Role of intraoperative ultrasound in breast conservation surgery for non-palpable residual disease after neoadjuvant chemotherapy: A Prospective pilot study

Complete clinical response after neoadjuvant chemotherapy (NACT) in breast cancer makes localization of residual lesion challenging. This may lead to margin positivity and excess resection volumes in breast conserving surgery (BCS). Subsequently the cosmetic outcome is also affected. Currently there is no standard method for the preoperative localization or the amount of breast tissue to be resected in BCS. Recent literature has stated that intraoperative ultrasound (IOUS) gives good results in terms of localization of residual lesion, reducing re-excision rates, facilitating minimal breast tissue resection and better cosmetic outcome.

Aim

To study the feasibility of intraoperative ultrasound in localization of non-palpable residual lesion(radiologically detected) in BCS after NACT and evaluate the efficiency of the procedure

Objectives

Primary:

1. To compare adequacy of margin status by IOUS with frozen section analysis and final histopathology report

Secondary :

1. To determine the rate of margin positivity and re-excision
2. To assess the impact of IOUS on resection volumes and cosmetic outcome

Methodology

Study type-  Prospective

Study setting-  Regional Cancer Centre, Trivandrum

Study population-  Patients with non-palpable residual lesion(radiologically detected) after NACT in breast cancer undergoing BCS in RCC, Trivandrum

Sample size- 30

Inclusion criteria

All patients with non-palpable residual lesion(radiologically detected) after NACT in breast cancer undergoing BCS in RCC, Trivandrum

Exclusion criteria

1. Multiple residual lesions
2. Patients with previous surgery of affected breast

Technique

The marking of skin projection of residual lesion, measurement of size and distance of lesion from skin(mm) is done by the sonologist just prior to surgery. On table, breast tissue is held in uniform position throughout the procedure by hand. Linear array transducer probe covered with a sterile  glove that enables it to be used in the surgical field) is positioned and residual lesion is localised. A guide wire or needle is inserted into the residual lesion. Lesion size, lesion-to-skin distance and the lesion-to-pectoral fascia distance are measured in millimeters.

After making the incision, the skin flap is raised with the goal of obtaining 1 cm margin of healthy breast tissue around the tumour. Tumor resection margins marked using blue dye over breast tissue by insulin syringe and extent of dissection is guided by repeated use of ultrasound from different angles. The location and depth of the lesion will be continuously monitored to ensure the maintenance of adequate resection margins. Subsequently, a spherical lump of breast tissue excised with the desired 1 cm margin. If tumour location does not permit a clear 1 cm deep margin, pectoralis major fascia is taken. The wound bed is examined by ultrasound for residual lesion. The excised specimen is examined by ultrasound to  confirm adequate margins. If the margin appeared less than 1cm desired margin, additional breast tissue is resected in that direction. The specimen will be subjected to frozen section analysis and the margin status will be compared.

Post procedure

All patients will undergo axillary dissection. According to the final histopathology report, patient will receive adjuvant treatment as per standard protocol.

Calculation of Volumes and Resection Ratio

Parameters

1. Tumor diameter

2. Three dimensions of the surgical specimen

Volumes

1.TV(tumor volume)

2.ORV(optimal resection volume)

3.TRV(total resection volume).

• Tumor is defined as sphere. The diameter of the tumor (pT) corresponds to largest distance(in cm) between points on lesion margin.

TV = 4/3 p r3

p=3.14

• ORV is defined as spherical volume of tumor with an added 1.0 cm margin of healthy breast tissue

ORV = 4/3 p (r + 1.0 cm)3

• TRV represents volume of surgical specimen  defined as an ellipsoid. The three dimensions of the surgical specimen (in cm), as measured by the pathologist.

TRV = 4/3 p abc

a, b, and c representing half of each of the three dimensions of surgical specimen

• ERV represents the excess resection volume obtained by calculating the difference between total and optimal resection volumes.

ERV = TRV-ORV

• CRR represents the calculated resection ratio

CRR = TRV/ORV

If re-excision is performed, the re-excision volumes(4/3p(r)3) will be calculated and TRV will be the sum of resection volumes. In a perfect excision, TRV = ORV and CRR= 1.0. If TRV is twice the size of ORV, then CRR will be  2.0.

Margin status

If no residual cancer cells are found at resection margin, margin will be considered negative. For negative margins, the distance to the nearest margin(mm) will be noted. Margins will be considered positive when cancer cells are microscopically present at resection margin.

Cosmesis assessment

Patient will be followed up as per standard protocol for breast cancer. Cosmesis will be assessed at one month by patient and treating surgeon team independently. Patients will rate cosmesis using visual analogue scale as not satisfied, satisfied or extremely satisfied. Surgeon team will rate as acceptable, good or excellent.