Clinical characteristics and survival of breast cancer patients with extramammary malignancies in a single Asian center over the past 23 years.

BACKGROUND

The rise of multiple primary malignant neoplasms (MPMNs) necessitates exploration. MPMNs represent 18% of U.S. cancers. Breast cancer is the predominant malignancy among female Americans. However, most studies on breast cancer with MPMNs are confined to case reports with small sample sizes. Hence, this article scrutinizes 280 patients diagnosed with breast cancer and extramammary primary malignancies via long-term follow-up.

METHODS

We reviewed 280 breast cancer cases with extramammary primary malignancies from January 2000 to December 2022 at our institute, excluding those diagnosed with stage IV breast cancer. The double primary malignant neoplasms (DPMNs) were used as focal points and segregated into the first primary breast cancer (FPBC) and second primary breast cancer (SPBC) subgroups. With a median follow-up period of 107 months (8.9 years), we examined the characteristics of these diseases in various patients.

RESULTS

Concerning breast cancer patients with extramammary primary malignancies, DPMNs were predominant, comprising 77.1% (216/280). Among these DPNMs, gynecology, thyroid, and lung were the primary site of extramammary tumors, predominantly. Nearly all (93.9%) of FPBC patients exhibited metachronous cancer whereas 55.9% of SPBC patients experienced this. The median interval between the onset of breast cancer and extramammary malignancy in metachronous FPBC and metachronous SPBC patients was 60 months and 48 months, respectively. Over time, both metachronous FPBC and metachronous SPBC patients demonstrated a diminishing prevalence of second tumors. The distinction lay in that in the metachronous FPBC group, second tumors ceased to occur after 300 months, whereas in the metachronous SPBC group, their emergence persisted. Synchronous cancer, negative ER/PR status, and advanced extramammary malignancy stage portend poor prognosis among patients with DPMNs.

CONCLUSIONS

Careful monitoring of MPMNs necessitates precise guidelines, differing amongst FPBC and SPBC patients. Synchronous cancer, ER/PR-negative, and advanced extramammary malignancy stage indicate poor prognosis in DPMNs patients.