PURPOSE: Most male breast cancer tumours are hormone receptor-positive; the 
patients therefore receive endocrine therapy. There is, however, a paucity of 
published data on toxicities experienced by male breast cancer patients who are 
prescribed endocrine therapy. In the present study, we examined rates of 
adherence to and toxicity from endocrine treatments in male breast cancer 
patients treated at a single institution.
PATIENTS AND METHODS: We conducted a retrospective study of male patients 
diagnosed with breast cancer at The Ottawa Hospital Cancer Centre during 
1981-2003. Data collected included patient age, hormone receptor status, therapy 
adherence, self-reported toxicities, and type and duration of endocrine 
therapies.
RESULTS: The review located 59 cases of early-stage and metastatic male breast 
cancer. Median patient age was 68.0 years. Tamoxifen was given to 38 patients 
(64.4%), anastrozole to 8 (13.6%), and letrozole to 5 (8.5%). Of patients who 
received endocrine therapy, 10 (25%) received adjuvant systemic chemotherapy. 
Toxicity was reported by 19 patients taking tamoxifen (50%), with hot flashes 
being the most common complaint (18.4%). Decreased libido, weight gain, and 
malaise were reported by 5 patients (13.2%). Rash and erectile dysfunction were 
reported by 3 patients (7.9%). Increased liver enzymes, pulmonary embolism, 
superficial thrombophlebitis, myalgia, depression, visual blurring, and loose 
stools were each reported in 1 patient (2.6%). Tamoxifen therapy was 
discontinued secondary to toxicity in 9 patients (23.7%). Of the patients 
treated with anastrozole, 3 (37.5%) reported toxicity, with 1 report each of 
decreased libido, leg swelling, and depression (12.5%). Toxicity was reported in 
2 patients taking letrozole (40%), with both reporting peripheral edema, and 1 
reporting hot flashes. No patient discontinued anastrozole or letrozole because 
of toxicity.
CONCLUSIONS: Few studies specifically report data on adherence to and toxicities 
from endocrine therapies in male breast cancer patients. The rate of 
discontinuation at our institution because of toxicity (23.7%) is similar to 
that reported in the female breast cancer population. Future prospective studies 
should explore strategies to improve adherence to endocrine therapy in this 
population.