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Table 1 Characteristics of the studies included in the meta-analysis

From: Prognosis of pregnancy-associated breast cancer: a meta-analysis

Study ID Country No. of PABC cases No. of controls PABC definition Cancer stage or grade Mean/median age of PABC Follow-up years Outcomes measured HR estimate HR 95% CI NOS score Matching criteria Adjusting variable
Mausner, 1969 [22] USA 73 647 Pregnancy & < 6 months postpartum Stage I II III, Grade I II III 35 5 OS indirect 1.36 1.07–1.73 7
Wallgren, 1977 [23] Sweden 15 58 Pregnancy & < 12 months postpartum Grade I II III < 30 10 OS indirect 1.35 0.71–2.58 7
Nugent, 1985 [24] USA 19 155 Pregnancy Stage I II III 32 5 OS indirect 0.96 0.55–1.67 6
Tretli, 1988-Pregnancy [25] Norway 20 40 Pregnancy Stage I II III 33 4 OS indirect 2.41 1.32–4.37 6 Diagnosed year, diagnosed age
Tretli, 1988-Postpartum [25] Norway 15 40 Unspecified Stage I II III 36 4 OS indirect 1.47 0.66–3.27 6
Greene, 1988 [26] USA 8 36 Pregnancy NA <35 14 OS indirect 1.50 0.18–12.62 6
Petrek, 1991 [27] USA 56 166 Pregnancy & < 12 months postpartum NA 5 OS paper 0.74 0.37–1.45 6 Node status
Zemlickis, 1992 [28] Canada 102 269 Pregnancy & postpartum (unspecified) Stage 0 I II III IV 33 25 CSS indirect 1.25 0.93–1.69 8 Stage, age at diagnosis
Ishida, 1992 [29] Japan 192 191 Pregnancy & < 24 months postpartum Stage 0 Tis I II III IV 32 10 OS indirect 2.00 1.27–3.16 6  
Guinee, 1994-Pregnancy [30] USA 26 139 Pregnancy NA 28(20–29) 10 OS paper 2.83 1.24–6.45 8 Tumour size, number of positive axillary nodes
Guinee, 1994-Postpartum [30] USA 40 139 < 12 Months postpartum NA 28(20–29) 10 OS paper 1.88 0.88–3.98 8
Von Schoultz, 1995 [31] Sweden 173 1740 Pregnancy & < 60 months postpartum NA < 50 7 DFS paper 1.02 0.72–1.43 9 Age, nodal status, tumour size, ER status
Ezzat, 1996-OS [32] Saudi Arabia 28 84 Pregnancy Stage I II III 20–45 7 OS paper 0.90 0.6–1.3 6 Year of diagnosis, date of beginning
Ezzat, 1996-DFS [32] Saudi Arabia 28 84 Pregnancy Stage I II III 20–45 7 DFS paper 1.10 0.8–1.5 6
Anderson, 1996-OS [33] USA 22 205 Pregnancy & < 12 months postpartum Stage 0 I II IIIa < 30 10 OS paper 2.40 1.28–4.50 8 Stage, axillary LN involvement, adjuvant CT, tumour size
Anderson, 1996-DFS [33] USA 22 205 Stage 0 I II IIIa < 30 10 DFS indirect 3.19 1.20–8.49 8
Bonnier, 1997-OS [34] France 154 308 Pregnancy & < 6 months postpartum Grade I II III 33.9(23.2–46.4) 5 OS paper 1.46 0.72–2.96 6 Clinical tumour size, microscopic lymph-node involvement, inflammatory cancer, age
Bonnier, 1997-DFS [34] France 154 308 Grade I II III 5 DFS paper 1.48 1.00–2.19 6
Olson, 1998 [35] USA 146 NA < 45 15 OS paper 7 Age, tumour size, lymph nodes, ER status, histology
Reeves, 2000 [36] UK Stage I II III IV < 60 > 10 OS paper 9 Age at diagnosis, year of diagnosis, hospital, weight in kg
Ibrahim, 2000 [37] Saudi Arabia 72 216 Pregnancy Stage I II III IV, Grade I II III 34 10 OS indirect 0.94 0.62–1.44 6 Age, stage, year of diagnosis
Daling, 2002 [38] USA 83 309 < 24 Months postpartum Stage I II III IV < 45 5 OS indirect 2.30 1.4–3.9 9 Age, diagnosis year
Aziz, 2003 [39] Pakistan 24 48 Pregnancy & < 12 months postpartum NA 32(20–45) 7 OS indirect 1.67 0.82–3.41 6 Age, tumour grade, tumour size, axillary lymph node status
Siegelmann-Danieli, 2003-OS [40] Israel 22 192 Pregnancy & < 12 months postpartum NA 33(25–27) 5 OS indirect 3.39 0.58–19.81 6
Siegelmann-Danieli, 2003-DFS [40] Israel 20 181 NA 33(25–28) 5 DFS indirect 4.81 1.46–15.9 6
Bladstrom, 2003 [41] Sweden 94 14,599 Pregnancy NA ≤45 5 OS paper 2.40 2.0–2.9 9 Age, time of diagnosis, time period interaction, number of children, age at first child’s birth
Bladstrom, 2003(2) [41] Sweden 94 14,599 Pregnancy NA ≤45 10 OS paper 1.20 0.9–1.7 9
Whiteman, 2004 [42] USA 59 355 < 12 Months postpartum NA 20–45 15 OS paper 1.51 1.02–2.23 9 Surgery, radiation therapy, race, oral contraceptive use, education, BMI, stage history of breast disease
Rodriguez, 2008 [43] USA 797 4177 Pregnancy & < 12 months postpartum Stage I II III IV < 55 13 OS paper 1.14 1.00–1.29 9 Race, tumour size, AJCC stage, surgery, hormone receptor
Stensheim, 2009-Pregnancy [44] Norway 59 13,106 Pregnancy NA < 50 5 CSS paper 1.23 0.82–1.81 7 Age, diagnostic period, initial extent of disease
Stensheim, 2009-Postpartum [44] Norway 46 13,106 < 6 Months postpartum NA < 50 5 CSS paper 1.95 1.36–2.78 7
Beadle, 2009-OS [45] USA 104 564 Pregnancy & < 12 months postpartum Stage I II III ≤35 10 OS indirect 1.24 0.87–1.79 6
Beadle, 2009-DFS (distant metastasis) [45] USA 104 564 Pregnancy & < 12 months postpartum Stage I II III ≤35 10 DFS indirect 1.35 0.98–1.85 6
Beadle, 2009-DFS (locoregional recurrence) [45] USA 104 564 Stage I II III ≤35 10 DFS indirect 1.44 0.78–2.66 6
Halaska, 2009-OS [46] Greece 32 32 Pregnancy & < 12 months postpartum Grade I II III < 45 10 OS indirect 1.42 0.58–3.48 6 Age at diagnosis, tumour size, axillary lymph node status, presence or absence of metastatic deposits
Halaska, 2009-DFS [46] Greece 32 32 Grade I II III < 45 10 DFS indirect 1.82 0.82–4.05 6
Largillier, 2009-OS [47] France 105 788 Pregnancy & < 12 months postpartum Grade I II III <35 10 OS paper 1.51 1.05–2.20 7
Largillier, 2009-DFS [47] France 105 788 Grade I II III <35 10 DFS paper 1.25 0.90–1.74 7
Phillips, 2009 [48] Multicentre 676 NA 10 OS paper 8 Study centre, education, BMI, time since last full-term pregnancy, age at diagnosis
Moreira, 2010 [49] Brazil 87 252 Pregnancy & < 12 months postpartum NA ≤ 45 10 OS paper 1.52 1.10–2.10 7 Registration institution, age, registration year
Johansson, 2011 [50] Sweden 1110 14,611 Pregnancy & < 24 months postpartum NA 15–44 15 OS paper 1.51 1.36–1.68 7 Age, calendar time, education
Murphy, 2012 [51] USA 99 186 Pregnancy & < 12 months postpartum Grade 0 I II III 35(24–48) 18 OS paper 0.59 0.29–1.17 7 Age, year of diagnosis Tumour grade, ER status, LN involvement
Azim, 2012-OS [52] Italy 65 130 Pregnancy NA < 50 6 OS paper 1.70 0.80–3.90 7 Age, year of surgery, pathological tumour size, pathological nodal status pN, neoadjuvant chemotherapy, ER
Azim, 2012-DFS [52] Italy 65 130 Pregnancy NA < 50 6 DFS paper 2.30 1.30–4.20 7 Age, pT, pN, neoadjuvant chemotherapy, Ki-67, HER2, perivascular invasion
Ali, 2012-OS [53] USA 40 40 Pregnancy & < 12 months postpartum Stage I II III IV 33(24–42) 16 OS indirect 2.15 1.13–4.09 7 Age and stage-matched
Ali, 2012-DFS [53] USA 40 40 Stage I II III IV 33(24–42) 16 DFS indirect 2.00 1.12–3.59 7
Amant, 2013-OS [54] Belgium 311 865 Pregnancy Stage I II III, Grade I II III 33(31–36) 5 OS paper 1.19 0.73–1.93 8 Age at diagnosis, stage, grading, histologic tumour type, ER/PR status, HER2, chemotherapy
Amant, 2013-DFS [54] Belgium 311 865 Pregnancy Stage I II III, Grade I II III 33(31–36) 5 DFS paper 1.34 0.93–1.91 8
Litton, 2013-OS [55] USA 75 150 Pregnancy Stage I II III 24–45 5 OS paper 1.87 1.04–3.36 7 Age at diagnosis, stage at diagnosis, year of diagnosis Age at diagnosis, year of diagnosis, clinical cancer stage, tumour nuclear grade
Litton, 2013-DFS [55] USA 75 150 Pregnancy Stage I II III 24–45 5 DFS paper 2.09 1.19–3.67 7
Valentini, 2013 [56] USA 75 269 Pregnancy & < 12 months postpartum NA 32.5(20–45) 15 OS paper 0.79 0.25–2.44 7 Age at diagnosis, tumour size, lymph node status, ER status, use of chemotherapy, oophorectomy
Dimitrakakis, 2013 [57] Greece 39 39 Pregnancy & < 12 months postpartum Stage I II III IV, Grade I II III 34.3 ± 5.0 5 OS paper 9.28 2.94–29.27 6 Stage, age, year of diagnosis Stage, ER status, grade, age at diagnosis
Calliha, 2013-OS [58] USA 76 86 Pregnancy & < 60 months postpartum Stage 0 I II III IV, Grade I II III ≤45 5 OS paper 2.65 1.09–6.42 6 Tumour biological subtype, clinical stage, year of diagnosis
Calliha, 2013-DFS [58] USA 74 84 Pregnancy & < 60 months postpartum Stage 0 I II III IV, Grade I II III ≤45 5 DFS paper 2.80 1.12–6.57 6 Tumour biological subtype, clinical stage, year of diagnosis, local recurrence
Bell, 2013-OS [59] Australia 13 377 Pregnancy & < 12 months postpartum NA < 48 5 OS paper 2.50 0.5–11.7 6
Bell, 2013-DFS [59] Australia 13 377 Pregnancy & < 12 months postpartum NA < 48 5 DFS paper 0.90 0.2–4.4 6
Moller, 2013 [60] UK Stage I II III IV 10–54 10 OS paper 7 Age, stage
Framarino-dei-Malatesta, 2014 [61] Italy 22 45 Pregnancy NA 37.2 ± 3.2 10 OS indirect 0.96 0.29–3.21 6 Age
Madaras, 2014 [62] Hungary 31 31 Pregnancy & < 12 months postpartum 34 10 OS indirect 5.76 2.09–15.98 7 Age, year of first breast cancer diagnosis
Nagatsuma, 2014 [63] Japan Stage 0 I II III IV, Grade I II III 26–44 10 OS paper 7 Age at diagnosis, AJCC clinical stage, histological tumour grade, oestrogen and progesterone receptor status, HER2 status
Strasser-Weippl, 2014 [64] China 109 1274 Pregnancy & < 60 months postpartum Grade I II III < 45 5 DFS paper 1.62 1.04–2.54 8 Age, oestrogen receptor, progesterone receptor, HER2 status, disease stage
Genin, 2015-OS [65] France 87 174 Pregnancy & < 12 months postpartum Grade I II III 35(27–40) 10 OS indirect 1.09 0.79–1.52 7 Age, year of diagnosis
Genin, 2015-DFS [65] France 87 174 Pregnancy & < 12 months postpartum Grade I II III 35(27–40) 10 DFS paper 1.87 1.05–3.33 7 Age, year of diagnosis Age, ER, HR status, tumour stage, HER2 status, Ki-67 rate
Iqbal, 2017 [14] Canada 501 5832 Pregnancy & < 21 months postpartum Stage I II III IV 20–45 5 OS paper 1.11 0.86–1.45 9 Year of diagnosis, age, tumour size, nodal status, oestrogen receptor status, progesterone receptor status, chemotherapy, radiotherapy, et al
Kim, 2017 [66] Korea 344 668 Pregnancy & < 12 months postpartum Stage 0 I II III IV, Grade I II III 20–45 10 OS indirect 1.85 1.28–2.67 8 Operation period, age, initial stage
Bae, 2018(1) [67] Korea 40 2770 Pregnancy & < 12 months postpartum Stage 0 I II III 33.5 (27–40) 5 CSS paper 4.00 1.20–12.90 8 Age, stage, chemotherapy
Bae, 2018(2) [68] Korea 411 83,381 Pregnancy & < 12 months postpartum Stage 0 I II III IV 20–49 15 OS paper 1.03 0.74–1.42 9 Age at diagnosis, stage, high versus low/intermediate, luminal subtype, HER2 subtype, et al
Boudy, 2018-DFS [16] France 49 51 Pregnancy Grade I II III < 46 5 DFS indirect 1.19 0.75–1.91 8 Propensity score
Boudy, 2018-CSS [16] France 49 51 Pregnancy Grade I II III < 46 5 CSS indirect 1.06 0.65–1.72 8
Johansson, 2018 [2] Sweden 778 1661 Pregnancy & < 24 months postpartum Stage 0 I II III IV 15–44 10 OS indirect 0.90 0.55–1.40 9 Age, period, education, region, tumour characteristics, pathologic T stage, N stage, ER/PR
Chuang, 2018 [69] China (Taiwan) Stage I II III 20–50 > 10 OS paper 9 Age and year of diagnosis, stage, tumour size, positive lymph nodes, histological grading, treatments
Ploquin, 2018-OS [15] France 111 253 Pregnancy Stage 0 I II III IV 22–46 5 OS paper 1.10 0.67–1.79 8 Age, clinical T stage, hormone receptor Clinical nodal status, age
Ploquin, 2018-DFS [15] France 111 253 Pregnancy Stage 0 I II III IV 22–46 5 DFS paper 1.15 0.78–1.68 8
Suleman, 2019-OS [70] Saudi Arabia 110 114 Pregnancy Stage I II III IV 20–48 > 10 OS indirect 2.58 1.26–5.26 7 Diagnosed year
Suleman, 2019-DFS [70] Saudi Arabia 110 114 Pregnancy Stage I II III IV 20–48 > 10 DFS indirect 1.18 0.70–1.97 7
Choi, 2019 [17] Korea 63 3804 Pregnancy & < 12 months postpartum NA < 50 10 OS paper 1.52 0.82–2.83 8 Histologic type, stage, ER, PR, age at diagnosis, Charlson comorbidity index
  1. BMI Body mass index, ER Oestrogen receptor, PR Progesterone receptor, HER-2 Human epidermal growth factor receptor-2