LOCOREGIONAL

Locoregional recurrence may occur in up to 22% of patients undergoing breast conservation surgery and radiation.⁸ Breast cancer 10-year local recurrence rates in women with negative surgical margins who undergo lumpectomy and radiotherapy may be as low as 10% or less.^9–12 Although overall recurrence rates are low, higher recurrence rates have been reported in select patient groups, such as those with high-grade ductal carcinoma in situ (DCIS).¹³ In addition, recurrence rates in younger women and in women who do not undergo radiation therapy have been reported as high as 35%.¹⁴

Despite the increasing utilization of accelerated partial breast irradiation, the long-term impact on recurrence rate for these newer techniques compared with whole breast irradiation is currently unknown. These techniques include interstitial radiotherapy with a multicatheter approach, intraoperative radiotherapy (IORT), using either electrons produced by linear accelerators or 50-kV x-rays (Intrabeam), the balloon-catheter technique (MammoSite), or three-dimensional conformal external-beam radiotherapy.

Serial surveillance mammography, as well as diagnostic mammography when there is clinical suspicion of breast recurrence, remains the cornerstone of the imaging approach to previously treated breast cancer patients (Figure 1). Complementary studies include breast ultrasound and MRI, as discussed in Chapter 3 (Figures 2 and 3). Cases presented in this chapter illustrate the spectrum of imaging manifestations of locally recurrent breast cancer.

FIGURE 1 Bilateral mediolateral oblique (MLO) mammograms, obtained in a 57-year-old woman 9 months after a pathologic diagnosis of DCIS was made from the right side of bilateral reduction mammoplasty specimens. New left supra-areolar masses are indicated by the arrow, and increased size and density were noted of left axillary lymph nodes.

FIGURE 2 Ultrasound of the same patient in Figure 1 shows one of multiple solid masses identified by ultrasound. This mass has particularly suspicious sonographic features: it is solid and irregularly marginated with no definable capsule, and a tail of suspected ductal extension can be seen extending to the right (arrow).

FIGURE 3 Contrast-enhanced axial breast MRI maximal intensity projection view of the same patient shows multiple intensely enhancing masses in the left subareolar region (arrow). Multifocal infiltrating ductal carcinoma was confirmed at subsequent mastectomy.

Local failure most commonly occurs in or near the lumpectomy bed, in the same quadrant, and may manifest in a manner similar to the initial presentation (e.g., microcalcifications developing where calcified DCIS has previously been treated). Such changes arising in a lumpectomy bed under surveillance need careful analysis, such as with magnification views, to differentiate from similar-appearing, treatment-related changes (e.g., calcification due to fat necrosis). In some cases, differentiation based on morphology may not be possible, and tissue sampling will be required.

In general, surgical scars are expected to contract over time. Post–partial mastectomy scars should be carefully scrutinized on follow-up mammograms for increased size or density, which may signify recurrent disease. Scar enhancement can be expected on MRI in the first year after surgery and radiation therapy, but should decline in intensity over time, and little enhancement should be seen by about 18 months after treatment. More than 18 months after breast conservation therapy, MRI can be very helpful in differentiating postoperative scarring from recurrence, with scars expected to show little, if any, enhancement, unlike most recurrent tumor masses.

Palpable lumps developing in the breast, axilla, or chest wall of a patient previously treated for breast cancer raise the specter of recurrent disease, but not infrequently are due to treatment-related mimics, such as fat necrosis masses. Depending on location, these can be evaluated with some combination of mammography, ultrasound, and tissue sampling. At times, such mimics are sufficiently characteristic that imaging alone can make the diagnosis, but histologic sampling may be necessary for confirmation.

Mammographic follow-up is warranted in patients who have undergone subcutaneous mastectomy because of the considerable amount of remaining breast tissue. The yield from mammographic surveillance of the breast after standard mastectomy or skin-sparing mastectomy and reconstruction has been questioned. Because most recurrences occur in the skin and subcutaneous tissues, they can usually be detected on physical examination. The overall annual recurrence rate of T1 or T2 tumors following mastectomy has been reported to be 1% to 2% during the first 5 years.¹⁵ Annual mammographic evaluation following mastectomy and transverse rectus abdominis musculocutaneous (TRAM) flap reconstruction has been advocated to screen for any residual breast tissue and to detect recurrences before they are palpable.¹⁶

The timing for mammographic follow-up after breast conserving therapy has not been standardized. At a minimum, a 6-month follow-up mammogram should be performed to establish the patient’s baseline after surgery. The incidence of a recurrence in the ipsilateral breast 20 years after surgery is 14.3% among women who undergo irradiation after lumpectomy and 39.2% among those who undergo lumpectomy without irradiation.¹⁷

Larger-field-of-view anatomic modalities, such as CT and MRI, are often more suitable to assess suspected chest wall or supraclavicular abnormalities. Because a growing number of patients with locally recurrent disease are being treated with curative intent, whole-body PET is recommended to confirm active tumor at sites identified as abnormal or suspicious with CT or MRI, and to search for distant metastases. Upstaging or downstaging may influence the choice of therapy.

BRACHIAL PLEXUS

Symptoms in the distribution of the brachial radial plexus may be due to recurrent tumor or the effects of therapy. MRI, combined with PET, offers the highest diagnostic yield. Whereas MRI provides exquisite anatomic detail, it may be unable to separate scarring and postoperative changes from tumor. PET, and more recently, PET/CT, improves specificity and, again, allows for a whole-body examination.

CHEST

Pathologic involvement of the internal mammary lymph nodes and mediastinal lymph nodes is best determined by PET.¹⁸ Although both areas are evaluable by CT, reliance on size alone has been shown to be inferior to assessment of metabolic activity in patients with non–small cell lung cancer (histologic gold standard).¹⁹ In one series of 73 patients, FDG PET was found to be twice as accurate as CT in identifying involved internal mammary or mediastinal nodes.²⁰

BONE

Bone metastases are covered in depth in Chapter 8. Imaging options include plain radiographs, CT, MRI, nuclear medicine bone scans, and PET. Plain radiographs are readily available, are relatively inexpensive, expose the patient to a low level of radiation, require no patient preparation, and are completed rapidly. Typically, a minimum 30% reduction in bone mineralization is necessary before a radiograph becomes abnormal. Additionally, radiographs provide limited coverage. These factors reduce sensitivity both at the site of concern and for distant disease. Most commonly, bone radiographs are performed in an effort to improve the specificity of a nuclear bone scan. Even this function is being replaced by the utilization of CT or MRI for scintigraphic correlation. Both of these modalities dramatically improve diagnostic accuracy, compared with plain radiographs, in bone and surrounding soft tissue. However, the screening method of choice remains the nuclear medicine bone scan. It is a whole-body scan, delivers low radiation, and is exquisitely sensitive to changes in bone metabolism. PET and PET/CT utilizing F-18 FDG and sodium fluoride (NaF), are covered in greater detail in Chapter 8. Preliminary data suggest an advantage for PET over bone scintigraphy in the identification of skeletal metastases (especially lytic metastases). NaF, also a positron-emitting pharmaceutical, is a bone-specific agent, whereas FDG PET allows a whole-body (bone and soft tissue) evaluation.

DISTANT METASTASES

The confirmation and quantitation of distant metastases has both therapeutic and prognostic implications. Imagers are often asked to provide answers to the following questions: (1) Are distant metastases present? (2) Is the disease focal or widespread? (3) What are the prognostic implications? (4) In the absence of symptoms, with elevated serum tumor markers, where is the disease? Since the answers to questions 1 to 3 are applicable to most patients under investigation for recurrence, in many centers, PET has become the modality of choice to search for breast cancer metastases following initial therapy. Whole-body surveys have shown FDG PET to be both sensitive and specific for detection of distant disease.^19–22

TEACHING POINTS

Younger patients treated for lymphoma with mantle radiation are at increased risk for a second malignancy (the incidence is 10% to 20% at 20 years of follow-up). Mantle radiation includes the neck, supraclavicular, infraclavicular, axillary, mediastinal, and hilar regions (Figure 7). The unshielded upper outer quadrants of the breasts receive the highest doses.

FIGURE 7 Mantle field radiation encompasses the nodal basins in the neck, supraclavicular and infraclavicular regions, axilla, mediastinum, and hila.

From Estabrook A, Giron G. Treatment of unusual malignant neoplasias and clinical presentations. In Roses DF (ed): Breast Cancer, 2nd ed. Philadelphia: Churchill Livingstone, 2005, p 705.

In women, if a second malignancy develops, it is most commonly breast cancer.

Travis and colleagues found 105 cases of breast cancer in a series of 3817 females treated for Hodgkin’s disease before the age of 30 years. The risk is dose dependent, and the highest risk is in those treated in adolescence (ages 10 to 20 years). Presumably, the breast tissue is most susceptible to radiation injury during earlier development.

In such patients, breast conservation therapy is often not an option because repeat radiation may not be possible.

The normal, early postoperative findings of mastectomy with tissue expander placement are demonstrated here. A described, normal variant source of fluorodeoxyglucose (FDG) activity on whole-body PET is also seen here in the pelvis. Endometrial activity is most commonly seen in premenopausal patients during the first (menstruation) or third (ovulation) week of the menstrual cycle. If endometrial activity is identified on PET in a postmenopausal patient, this warrants further investigation, because endometrial carcinoma can manifest this way.

TEACHING POINTS

This patient had a protracted recovery from surgery. In the same procedure, she underwent hysterectomy, bilateral oophorectomy, and prophylactic left mastectomy, as well as bilateral breast reconstruction using myocutaneous abdominal wall flaps (TRAM flaps). In this procedure, a portion of the abdominal wall, including the rectus abdominis muscle and abdominal wall fat and skin, is transposed to the chest as a pedicle or free flap to reconstruct the breast. In a pedicle procedure, as was performed here, the flap, a large ellipse of lower abdominal fat and skin obtained with a transverse abdominal incision, is tunneled underneath the anterior chest wall into position. The flap remains attached to the rectus muscle, which provides the blood supply. The imaging findings seen here show the typical CT features of such reconstructed breasts, and findings compatible with the abdominal wound infection and necrosis complicating this procedure.