Organising pneumonia caused by hormone (tamoxifen) therapy after radiotherapy for breast cancer: a case report and review of the literature.

Background: Five-year treatment with tamoxifen (TAM) has been the traditional standard of care for breast cancer. Organising pneumonia (OP) is a rare but significant complication of radiation therapy for breast cancer. The effect of TAM leading to OP has not yet been clearly documented. Case Description: This report describes the case of a 38-year-old female who developed progressive aggravation of round-like patchy bilateral pulmonary infiltrated with a reverse halo sign but without any clinical symptoms 5 months after TAM therapy, following breast-conserving surgery and radiotherapy (RT) for breast carcinoma. A lung biopsy was performed and revealed a histological pattern of OP. TAM therapy was discontinued, and subsequent gradual radiological improvement was observed. As there was no proof for TAM had caused the incident, TAM was re-administrated. Eight months after reinstitution of TAM, the same patchy migratory bilateral pulmonary infiltrated with reverse halo sign was found on chest CT with the patient claiming no discomforts nor any clinical symptoms. The diagnosis of TAM-related OP was made based on the exclusion of other causes and recurrence with the re-administration of TAM. The multidisciplinary team (MDT) concluded that TAM should be withdrawn and a "wait-and-see" approach was taken after a comprehensive assessment, instead of altering the medication or performing prophylactic mastectomy. Conclusions: The withdrawal and rechallenge of TAM strongly suggest that it may play a role as a cofactor in the occurrence of OP after RT for breast cancer, and RT may also be a cofactor in the occurrence of OP. It is extremely important to be alerted to the possibility of OP after concurrent or sequential hormonal therapy and RT.