PDR brachytherapy with flexible implants for interstitial boost after breast-conserving surgery and external beam radiation therapy

Pulsed-dose-rate peri-operative brachytherapy as an interstitial boost in organ-sparing treatment of breast cancer

Purpose

To evaluate peri-operative multicatheter interstitial pulsed-dose-rate brachytherapy (PDR-BT) with an intra-operative catheter placement to boost the tumor excision site in breast cancer patients treated conservatively.

Material and methods

Between May 2002 and October 2008, 96 consecutive T1-3N0-2M0 breast cancer patients underwent breast-conserving therapy (BCT) including peri-operative PDR-BT boost, followed by whole breast external beam radiotherapy (WBRT). The BT dose of 15 Gy (1 Gy/pulse/h) was given on the following day after surgery.

Results

No increased bleeding or delayed wound healing related to the implants were observed. The only side effects included one case of temporary peri-operative breast infection and 3 cases of fat necrosis, both early and late. In 11 patients (11.4%), subsequent WBRT was omitted owing to the final pathology findings. These included eight patients who underwent mastectomy due to multiple adverse prognostic pathological features, one case of lobular carcinoma in situ, and two cases with no malignant tumor. With a median follow-up of 12 years (range: 7-14 years), among 85 patients who completed BCT, there was one ipsilateral breast tumor and one locoregional nodal recurrence. Six patients developed distant metastases and one was diagnosed with angiosarcoma within irradiated breast. The actuarial 5- and 10-year disease free survival was 90% (95% CI: 84-96%) and 87% (95% CI: 80-94%), respectively, for the patients with invasive breast cancer, and 91% (95% CI: 84-97%) and 89% (95% CI: 82-96%), respectively, for patients who completed BCT. Good cosmetic outcome by self-assessment was achieved in 58 out of 64 (91%) evaluable patients.

Conclusions

Peri-operative PDR-BT boost with intra-operative tube placement followed by EBRT is feasible and devoid of considerable toxicity, and provides excellent long-term local control. However, this strategy necessitates careful patient selection and histological confirmation of primary diagnosis.

A review of the clinical experience in pulsed dose rate brachytherapy

Pulsed dose rate (PDR) brachytherapy is a treatment modality that combines physical advantages of high dose rate (HDR) brachytherapy with the radiobiological advantages of low dose rate brachytherapy. The aim of this review was to describe the effective clinical use of PDR brachytherapy worldwide in different tumour locations. We found 66 articles reporting on clinical PDR brachytherapy including the treatment procedure and outcome. Moreover, PDR brachytherapy has been applied in almost all tumour sites for which brachytherapy is indicated and with good local control and low toxicity. The main advantage of PDR is, because of the small pulse sizes used, the ability to spare normal tissue. In certain cases, HDR resembles PDR brachytherapy by the use of multifractionated low-fraction dose.

Pulsed dose rate brachytherapy - is it the right way?

Pulsed dose rate (PDR-BT) treatment is a brachytherapy modality that combines physical advantages of high-dose-rate (HDR-BT) technology (isodose optimization, radiation safety) with the radiobiological advantages of low-dose-rate (LDR-BT) brachytherapy. Pulsed brachytherapy consists of using stronger radiation source than for LDR-BT and producing series of short exposures of 10 to 30 minutes in every hour to approximately the same total dose in the same overall time as with the LDR-BT. Modern afterloading equipment offers certain advantages over interstitial or intracavitary insertion of separate needles, tubes, seeds or wires. Isodose volumes in tissues can be created flexibly by a combination of careful placement of the catheter and the adjustment of the dwell times of the computerized stepping source. Automatic removal of the radiation sources into a shielded safe eliminates radiation exposures to staff and visitors. Radiation exposure is also eliminated to the staff who formerly loaded and unloaded multiplicity of radioactive sources into the catheters, ovoids, tubes etc. This review based on summarized clinical investigations, analyses the feasibility and the background to introduce this brachytherapy technique and chosen clinical applications of PDR-BT.

Pulsed dose rate brachytherapy

Pulsed dose rate (PDR) is a new modality for dose delivery in brachytherapy. It uses modern afterloading technology (miniaturized source, cable driven, software controlled), with source activities in the range of 1 Ci, which is actually one tenth of the normal activity used for high dose rate (HDR) brachytherapy. Modern technology allows dose optimization, and source strength in the above-mentioned range creates a new dose rate condition. For small fractions (pulses) with short interpulse intervals, PDR mimics the radiobiology of high dose rate brachytherapy, whereas for bigger doses per fraction, dose adjustments are needed to compensate for the loss of therapeutic ratio. Clinical series showed good figures for local control and toxicity. Almost every clinical site has been reported to have been treated with PDR, with some thousand of patients having been reported. Technical difficulties in some body sites can be overcome by slightly modifying the implant technique. PDR brachytherapy is an ideal environment for the development of new dose fractionation schedules. It creates unique conditions in which to operate. Knowledge of tissue repair kinetics is extremely important for adequate selection of dose per pulse and interpulse interval. Therapeutic ratio can be improved by adjusting interpulse intervals to the repair half-times for normal tissues. On the other hand, superfractionated schedules with low dose per pulse can be explored in conditions of tumor hypoxia, thanks to the predicted hypersensitivity at low dose per fraction. The use of chemical agents (nicotinamide and others) in concomitance with this superfractionated schedules is foreseen in controlled clinical trials. In conclusion, PDR brachytherapy can be considered a new paradigm for dose delivery. It is safe and reliable, can be used in the setting of image-guided radiation therapy, and exploit the differential effect of ionizing radiations by a thorough knowledge of tissue kinetics for an improved therapeutic ratio.

Safety aspects of pulsed dose rate brachytherapy: analysis of errors in 1,300 treatment sessions

PURPOSE

To determine the safety of pulsed-dose-rate (PDR) brachytherapy by analyzing errors and technical failures during treatment.

METHODS AND MATERIALS

More than 1,300 patients underwent treatment with PDR brachytherapy, using five PDR remote afterloaders. Most patients were treated with consecutive pulse schemes, also outside regular office hours. Tumors were located in the breast, esophagus, prostate, bladder, gynecology, anus/rectum, orbit, head/neck, with a miscellaneous group of small numbers, such as the lip, nose, and bile duct. Errors and technical failures were analyzed for 1,300 treatment sessions, for which nearly 20,000 pulses were delivered. For each tumor localization, the number and type of occurring errors were determined, as were which localizations were more error prone than others.

RESULTS

By routinely using the built-in dummy check source, only 0.2% of all pulses showed an error during the phase of the pulse when the active source was outside the afterloader. Localizations treated using flexible catheters had greater error frequencies than those treated with straight needles or rigid applicators. Disturbed pulse frequencies were in the range of 0.6% for the anus/rectum on a classic version 1 afterloader to 14.9% for orbital tumors using a version 2 afterloader. Exceeding the planned overall treatment time by >10% was observed in only 1% of all treatments. Patients received their dose as originally planned in 98% of all treatments.

CONCLUSIONS

According to the experience in our institute with 1,300 PDR treatments, we found that PDR is a safe brachytherapy treatment modality, both during and outside of office hours.

Intraoperative radiotherapy (IORT) as a boost in patients with early-stage breast cancer -- acute toxicity

BACKGROUND

We report on acute toxicities as well as the early cosmetic outcome of patients receiving intraoperative radiotherapy (IORT) followed by whole-breast radiotherapy (WBRT) compared to patients treated with standard WBRT alone.

PATIENTS AND METHODS

From 2/2002 until 2/2005, 84 breast cancer patients were treated with IORT during breast-conserving surgery (BCS) as a boost (20 Gy/50 kV X-rays) followed by WBRT. After wound healing, all IORT patients were treated with WBRT at a total dose of 46 Gy. For the purpose of comparison, 53 patients treated consecutively between 1/2003 and 12/2004 in our institution with BCS followed by WBRT at a total dose of 50-66 Gy, were analyzed. All patients had a defined followup schedule. Toxicities were prospectively documented using the CTC/EORTC Score. Cosmesis was evaluated after 6 months using a 1-4 score.

RESULTS

Treatment was well tolerated with no grade 3/4 acute toxicity. Rare adverse effects following IORT included wound healing problems (2%), erythema grade I-II (3%), palpable seroma (6%) and mastitis (2-4%). The number of patients with induration of the tumor bed was comparably low.

CONCLUSION

IORT with the IntrabeamTM system applied as a boost during BCS, followed by 46 Gy WBRT, exerts similar acute toxicity as standard WBRT. Further follow-up is needed to assess long-term toxicity and efficacy.

Pulsed Dose-Rate Perioperative Interstitial Brachytherapy for Soft Tissue Sarcomas of the Extremities and Skeletal Muscles of the Trunk

BACKGROUND

This study evaluated the role of pulsed dose-rate (PDR) brachytherapy (BRT), delivered alone or as a boost to external beam radiotherapy, as adjuvant therapy for the local control of soft tissue sarcomas of the extremities and skeletal muscles of the trunk that have undergone surgical treatment.

METHODS

Between July 1998 and January 2002, 42 patients were treated with a combination of surgery and BRT alone (18 patients) or BRT/external beam radiotherapy (24 patients) for the treatment of primary (n = 32) and recurrent (n = 10) soft tissue sarcomas located in the proximal extremity (n = 17), distal extremity (n = 17), and trunk (n = 8). Tumor size was <5 cm in 20 cases and >5 cm in 22 cases, with histological grading of 1 (n = 7), 2 (n = 18), or 3 (n = 17). The median BRT dose delivered was 15 Gy, and the median external beam irradiation dose was 50 Gy.

RESULTS

With a median follow-up of 34 months, the 36-month survival was 83.9% (SE, 6.1%), and the local control was 89%.

CONCLUSIONS

PDR interstitial BRT for soft tissue sarcoma is an effective, well-tolerated adjuvant radiation treatment that offers several practical advantages, among which are low acute and late toxicity with maximum normal tissue and critical structure sparing and overall shorter radiotherapy and hospital stay.

[Brachytherapy boost for breast cancer: what do we know? Where do we go?]

Since many years, Brachytherapy (BT) appears to play an important role in the treatment of many solid tumors. For breast cancer, BT is usually used as boost after postoperative external beam radiation therapy. In certain circumstances, BT can be used as sole radiation technique focalized on the tumor bed or more rarely, as second conservative treatment in case of local recurrence for woman refusing salvage mastectomy. Boost BT is most often applied via an interstitial technique while the dose rate can vary from low to high dose rate through pulse dose rate. All of those boost techniques were published and some of them compared the results obtained with BT and external beam electron therapy. The analysis of the published phase II and III trials was not able to show significant differences between the two boost techniques in term of local control as well as late skin side effects. However, we noted that the patients who received BT boost presented a higher risk of local recurrence compare to those treated with electron therapy, due to age, margin status or presence of extensive intraductal component. Only a phase III trial randomizing BT boost vs electron therapy boost could show a possible improvement of local control rate in the BT arm; however, this trial should enroll patients with a real high risk of local recurrence in order to take benefit from the dosimetric advantages of BT.

Indications and technical aspects of brachytherapy in breast conserving treatment of breast cancer

Improved local control rates have been demonstrated in retrospective studies as well as in randomised trials on brachytherapy with increasing doses to the tumour bed. The higher local control obtained by interstitial breast implants, as compared to external photon or electron beam boosts, have been mainly attributed to the higher doses actually delivered to the tumour bed by these implants for the same nominal dose as compared to external beam radiotherapy (RT). On the other hand, poor cosmesis has also been correlated with radiation dose to the breast skin (radiation teleangiectases), and breast tissue (retraction due to fibrosis), the latter depending not only on RT dose but also on the treated boost volume. For this reason, a possible benefit of interstitial implants will only be realized when the gain in local control goes together with minimal cosmetic damage. Therefore, the ballistic advantages of interstitial implants have to be maximally exploited: i.e. the treated volume should be maximally adapted to the target volume, and additional irradiation of the breast skin by the boost technique should be avoided. This paper deals in detail with the technical aspects of breast brachytherapy that seem to be relevant for high quality outcome.

A real-time image-guided intraoperative high-dose-rate brachytherapy system

PURPOSE

To develop a real-time, image-guided intraoperative high-dose-rate brachytherapy system.

METHODS AND MATERIALS

The surface applicator, a catheter array on a 1-mm-thick soft and semitransparent silicone rubber sheet, was directly sutured on the surgical bed. A three-dimensional video camera was then used to instantly capture images of the catheters and the surgical surface. Tracing the catheters on the images allowed us to automatically determine the dwell source positions. Dwell times in the dwell positions were optimized to minimize the dose variation and deviation from the treatment prescription. A dose-texture plot was created to quantify the dose distribution.

RESULTS

Treatment planning time was reduced from hours to a few minutes. Phantom tests have shown that the new source localization is accurate with sigma<1.5 mm. All hot spots and cold spots had been eliminated after the dwell-time optimization.

CONCLUSIONS

This real-time, image-guided planning system can provide optimal image-guided intraoperative high-dose-rate brachytherapy with geometric and dosimetric improvements and a short planning time.

Office hours pulsed brachytherapy boost in breast cancer

BACKGROUND AND PURPOSE

Radiobiological studies suggest equivalent biological effects between continuous low dose rate brachytherapy (CLDR) and pulsed brachytherapy (PB) when pulses are applied without interruption every hour. However, radiation protection and institute-specific demands requested the design of a practical PB protocol substituting the CLDR boost in breast cancer patients. An office hours scheme was designed, considering the CLDR dose rate, the overall treatment time, pulse frequency and tissue repair characteristics. Radiobiological details are presented as well as the logistics and technical feasibility of the scheme after treatment of the first 100 patients.

MATERIALS AND METHODS

Biologically effective doses (BEDs) were calculated according to the linear quadratic model for incomplete repair. Radiobiological parameters included an alpha/beta value of 3 Gy for normal tissue late effects and 10 Gy for early normal tissue or tumour effects. Tissue repair half-time ranged from 0.1 to 6 h. The reference CLDR dose rate of 0.80 Gy/h was obtained retrospectively from analysis of patients' data. The treatment procedure was evaluated with regard to variations in implant characteristics after treatment of 100 patients.

RESULTS

A PB protocol was designed consisting of two treatment blocks separated by a night break. Dose delivery in PB was 20 Gy in two 10 Gy blocks and, for application of the 15 Gy boost, one 10 Gy block plus one 5 Gy block. The dose per pulse was 1.67 Gy, applied with a period time of approximately 1.5 h. An inter-patient variation of 30% (1 SD) was observed in the instantaneous source strength. Taking also the spread in implant size into account, the net variation in pulse duration amounted to 38%.

CONCLUSION

An office hours PB boost regimen was designed for substitution of the CLDR boost in breast-conserving therapy on the basis of the BED. First treatment experience shows the office hour regimen to be convenient to the patients and no technical perturbations were encountered.

Contemporary role of modern brachytherapy techniques in the management of malignant thoracic tumors

Sole brachytherapy for carcinoma of the lung is most often performed using high-dose-rate (HDR) remote afterloading equipment, which delivers the treatment within the tracheobronchial tree in an outpatient setting. It provides excellent, rapid palliation in advanced stages, and can also be used selectively for curative intent in early stages. In better-performance patients, fractionated external beam radiation therapy (EBRT) is preferred to brachytherapy as an initial treatment because it appears to provide a modest gain in survival, and more sustained palliation. In patients with centrally located tumors and limited extent of disease, the combination of external and endoluminal irradiation enables curative treatment options. Intraoperative brachytherapy may complement standard adjuvant treatment in incompletely resected, unresectable, or medically inoperable patients, and has the potential to improve local control in selected cases. Due to the rarity of the disease, the role of endoluminal brachytherapy in the treatment regimen of tracheal neoplasms is not yet clearly defined. The risk of fatal bleeding after endoluminal brachytherapy appears to be correlated with tumor localization and fraction size, but in the majority of cases fatal bleeds are caused by progression of local disease. The use of a distanceable applicator provides a central positioning of the source, prevents the delivery of high-contact doses to the mucosa, and may reduce toxicity. The standard technique for interstitial brachytherapy after breast-conserving surgery and adjuvant EBRT is the use of low-dose-rate (LDR) brachytherapy, but it may also be applied by means of pulsed-dose-rate (PDR) or HDR techniques. Prospective trials comparing different boost techniques and indications are needed to define more precisely the subgroup of patients who are most suitable for interstitial brachytherapy. Reirradiation of chest wall local recurrences using brachytherapy molds is effective and provides a high local control rate with acceptable toxicity.

A method to improve the dose distribution of interstitial breast implants using geometrically optimized stepping source techniques and dose normalization

BACKGROUND AND PURPOSE

The standard linear source breast implant of our institution was compared with alternative linear source implant geometries and a stepping source implant, to evaluate the possibility of minimizing the treated volume. Normalization to a higher isodose than the conventional 85% of the mean central dose (MCD) was investigated for the stepping source implant to reduce the thickness of the treated volume and to increase dose uniformity. The purpose of this study was to develop an implant geometry yielding a high conformity and a more uniform dose distribution over the target volume.

MATERIALS AND METHODS

The dose distributions of four implant geometries were compared for a planning target volume (PTV) of 48 cm(3). Implants #1 (standard) and #2 had linear sources arranged in a triangular pattern of equal lengths and lengths adapted to the shape of the PTV. Implants #3 and #4 were squared pattern arranged implants with linear sources and a stepping source with geometric optimized dwell times. The active lengths were adapted to the shape of the PTV. Using implant #4 for PTVs of different volumes, the reference dose (RD) was normalized to 85 and 91% of the MCD.

RESULTS

Comparing implants #2, #3, and #4 with #1, the treated volume (V(100)) encompassed by the reference isodose was reduced by 22, 35, and 37%, respectively. The volumes receiving a dose of at least 125% (V(125)) of the reference dose was reduced by 16, 30, and 30%, respectively. The conformation number increased being 0.30, 0.39, 0.47, and 0.48 for implants #1, #2, #3, and #4, respectively. The average reduction of V(125) when the dose was normalized to 91% compared with 85% of the MCD was 18%.

CONCLUSIONS

A conformal treatment to a PTV could be best achieved with a geometrically optimized stepping source plan with needles arranged in a squared pattern. Reduction of high dose volumes within the implant was obtained by normalizing the RD to 91% instead of 85% of the MCD.

Early results of pulsed-dose-rate interstitial brachytherapy for head and neck malignancies after limited surgery

PURPOSE

The aim of this study was to evaluate the relative incidence of toxicity and local control in patients with head and neck malignancies who underwent interstitial pulsed-dose-rate (PDR) brachytherapy (iBT).

PATIENTS AND METHODS

From October 1997 to December 1998, 61 patients underwent interstitial PDR brachytherapy procedures in our department; 47 were patients with head and neck cancer. Forty patients received brachytherapy as part of their curative treatment regimen, and 7 patients were implanted for palliative purposes and excluded from the analysis of therapy efficacy. Twenty-four patients had interstitial brachytherapy procedures alone with D(REF) = 50 Gy; in 23 patients, iBT procedures were performed with D(REF) = 24 Gy in combination with external radiation. A dose per pulse (dp) of 0.5 Gy was prescribed for 38/47 patients, and a dp = 0.7 Gy for 9/47 patients. The pulses were delivered 24 h a day, with a time interval of 1 h between two pulses, resulting in an effective dose rate of 0.5 Gy/h or 0.7 Gy/h. A follow-up of the patients was done to analyze acute and delayed toxicity, local control, and survival. The analysis was performed after median follow-up of 12 months (5-18 months).

RESULTS

After a median follow-up of 12 months, soft tissue necrosis was seen in one patient and bone necrosis in another. No other serious side effects were observed. Permanent locoregional tumor control was achieved in 37 of 40 patients. No distant metastases were observed.

CONCLUSIONS

PDR interstitial brachytherapy with 0.5-0.7 Gy/h is a safe therapy. These preliminary results suggest that PDR interstitial brachytherapy of head and neck cancer is comparable with low-dose-rate (LDR) brachytherapy.

Feasibility and tolerance of pulsed dose rate interstitial brachytherapy

PURPOSE

Pulsed dose rate (PDR) treatment is a new approach that associates the physical advantages of high-dose-rate (HDR) technology with the potential radiobiological advantages of low-dose-rate (LDR) brachytherapy. This retrospective study analyzes the feasibility, toxicity, and preliminary oncologic results in a series of 43 patients treated with PDR interstitial brachytherapy.

METHODS AND MATERIALS

Twenty-four patients with pelvic, 17 patients with head and neck, and 2 patients with breast cancers were treated. Twenty-eight patients had primary and 15 recurrent tumors; 14 had received prior external irradiation to the same site. The doses per pulse at the prescription isodose were 0.4-1 Gy (median 0.5 Gy), delivered using a single cable-driven 0.3-1.0 Ci 192-iridium source (PDR Nucletron Micro-Selectron).

RESULTS

The median treated volumes (at the prescribed isodose) were 28 cc for pelvic, 8.33 cc for head and neck, and 40 cc for breast malignancies. Of 14,499 source and 14,499 dummy source transfer procedures, 3 technical machine failure events were observed (0.02%). Grade 3 acute toxicities were seen in 5/43 patients (4 oral stomatitis, 1 vaginal mucositis) and grade 4 acute toxicity in one patient (rectovaginal fistula). Grade 3-4 late complications were observed in 4/41 (9.8%) patients: 1 pubic fracture, 1 rectovaginal fistula, 1 vesicovaginal fistula and 1 local necrosis. With a median follow-up of 18 months, 10/41 patients progressed locoregionally (6 pelvic, 4 head and neck), 3 developed local recurrence and distant metastasis (3 pelvic), 3 only distant metastasis (2 pelvic, 1 head and neck). Two patients are lost to follow-up.

CONCLUSION

PDR interstitial brachytherapy for pelvic, head and neck, and breast malignancies is feasible and the acute and late toxicities seem acceptable. Although the physical advantages of PDR are clear, further follow-up is required to determine how results compare with those obtained with standard LDR brachytherapy.

[In vitro studies of PDR brachytherapy]

BACKGROUND

Calculations on the basis of the LQ-model have been focussed on the possible radiobiological equivalence between common continuous low dose rate irradiation (CLDR) and a superfractionated irradiation (PDR = pulsed dose rate) provided that the same total dose will be prescribed in the same overall time as with the low doserate. A clinically usable fractionation scheme for brachytherapy was recommended by Brenner and Hall and should replace the classical CLDR brachytherapy with line sources with an afterloading technique using a stepping source. The hypothes is that LDR equivalency can be achieved by superfractionation was tested by means of in vitro experiments on V79 cells in monolayer and spheroid cultures as well as on HeLa monolayers.

MATERIALS AND METHODS

Simulating the clinical situation in PDR brachytherapy, fractionation experiments were carried out in the dose rate gradient of afterloading sources. Different dose levels were produced with the same number of fractions in the same overall incubation time. The fractionation schedules which were to be compared with a CLDR reference curve were: 40 x 0.47 Gy, 20 x 0.94 Gy, 10 x 1.88 Gy, 5 x 3.76 Gy, 2 x 9.4 Gy given in a period of 20 h and 1 x 18.8 Gy as a "single dose" exposition. As measured by flow cytometry, the influence of the dose rate in the pulse on cell survival and on cell cycle distribution under superfractionation was examined on V79 cells.

RESULTS

V79 spheroids as a model for a slowly growing tumor, reacted according to the radiobiological calculations, as a CLDR equivalency was achieved with increasing fractionation. Rapidly growing V79 monolayer cells showed an inverse fractionation effect. A superfractionated irradiation with pulses of 0.94 Gy/h respectively 0.47 Gy/0.5 h was significantly more effective than the CLDR irradiation. This inverse fractionation effect in log-phase V79 cells could be attributed to the accumulation of cycling cells in the radiosensitive G2/M phase (G2 block) during protected exposure which was drastically more pronounced for the pulsed scheme. HeLa cells were rather insensitive to changes of fractionation. Superfractionation as well as hypofractionation yielded CLDR equivalent survival curves.

CONCLUSIONS

The fractionation scheme, derived from the PDR theory to achieve CLDR equivalent effects, is valid for many cell lines, however not for all. Proliferation and dose rate dependend cell cycle effects modify predictions derived from the sublethal damage recovery model and can influence acute irradiation effects significantly. Dose rate sensitivity and rapid proliferation favour cell cycle effects and substantiate, applied to the clinical situation, the possibility of a higher effectiveness of the pulsed irradiation on rapidly growing tumors.