Journal of Cancer Research and Therapeutics Medknow Publications on behalf of the Association of Radiation Oncologists of India (AROI) ISSN: 0973-1482 EISSN: 1998-4138 Vol. 1, Num. 2, 2005, pp. 79-83

Journal of Cancer Research and Therapeutics, Vol. 1, No. 2, April-June, 2005, pp. 79-83

Original Article

Role of template guided interstitial implants in breast conservation therapy

Srinivas SatishK, Reddy KS, Vivekanandam S, Parthasarathy V

Department of Radiotherapy, Regional Cancer centre, JIPMER, Pondicherry - 6
Correspondence Address:Department of Radiotherapy, Regional Cancer centre, JIPMER, Pondicherry - 6, dr_satishsrinivas@rediffmail.com

Code Number: cr05017

Abstract

Breast conservation therapy is currently considered as a viable alternative to mastectomy in early breast cancer. Radiotherapy by virtue of its ability to reduce local recurrences is an integral component of breast conservation therapy. Apart from irradiating the whole breast, the tumor bed is usually delivered a boost dose in breast conservation therapy to increase the local control rate. One of the methods which has been adopted to selectively boost the tumor bed to high doses is the use of per-operative high dose rate interstitial implants.

This particular paper deals with our department's experience with breast conservation therapy using per-operative template guided, High Dose Rate (HDR) interstitial implants in early breast cancer. Local control rates, disease free survival and cosmetic benefit with this technique will be discussed along with literature review.

Keywords: Breast conservation therapy, Breast conservation and surgery, Radiotherapy, External beam radiotherapy, Interstitial implantation, Tumor bed boost, HDR Brachytherapy, Template, Disease free survival, Overall survival

INTRODUCTION

The treatment of cancer breast has seen significant changes over the past century. From the days of Halsted and his mutilating surgeries for cancer breast to the current era of breast conservation, radiotherapy has steadily integrated itself into the management of cancer breast. Today with the availability of modern day diagnostic imaging facilities enabling the diagnosis of early stage breast cancer and with the integration of sophisticated radiotherapy techniques in the management of cancer breast, breast conservation therapy (BCT) has been accepted as an alternative to mastectomy in the management of early stage breast cancer.

Standard BCT involves quadrantectomy, axillary sampling, radiation of the residual breast tissue (with /without regional nodal irradiation) and addition of appropriate systemic therapy where needed. The main role of radiation in BCT is in the prevention of local recurrence without affecting cosmetic outcome. Conventionally Radiotherapy (RT) in BCT includes external beam radiotherapy (EBRT) of 50Gy to the whole breast usually delivered with tangential beams in standard fraction size of 2 Gy. A supplementary tumor bed boost dose of 15 Gy - 20 Gy either with electrons or photons or an interstitial implant is added to decrease the rate of local recurrence. As most of the studies in BCT have shown that local failure occurs around the tumor bed the concept of tumor bed RT alone as an alternative to whole breast RT in BCT, is being evaluated in patients with low risk of relapse.

Against this backdrop a non randomized preliminary study was conducted at RCC JIPMER, to study the feasibility of boosting the tumor bed with a template guided, intra-operative high dose rate (HDR) rigid interstitial implant where the tumor bed was implanted immediately after breast conservation surgery in the same sitting. The template was individually created in the department for each patient based on the patient′s breast anatomy and tumor characteristics. Apart from the feasibility of the study, this paper also describes the long term local control, disease free survival (DFS) and cosmetic result achieved with this technique of tumor bed boost. The paper also compares results of this study with data of other similar studies on boost RT in BCT.

MATERIALS AND METHODS

This non-randomized pilot study was conducted at our institute from 1998-2000. Ten patients with early stage breast cancer (stage I and II) were recruited into the study. The patient and tumor characteristics are summarized in [Table - 1].

Analysis of the data in [Table - 1] reveals that majority of the patients included were young, pre-menopausal, with larger tumors and node positive disease. None of our patients had systemic metastasis at the time of BCT based on clinical examination, liver function tests, chest X-ray (CXR) and ultrasound (USG) abdomen. Skeletal survey was done in those patients with symptoms of bone pain. All the patients were subjected to mammogram to rule out multicentric ipsilateral disease as well as contralateral breast disease. All the patients had invasive ductal carcinoma which was diagnosed initially with Fine needle aspiration cytology and later confirmed by post-op specimen biopsy. Post-operative specimen analysis revealed positive margins in 60% of patients (where all these 6 patients had focally positive margins only) and negative margins in the rest. Moreover all the 6 patients with positive post-op margins had stage T₂ tumors. Extensive intraductal component (EIC) defined as > 25% of tumor composed of intraductal component was seen in one of the patients. The lone patient who had EIC positive disease had negative resected margin enabling her inclusion in this trial.

Treatment Protocol

Surgery
All the patients initially underwent BCS which consisted of macroscopic wide local excision of the breast tumor along with a level I and II axillary dissection.

Radiotherapy
HDR BRACHYTHERAPY (HDR BT) - In the same sitting after breast conservation surgery the patients were subjected to tumor bed implantation with a rigid metal implant guided by a template which was individually constructed for each patient. The template consisting of two rectangular slabs of Aquaplast was drilled with holes to house the metal catheters before the surgery keeping in mind the implant geometry. All the implants were double plane implants, where catheters in the same plane, were separated by a distance of 1 cm. The inter-planar separation was 2 cm where the upper plane was placed 1.5 cm below the skin surface to decrease the occurrence of telengectasia. The target volume of the implant included the tumor bed with 2 cm macroscopic margin all around. The mean volume of implantation was 60cc. Radiation was started 48 hrs after surgery after edema subsided. Before commencing radiation the implant geometry was verified with orthogonal simulation films and the dosimetry was performed using Nucletron PLATO Treatment Planning System. The basal dose rate was calculated at the intersource position followed by dose normalization to these points. The dose was then prescribed to the 85% referral isodose curve. Brachytherapy was delivered with HDR Microselectron machine using Ir-192 isotope. The dose fractionation schedule used was 15 Gy (HDR-dose) in 6# over 3 days with inter-fraction interval of 6 hrs. The template was retained during the entire duration of Brachytherapy (7 days). This was done to maintain implant geometry and minimize dose in-homogeneity known to occur in flexible implants following crowding of catheters due to tissue edema. Precautions were taken to minimize the compression of breast between the templates during the entire duration of Brachytherapy. [Figure - 1] shows the template guided double plane implant for a lesion in the upper outer quadrant of the right breast.

a) EBRT - External beam irradiation of the whole breast and ipsilateral regional nodes was started one week after the completion of tumor bed irradiation and delivered with Tele-cobalt gamma photons. In all the patients the regional nodes were irradiated with a direct anterior field while tangential beams were used to treat the whole breast. The radiation dose used to treat the whole breast and regional nodes was 46 Gy in 23# over 4.5 weeks. The overall treatment time of radiation (HDRBT + EBRT) was 6.5 weeks.

SYSTEMIC THERAPY - After RT all patients with node positive disease were given 6 cycles of chemotherapy with CAF schedule (Cyclophosphamide, Doxorubicin and 5FU). In addition all postmenopausal women received Tab.Tamoxifen 20 mg O.D. for 5 years.

FOLLOW UP AND ASSESSMENT-All the 10 patients completed the treatment and were placed on follow-up. The median follow-up recorded in this study was 4.3 yrs (range 3- 6 yrs). During the follow up visits, factors assessed were - local control, disease free survival (DFS) and cosmesis. Tumor control was assessed by clinical examination, serum biochemistry, and radiological investigations (annual CXR, USG and Mammogram). Cosmesis was assessed objectively by the treating physician and subjectively by the patient. Clinical examination was the basis for the objective cosmetic evaluation. The overall cosmetic outcome was scored according to the scale shown in [Table - 2].[1]

Overall the cosmesis was rated as excellent, good and acceptable as follows -
Excellent - Perfect symmetry, no visible distortion.
Good - Slight distortion of nipple /skin with visible telengectasia and mild hyperpigmentation.
Acceptable - Moderate distortion of nipple, breast asymmetry, moderate hyperpigmentation, prominent skin retraction or telengectasia.
Poor - Marked distortion of nipple, breast asymmetry, edema, fibrosis, severe hyperpigmentation.

RESULTS

Local Control
None of the patients experienced local relapse to date and the local control achieved in this study was 100%

Disease Free Survival (DFS)
Two patients (20%) developed distant metastasis during follow-up. Both these patients received subsequently appropriate palliative RT along with second line chemotherapy and are alive at the time of this report. The disease free survival achieved in this study to date was 80% while the overall survival was 100%.

Toxicity
Acute - After brachytherapy, in all the patients transient erythema and skin reaction at the needle puncture sites was observed, which healed subsequently with conservative treatment. In addition 7 patients (70%) had acute grade- II skin reactions in the form of dry desquamation and 30% had grade- III skin reaction in the form of moist desquamation at the end of teletherapy. In all the patients the skin reactions were self limiting and subsided within 3 weeks of completion of RT with conservative management. None of the patients experienced local infection.

Late - At 4 Years, 3 patients (30%) had mild hyper-pigmentation at the needle puncture site while 2 (20%) had moderate hyper-pigmentation over the boost area as well as telengectasia over the needle puncture sites. Breast parenchymal fibrosis over the tumor bed was noted in all the patients with varying severity. While 6 patients (60%) had grade II fibrosis over the tumor bed the remaining 40% had grade III fibrosis. The fibrosis over the remaining breast tissue outside the tumor boost area was minimal. Prominent skin reaction was observed in 2 patients (20%). Overall the cosmetic outcome was rated as good in 6 patients (60%) and fair (acceptable) in 4 (40%). No other late toxicity was recorded in our study.

The results of this study are summarized in [Table - 3].

Example of net cosmetic result obtained in the study at 4 years is denoted in [Figure - 2].

DISCUSSION

The main rationale behind tumor bed boost RT after whole breast RT of 50 Gy is that > 60% of local recurrences occur in the tumor bed or in its vicinity which has been revealed by numerous studies.[2] This clinical observation was co-related by the pathological findings of Holland et al[3] that residual tumor is present within 2-3 cm of the tumor bed. These findings in turn produced the concept of aggressive tumor bed RT to take care of residual local disease after BCS.

Studies have shown a dose response relationship between tumor bed dose and local control, with doses above 50 Gy. Van Limbergen et al[4] in his study showed that tumor bed boost RT doses of 15 Gy and above decrease local recurrences by a factor of 2. This was further proved in the EORTC trial,[5] in which the patients received 50 Gy EBRT+ 16 Gy boost to the tumor bed .The study showed a local recurrence rate of 2.5% at 5 years in the tumor bed boost arm. Today the American Brachytherapy society has clearly laid down guidelines[6] that it is better to boost the tumor bed with electrons or implant in patients with either-

a) Close, positive, or unknown margins.
b) Presence of EIC
c) Younger patients.

The EORTC trial[5] as well as the Budapest trial[7] clearly showed the benefit of tumor bed boost in improving local control rate in younger patients, particularly in those patients with age < 40 years. In both these studies the local recurrence rate doubled in the patients < 40 years when the tumor bed was not boosted. The inclusion of patients with positive margins after lumpectomy has always remained controversial. Vicini et al[8] showed that in the absence of EIC, local control could be achieved by supplementing whole breast RT with tumor bed boost RT even in patients with positive post-op margins without submitting them to a re-excision as repeat excision would negatively influence the cosmetic outcome. These findings of Vicini are substantiated by the Hungarian trial[7] where the tumor bed boost decreased local recurrence in patients with positive post-op margins rate from 46.7% to 8.3%. Holland et al[3] in his study described the higher risk of residual tumor around the tumor bed in patients with EIC positive tumors in comparison to patients with EIC negative tumors (74% vs. 42%). Fodor et al[9] in his study on BCT in EIC positive patients recorded a local recurrence rate of 27.2 % where the tumor bed boost RT was not given. Krishnan at al[10] in his study showed that at 10 years, the local recurrence rates could be brought down to 9.1% by boosting the tumor bed in patients whose tumors showed EIC.

Conventional techniques used to boost the tumor bed include electrons, photons and interstitial implants. Frazier et al,[11] Perez et al,[12] and EORTC trial[5] have showed no significant differences in local control with either technique. Van Limbergen et al[13] in his study claims superior dosimetry and cosmesis with interstitial implants in tumor depth > 28 mm. However the EORTC trial[5] showed no difference in cosmesis with electrons, photons or brachytherapy. Factors usually affecting cosmesis are tumor location in lower quadrants, post-op infection and larger excised volume.

Interstitial implants can be flexible or rigid type. The rigid implants are advantageous in that they enable accurate placement of needles with appropriate spacing between individual needles in the respective planes, thereby maintaining dose homogeneity as well as preventing the emergence of hot spots / cold spots. However the rigid templates are less comfortable to the patients and need adequate analgesic cover.

Interstitial implants can be performed in 2 settings -
a) As a separate post operative setting or
b) As an intra operative setting immediately after BCS

The latter is advantageous in that it allows accurate placement of catheters to cover the tumor bed as well as it allows radiation to begin immediately after BCS thereby decreasing the overall treatment time by nearly 2 weeks. However the main disadvantage of the intra operative technique is insufficient knowledge of the pathological status of tumor margin and the presence of high risk factors like EIC.

Both LDR & HDR have been used in tumor bed boost studies. Trials using HDR have studied both single fraction and multiple dose fractions. One of the largest studies with HDR using single dose of 10 Gy by Hammer et al[14] proved the feasibility and effectiveness of HDR BT with respect to local control and cosmesis. Jacobs et al[15] found that tumor bed boost RT with a single fraction of HDR dose of 12 Gy produced better local control and cosmesis than electrons. Data with fractionated HDR BT in tumor bed boost RT is limited and numbers of fractions used have ranged from 2-6 wherein some studies have also used hyper-fractionated RT (2# / day with inter-fraction interval of 6 hrs) with an idea of increasing overall tumor bed dose. Some of the long term results of local control and cosmesis obtained by boosting the tumor bed with fractionated HDR BT have been shown in [Table - 4]. Data analysis from the above table clearly proves the effectiveness of HDRBT. The long term local control and cosmesis is comparable with that achieved with electrons. It is of importance, that most of the above trials included patients with high risk of relapse. For boost RT, fractionating the HDR dose enables delivery of higher total BED dose to the tumor bed thereby improving local control. An important consequence of HDR boost is tumor bed fibrosis, which in spite of being moderate to severe does not significantly affect cosmesis. This is validated by all the studies mentioned above which have recorded a good cosmetic result of 60-70%

Present Study
The present study shows the feasibility of boosting the tumor bed with a template guided rigid implant employing fractionated HDR dose fractionation. The local control, disease free survival and overall survival recorded in this study is comparable to results quoted in western literature particularly the Virginia study by Manning et al[16] In a developing country where cost of primary treatment, lack of treatment resources, fear of disease recurrence and cost of treatment relapse are important impediments to widespread use of BCT, the use of custom made templates, post-op tumor bed implantation and the use of electron boost will only increase treatment cost thereby rendering BCT available to only a few affordable patients. By fabricating a template which can be created on a patient to patient basis in the department at a very nominal cost, as well as implanting the tumor bed during BCS; the overall treatment time and the cost factor in BCT can be brought down thereby increasing the availability of this procedure to most of our patients. In addition reduction in treatment time not only improves patient acceptability but also increases local control.

In our study we have included 6 patients with positive post-op margins for breast conservation as these patients had only focally positive margins. Similarly a lone patient with EIC positive disease and negative resection margin was also included. The use of peri-operative implants and lack of frozen section facility at the time of this study, have rendered the verification and re-excision of surgical margins impossible. A higher boost dose was not prescribed for patients with positive resection margins and EIC positive disease as we felt that the planned boost dose was adequate and that any further dose escalation would affect cosmesis which is the basis for breast conservation. The excellent long term local control as well as the good cosmetic result recorded in our study, validates our stance.

The only lacuna in this pilot study is the small number of patients recruited which prevents the use of statistical analysis to substantiate this claim. Around 90% of the breast cancer patients presenting to our institute have either locally advanced or systemic disease. Among the remaining 10%, not all patients are willing to undergo breast conservation. Hence only ten patients were included in this pilot study and we have honestly presented the actual number of patients on whom this study was initially performed. These being an ongoing trial, more number of patients have since been accrued. As the remaining patients have not completed the prescribed duration of follow-up, their data has not been included for analysis. In due course of time data of these patients will also be published with statistical analysis.

CONCLUSION

References

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