Interstitial thermoradiotherapy for recurrent or persistent tumours

Combined Hyperthermia and Re-Irradiation in Non-Breast Cancer Patients: A Systematic Review

PURPOSE

This systematic literature review summarizes clinical studies and trials involving combined non-ablative hyperthermia and re-irradiation in locoregionally recurrent cancer except breast cancer.

METHODS

One database and one registry, MEDLINE and clinicaltrials.gov, respectively, were searched for studies on combined non-ablative hyperthermia and re-irradiation in non-breast cancer patients. Extracted study characteristics included treatment modalities and re-irradiation dose concepts. Outcomes of interest were tumor response, survival measures, toxicity data and palliation. Within-study bias assessment included the identification of conflict of interest (COI). The final search was performed on 29 August 2022.

RESULTS

Twenty-three articles were included in the final analysis, reporting on 603 patients with eight major tumor types. Twelve articles (52%) were retrospective studies. Only one randomized trial was identified. No COI statement was declared in 11 studies. Four of the remaining twelve studies exhibited significant COI. Low study and patient numbers, high heterogeneity in treatment modalities and endpoints, as well as significant within- and across-study bias impeded the synthesis of results.

CONCLUSION

Outside of locoregionally recurrent breast cancer, the role of combined moderate hyperthermia and re-irradiation can so far not be established. This review underscores the necessity for more clinical trials to generate higher levels of clinical evidence for combined re-irradiation and hyperthermia.

A ferrite core/metallic sheath thermoseed for interstitial thermal therapies

An alternative form of ferromagnetic seed for thermal therapy has been developed following Matsuki, Murakami, and their colleagues [1]-[4]. A nearly lossless ceramic ferrite core (FC) is surrounded by an electrically conductive sheath. The FC has a high relative intrinsic permeability, typically 3000 at low magnetic field strengths, and a sharp transition from the ferrimagnetic state to the nonmagnetic state. The sheath is either a metallic tube or coating on the core. When this composite seed is excited with a radiofrequency magnetic field, large eddy currents are induced in the metallic sheath (MS) due to the concentrated magnetic flux in the core leading to Joule heating. Advantages of this configuration are that this ferrite core/metallic sheath (FC/MS) thermoseed has high power absorption efficiency and a sharp transition compared to ferromagnetic alloy systems; means of optimizing efficiency are apparent from simple expressions; the outer sheath can be of any biocompatible metal; the production method for the ferrites leads to large quantities of seeds with reproducible properties. The FC/MS configuration solves many of the technical problems that have hindered the clinical implementation of thermally regulating ferromagnetic implants for thermal therapies.

Phase III study of interstitial thermoradiotherapy compared with interstitial radiotherapy alone in the treatment of recurrent or persistent human tumors. A prospectively controlled randomized study by the Radiation Therapy Group

PURPOSE

The objectives of this randomized trial were to determine if interstitial thermoradiotherapy (ITRT) improves tumor regression/control in accessible lesions in comparison with interstitial radiotherapy (IRT) alone and to assess the skin and soft tissue complications with either modality.

METHODS AND MATERIALS

From January 1986 to June 1992, 184 patients with persistent or recurrent tumors after previous radiotherapy and/or surgery, which were amenable to interstitial radiotherapy, were accessioned to a protocol developed by the Radiation Therapy Oncology Group (RTOG). One hundred seventy-three cases were analyzed (87 patients in the IRT group and 86 in the ITRT arm). The two arms were well balanced regarding stratification criteria. Most tumors were in the head and neck (40% in the IRT group and 46% in the ITRT group), and pelvis (42% and 43%, respectively). Eighty-four percent of patients in both arms had prior radiation therapy (> or = 40 Gy); 50% and 40%, respectively, had prior surgery, and 34% in each arm had prior chemotherapy. The dose of radiation therapy administered was dependent on the previous radiation dose and did not exceed a total cumulative dose of 100 Gy. Hyperthermia was delivered in one or two sessions, either before or before and after interstitial implant. The intended goal of the hyperthermia was to maintain a minimal tumor temperature of 42.5 degrees C for 30 to 60 min.

RESULTS

There was no difference in any of the study end points between the two arms. Complete response (CR) was 53% and 55% in both arms. Two-year survival was 34% and 35%, respectively. Complete response rate for persistent lesions was 69% and 63% in the two treatment arms as compared with 40% and 48% for recurrent lesions. A set of minimal adequacy criteria for the delivery of hyperthermia was developed. When these criteria were applied, only one patient had an adequate hyperthermia session. Acute Grade 3 and 4 toxicities were 12% for IRT and 22 % for ITRT. Late Grade 3 and 4 toxicities were 15% for IRT and 20% for ITRT. The difference was not significant.

CONCLUSIONS

Interstitial hyperthermia, as applied in this randomized study, did not show any additional beneficial effects over interstitial radiotherapy alone. Delivery of hyperthermia remains a major obstacle (since only one patient met the basic minimum adequacy criteria as defined in this study). The benefit of hyperthermia in addition to radiation therapy still remains to be proven in properly randomized prospective clinical trials after substantial technical improvements in heat delivery and dosimetry are achieved.

Interstitial hyperthermia and high dose rate brachytherapy in the treatment of anal cancer: a phase I/II study

PURPOSE

The rate of local failure is sufficiently high following sphincter conserving surgery and radiation therapy for advanced anal cancers to warrant investigation of improved local treatment techniques. This Phase I/II study was undertaken to investigate the site-specific toxicities and response of Stage II and III anal cancers to interstitial thermoradiotherapy using a hot water interstitial system.

METHODS AND MATERIALS

Between September 1988 and March 1991, 14 patients with primary carcinomas of the anal canal, UICC Stage T2-3, N0-1, M0, were treated with split-course external beam irradiation to the pelvis (30 Gy + 20 Gy) and 1 or 2 interstitial Iridium-192 high dose rate (Ir-192 HDR) implants (6-8 Gy each) immediately followed by interstitial hyperthermia (HT). Patients with tumor diameters > 3 cm were scheduled to receive chemotherapy consisting of 2 courses of 5-fluorouracil and mitomycin C given concomitantly with external beam radiation. Interstitial hyperthermia was induced by circulating warm water through the needles that were implanted to hold the Ir-192 source. The treatment goal was to achieve and maintain a temperature of 42.5 degrees C over a time period of 40 min. A 3-point thermocouple probe inserted into one or two additional needles was used for thermometry. The temperatures were recorded by manual mapping along these needles at steps of 0.5 or 1 cm.

RESULTS

A total of 20 Ir-192 HDR-HT implants were performed in 14 patients. All but two patients completed the external beam irradiation; five patients received concomitant chemotherapy. Analysis of thermal parameters showed that minimum intratumoral temperatures (Tmin) of 42 degrees C, 42.5 degrees C, 43 degrees C, and 44 degrees C were achieved in 64%, 37.5%, 14%, and 7% of patients, respectively. Intratumoral mean Tmin, mean average, and mean maximum temperatures for these patients were 41.7 degrees C, 42.4 degrees C, and 43.4 degrees C, respectively. Brachytherapy and HT were well tolerated. Clinical complete responses (cCR) were obtained in 11/14 (78.5%) patients, complete histopathological responses (pCR) in 10/14 (71%). Only one patient with pCR recurred and succumbed to her disease. Patients with persistent disease (1 minimal and 3 partial responders, including 1 cCR) underwent abdominal-perineal resection but subsequently died from local-regional recurrence. One patient with pCR died from unrelated causes. Median survival for all patients from onset of radiation to death or last follow-up is 26 months. Eight patients are alive disease-free after a follow-up ranging from 16-44 months (median: 30, mean: 30 months). Treatment complications were limited to two patients who developed persistent ulcers. Sphincter function was maintained in 50% of patients.

CONCLUSION

This study demonstrates that interstitial warm water hyperthermia in combination with brachytherapy for anal carcinomas is feasible and did not add to complications when compared to studies employing external beam irradiation and brachytherapy alone. The thermal parameters obtained by the warm water system compare favorably to those reported by others using radiofrequency and microwave systems.

Interstitial thermoradiotherapy with ferromagnetic implants for locally advanced and recurrent neoplasms

PURPOSE

The University of Arizona, University of California at San Francisco, City of Hope Medical Center, and University of Wisconsin participated in a Phase I/II protocol to assess the heating ability and the toxicity of interstitial thermoradiotherapy using ferromagnetic implantation.

METHODS AND MATERIALS

Forty-four patients with advanced primary or recurrent extra-cranial solid malignancies were enrolled in this study. Fourteen gauge catheters were implanted into tumors and, once in the department of Radiation Oncology, loaded with ferromagnetic seeds to deliver a 60 min hyperthermia treatment. Multi-point thermometry was continuously used throughout the heating sessions for all patients, sampling the periphery as well as the core of the tumor. After 192Iridium brachytherapy, 18 patients then had an additional treatment. The mean radiation dose while on protocol was 50.0 Gy, with total doses (including prior radiotherapy) ranging from 20.3-151.8 Gy (median = 88.7 Gy). Response and toxicity were assessed by inspection, palpation, and/or radiologic studies. Forty-one patients were evaluable for response, and there were 55 analyzable hyperthermia treatment sessions.

RESULTS

The complete response rate was 61% (25/41). The partial response rate was 31.7% and only 7.3% failed to respond. Median duration of local control has not yet been reached. The mean maximum, minimum, and mean time-averaged temperatures for all in-tissue sensors were 43.7 degrees C, 38.7 degrees C, and 41.0 degrees C, respectively. Tumor size was the only factor significantly correlated with temperatures or with complete response rate; larger tumors attained higher temperatures but smaller tumors had a higher response probability. Nineteen patients (43%) experienced toxicities, however there was only a 7% (3/44) rate of serious complications (Grade 3 or 4). Prior treatment with hyperthermia was the only factor significantly correlated with serious toxicity.

CONCLUSION

These results, a 93% total response with only 7% serious toxicity, are encouraging especially in the context of the patient population treated. Phase II/III studies involving ferromagnetic implantation are warranted.

Thermoradiotherapy with combined interstitial and external hyperthermia in advanced tumours in the head and neck with depth > or = 3 cm

Advanced tumours in the head and neck 3-6 cm depth are too deep to be completely heated by external 915 MHz microwaves. A preliminary study was performed using interstitial plus external hyperthermia combined with external beam radiation therapy to heat tumours to depths > or = 3 cm. Nine advanced metastatic lesions of squamous cell carcinoma located in the head and neck were treated between 1987 and 1990 with the combined hyperthermia technique and radiation doses of 38-60 Gy (mean of 49 +/- 3 Gy). The mean tumour volume was 58 +/- 9 (SE) cm3 (range 24-94 cm3) with a mean tumour depth of 3.9 +/- 0.3 cm (range 3-5.5 cm). The deeper aspects of the tumour were heated by interstitial 915 MHz microwave antennas and the superficial aspects heated by external 915 MHz applicators. A single plane of polyurethane closed-end catheters, 16 Ga, were inserted under local anaesthesia approximately 1.5-2 cm apart in parallel arrays at the base of a lesion behind the sternomastoid muscle, or an equivalent site in a dissected neck, extending forward and angled deeply no more than 15 degrees. Hyperthermia was administered twice weekly immediately after radiation therapy in a mean of 5.3 +/- 0.7 external heat sessions (range 3-7) and a mean of 3.5 +/- 0.6 interstitial heat sessions (range of 1-6). Interstitial hyperthermia was usually administered in alternating sessions with external hyperthermia, but in some patients all of the sessions of one modality were administered followed by all of the sessions of the other modality. In no case were both interstitial and external heatings performed on the same day. Surface thermometers were used to monitor skin temperature during external hyperthermia sessions. Results showed that by 8 weeks after completion of treatment, six lesions exhibited a complete response (67%) and three a partial response (33%). One of the partial responses continued to regress and became a complete response (78% complete response). The recurrence rate in complete responders was 14% (1/7) with time to recurrence of 7.7 months. Six lesions were recurrence-free at last follow-up of 21.3 +/- 8.8 months. Skin reactions were absent in four fields (44%), erythema was noted in five (56%) and thermal blistering in one (11%). Ulceration occurred only in association with tumour breakdown when the skin was infiltrated by tumour (three patients, 33%).(ABSTRACT TRUNCATED AT 400 WORDS)

Analysis of temperature distributions of interstitial hyperthermia using a hot water system

PURPOSE

Interstitial hyperthermia is being increasingly used as an adjunct to brachytherapy in the treatment of implantable tumors. Of the several interstitial hyperthermia systems available, perhaps the simplest to use are the circulating hot water systems. An analysis of the thermal distributions obtained during our initial experience with interstitial hyperthermia using steel needles and the KHS-9 hot water system was therefore undertaken.

METHODS AND MATERIALS

Between September 1988 and June 1991, 23 patients were treated with interstitial Iridium-192 high dose-rate brachytherapy immediately followed by interstitial hot water hyperthermia. A total of 32 implants were performed in these patients, of whom 14 presented with primary anal carcinomas, six with recurrent gynecological tumors, and three with subcutaneous metastases from malignant melanoma. All but the patients with anal cancers had failed in previously irradiated sites. One or two heat treatments were delivered to each tumor with the goal to reach and maintain an intratumoral temperature 42.5 degrees C over a period of 40 min. Temperature measurements were carried out by mapping three-point thermocouple probes along the track of one or two needles parallel to the implanted needles.

RESULTS

Minimum intratumoral temperatures exceeded 42.0 degrees C in 41%, 42.5 degrees C in 19%, 43.0 degrees C in 13%, and 44.0 degrees C in 3% of treatments. The average minimum, maximum, and mean intratumoral temperatures for all treatments were 41.7 degrees C, 43.5 degrees C, and 42.6 degrees C, respectively.

CONCLUSION

The temperature profiles obtained in this series compare favorable to those reported in literature for radiofrequency local current field systems and suggest the hot water device may be an alternative heating method. It is relatively simple to use, does not require shielding of the treatment room, and can easily be adapted to currently used brachytherapy systems. Further patient accrual and longer follow-up will be needed to assess the clinical results in terms of tumor response and duration of response.

Evaluation of microwave interstitial antennas in the phantom with varying cross-section

Dipole-regular microwave interstitial antennas are characterized with a "dead" space located along the tip segment of the antenna. The length of the "dead" space is on the order of 2 cm or larger, depending on the antenna's insertion depth. If the insertion depth is smaller than 4 cm, then coupling of the antennas to tissue becomes a problem. Catheters that facilitate the placement of antennas into tumor frequently protrude beyond the tissue. This provides the opportunity of exposing part of the antenna tips (with low radiation output) beyond the tissue. Decoupling of this part of the antennas from the tissue reduced the dead space and improved microwave power transfer to the tissue. This concept was investigated using a muscle equivalent phantom consisting of five segments with thicknesses varying from 3 cm to 8 cm. The transfer of microwave power to the phantom and SAR distributions along the central axis of a rectangular array of four antennas were evaluated by measuring rates of temperature rise. The protrusion lengths that improved the array performance were found for each segment of the phantom.

Radiation and thermal sensitivities of murine tumor (FSa-II) cells recurrent after a heavy irradiation

Radiation and thermal sensitivities, and cell doubling times (Tds) of C3Hf/Sed mouse FSa-II cells recurring after a heavy irradiation were examined in vitro. Tumors in the leg were irradiated with gamma-rays and observed for late recurrence (in vivo clones), or removed immediately after irradiation and single cell suspensions were plated for colony formation (in vitro clones). Five subclones were selected from original cells in vitro. Survival curves were fitted to the multi-target and linear quadratic models. Surviving fractions at 2 (SF2) and 10 Gy (SF10) irradiations, and those at 30 and 60 min heatings at 44 degrees C (SF30 and SF60), were obtained for each clone. Although, Tds of subclones were slightly longer than those of the parental cells, those of recurrent clones were prolonged substantially with an exception of one cell line. Radiosensitivities of FSa-II parental cells tested in vitro and in vivo were equally radioresistant. Thermal sensitivities of parental cells tested in vitro and in vivo were also identical. All subclones were more radiosensitive compared to the parental cells. The in vitro recurrent clones showed smaller D0 (radiation dose to reduce survival from S to S/e in the exponential portion of survival curve) than the D0 of the parental cells. The SF2 values of four in vitro recurrent clones were greater than that of the parental cells whereas those of two lines were smaller. It was of interest that the in vivo recurrent tumor cells showed a wide variation in the radiation sensitivity. Among 9 tumor cell lines examined, 4 lines were more sensitive and 4 were more resistant compared to the original. FSa-II subclones as well as both in vitro and in vivo recurrent clones showed a wide variation in thermal sensitivity. No consistent changes in the shoulder or in the slope were found. The SF30 or SF60 showed that 5 out of 9 in vivo recurrent clones and 4 out of 9 in vitro clones were more resistant compared to the original cells. No correlation was observed between thermal and radiation sensitivities. The Td was not related with radiation or thermal sensitivity.

Interstitial thermoradiotherapy: thermal dosimetry and clinical results

From August 1977 to August 1986, 72 patients with advanced primary or recurrent cancers were treated using interstitial thermoradiotherapy. Sites treated included the pelvis in 49 patients, the head and neck in 15, and other sites in six. Median tumor volume was 52 cm3, and all but nine patients had received prior irradiation. In 69 patients, hollow stainless steel catheters were implanted and used as electrodes with a 0.5 MHz radiofrequency (RF) generator, whereas in three patients, standard plastic Henschke tubes were used with a commercially available interstitial microwave (MW) system operating at 915 MHz. Most patients were heated intraoperatively for 30 minutes, aiming for a minimum measured intratumoral temperature (Tmin) of 42 degrees C. The implant was occasionally preceded by external irradiation, and after hyperthermia, the catheters were afterloaded with 192Ir for brachytherapy. Tmin exceeded 42 degrees, 42.5 degrees, 43 degrees, and 44 degrees in 25, 16, 12, and 3, respectively, of 70 patients with temperature data available, and the probability of successful heating was independent of tumor volume or site. Twenty-five of 69 (36%) evaluable patients achieved a complete response (CR). Probability of CR demonstrated a significant univariate dependence upon Tmin, radiation dose, site treated, and tumor volume, but multivariate analysis showed only three significant predictor variables: tumor volume, radiation dose, and Tmin. The probability of a CR ranged from 95% for patients with small tumors receiving high doses of radiation and adequate heat, to 5% for patients with large tumors receiving low radiation doses and less than adequate heat. Of 25 patients with CR, 10 relapsed; median response duration was less than 18 months, depended marginally upon disease site, and was independent of Tmin, radiation dose, and tumor volume. Seventeen patients sustained a complication, of which nine were severe enough to require hospitalization or surgery. All severe complications occurred in patients with pelvic tumors. The probability of a complication of any severity had a significant univariate association with maximum intratumoral temperature (Tmax) and tumor size. We conclude that interstitial thermoradiotherapy offers the promise of heating large tumors in locations where externally applied hyperthermia has not been successful.

Interstitial thermoradiotherapy for recurrent head and neck cancer

From 1985 to 1987, 22 head and neck sites in 20 patients with recurrent tumors were treated with interstitial thermoradiotherapy (ITRT). The sites treated were 15 neck (68%), four tongue (18%), two parotid (9%), and one buccal mucosa (4%). Squamous cell carcinoma was diagnosed in 21 sites and adenocarcinoma in the other. All patients had prior radiotherapy (RT), including 15 who underwent a combination of RT and surgery. Interstitial RT with iridium 192 (mean dose, 40 Gy) was combined with interstitial microwave hyperthermia (mean thermal dose, 90 units). Complete response (CR) was obtained in 15 (68%) sites and partial response (PR) in seven (32%) sites. There were no local recurrences in the 15 CR patients during a period of observation of up to 30 months. Of the seven PR patients, one had radical neck dissection and is free of tumor after 28 months. Tumor volume was an important factor influencing CR (P less than .001), whereas RT and thermal dose were not (P = .3). Of the 20 patients treated, 19 experienced major subjective benefit. Serious complications occurred in two patients: one had localized soft tissue necrosis, the other had aspiration pneumonia. ITRT was well-tolerated by patients despite prior aggressive therapy. High objective response rate and low toxicity demonstrate the value of this treatment combination in the management of patients with postradiation recurrence of head and neck tumors.

Microwave applicator for transurethral hyperthermia of benign prostatic hyperplasia

An applicator for heating the prostate gland using a transurethral approach is described. This technique uses three microwave antennas and a thermometry sensor attached to the outer surface of a balloon (Foley) type urological catheter. Each microwave antenna also includes a built-in thermistor to control temperature and balance power. The balloon catheter assures rapid and reproducible localization of the antennas in the prostatic urethra. The two-dimensional SAR and steady-state temperature distributions surrounding the applicator in tissue equivalent phantom are reported. Longitudinal temperature distributions measured in situ at the applicator-urethral interface and the longitudinal and radial temperature distributions measured in normal canine prostate are presented and discussed. The technique appears to be capable of elevating temperature to greater than 42 degrees C in a cylindrically symmetrical volume up to 5 cm length and 0.5 cm radial penetration surrounding the applicator.

The current and potential role of hyperthermia in radiotherapy

Current clinical experience strongly suggests that hyperthermia will become an important modality as an adjuvant to radiotherapy in the treatment of locally advanced solid tumors. Hyperthermia must therefore be considered a topic of general interest. Biologically, hyperthermia has two different types of interactions with radiation. Firstly, heat has a radiosensitizing effect. This is most prominent with simultaneous application, but is of the same magnitude in both tumor and normal tissue and will not improve the therapeutic ratio unless the tumor is heated to a higher temperature than the normal tissue. Secondly, hyperthermia exhibits a direct cytotoxic effect, and a moderate heat treatment alone can almost selectively destroy tumor cells in a nutritionally deprived chronically hypoxic and acidic environment. Because such cells are the most radioresistant, a smaller radiation dose is needed to control the remaining more radiosensitive cells. If critical, irradiated normal tissues are also heated, the cytotoxicity is best utilised if heat is given at least 3-4 hours after irradiation. The magnitude of both the sensitizing and the cytotoxic effect depends on temperature and heating time. Clinically, heating of superficial tumors (e.g. breast, neck nodes and malignant melanoma) has confirmed the biological rationale for using hyperthermia as an adjuvant to radiotherapy. An overview of available data gives thermal enhancement ratios of approximately 1.5 in several superficial tumor sites after external heating. From a practical point of view, true simultaneous treatment is almost impossible using external heating, and the major effect of the combined treatment will have to rely on hyperthermic cytotoxicity. This makes the design of clinical schedules less complicated since only a few heat fractions may be needed to achieve an optimal effect. On this basis, several randomized clinical trials have been activated with the aim to evaluate the role of adjuvant hyperthermia in the primary treatment of advanced (superficial) tumors. In addition, studies are underway to specifically elucidate the clinical relevance of thermotolerance and other biological issues. So far, the clinical evaluation has almost solely been limited to superficial tumors, or to situations where interstitial heating is feasible. External heating of "deep" seated tumors is still preliminary, and most studies are in Phase I-II, with emphasis on toxicity and feasibility. The initial results are promising with regard to improved tumor control and acceptable toxicity.

The accuracy of temperature measurement from within an interstitial microwave antenna

Temperature measurement from within microwave interstitial antennas is a promising new development for hyperthermia. These antennas could enable the development of multipoint temperature regulation, leading to improved control of temperature distributions and therefore more effective hyperthermia treatments. In the complex environment of an antenna within a plastic catheter, measured temperatures were found to differ from the estimated local tissue temperature by up to 8 degrees C. In the design evaluated in this report the primary source of this error appears to be self-heating distal to the antenna junction, particularly in the outer copper conductor. The magnitude of self-heating is directly proportional to applied microwave power. Catheter wall thickness, tissue perfusion, and longitudinal temperature gradient also influence the measured temperature.