Prognosis Of Synchronous Bilateral Breast Cancer

Dissections

OBSERVATIONAL 28 August 2009

Evidence-based Medicine for Surgeons Prognosis of synchronous bilateral breast cancer

Authors: Irvine T, Allen DS, Gillett C, et al Journal: British Journal of Surgery 2009; 96: 376–380 Centre: Hedley Atkins Breast Unit, Guy’s Hospital, London, UK

BACKGROUND

Breast cancer is the commonest female malignancy. Data regarding the incidence of synchronous bilateral breast cancer (SBBC) are sparse; most studies indicate that fewer than 2% of patients have synchronous bilateral breast cancer. By allocating adjuvant systemic therapy according to the tumour with the worst prognosis, the assumption is being made that overall prognosis is not affected by the second lesion. There are few published data on SBBC that address this issue.

IN

SUMMARY

Prognosis of synchronous bilateral breast cancer

RESEARCH QUESTION Population Data on women with with bilateral synchronous invasive breast cancers, obtained from the Guy's Hospital breast cancer database. Indicator variable Patients with SBBC of any histological subtype, deemed to have operable disease at presentation. Outcome variable Primary: overall and disease-free survival after a minimum of 5.5 yrs of follow up. Comparison Matched controls with unilateral breast cancer.

SBBC

Matched controls

68

128

5-yr disease-free

68%

72%

10-yr disease free

57%

55%

5-yr overall

81%

81%

69%

60%

Number Survival after treatment

10-yr overall

None of the differences were statistically significant Forty (59%) of the women with SBBC had bilateral mastectomy and 21 (31%) had bilateral breast-conserving surgery. The remaining 7women had mastectomy for one tumour and breast-conserving surgery for the other. Fifty-six (82%) of the women with SBBC were estrogen receptor positive for one or both tumours. Thirty-two women did not receive any systemic therapy; 28 of these patients had known receptor status and all had estrogen receptor-positive tumours. Authors' claim(s): “...Prognosis was determined by the tumour with the worst prognosis, with no additional worsening of outcome incurred from the second tumour.”

THE TISSUE REPORT In situations where the disease being studied is rare and there is a need for follow up over extended periods of time, prospective studies are rare and difficult to carry out. A well done, case-controlled study may provide the best alternative. The rareness of the clinical condition limits such studies to large centres that have a declared interest in the problem, such as the source of the this one.

EBM-O-METER Evidence level

Overall rating

Bias levels

Double blind RCT

Sampling

Randomized controlled trial (RCT) Prospective cohort study - not randomized Case controlled study Case series - retrospective

Trash Life's too short for this

Swiss cheese Full of holes

Safe Holds water



Newsworthy “Just do it”

Comparison Measurement

l | Novel l | Feasible l Ethical l | Resource saving l

Interesting

The devil is in the details (more on the paper) ...

© Dr Arjun Rajagopalan



SAMPLING Sample type Simple random Stratified random Cluster Consecutive Convenience Judgmental

Inclusion criteria

Exclusion criteria

Bilateral synchronous invasive breast cancers of any histological subtype, deemed to have operable disease at presentation.  All women who had a contralateral invasive breast cancer diagnosed within 6 months of the first primary ?

Final score card

Primary treatment elsewhere  Locally advanced disease at presentation  Unilateral or bilateral ductal carcinoma in situ 

SBBC

Controls

?

?

Accessible

94

?

Intended

92

136

Drop outs

?

?

68

128

Target

Study

 = Reasonable | ? = Arguable |  = Questionable Duration of the study: all women in the Guy’s Hospital breast cancer database up to the end of 2001 Sampling bias: In situations where the disease being studied is rare and there is a need for follow up over extended periods of time, prospective studies are rare and difficult to carry out. A well done, case-controlled study may provide the best alternative.

COMPARISON Randomized

Case-control

Non-random

Historical

None

Controls - details Allocation details

The tumour with the worst prognosis was determined for each woman with SBBC using the Guys Risk prognostic model. Two controls were matched to each woman with SBBC when possible, using age within 10 years at time of diagnosis, date of diagnosis within 5 years and menopausal status. The characteristics of the tumour with the worst prognosis were matched for clinical tumour size within 5 mm (in the absence of records of clinical tumour size, pathological size was used), pathological tumour type and grade, and axillary lymph node and oestrogen receptor status.

Comparability

The two groups were comparable in all major aspects.

Disparity

It was possible to find only one control that matched these criteria for 8 women. All others had two controls.

Comparison bias: None of significance.

MEASUREMENT Measurement error

1.Survival data at 5 and 10 years - disease-free and overall

Y

-

Y

-

-

Measurement bias: None of note. The outcomes measured are simple, objective, discrete variables.

© Dr Arjun Rajagopalan

Blinding

N

Scoring

?

Protocols

Y

Training

Device suited to task

Observer error Gold std.

Device error Repetition

Device used

-

-