Syllabi - General Surgery - Diagnosis Scenario

You see a 44 year old lady in your multidisciplinary follow-up breast clinic. She had a wide local excision and axillary clearance for a 1.7cm Grade 2 ductal carcinoma 2 years ago. Two of 17 axillary nodes were positive for tumour, and she recieved postoperative radiotherapy to the breast tissue, sandwiched with 6 cycles of CMF chemotherapy. Ever since the radiotherapy, the area under the surgical scar has been very firm. A routine follow-up mammogram show increasing density and architectural distortion in this area, and there is a concern about local recurrence. A core biopsy was unsatisfactory because of the very hard consistency of the tissue. Because of the size and site of the mammographic abnormality, a diagnostic excision biopsy is likely to leave a very poor cosmetic result. The patient is very keen to avoid a mastectomy if at all possible. You explain that you cannot be sure whether she has local recurrence or not. She asks (a) What is the best method of investigating this without further surgery? (b) How good is this method?

Together, you formulate the question:
In a patient with a history of breast cancer and breast conserving surgery what is the best method for detecting local recurrence? AND How accurate is it?

You search Medline using the terms 'breast neoplasms' and 'screening' and 'mastectomy'. You find an article by Drew et al and decide to review it. Ann Surg Oncol 1998;5:265-70

Read the article and decide:

Are the results of this study of diagnosis valid?
Are the results of the study important?
Can you apply this valid, important evidence about diagnosis to the treatment of your patient?

Completed Diagnosis Worksheet for Evidence-Based General Surgery

Citation

Drew PJ, Kerin MJ, Turnbull LW, Imrie M, Carleton PJ, Fox JN & Monson JRT. Routine screening for local recurrence following breast-conserving therapy for cancer with dynamic contrast-enhanced magnetic resonance imaging of the breast.
Ann Surg Oncol 1998;5:265-70

Are the results of this diagnostic study valid?

Was there an independent, blind comparison with a reference ("gold") standard of diagnosis?: Yes. The standard used (mammography plus palpation, but without routine use of ultrasound) could be criticised as suboptimal, but is representative of contemporary specialist practice in the UK.
Was the diagnostic test evaluated in an appropriate spectrum of patients (like those in whom it would be used in practice)?: Probably. The new test (MRI) was offered to women undergoing breast-conserving therapy. The paper does not mention any exclusions, and it does not say how many women refused to take part, nor whether they were different from those who participated.
Was the reference standard applied regardless of the result of the new diagnostic test?: Yes

Are the valid results of this diagnostic study important?

	Outcome
MRI Result	Cancer	Benign	Likelihood Ratio
Positive	9/9	6/96	16*
Negative	0/9	90/96	0

Can I apply this valid, important evidence about a diagnostic test in caring for my patient?

Is the diagnostic test available, affordable, accurate and precise in my setting?: Is the diagnostic test available, affordable, accurate and precise in my setting?
Can I generate a clinically sensible estimate of my patient's pre-test probability of having local recurrence?: The scenario suggests that there is enough clinical thickening to raise concern, but no convincing features of recurrence. From experience, I would guess at a pretest probability of cancer of maybe 20% in this situation.
Will the resulting post-test probabilities affect my management and help the patient?: The pre-test odds are 1:5, x the LR of 16 = post test odds of 16:5 or 3.2:1. This is equivalent to a post-test probability of having recurrent cancer of 76% if the MRI is positive: this would certainly be enough to recommend biopsy.
Would the consequences of the test help my patient?: Yes, provided she was not so determined to avoid surgery that nothing could sway her.

Clinical Bottom Line

This looks like a considerable advance for the diagnosis of local recurrence after breast conserving surgery. We need to be sure that it can be done everywhere, not just by one group of experts.

Additional Notes

Breast cancer recurrence: MRI may help in the diagnosis

Clinical Bottom Line

MRI may be helpful in the diagnosis of local recurrence of breast cancer.

Citation

Clinical Question

In a patient with a history of breast cancer and breast conserving surgery, what is the best method for detecting local recurrence?

Search Terms

breast cancer and recurrence and screening in Medline

The Study

The Study Patients: women with breast cancer undergoing breast conserving surgery

Study Feature	Yes	Can't Tell
Independent?	x
Blind?	x
Standard applied regardless of test result?	x
Appropriate spectrum...?		x

Target disorder and Gold Standard: mammography and palpation
Diagnostic test: MRI

The Evidence

	Disorder
	Present		Absent
Test Result	Num.	Prop.	Num.	Prop.	LR
Positive	9	a	6	b	16.00
Negative	0	c	90	d	0.00

Sensitivity: 100%; CI: 100 to 100
Specificity: 94%; CI: 89 to 98
Prevalence: 9%; CI: 3 to 14
Positive Predictive Value: 60%; CI: 51 to 69
Negative Predictive Value: 100%; CI: 100 to 100

Comments

Small numbers

Particular to my patient:
Pre-test probability: 20%
Test Result Post-test probability
Positive 80%
Negative 0%