocrine, TR – treatment received Discussion In this Australian study, male breast cancer accounted for only 0.6% of all cases seen over the 10yr period. In line with other studies, invasive lobular cancer, triple negative and HER2 positive disease was infrequently seen in males, but with a higher likelihood of being node positive. There were no cases of medullary carcinoma in males but a higher than previously reported incidence of DCIS. Males with HR+, HER2-, node positive EBC were significantly less likely to receive chemotherapy and endocrine treatment, with all other subgroups showing similar systemic treatment for both genders. Citation Format: Arlene C, Chris L, Chih H, Willsher P. Male breast cancer: Tumour characteristics and treatment compared with females in Australia – 99,768 breast cancers over a 10 year period [abstract]. In: Proceedings of the 2018 San Antonio Breast Cancer Symposium; 2018 Dec 4-8; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2019;79(4 Suppl):Abstract nr P6-19-04.