Appendix 1. CENTRAL search strategy

#1 MeSH descriptor: [Breast Neoplasms] explode all trees

#2 (advanced breast cancer* or advanced breast neoplas* or advanced breast tumour* or advanced breast tumor*):ti,ab,kw

#3 (metastatic breast cancer* or metastatic breast neoplas* or metastatic breast tumour* or metastatic breast tumor*):ti,ab,kw

#4 #1 and (#2 or #3)

#5 MeSH descriptor: [Mastectomy] explode all trees

#6 MeSH descriptor: [Mastectomy, Radical] explode all trees

#7 MeSH descriptor: [Mastectomy, Segmental] explode all trees

#8 MeSH descriptor: [Mastectomy, Simple] explode all trees

#9 MeSH descriptor: [Mastectomy, Subcutaneous] explode all trees

#10 (Mastectom* or Segmentectom* or partial mastectom* or limited resection mastectom* or Lumpectom* or Local Excision Mastectom* or breast‐conserving surger* or Extended Radical Mastectom*):ti,ab,kw

#11 #5 or #6 or #7 or #8 or #9 or #10

#12 #4 and #11

Search updates (24 Ferbruary 2016)

#1 MeSH descriptor: [Breast Neoplasms] explode all trees
#2 breast near cancer*
#3 breast near neoplasm*
#4 breast near carcinoma*
#5 breast near tumour*
#6 breast near tumor*
#7 #1 or #2 or #3 or #4 or #5 or #6
#8 #7 and (advance* or metasta* or stage IV or stage 4 or stage four)
#9 ("advanced breast cancer*" or "advanced breast neoplas*" or "advanced breast tumour*" or "advanced breast tumor*"):ti,ab,kw
#10 ("metastatic breast cancer*" or "metastatic breast neoplas*" or "metastatic breast tumour*" or "metastatic breast tumor*"):ti,ab,kw
#11 #8 or #9 or #10
#12 MeSH descriptor: [Mastectomy] explode all trees
#13 MeSH descriptor: [Mastectomy, Radical] explode all trees
#14 MeSH descriptor: [Mastectomy, Segmental] explode all trees
#15 MeSH descriptor: [Mastectomy, Simple] explode all trees
#16 MeSH descriptor: [Mastectomy, Subcutaneous] explode all trees
#17 (Mastectom* or Segmentectom* or Lumpectom*):ti,ab,kw
#18 "breast surger*":ti,ab,kw
#19 "breast resection":ti,ab,kw
#20 "breast amputation":ti,ab,kw
#21 "breast‐conserving surger*":ti,ab,kw
#22 #12 or #13 or #14 or #15 or #16 or #17 or #18 or #19 or #20 or #21
#23 #11 and #22

Appendix 2. MEDLINE search strategy

1. randomized controlled trial[pt] OR controlled clinical trial[pt] OR randomized[tiab] OR placebo[tiab] OR drug therapy[sh] OR randomly[tiab] OR trial[tiab] OR groups[tiab]

2. (((Breast neoplasms[mh] OR ((breast[mh] OR breast diseases[mh]) AND neoplasms[mh])) AND humans[mh]) OR DCIS[tiab] OR LCIS[tiab] OR ductal carcinoma in situ[tiab] OR lobular carcinoma in situ[tiab] OR (breast[tiab] AND (ductal carcinoma*[ti] OR lobular carcinoma*[ti])) OR ((Breast[ti] OR mammary[ti]) AND (cancer*[ti] OR neoplas*[ti] OR tumor*[ti] OR tumour*[ti] OR carcinoma*[ti] OR malignan*[ti] OR sarcoma[ti] OR lymphoma[ti]))) AND (Neoplasm Metastasis[Mh] OR secondary[sh] OR Neoplasm Recurrence, Local[mh] OR metast*[tiab] OR advanced[tiab] OR recurren*[tiab] OR HER‐2*[tiab] OR HER2*[tiab] OR N1[tiab] OR N2[tiab] OR N2a[tiab] OR N2b[tiab] OR N3[tiab] OR N3a[tiab] OR N3b[tiab] OR N3c[tiab] OR M1[tiab] OR pN1*[tiab] OR pN2*[tiab] OR pN3*[tiab] OR stage IV[tiab] OR stage four[tiab] OR stage 4[tiab] OR local*[tiab] OR loco*[tiab] OR region*[tiab] OR LABC[tiab] OR T3[tiab] OR T4[tiab] OR Stage III*[tiab] OR Stage three*[tiab] OR stage 3*[tiab])

3. (“Mastectomy” [Mesh]) OR (Mastectomies) OR (Mammectomy) OR (Mammectomies) OR (Mastectomies, Segmental) OR (Segmental Mastectomies) OR (Segmental Mastectomy) OR (Segmentectomy) OR (Segmentectomies) OR (Partial Mastectomy) OR (Mastectomies, Partial) OR (Mastectomy, Partial) OR (Partial Mastectomies) OR (Limited Resection Mastectomy) OR (Limited Resection Mastectomies) OR (Mastectomies, Limited Resection) OR (Mastectomy, Limited Resection) OR (Resection Mastectomies, Limited) OR (Resection Mastectomy, Limited) OR (Lumpectomy) OR (Local Excision Mastectomy) OR (Excision Mastectomies, Local) OR (Excision Mastectomy, Local) OR (Local Excision Mastectomies) OR (Mastectomies, Local Excision) OR (Mastectomy, Local Excision) OR (Breast‐Conserving Surgery) OR (Breast Conserving Surgery) OR (Breast‐Conserving Surgeries) OR (Surgeries, Breast‐Conserving) OR (Surgery, Breast‐Conserving) OR (Surgery, Breast Conserving) OR (Extended Radical Mastectomies) OR (Extended Radical Mastectomy) OR (Mastectomies, Extended Radical) OR (Radical Mastectomies, Extended) OR (Radical Mastectomy, Extended)

4. #1 AND #2 AND #3

5. #4 NOT (animals [mh] NOT humans [mh])

Appendix 3. Embase search strategy

1. random* OR factorial* OR crossover* OR cross NEXT/1 over* OR placebo* OR (doubl* AND blind*) OR (singl* AND blind*) OR assign* OR allocat* OR volunteer*OR 'crossover procedure'/exp OR 'double blind procedure'/exp OR 'randomized controlled trial'/exp OR 'single blind procedure'/exp

2. 'advanced breast cancer'/exp OR 'advanced breast cancer'

3. 'advanced breast carcinoma'

4. 'advanced breast neoplasm'

5. 'advanced breast tumour'

6. 'advanced breast tumor'

7. 'metastatic breast cancer'/exp OR 'metastatic breast cancer'

8. 'metastatic breast carcinoma'

9. 'metastatic breast neoplasm'

10. 'metastatic breast tumour'

11. 'metastatic breast tumor'

12. #2 OR #3 OR #4 OR #5 OR #6 OR #7 OR #8 OR #9 OR #10 OR #11

13. 'breast surgery'/exp OR 'breast surgery'

14. 'mastectomy'/exp OR 'mastectomy'

15. 'partial mastectomy'/exp OR 'partial mastectomy'

16. 'breast conserving surgery'/exp OR 'breast conserving surgery'

17. 'breast sparing surgery'/exp OR 'breast sparing surgery'

18. 'lumpectomy'/exp OR lumpectomy

19. 'partial breast resection'/exp OR 'partial breast resection'

20. 'breast amputation'/exp OR 'breast amputation'

21. 'breast resection'/exp OR 'breast resection'

22. 'extended radical mastectomy'

23. 'modified radical mastectomy'

24. 'simple mastectomy'

25. 'radical mastectomy'/exp OR 'radical mastectomy'

26. 'total mastectomy'/exp OR 'total mastectomy'

27. #13 OR #14 OR #15 OR #16 OR #17 OR #18 OR #19 OR #20 OR #21 OR #22 OR #23 OR #24 OR #25 OR #26

28. #1 AND #12 AND #27

29. #28 NOT ([animals]/lim NOT [humans]/lim)

30. #29 AND [embase]/lim

Appendix 4. Embase (via OvidSP) search strategy

Appendix 5. WHO ICTRP search strategy

Basic searches:

1. Breast surgery for metastatic breast cancer

2. Metastatic breast cancer AND breast surger*

3. Metastatic breast cancer AND mastectom*

4. Metastatic breast cancer AND lumpectom*

5. Advanced breast cancer AND breast surger*

6. Advanced breast cancer AND mastectom*

7. Advanced breast cancer AND lumpectom*

Advanced searches:

1. Title: breast surgery for metastatic breast cancer

Recruitment: ALL

2. Condition: metastatic breast cancer

Intervention: mastectom* OR lumpectom* OR breast surger* OR breast conserving surger*

Recruitment: ALL

3. Condition: advanced breast cancer

Intervention: mastectom* OR lumpectom* OR breast surger* OR breast conserving surger*

Recruitment: ALL

Appendix 6. ClinicalTrials.gov search strategy

Basic searches:

1. Breast surgery for metastatic breast cancer

2. Metastatic breast cancer AND breast surgery

3. Metastatic breast cancer AND mastectomy

4. Metastatic breast cancer AND lumpectomy

5. Advanced breast cancer AND breast surgery

6. Advanced breast cancer AND mastectomy

7. Advanced breast cancer AND lumpectomy

Advanced searches:

1. Title: breast surgery for metastatic breast cancer

Recruitment: All studies

Study results: All studies

Study type: All studies

Gender: All studies

2. Condition: metastatic breast cancer

Intervention: mastectomy OR lumpectomy OR breast surgery OR breast conserving surgery

Recruitment: All studies

Study results: All studies

Study type: All studies

Gender: All studies

3. Condition: advanced breast cancer

Intervention: mastectomy OR lumpectomy OR breast surgery OR breast conserving surgery

Recruitment: All studies

Study results: All studies

Study type: All studies

Gender: All studies