© 2003 AlphaMed Press
A Role for Curative Surgery in the Treatment of Selected Patients with Metastatic Breast Cancera Departments of Surgical Oncology, b Thoracic and Cardiovascular Surgery, c Neurosurgery, and d Breast Medical Oncology, The University of Texas M.D. Anderson Cancer Center, Houston, Texas, USA Correspondence: S. Eva Singletary, M.D., FACS, Department of Surgical Oncology, The University of Texas M.D. Anderson Cancer Center, 1515 Holcombe Boulevard, Box 444, Houston, Texas 77030-4095, USA. Telephone: 713-792-6937; Fax: 713-792-2225; e-mail: esinglet{at}mdanderson.org
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Although metastatic breast cancer is widely believed to carry a grim prognosis, treatment developments over the past 25 years have greatly improved survival outcomes in these patients. In selected cases, aggressive treatment approaches may occasionally result in long-term survival of 15 years or more. This review considers the role of surgery in the treatment of single or multiple metastatic lesions restricted to one site. For each site, available literature from 19922002 was assessed to determine the role of surgery on survival outcomes and to determine appropriate criteria for selecting the best candidates for surgery. For lung, liver, brain, and sternum metastases, the use of surgery with or without adjuvant therapy resulted in greater median survival times and 5-year survival rates. The best candidate for surgery had no evidence of additional metastatic disease, good performance status, and a long disease-free interval after treatment of the primary tumor. Current treatment standards for breast cancer follow-up do not include imaging studies other than mammography. The addition of chest x-rays as part of routine follow-up should be considered as a cost-effective approach for early assessment of metastases to the lung or sternum that may be appropriate for surgical excision. Key Words. Breast cancer • Metastasis • Surgery • Median survival
The traditional belief of both patients and their physicians has been that metastatic breast cancer offers only the grimmest prognosis, with average survival times of 12 years. This belief has fostered treatment regimens based on the notion that palliative treatment is the optimal choice for most patients, with more aggressive therapeutic approaches likely to result in useless patient distress. It is certainly true that, in the absence of intercurrent causes of death, most patients who develop breast cancer metastases ultimately die of their disease, with an overall survival rate of approximately 2% at 20 years after diagnosis with metastases [1]. It is equally true, however, that new treatment modalities developed over the past 25 years have resulted in significantly improved median survival times for patients with metastatic disease. A recent study by Giordano and colleagues [2] examined outcomes in 1,986 breast cancer patients who received similar treatment for their primary disease at a single institution between the years of 1974 and 2000. Of the original patient sample, 843 developed recurrent disease. Those patients who were diagnosed with recurrent disease in the interval from 19741979 had a median survival of 15 months, with 3- and 5-year overall survival rates of 15% and 10%, respectively. Patient outcomes improved steadily over the following 20 years, with patients diagnosed with recurrent disease in the interval from 19952000 showing a median survival of 51 months, and 3- and 5-year overall survival rates of 61% and 40%, respectively. With these longer median survival times, the treatment paradigm for metastatic breast cancer is evolving. A recent paper by OShaughnessy [3] outlines a clinical strategy based on prolonged tumor control with minimal toxicity. For patients who have no significant symptoms and who respond to first-line therapy (typically hormonal for patients whose metastatic disease is estrogen-receptor or progesterone-receptor positive), such a strategy can result in long progression-free intervals and postponement of the need for more toxic therapies. A more aggressive treatment approach may be appropriate for those patients in whom metastatic disease is limited to a solitary lesion or to multiple lesions at a single organ site. When those patients can be rendered clinically disease free by local treatment (surgery or radiation), there is the potential of achieving a complete remission from chemotherapy, and patients can remain disease free for prolonged periods of time (1520 years or more). In a clinical trial conducted at the M.D. Anderson Cancer Center by Holmes and colleagues [4], patients with solitary metastases were treated with surgical resection with or without radiation therapy, followed by systemic chemotherapy, consisting of fluorouracil, doxorubicin, and cyclophosphamide, and hormonal therapy, consisting of tamoxifen. Nearly 25% of patients were alive without disease 15 years after treatment, and only two additional events occurred at a maximum follow-up of 26 years [4, 5]. Related reports from Borner and colleagues [6] and from Nieto and colleagues [7] provide additional evidence that an aggressive multimodal therapy can significantly increase disease-free survival in selected patients with limited metastastic disease. Breast cancer metastases isolated to a single organ commonly occur in lung, liver, brain, and bone. This review article considers the role of surgery with or without adjuvant therapy in the treatment of single or multiple metastatic lesions restricted to one of these specific sites. For each site, available literature from 19922002 was assessed to determine the role of surgery on survival outcomes and to determine appropriate criteria for selecting the best candidates for surgery.
Lung Approximately 3% of all women with breast cancer develop a solitary pulmonary lesion detectable by chest x-ray, of which 33%40% will be breast metastases [8, 9]. Lung resection for metastatic disease was first reported in 1882 by Weinlechner [10] and, in 1939, Churchill performed the first resection of a pulmonary metastasis leading to long-term survival [11]. Since that time, surgery has become a standard treatment in patients with solitary pulmonary metastases, with 5-year survival rates of approximately 35%, depending on the primary site [12].
Table 1
Positive survival outcomes after surgery, with or without chemotherapy, were associated with a long disease-free interval (DFI) after treatment of the primary tumor (1236 months) [14, 16, 19], with complete resection of the tumor [9, 17, 19], and with estrogen-receptor-positive status [14]. In the largest study in that series (n = 467) [19], the best candidates (DFI greater than 36 months and complete resection) had a 5-year survival rate of 50% and a 15-year survival rate of 25% after surgery, with or without chemotherapy, indicating that this treatment approach is curative in this select group of patients. Even without the potential survival benefit associated with surgical resection of metastases, there is an obvious additional reason for recommending at least limited surgery for breast cancer patients with isolated pulmonary lesions. As indicated above [8, 9], only about one-third of such lesions will prove to be breast cancer metastases, while the remaining two-thirds will be other types of tumors, chiefly primary lung cancer. Early identification of the tumor is critical for determining appropriate treatment strategies.
Liver Of all patients with metastatic breast cancer, approximately 5% will have metastasis confined to the liver with no evidence of extrahepatic disease [21, 22]. Even with systemic chemotherapy, the median survival time for patients with metastatic disease to the liver only or with limited disease elsewhere is only 19 months, with pretaxane chemotherapy regimens, or 2226 months with taxane-containing regimens [23]. Hormonal therapy is of limited use, as most breast tumors that metastasize to the liver are hormone-receptor negative [24]. Because of the lack of effective systemic therapy, surgery has been proposed as a potential therapeutic tool for increasing survival in patients with isolated hepatic metastases.
Only a small number of retrospective studies have examined outcomes in breast cancer patients with isolated hepatic metastases treated with surgery, and the patient numbers in those studies are relatively small. Nonetheless, there is evidence that the use of surgery with or without chemotherapy in treating these patients can significantly increase survival. As shown in Table 2
In unpublished data from the University of Texas M.D. Anderson Cancer Center, 21 patients underwent resection and/or radiofrequency ablation with curative intent for isolated liver metastases between January 1987 and July 2000. Liver metastases developed after a median time of 35 months (range 0144) from initial diagnosis. Fourteen patients had a solitary metastasis and seven had two lesions. The vast majority (81%) of patients received adjuvant chemotherapy for the primary tumor or neoadjuvant chemotherapy for the liver recurrence. The type of surgery included major hepatectomy (resection of one or more lobes) in seven patients, minor hepatectomy in nine patients, and radiofrequency ablation alone or in combination with resection in five patients. There were no perioperative mortalities. The median disease-free survival time was 40 months, and the disease-free 3-year survival rate was 55%. These survival results are comparable with those reported in the literature (Table 2 Perhaps because of the small numbers of patients for whom data are available, there is also a limited amount of data about prognostic factors for increased survival after surgery in breast cancer patients with isolated hepatic metastases. Most would agree that the patient should show normal performance status and normal liver function tests. Two studies agreed that the size and number of hepatic metastases did not influence survival, but disagreed about whether the interval between treatment of the primary tumor and detection of the metastasis was an important factor [28, 30]. Selzner and colleagues did not find an effect on survival based on extent of liver resection [28]. Raab and colleagues reported a significant effect related to achieving a margin-negative resection of all metastatic liver lesions, with a median survival time of 42 months in patients receiving complete resection compared with 5 months in patients receiving palliative surgery [26]. Of special interest, two studies reported that the presence of extrahepatic metastases did not affect survival in patients in whom hepatic metastases had been surgically removed [28, 30]. This may be because, with the exception of brain lesions, metastases at other sites tend to develop more slowly, and the hepatic metastasis is the rate-limiting factor for patient survival.
Brain
In up to one-third of breast cancer patients with brain metastases, the brain is the only site of metastasis [33, 38, 39]. For those patients, depending upon the size and location of their lesions, surgical excision added to WBRT can significantly increase survival. In the five studies shown in Table 3
The presence of leptomeningeal disease is a very poor prognostic sign and contraindicates surgical excision of brain metastases [43]. Patients are generally considered good candidates for surgical therapy if they have a single, operable brain lesion and well-controlled systemic disease. However, a study by Wronski and colleagues [43] did not find any significant differences in outcomes among patients with single or multiple brain metastases or patients who had concurrent lung metastases. They also did not find any difference in outcome related to the interval between diagnosis of the primary tumor and diagnosis of the metastasis, but two other studies [40, 41] did report longer survival associated with a longer DFI. Over the past 10 years, there has been increasing interest in the use of single-fraction stereotactically delivered radiation therapy (commonly called sterotactic radiosurgery or SRS) as a substitute for surgical excision in the treatment of brain metastases. SRS delivers an intense dose of radiation to a well-defined area within the brain. It has the advantage of being noninvasive and, because of the sharp dose gradient used, collateral damage to surrounding normal tissue is minimized. In three studies that have used SRS for the treatment of brain metastases of various origin, median survival times have ranged from 68 months, and 1-year survival rates have ranged from 38%44% [4648]. One study reported a 5-year survival rate of 16% [48]. While these results are an improvement over the use of WBRT alone, they still lag behind results obtained using a combination of surgical excision and WBRT. In addition, larger lesions (>3 cm maximum diameter) may not respond as well to SRS [43]. Intuitively, treatment of these larger lesions also carries a higher risk of radiation damage to surrounding normal tissue. At present, the most prudent therapeutic strategy may be to use surgical excision where possible, reserving SRS for those cases in which the tumor is located in an inaccessible site or is otherwise inoperable.
Bone The usual first treatment choice for bone metastases not at risk for fracture is systemic therapy, either hormonal therapy or chemotherapy. This is especially true for isolated lesions, which account for approximately 20% of all bone metastases [50]. Isolated bone metastases have a somewhat indolent course and generally respond well to hormonal therapy [5153]. For patients in whom the metastases are hormone-receptor negative, or who become refractory to hormonal treatment, chemotherapy has been shown to be effective [54]. In metastatic disease confined to the skeletal system and treated with hormonal therapy with or without chemotherapy, a median survival time of 48 months and a 5-year survival rate of 39% have been reported [51, 55]. More recently, osteoclast inhibitory therapy using bisphosphonates has become widely used [56]. Radiation therapy, either locally or through the systemic administration of radioisotopes, has also been used effectively in these patients, providing pain relief and, in some cases, evidence of bone healing [57, 58]. The use of surgery for the treatment of bone metastases has typically been reserved for lesions that are not responsive to systemic therapy and that are associated with a serious potential for decline in quality of life in order to reduce fractures, treat spinal cord or nerve compressions, and prophylactically fix imminent fractures. The most common goals of surgery are to maintain or restore mobility and to decrease pain, and the most common use is for the treatment of long bone fractures. Surgical treatment of impending or actual long bone fractures is generally performed to stabilize the bone rather than remove the tumor. The use of surgery as a curative treatment option for bone metastases has been actively considered in the case of isolated metastases to the sternum. Two studies from the 1980s presented results from a limited number of patients indicating that surgical resection of solitary sternal metastases, where there was no evidence of systemic spread, may have led to significantly better survival. Takanami and Ohnishi [59] treated three patients, each with a single sternal metastasis from breast cancer, with partial resection of the sternum. Two patients died within 14 months, but the third was alive and disease free 7 years after surgery. Noguchi and coworkers [60] treated nine patients with solitary sternal metastases from breast cancer with either partial (n = 8) or total (n = 1) resection of the sternum. The median survival time for all nine patients was 30 months. Of the five patients who had no mediastinal or parasternal lymph node metastases, three survived more than 6 years. More recently, Incarbone and colleagues reviewed results from their institution from 52 patients who underwent surgical resection for tumors involving the sternum [61]. Of these, 11 involved breast cancer metastases. These patients showed a 60% 5-year survival rate and a median survival time described by the authors as "remarkably long." Noguchi and colleagues [60] suggested that resection of sternal metastases may lead to long-term survival because these lesions remain solitary for a long time, possibly because of isolation from the venous plexus that provides a transmission route to other bones.
As shown in Figure 1
Approximately one-half of the reviewed studies reported perioperative morbidity and mortality (Table 4
It is important to note that the results shown in these studies may be influenced by selection bias. It may be that patients selected for surgery had better prognostic features than those treated with chemotherapy alone. Unfortunately, because of the lack of studies that directly compared outcomes in these two groups, there are few data that bear directly on this issue. In two lung metastasis studies that compared outcomes in patients receiving surgery compared with those receiving chemotherapy [15, 18], there were no significant differences in relevant patient characteristics including stage, histology, hormone receptor levels of the primary tumor, number of metastases, and length of DFI. However, these studies did not report whether there were differences in performance statuses between the two treatment groups, and this can be an important predictor of survival. Patients with poor performance statuses are generally considered to be poor surgical risks and are often recommended for alternative nonsurgical therapies. This could introduce an important source of bias into an assessment of the value of surgery. Publication bias against series in which there was no survival benefit may also affect the results presented here. It might be argued that the relatively small number of cases reported in these studies (e.g., 744 lung metastases from breast) is only a fraction of the total cases in which surgery was used as a treatment option. However, the absolute number of breast metastases that are eligible for resection is likely to be relatively small. For example, while approximately 1%1.5% of women with breast cancer develop metastasis to the lung, only about 25% of those patients may be recommended for surgery [9]. A review of the M.D. Anderson Cancer Center database starting in 1984 (most reliably captured after 1997) revealed only 56 patients who underwent thoracotomy for breast cancer metastasis to the lung. Thus, the small number of reported cases is not itself a reliable indicator of publication bias. It is also important to note that a 2002 analysis of 467 patients from the International Registry of Lung Metastases (the single largest database on metastasis to the lung) showed patient outcomes consistent with those from smaller studies reported here. Thus, we do not believe that publication bias seriously undermined our conclusions about the potential value of surgery in the treatment of lung metastases.
The data reviewed here indicate that surgery combined with adjuvant therapy, compared with radiation or systemic therapy alone, can result in significantly better survival in breast cancer patients with metastatic disease in the lung, liver, brain, or sternum. As discussed above, several kinds of bias might influence these results. Nonetheless, the data are suggestive and support the need for well-designed clinical trials to determine the exact role of surgical intervention in patients with metastatic breast cancer. Such trials will admittedly be difficult to implement. Not only are the absolute numbers of eligible patients likely to be small, but accrual of patients into clinical trials is a continuing challenge. As of 1991, only 1%3% of the available patient population was being recruited into cooperative group adjuvant trials, with only 10%30% of eligible patients finally enrolled in studies [62]. For breast cancer, less than 2% of patients are included in clinical trials [63]. In the case of patients with stage IV breast cancer, a significant barrier to patient accrual may be reluctance of the patient or physician to consider aggressive therapy in what has historically been considered to be end-stage disease. Across the four sites (lung, liver, brain, bone), better patient outcome after surgery was associated with good performance status, long DFI after treatment of the primary tumor, complete resection of the tumor, and restriction of metastasis to single tumors or to multiple tumors at a single site. Complete resection constitutes proper surgery for any tumor, and it is not surprising that it would also have a significant effect on outcomes for metastastic lesions. In metastasis to the lung, for example, complete resection can offer 5-year survival rates as high as 50% compared with the 18% associated with incomplete resection [19]. The last criterion (restriction to a single tumor or a single site) argues for the early detection of the metastatic lesion(s), before more advanced disease progression occurs. Early detection of lung, liver, and bone metastases would require the routine use of chest x-rays, abdominal ultrasounds, and bone scans as part of the routine follow-up for breast cancer. In the case of brain metastases, even very small lesions generally result in neurological symptoms that are clinically detectable, removing the need for advanced imaging techniques in asymptomatic patients. In the practice guidelines of the National Comprehensive Cancer Network [64], the current recommendations for follow-up of breast cancer patients are: A) history and physical exam every 46 months for 5 years, then every 12 months; B) mammogram every 12 months (or 6 months, after radiotherapy if breast-conserving surgery was used); and C) pelvic exam every 12 months in women on tamoxifen, if the uterus is present. These guidelines were based in part on the results of a large multicenter trial conducted in Italy comparing outcomes in patients with differing follow-up protocols [65, 66]. One group of patients received yearly mammograms and physical examinations, and the second group received intensive surveillance that included bone scans, liver sonograms, chest x-rays, and laboratory tests in addition to the mammogram and physical exam. The results of the trial indicated that the tests used in the intensive surveillance regimen did not improve survival or influence quality of life and, thus, should not be included in routine follow-up. However, as suggested by Cocconi [67], it may not be surprising that the outcomes in the two groups were similar, since the recommended treatment protocol would have been largely palliative, regardless of when the metastasis was discovered. The question then becomes: would the inclusion of these tests in routine breast cancer follow-up be more cost effective if a different treatment protocol with the potential for an improved outcome was recommended for patients with solitary metastases? For bone metastases in the spine or long bones, it seems unlikely that earlier detection would significantly alter current treatment recommendations. Since bone resections constitute radical surgery, with extended and painful recovery times, most metastases would continue to be treated primarily with hormonal therapy or chemotherapy, with surgery reserved for fracture reduction or stabilization. Brain metastases, as mentioned above, are typically symptomatic from a very early stage, and patients would derive little benefit from the addition of costly screening tests. Metastasis to the liver is generally a late event, usually accompanied by systemic disease. Ultrasound imaging is effective in detecting hepatic lesions, but the cost to include this in routine screening to detect the rare isolated event may be prohibitive. It may, however, be cost effective to reconsider the routine use of chest x-rays for follow-up of breast cancer patients. This diagnostic tool would be effective in detecting early metastasis to the lung or sternum, which often occurs as a solitary lesion. Based on current estimates of breast cancer incidence [68], this would involve screening 192,000 patients per year for the detection of approximately 3,000 metastases to the lung or sternum. In both of these sites, the use of surgical excision in addition to standard medical treatment has been shown to significantly improve median survival. As the treatment recommendations for breast cancer continue to evolve, so too does the definition of what constitutes a "cure." We are perhaps approaching a time where breast cancer can be "cured" in the sense that it can be rendered harmless. By moving away from the treatment paradigm aimed at removing or destroying every cancerous cell, we can redefine a "cure" as a prolonged period of survival without significant symptoms. Under this new paradigm, cancer can be thought of as being reduced to a commensal organism, the biological equivalent of an epiphyte, such as Spanish moss, that depends on the oak tree to live but does nothing to harm its host organism. Metastatic breast cancer to the lung or sternum, if detected early and treated aggressively, holds the possibility of such a cure.
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