**4. Current debates on the best treatment options**

An important question arises: is SRT efficacious as surgery in achieving local control (Rao et al. 2007)? As reviewed by Sperduto (2003), SRT is as good as or even better than surgical resection in term of local control. Another prospective study has addressed this question (Mucacevic et al. 2006). Mucacevic et al. 2006 found that local control was superior in SRT treated patients compared to surgery, and that SRT group had a greater improvement in quality of life even if a higher rate of distant brain failure was present.

Another question is: can SRT be used only for multiple brain metastases? Previous studies suggested that use of radiosurgery for brain metastases should be limited to patients with three or fewer lesions (Gupta 2005, Andrews et al. 2004). A recent randomized trial, compared whole-brain radiation therapy (WBRT) plus radiosurgery boost to metastatic foci. This trial has demonstrated a significant advantage of radiosurgery boost over WBRT alone in terms of freedom from local failure, and that the result also present among patients with 2, 3, or 4 metastases (Andrews et al. 2004). Survival also did not depend on number of metastases. The drawback of this technique is the risk of radiation necrosis. Chang et al. (2000) found that radionecrosis occurred in the 5.4% of patient treated and only 7 tumors

Brain Metastases: Biology and Comprehensive

and Shiff 2007).

2006).

Strategy from Radiotherapy to Metabolic Inhibitors and Hyperthermia 173

Breast cancer is sensitive to chemotherapy (Cavaliere and Shiff 2007). Rosner et al (1986) have shown a 50% response rate among 100 women treated with different regimens. The most common agents are: cyclophosphamide, doxorubicin, 5-fluorouracil, methotrexate, and vincristine. All these agents do not cross BBB notwithstanding a response by metastatic foci have been obtained. This outlines that BBB is not so important and that the appropriate regimen and the chemosensitivity of the metastases are more important. Boogerd et al. 1992, reported a 59% RR, and according to Rosner et al. (1986), suggest that chemotherapeutics may cross BBB at a sufficient concentration to achieve a clinical effect. Another interesting and a standard drug on breast cancer is doxorubicin. Doxorubicin does not cross easily BBB however when encapsulated in liposomes its penetration can increase (Siegal et al. 1995). Caraglia et al. (2006) used liposomal doxorubicin and temozolomide (TMZ) in 19 patients with brain metastases. This association resulted in a RR of 37%; furthermore 8 patients had complete response and 2 a partial response. Temozolamide has limited activity against breast cancer so the majority of the response may be attributed to doxorubicin (Cavaliere

The incidence of metastases in breast cancer increases with the increase in HER2 overexpression. HER2 is an 185KDa transmembrane tyrosine kinase with extensive homology to the epidermal growth factor receptor. Trastuzumab is a monoclonal antibody (MOaBs) now approved as a first line chemotherapy in patients with positivity for HER2 receptors. After its introduction however an increased incidence in brain metastases has been noted. Retrospective studies documented an incidence between the 25% and the 40%, suggesting that HER-2 positive tumors have a biological predisposition to metastasize to brain (Lin and Winer 2007). The reasons for this increased incidence, as reported by Lin and Winer (2007), are multifactorial and include biological and treatment related factors. This last factor seems linked to the low penetration across BBB of Trastuzumab. Recently, to overcome this problem, Lapatinib has been suggested. Lapatinib has a dual inhibitor activity on epidermal growth factor and on HER2 and in preliminary has shown an objective response in two patients among 39 treated (Lin et al. 2006). Other studies with lapatinib and

The incidence of brain metastases in melanoma is high and can reach the 43%. Melanoma is relatively chemoresistant. The various biological treatments such as interferon or interleukin-2 and chemotherapeutics (dacarbazine) have shown a limited activity. Temozolomide (TMZ) has demonstrated a relatively important response against brain metastases from melanoma. TMZ is a third generation alkylating agent that can be taken orally. Its small size and lipophilic properties, allows TMZ to cross easily BBB. CNS concentrations can reach 30% of the plasma concentrations. When it has reached the CNS, TMZ is converted to the active metabolite (MTIC). TMZ has been used as a single agent or combined with WBRT (Cavaliere and Shiff 2007). For example, in a phase II study on 151 patients ( Agarwala et al. 2004), , 39 patients (26%) showed a stable disease. Other authors have reported similar results, futhermore the association of TMZ with WBRT resulted in a better overall survival compared to TMZ alone (9 months versus 5 months) (Hoffman et al.

Multiple attempts have been made to improve the results of WBRT alone or combined with SRT/CFRT, by adding radiosensitizing agents. All the trials failed to demonstrate any

other HER2 inhibitors are currently been tested (Lin and Winer 2007).

**4.2 Hyperthermia and metabolic inhibitors, the future?** 

required subsequent surgical resection. Regarding toxicity by adding SRT + WBRT however, Aoyama et al. (2006) found no difference between the group treated with SRT alone or the group treated with SRT + WBRT. Furthermore they found that the patients in whom WBRT was omitted had a higher rate of failure in the brain (76%vs. 48%) and required salvage therapy more often for recurrent brain metastases.

Study by Hidefumi et al. 2006, has clearly evidenced that WBRT associated to SRT improve the survival of patients with 1 to 4 brain metastases. Furthermore these authors outlined that intracranial relapse occurred more frequently in patients who did not receive WBRT. A recent study however indicate that SRT boost after WBRT for single brain metastases improves survival in select patients, whereas for patients up to four metastases the association improves local control not overall survival (Eichler and Loeffler 2007). Patchell et al. (1998) and Sneed et al. (2002) however disagree and from their retrospective and prospective data suggest that omitting WBRT does not result in shorter survival. They outline that the status of systemic disease is the predominant determinant of patient's prognosis. To our opinion WBRT can omitted on selected patients with high risk of radionecrosis (increased accumulation of gadolinium in tumor area, neuro cognitive deterioration, persistence of headache and peritumoral edema) or if a close follow-up can be ensured to the patients treated with SRT. If patients do not show increased risk of radionecrosis, have a Karnofsky index > 70% and the systemic

disease is minimal WBRT is however mandatory.

#### **4.1 Chemotherapy**

As outlined by Nguyen and De Angelis 2004, chemotherapy has a limited role in treating brain metastases and is used after failure of surgery and or radiation therapy. Many chemotherapy drugs do not cross the blood-brain barrier but can reach malignant tumors in the brain, presumably through a local breakdown in the blood-brain barrier. In some chemotherapy-sensitive tumors like, lymphoma, small cell lung cancer (SCLC) and breast cancer (Eichler and Loeffler 2007), chemotherapy can induce remissions, but its routine use is still under evaluation. But for most tumors, chemotherapy for brain metastases is ineffective, may be because of the existence of the BBB. In fact, many drugs do not cross easily BBB, and do not remain in the brain long enough or at high concentration to ensure adequate cancer killing effect (Tosoni et al. 2004). Drugs active on primary tumors may not be as active on metastases (Chang et al. 2007, Cavaliere and Shiff 2007). On the contrary other authors outline that brain metastases are as responsive as primary systemic cancer. This has been demonstrated by numerous phase II studies (Tosoni et al. 2004).

Different chemotherapeutic regimens have been used for treating brain metastases from SCLC [52, 101]. Drugs have been used as single agent or combined to other drugs or associated with WBRT or SRT. The most active single drugs are cisplatinum (CCP), and temozolomide (TMZ) (Nguyen and De Angelis 2004). Cisplatinum alone has shown a response rate (RR) of 30% (Tosoni et al. 2004). A better response of 50% rate has been obtained combining to cisplatinum, etoposide, cyclophosphamide, methotrexate, and 5 fluouracil (Tosoni et al. 2004). The association with WBRT was better in term of overall survival and in treatment response (57% vs 22%) compared to patients who had received only WBRT (Postmus et al. 2000).

required subsequent surgical resection. Regarding toxicity by adding SRT + WBRT however, Aoyama et al. (2006) found no difference between the group treated with SRT alone or the group treated with SRT + WBRT. Furthermore they found that the patients in whom WBRT was omitted had a higher rate of failure in the brain (76%vs. 48%) and required salvage

Study by Hidefumi et al. 2006, has clearly evidenced that WBRT associated to SRT improve the survival of patients with 1 to 4 brain metastases. Furthermore these authors outlined that intracranial relapse occurred more frequently in patients who did not receive WBRT. A recent study however indicate that SRT boost after WBRT for single brain metastases improves survival in select patients, whereas for patients up to four metastases the association improves local control not overall survival (Eichler and Loeffler 2007). Patchell et al. (1998) and Sneed et al. (2002) however disagree and from their retrospective and prospective data suggest that omitting WBRT does not result in shorter survival. They outline that the status of systemic disease is the predominant determinant of patient's prognosis. To our opinion WBRT can omitted on selected patients with high risk of radionecrosis (increased accumulation of gadolinium in tumor area, neuro cognitive deterioration, persistence of headache and peritumoral edema) or if a close follow-up can be ensured to the patients treated with SRT. If patients do not show increased risk of

As outlined by Nguyen and De Angelis 2004, chemotherapy has a limited role in treating brain metastases and is used after failure of surgery and or radiation therapy. Many chemotherapy drugs do not cross the blood-brain barrier but can reach malignant tumors in the brain, presumably through a local breakdown in the blood-brain barrier. In some chemotherapy-sensitive tumors like, lymphoma, small cell lung cancer (SCLC) and breast cancer (Eichler and Loeffler 2007), chemotherapy can induce remissions, but its routine use is still under evaluation. But for most tumors, chemotherapy for brain metastases is ineffective, may be because of the existence of the BBB. In fact, many drugs do not cross easily BBB, and do not remain in the brain long enough or at high concentration to ensure adequate cancer killing effect (Tosoni et al. 2004). Drugs active on primary tumors may not be as active on metastases (Chang et al. 2007, Cavaliere and Shiff 2007). On the contrary other authors outline that brain metastases are as responsive as primary systemic cancer.

Different chemotherapeutic regimens have been used for treating brain metastases from SCLC [52, 101]. Drugs have been used as single agent or combined to other drugs or associated with WBRT or SRT. The most active single drugs are cisplatinum (CCP), and temozolomide (TMZ) (Nguyen and De Angelis 2004). Cisplatinum alone has shown a response rate (RR) of 30% (Tosoni et al. 2004). A better response of 50% rate has been obtained combining to cisplatinum, etoposide, cyclophosphamide, methotrexate, and 5 fluouracil (Tosoni et al. 2004). The association with WBRT was better in term of overall survival and in treatment response (57% vs 22%) compared to patients who had received

This has been demonstrated by numerous phase II studies (Tosoni et al. 2004).

therapy more often for recurrent brain metastases.

radionecrosis, have a Karnofsky index > 70% and the systemic

disease is minimal WBRT is however mandatory.

**4.1 Chemotherapy** 

only WBRT (Postmus et al. 2000).

Breast cancer is sensitive to chemotherapy (Cavaliere and Shiff 2007). Rosner et al (1986) have shown a 50% response rate among 100 women treated with different regimens. The most common agents are: cyclophosphamide, doxorubicin, 5-fluorouracil, methotrexate, and vincristine. All these agents do not cross BBB notwithstanding a response by metastatic foci have been obtained. This outlines that BBB is not so important and that the appropriate regimen and the chemosensitivity of the metastases are more important. Boogerd et al. 1992, reported a 59% RR, and according to Rosner et al. (1986), suggest that chemotherapeutics may cross BBB at a sufficient concentration to achieve a clinical effect. Another interesting and a standard drug on breast cancer is doxorubicin. Doxorubicin does not cross easily BBB however when encapsulated in liposomes its penetration can increase (Siegal et al. 1995). Caraglia et al. (2006) used liposomal doxorubicin and temozolomide (TMZ) in 19 patients with brain metastases. This association resulted in a RR of 37%; furthermore 8 patients had complete response and 2 a partial response. Temozolamide has limited activity against breast cancer so the majority of the response may be attributed to doxorubicin (Cavaliere and Shiff 2007).

The incidence of metastases in breast cancer increases with the increase in HER2 overexpression. HER2 is an 185KDa transmembrane tyrosine kinase with extensive homology to the epidermal growth factor receptor. Trastuzumab is a monoclonal antibody (MOaBs) now approved as a first line chemotherapy in patients with positivity for HER2 receptors. After its introduction however an increased incidence in brain metastases has been noted. Retrospective studies documented an incidence between the 25% and the 40%, suggesting that HER-2 positive tumors have a biological predisposition to metastasize to brain (Lin and Winer 2007). The reasons for this increased incidence, as reported by Lin and Winer (2007), are multifactorial and include biological and treatment related factors. This last factor seems linked to the low penetration across BBB of Trastuzumab. Recently, to overcome this problem, Lapatinib has been suggested. Lapatinib has a dual inhibitor activity on epidermal growth factor and on HER2 and in preliminary has shown an objective response in two patients among 39 treated (Lin et al. 2006). Other studies with lapatinib and other HER2 inhibitors are currently been tested (Lin and Winer 2007).

The incidence of brain metastases in melanoma is high and can reach the 43%. Melanoma is relatively chemoresistant. The various biological treatments such as interferon or interleukin-2 and chemotherapeutics (dacarbazine) have shown a limited activity. Temozolomide (TMZ) has demonstrated a relatively important response against brain metastases from melanoma. TMZ is a third generation alkylating agent that can be taken orally. Its small size and lipophilic properties, allows TMZ to cross easily BBB. CNS concentrations can reach 30% of the plasma concentrations. When it has reached the CNS, TMZ is converted to the active metabolite (MTIC). TMZ has been used as a single agent or combined with WBRT (Cavaliere and Shiff 2007). For example, in a phase II study on 151 patients ( Agarwala et al. 2004), , 39 patients (26%) showed a stable disease. Other authors have reported similar results, futhermore the association of TMZ with WBRT resulted in a better overall survival compared to TMZ alone (9 months versus 5 months) (Hoffman et al. 2006).

#### **4.2 Hyperthermia and metabolic inhibitors, the future?**

Multiple attempts have been made to improve the results of WBRT alone or combined with SRT/CFRT, by adding radiosensitizing agents. All the trials failed to demonstrate any

Brain Metastases: Biology and Comprehensive

Gillies et al. 2008, and Lee et al. 2008).

metastases (personal communication).

**5. Discussion and conclusions** 

metastatic cancer.

glycolysis or "Warburg effect" (Warburg 1956).

Strategy from Radiotherapy to Metabolic Inhibitors and Hyperthermia 175

metastases consume glucose in presence of a low oxygen tension, the so called aerobic

Palmieri et al. 2009 have confirmed the "Warburg effect" analyzing resected human brain metastases of breast cancer through real time PCR. They demonstrated an upregulation of hexokinase-2, an enzyme that mediates the first step of glucose metabolism, its upregulation is associated with a poor prognosis (Palmieri et al.2009). Hennipman et al. (1988) suggested an association of an increasing rate of enzymes implicated in glycolysis in breast cancer metastases and that their activities were higher in metastases compared to the primary tumors (Richardson et al. 2008). Another study on MCF10 model of mammary carcinoma by Richardson, confirms the major shift toward aerobic glycolysis (Gambhir et al. 2001). Increased glycolysis at metastatic site has been confirmed by [18F] 2-fluoro-2-deoxy-Dglucose positron emission tomography (PET) (Richardson et al. 2008, Gambhir et al. 2001,

Our group (Guais et al. 2010) has developed a drugs combination able to alter two different steps of tumor metabolism (pyruvate dehydrogenase and ATP citrate lyase). The first drug is α-lipoic acid (ALA), which, as is the case for dichloroacetate, inhibits the enzyme Pyruvate Dehydrogenase Kinase-1 (PDHK1). Inhibition of PDHK1 can restore the activity of pyruvate dehydrogenase, thus possibly redirecting aerobic glycolysis to respiration and thus decreasing the amount of lactate produced. The second drug is hydroxycitrate (HCA), which inhibits ATP citrate lyase. The efficacy of this combination appears in animals to be similar to conventional chemotherapy (cisplatin or 5-FU), as it results in both significant tumor growth inhibition and enhanced survival (Schwartz et al. 2010). Similar results have been obtained in one case of pancreatic patient metastatic to liver (Guais et al. 2010). An unpublished result, of a patient with head and neck cancer with brain metastases treated with ALA and HCA and chemotherapy has shown a complete disappearance of brain

Immunohistochemistry studies on several specimens of primitive and metastatic human cancers, such as colon, breast, lung, ovarian and pancreas, have, also revealed an overexpression of hypoxia- inducible factor 1 (HIF) (Zhong et al. 1999). This overexpression supports two basic biological behavior of cancer and its metastases, an altered glucose transport and a limited diffusion of O2, glucose and nutrients (Liu et al. 2002). Hypoxic tumor cells become hypersensitized to glycolytic inhibitors (Liu et al. 2002) and to hyperthermia (Baronzio et al. 2006), reinforcing our hypotheses on metabolic treatment of

Patients with brain metastases have usually a short survival. Historical studies have demonstrated that with no treatments the survival is of the order of one - two months, due to systemic progression in sites other than brain. Although brain metastases incidence is increasing, there is no consensus for their treatment. Currently, treatment options include WBRT, surgery, chemotherapy and SRT/CRT. WBRT has the advantage of being easily and widely available and is able to extend survival to three to six months. In the case of solitary metastases, the addition of surgical resection to WBRT has doubled the survival, in the range of 10 - 12 months (Patchell et al. 1990, Heilbrun and Adler 2010). However, many patients have metastases in locations not amenable to surgical resection. STRT, for these patients has demonstrated in terms of survival and palliation to be a reliable clinical tool

benefit either in local control or in survival (Eichler and Loeffler 2007). When brain metastases reach a critical mass > 1-2 mm3 (106 cells) and a distance from host nutritive vessel > of 100-200 μm develop area of hypoxia and angiogenesis. Hypoxia results in radioresistance (Wouters et al. 2007). Actually, no definitive clinical therapies exist for overcoming tumour hypoxia out of hyperthermia (HT) (Pontiggia et al. 1990, Baronzio et al. 2006). HT is a treatment raising the temperature of tumor - loaded tissue to 40-43 degrees C. It is deprived of important side effects and has shown to enhance the effects of radiotherapy and to potentiate the efficacy of certain drugs, such as nitrosurea, cisplatinum, metothrexate (Baronzio et al. 2006, Dewey et al 1977). HT combined with radiation has been reported to yield higher complete and durable responses than radiation alone in superficial tumors. Despite difficulties in increasing human tumor temperatures, recent clinical trials have shown that a combination of hyperthermia with radiation is superior to radiation alone in controlling many human tumors (Dewey et al. 1977, Gabriele and Roca 2006). The increased effect seen by combining cytotoxic agents with hyperthermia is complex, but may be due to altered drug pharmacokinetics such as increased solubility (e.g. nitrosureas and alkylating agents), altered plasma protein binding (e.g. cisplatinum) and activation of enzymatic processes (e.g. anthracyclines) (Luk and Hulse 1980, Gerweek 1985). Hyperthermia does not usually cause marked increase in radiation side effects. Regarding brain, Seegenschmiedt et al. (1995), in their review affirmed that treatment toxicity to brain, is relatively low and longterm side effects are similar to that observed to RT alone. Ikeda et al. (1994), studied the toxicity of radiofrequency interstitial HT in dog and found alteration of Blood Brain Barrier (BBB). Other authors outlined that the maximum tolerated heat dose to CNS lies in the range of 40-60 min at 42-42.5°C or 10-30 min at 43°C (Gerweek 1985). A recent review by Sharma and Hoopes (2003) has reported that HT specifically alters the mammalian CNS. The morphological alterations for temperature in the range 40°C to 42 °C for 4 hours has been demonstrated for the axons, the glial cells and the vascular endothelium. Sneed and Stea 1995, demonstrated in a randomized study that HT has an acceptable toxicity, in fact no grade 5 toxicity was found outside 4 patients on 112 ( 3.5% ) with grade 2 and 7 (Sneed et al. 1995).

There are only a small number of studies on brain metastases with HT. In an interesting study reported by Pontiggia on 17 patients with lung cancer,the patients were treated with nitrosurea and capacitive HT for 60'. Sixteen patients out of 17 responded with clinical improvement and radiological regression of the disease. The survival time was in median 12.7 months (Pontiggia et al. 1995).

Hyperthermia is a useful adjunct to chemotherapy and radiotherapy; however, new therapeutic strategies easily applicable in many institutions are to be developed.

The search for functional characteristics that allow cancer cells to spread to brain and development of new animal models will open new opportunities in target and drug discovery (Gril et al. 2010). Metabolic profiles of cells with metastatic propensity to brain may be one of these targets. In fact, studies by proteomics have demonstrated that breast cancer cells that metastasize to brain , have a unique protein profile consistent with increased expression of enzymes involved in glycolysis, tricarboxylic acid cycle, and oxidative phosphorylation pathways, permitting to these cells to have an enhanced proliferation and adaptation (Chen et al. 2007). Studies by Blasberg et al. (1985), using 14Cdeoxyglucose and quantitative autoradiography in metastatic walker 256 brain tumors confirm that glucose utilization is of primary importance in metastatic cells and that brain

benefit either in local control or in survival (Eichler and Loeffler 2007). When brain metastases reach a critical mass > 1-2 mm3 (106 cells) and a distance from host nutritive vessel > of 100-200 μm develop area of hypoxia and angiogenesis. Hypoxia results in radioresistance (Wouters et al. 2007). Actually, no definitive clinical therapies exist for overcoming tumour hypoxia out of hyperthermia (HT) (Pontiggia et al. 1990, Baronzio et al. 2006). HT is a treatment raising the temperature of tumor - loaded tissue to 40-43 degrees C. It is deprived of important side effects and has shown to enhance the effects of radiotherapy and to potentiate the efficacy of certain drugs, such as nitrosurea, cisplatinum, metothrexate (Baronzio et al. 2006, Dewey et al 1977). HT combined with radiation has been reported to yield higher complete and durable responses than radiation alone in superficial tumors. Despite difficulties in increasing human tumor temperatures, recent clinical trials have shown that a combination of hyperthermia with radiation is superior to radiation alone in controlling many human tumors (Dewey et al. 1977, Gabriele and Roca 2006). The increased effect seen by combining cytotoxic agents with hyperthermia is complex, but may be due to altered drug pharmacokinetics such as increased solubility (e.g. nitrosureas and alkylating agents), altered plasma protein binding (e.g. cisplatinum) and activation of enzymatic processes (e.g. anthracyclines) (Luk and Hulse 1980, Gerweek 1985). Hyperthermia does not usually cause marked increase in radiation side effects. Regarding brain, Seegenschmiedt et al. (1995), in their review affirmed that treatment toxicity to brain, is relatively low and longterm side effects are similar to that observed to RT alone. Ikeda et al. (1994), studied the toxicity of radiofrequency interstitial HT in dog and found alteration of Blood Brain Barrier (BBB). Other authors outlined that the maximum tolerated heat dose to CNS lies in the range of 40-60 min at 42-42.5°C or 10-30 min at 43°C (Gerweek 1985). A recent review by Sharma and Hoopes (2003) has reported that HT specifically alters the mammalian CNS. The morphological alterations for temperature in the range 40°C to 42 °C for 4 hours has been demonstrated for the axons, the glial cells and the vascular endothelium. Sneed and Stea 1995, demonstrated in a randomized study that HT has an acceptable toxicity, in fact no grade 5 toxicity was found outside 4 patients on 112 ( 3.5% ) with grade 2 and 7 (Sneed et al.

There are only a small number of studies on brain metastases with HT. In an interesting study reported by Pontiggia on 17 patients with lung cancer,the patients were treated with nitrosurea and capacitive HT for 60'. Sixteen patients out of 17 responded with clinical improvement and radiological regression of the disease. The survival time was in median

Hyperthermia is a useful adjunct to chemotherapy and radiotherapy; however, new

The search for functional characteristics that allow cancer cells to spread to brain and development of new animal models will open new opportunities in target and drug discovery (Gril et al. 2010). Metabolic profiles of cells with metastatic propensity to brain may be one of these targets. In fact, studies by proteomics have demonstrated that breast cancer cells that metastasize to brain , have a unique protein profile consistent with increased expression of enzymes involved in glycolysis, tricarboxylic acid cycle, and oxidative phosphorylation pathways, permitting to these cells to have an enhanced proliferation and adaptation (Chen et al. 2007). Studies by Blasberg et al. (1985), using 14Cdeoxyglucose and quantitative autoradiography in metastatic walker 256 brain tumors confirm that glucose utilization is of primary importance in metastatic cells and that brain

therapeutic strategies easily applicable in many institutions are to be developed.

1995).

12.7 months (Pontiggia et al. 1995).

metastases consume glucose in presence of a low oxygen tension, the so called aerobic glycolysis or "Warburg effect" (Warburg 1956).

Palmieri et al. 2009 have confirmed the "Warburg effect" analyzing resected human brain metastases of breast cancer through real time PCR. They demonstrated an upregulation of hexokinase-2, an enzyme that mediates the first step of glucose metabolism, its upregulation is associated with a poor prognosis (Palmieri et al.2009). Hennipman et al. (1988) suggested an association of an increasing rate of enzymes implicated in glycolysis in breast cancer metastases and that their activities were higher in metastases compared to the primary tumors (Richardson et al. 2008). Another study on MCF10 model of mammary carcinoma by Richardson, confirms the major shift toward aerobic glycolysis (Gambhir et al. 2001). Increased glycolysis at metastatic site has been confirmed by [18F] 2-fluoro-2-deoxy-Dglucose positron emission tomography (PET) (Richardson et al. 2008, Gambhir et al. 2001, Gillies et al. 2008, and Lee et al. 2008).

Our group (Guais et al. 2010) has developed a drugs combination able to alter two different steps of tumor metabolism (pyruvate dehydrogenase and ATP citrate lyase). The first drug is α-lipoic acid (ALA), which, as is the case for dichloroacetate, inhibits the enzyme Pyruvate Dehydrogenase Kinase-1 (PDHK1). Inhibition of PDHK1 can restore the activity of pyruvate dehydrogenase, thus possibly redirecting aerobic glycolysis to respiration and thus decreasing the amount of lactate produced. The second drug is hydroxycitrate (HCA), which inhibits ATP citrate lyase. The efficacy of this combination appears in animals to be similar to conventional chemotherapy (cisplatin or 5-FU), as it results in both significant tumor growth inhibition and enhanced survival (Schwartz et al. 2010). Similar results have been obtained in one case of pancreatic patient metastatic to liver (Guais et al. 2010). An unpublished result, of a patient with head and neck cancer with brain metastases treated with ALA and HCA and chemotherapy has shown a complete disappearance of brain metastases (personal communication).

Immunohistochemistry studies on several specimens of primitive and metastatic human cancers, such as colon, breast, lung, ovarian and pancreas, have, also revealed an overexpression of hypoxia- inducible factor 1 (HIF) (Zhong et al. 1999). This overexpression supports two basic biological behavior of cancer and its metastases, an altered glucose transport and a limited diffusion of O2, glucose and nutrients (Liu et al. 2002). Hypoxic tumor cells become hypersensitized to glycolytic inhibitors (Liu et al. 2002) and to hyperthermia (Baronzio et al. 2006), reinforcing our hypotheses on metabolic treatment of metastatic cancer.
