We identified 74 patients diagnosed with PABC with a mean age of 34.5. There were 28 patients (37.8%) with PABC-P and 46 patients (62.2%) with PABC-PP diagnosed within the first 12 months after delivery. When comparing with PABC-P and PABC-PP, there was no significant difference in age at diagnosis (Mean ± SD: PABC-P: 34.4 ± 3.4 vs PABC-PP: 34.5 ± 4.0, p = 0.87), BMI (Median IQR: PABC-P: 27.8 [22.8, 31.6] vs PABC-PP: 26.1 [22.5, 31.0], p = 0.52), or medical comorbidities (Table 1).
The majority of patients presented complaining of a palpable mass (86.5%, n = 64), pain (17.6%, n = 13), or erythema (6.8%, n = 5) (Table 1). Other common presenting complaints included decreased milk production (6.5% of PABC-PP, n = 3), change in bra size (2.7%, n = 2), presumed abscess (2.7%, n = 2), and nipple retraction (2.7%, n = 2). The patient’s mass was initially palpated by their physician 4.1% of the time (n = 3). Patients experienced symptoms for a median of 1 month [IQR: 0.25, 4.0] prior to presentation (Table 1). The overall clinical stage distribution at diagnosis was: Stage 0, 6.9%; I, 18.1%; II, 47.2%; III, 22.2%; and IV, 5.6%. There was no significant difference in clinical stage at presentation in PABC-P and PABC-PP (p = 0.18) (Table 2).
Patients with PABC-P were diagnosed at a median gestational age of 27.1 [IQR: 9.8, 32.6] weeks, underwent surgery at 34.2 [IQR: 15.9, 52.6] weeks, and delivered at 37.4 [IQR: 35.6, 39.0] weeks, most commonly via vaginal delivery (52.7%) (Table 1). Patients diagnosed postpartum were diagnosed on average 16.3 weeks postpartum.
Overall, 90.5% of patients elected to undergo genetic testing (Table 1). There was no significant difference in the rate of genetic testing between patients with PABC-P and PABC-PP (82.1% vs 95.7%, p = 0.097). Among those tested, the majority (52.2%, n = 35) of patients overall did not have any identifiable mutation, but PABC-PP patients were less likely to have a pathogenic mutation (63.6%, n = 28) than PABC-P patients (30.4%, n = 7; p = 0.01). BRCA1 mutations were observed in 26.1% (n = 6) of PABC-P patients and 22.7% (n = 10) of PABC-PP patients (p = 0.76). BRCA2 mutations were observed in 4.3% (n = 1) of PABC-P patients and 4.5% (n = 2) of PABC-PP patients (P = 0.76). One BARD1 mutation was observed (PABC-P: 4.3% vs PABC-PP: 0%, p = 0.34). Of note, 16.4% (n = 11) of patients, including 30.4% (n = 7) of PABC-P patients and 9.1% (n = 4) of PABC-PP patients (p = 0.04), were found to have a VUS (Table 1).
Regarding tumor biology, most (68.1%, n = 49) patients had histologic grade 3 disease (PABC-P: 75.0%, n = 21 vs PABC-PP: 63.6%, n = 28; p = 0.62) (Table 2). Triple negative (Estrogen receptor (ER) negative, progesterone receptor (PR) negative, Her 2 negative) tumors were seen in 29.7% (n = 22) of patients (PABC-P: 32.1%, n = 9 vs PABC-PP: 28.3%, n = 13; p = 0.72). Hormone receptor positive (+) tumors (ER + and/or PR+) were seen in 58.1% (n = 43) of women (PABC-P: 57.1%, n = 16 vs PABC-PP: 58.7%, n = 27; p = 0.90). Her2 + tumors were seen in 25.7% (n = 19) of patients (PABC-P: 25.0%, n = 7 vs PABC-PP: 26.1%, n = 12; p = 0.92) (Table 2).
Overall, 45.9% of patients received neoadjuvant chemotherapy, and while patients with PABC-PP were more likely to receive neoadjuvant chemotherapy the finding was not statistically significant (32.1%, n = 9 vs 54.3%, n = 25; p = 0.06) (Table 3). There was no significant difference in the time to the start of neoadjuvant chemotherapy (median 20.0 days [IQR: 16.0, 36.0] vs 18.0 days [IQR: 14.0, 29.0] days, p = 0.27) or in the number of cycles of neoadjuvant chemotherapy (median 6 cycles [IQR: 5.0, 8.0] vs 6 cycles [IQR: 4.0, 8.0], p = 0.82) for patients with PABC-P and PABC-PP, respectively. In patients treated with surgery initially, the median time from diagnosis to surgery was longer for patients with PABC-PP compare to PABC-P but was not statistically significant (35.0 days [IQR: 19.0, 160.5] vs 89.0 days [IQR: 33.0, 158.0] days, p = 0.17).
Postoperative pathology showed similar rates of pathologic complete response following neoadjuvant chemotherapy (33.3%, n = 3 vs 40.0%, n = 10; p = 0.99) for PABC-P and PABC-PP (Table 2).
Overall 18 patients (24.3%) were treated with lumpectomy and 56 patients (75.7%) with mastectomy. There was no significant difference in the rate of lumpectomy (25.0%, n = 7 vs 23.9%, n = 11; p = 0.92) or mastectomy (75.0%, n = 21 vs 76.1%, n = 35; p = 0.92) performed in patients with PABC-P and PABC-PP, respectively (Table 3). The most common type of mastectomy performed was a modified radical mastectomy (31.1%, n = 23) followed by skin sparing mastectomy (21.6%, n = 15), simple mastectomy (12.2%, n = 9), and nipple sparing mastectomy (10.8%, n = 8), with no significant difference in procedure performed regardless of whether patients were diagnosed during pregnancy or postpartum. Sentinel lymph node biopsy (39.3%, n = 11 vs 52.2%, n = 24; p = 0.28) and axillary dissection (14.3%, n = 4 vs 4.3%, n = 2; p = 0.19) were also statistically as likely to be performed in patients with PABC-P and PABC-PP, respectively. The rate of immediate breast reconstruction did not differ for PABC-P and PABC-PP patients (42.9%, n = 9 vs 65.7%, n = 23; p = 0.094). Of those undergoing immediate reconstruction, the majority had a tissue expander placed (PABC-P: 38.1%, n = 8 vs PABC-PP: 51.4%, n = 18; p = 0.31). A small number of patients underwent immediate direct to implant reconstruction (5.4%, n = 3), immediate autologous reconstruction (5.4%, n = 3), or delayed reconstruction (5.4%, n = 3). Contralateral prophylactic mastectomy was performed at the time of the initial surgery in 43.2% (n = 32) of patients (PABC-P: 39.3%, n = 11 vs PABC-PP: 45.7%, n = 21; p = 0.59). Patients with a known pathogenic mutation were more likely to undergo contralateral prophylactic surgery at the time of initial management as compared to patients with a VUS or no identified mutation (81.3% vs 33.3%, p < 0.001). Margin re-excision was required and performed in 12.2% (n = 9) of patients (PABC-P: 10.7%, n = 3 vs PABC-PP: 13.0%, n = 6; p = 0.99) (Table 3).
The majority (79.7%, n = 59) of patients did not experience any postoperative complications, regardless of whether they underwent lumpectomy or mastectomy (lumpectomy: 83.3%, n = 15 vs mastectomy: 78.6%, n = 44; p = 0.99) or if they were diagnosed and treated during pregnancy or postpartum (PABC-P: 89.3%, n = 25 vs PABC-PP: 73.9%, n = 34; p = 0.11) (Table 4). Notably, 60% (n = 9) of the total observed complications (n = 15) were seen in PABC-PP patients who had mastectomy with immediate reconstruction. There was a statistically significant difference in the rate of complications between PABC-P patients undergoing mastectomy with immediate reconstruction (n = 0, 0%) as compared to the PABC-PP patients (n = 9, 39%; p = 0.035).
Seroma was the most commonly observed complication after both lumpectomy and mastectomy (lumpectomy: 16.7%, n = 3 vs mastectomy: 8.9%, n = 5; p = 0.39) (Table 4). Superficial and deep surgical site infections were observed in 5.4% (n = 3) and 1.8% (n = 1) of patients undergoing mastectomy, respectively; no infections were observed following lumpectomy (Table 4). One patient was diagnosed with partial nipple necrosis which was managed conservatively (Table 4). Two patients, one of whom was treated with lumpectomy and the other who was treated with mastectomy with reconstruction, experienced wound dehiscence (Lumpectomy: 5.6% vs Mastectomy: 1.8%; p = 0.43) (Table 4). There were no milk duct fistulas observed (Table 4). Seven of the PABC-PP patients (9.5%) required reoperation for surgical complications within 30 days of their initial surgery (Table 4). Indications for reoperation included flap necrosis (n = 3), removal of an infected tissue expander (n = 1), surgical site washout (n = 2), and recurrent chest wall mass (n = 1) in a patient with stage IV disease. Patients with PABC-PP were more likely to require reoperation than patients with PABC-P (PABC-P: 0% vs PABC-PP: 15.2%, n = 7; p = 0.04) (Table 4). There were two readmissions during this period of time (2.7%), both of whom were admitted after their reoperation (Table 4).
Postoperatively, 86.8% (n = 33) of patients received adjuvant endocrine therapy, 62.0% (n = 44) received adjuvant radiation, and 61.6% (n = 45) received adjuvant chemotherapy (Table 3). Patients diagnosed in the postpartum period were not significantly more likely to receive adjuvant radiation than patients diagnosed during pregnancy (PABC-P: 48.1%, n = 13 vs 70.5%, n = 31; p = 0.06) (Table 3). Likewise, patients who underwent lumpectomy were not more likely to get radiation than patients who were treated with mastectomy (lumpectomy: 70.6%, n = 12 vs mastectomy: 59.3%, n = 32; p = 0.40). The median time in days to radiation after surgery, including patients treated with systemic therapy prior to radiation therapy, was not significantly different for PABC-P and PABC-PP (75.0 [IQR: 42.0, 191.0] vs 62.0 [IQR: 42.0, 156.0] days, p = 0.45).