Bone marrow experts are still debating the value of purging

The Kadota Fund International Forum 2004--clinical group consensus

The results from experimental studies indicate that hyperthermia is both an effective complementary treatment to, and a strong sensitiser of, radiotherapy and many cytotoxic drugs. Since the first international hyperthermia conference in 1975, Washington DC, techniques to increase tumour temperature have been developed and tested clinically. Hyperthermia can be applied by several methods: local hyperthermia by external or internal energy sources, perfusion hyperthermia of organs, limbs, or body cavities, and whole body hyperthermia. The clinical value of hyperthermia in combination with other treatment modalities has been shown by randomised trials. Significant improvement in clinical outcome has been demonstrated for tumours of the head and neck, breast, brain, bladder, cervix, rectum, lung, oesophagus, for melanoma and sarcoma. The addition of hyperthermia resulted in remarkably higher (complete) response rates, accompanied by improved local tumour control rates, better palliative effects, and/or better overall survival rates. Toxicity from hyperthermia cannot always be avoided, but is usually of limited clinical relevance. In spite of these good clinical results, hyperthermia has received little attention. Problems with acceptance concern the limited availability of equipment, the lack of awareness concerning clinical results, and the lack of financial resources. In this paper the most relevant literature describing the clinical effects of hyperthermia is reviewed and discussed, and means to overcome the lack of awareness and use of this modality is described.

In vitro and in vivo purging of B lymphoma cells from stem-cell products using anti-CD20 Abs

BACKGROUND

Autologous stem-cell transplantation has proved curative therapy for relapsed NHL. However, recurrence of underlying disease remains the major cause of treatment failure in this setting.

METHODS

Development of effective MAb therapy directed against the B cell surface antigen CD20 has added a valuable tool of clearing contaminating lymphoma cells from stem-cell products by either in vitro or in vivo application.

RESULTS

Transplantation of successfully in vitro purged bone marrow using Mabs has been correlated with prolonged survival in large Phase-II study. So far, no randomized trial could demonstrate a therapeutic benefit for in vitro purging. The anti-CD20 Mab rituximab has been used for in vivo purging at the time of stem cell collection or peritransplantation. This method has been shown to be safe and feasible. In the majority of patients the combination of rituximab with anti-lymphoma chemotherapy meant the collected stem cell products were free of molecularly-detectable lymphoma cells.

DISCUSSION

The increasing ability to kill all lymphoma cells in vivo by regimens including myeloablative therapy renders contaminating lymphoma cells of the autologous stem cell product the main source for disease recurrence. Clearing of these cells remains a prerequisite for curative stem-cell transplantation. Establishment of safe and effective therapeutic schedules using Mabs will enhance the chance for collection of lymphoma-free hematopoietic stems cells.

Heating the patient: a promising approach?

There is a clear rationale for using hyperthermia in cancer treatment. Treatment at temperatures between 40 and 44 degrees C is cytotoxic for cells in an environment with a low pO(2) and low pH, conditions that are found specifically within tumour tissue, due to insufficient blood perfusion. Under such conditions radiotherapy is less effective, and systemically applied cytotoxic agents will reach such areas in lower concentrations than in well perfused areas. Therefore, the addition of hyperthermia to radiotherapy or chemotherapy will result in at least an additive effect. Furthermore, the effects of both radiotherapy and many drugs are enhanced at an increased temperature. Hyperthermia can be applied by several methods: local hyperthermia by external or internal energy sources, regional hyperthermia by perfusion of organs or limbs, or by irrigation of body cavities, and whole body hyperthermia. The use of hyperthermia alone has resulted in complete overall response rates of 13%. The clinical value of hyperthermia in addition to other treatment modalities has been shown in randomised trials. Significant improvement in clinical outcome has been demonstrated for tumours of the head and neck, breast, brain, bladder, cervix, rectum, lung, oesophagus, vulva and vagina, and also for melanoma. Additional hyperthermia resulted in remarkably higher (complete) response rates, accompanied by improved local tumour control rates, better palliative effects and/or better overall survival rates. Generally, when combined with radiotherapy, no increase in radiation toxicity could be demonstrated. Whether toxicity from chemotherapy is enhanced depends on sequence of the two modalities, and on which tissues are heated. Toxicity from hyperthermia cannot always be avoided, but is usually of limited clinical relevance. Recent developments include improvements in heating techniques and thermometry, development of hyperthermia treatment planning models, studies on heat shock proteins and an effect on anti-cancer immune responses, drug targeting to tumours, bone marrow purging, combination with drugs targeting tumour vasculature, and the role of hyperthermia in gene therapy. The clinical results achieved to date have confirmed the expectations raised by results from experimental studies. These findings justify using hyperthermia as part of standard treatment in tumour sites for which its efficacy has been proven and, furthermore, to initiate new studies with other tumours. Hyperthermia is certainly a promising approach and deserves more attention than it has received until now.