Initial brachytherapy in the breast conservation approach to breast cancer

Early stage breast cancer conserving treatment: High dose rate brachytherapy boost to the tumour bed

INTRODUCTION

The dose administered to the tumour bed is a risk-factor for local recurrence in localised breast cancer following breast-conserving surgery.

MATERIALS AND METHODS

All patients (n=94) received 50 Gy external beam radiotherapy and one application of 700 cGy at 85% isodose with high dose rate brachytherapy.

RESULTS

Of the cases, 84% were infiltrating ductal carcinoma; 31.2% were G3; 28% were intraductal component > 25%; 54% had margin < 1 cm or unknown. With a mean follow-up of 65 months (range: 36-107 months), the overall actuarial survival at 5 and 8 years was 93.2% and 84.2%, respectively; disease-free survival was 88.3% and 84.6%, respectively; local control was 92.2% and 88.75%, respectively. Local recurrence rate was 5.3%, and distant dissemination rate was 8.5%. Among the risk-factors analysed, only the presence of 4 or more lymph node involvement implied a higher risk for local recurrence (p =0.0001). For distant dissemination, the risk-factors were: 4 or more lymph nodes involved (p = 0.0001),G3 (p =0.029), tumour >3 cm (p = 0.001), irradiation volume with external beam radiotherapy (p =0.0001), and presence of local recurrence (p = 0.001).

CONCLUSION

High dose rate brachytherapy is an effective method for reducing local recurrence, and increasing local control.

Novel approaches to postoperative radiation therapy as part of breast-conserving therapy for early-stage breast cancer

Breast-conserving therapy (BCT) consists of segmental mastectomy followed by postoperative radiation therapy (RT) to the whole breast. At least 6 prospective randomized trials have proven the equivalence of BCT to mastectomy. However, BCT remains underused and, most importantly, a sizable proportion of patients with invasive breast cancer fail to complete the recommended protocol of breast preservation by omitting postoperative RT. The inconvenience of complying with the standard 6-week radiation regimen, which includes approximately 30 daily visits, at least partially explains this lack of adherence. New clinical studies have generated preliminary evidence that more convenient, shorter radiation regimens might reveal equivalence to the current standard. Moreover, the availability of modern technology to deliver and target ionizing radiation by improving homogeneity of radiation dose has made it possible to safely explore the use of greater radiation doses per fraction. Finally, currently ongoing research trials will enable the identification of specific subsets of patients who are likely to be safely treated by partial-breast radiation (instead of radiation to the whole breast) with more accelerated regimens. This article reviews the available data and the current ongoing research on novel RT techniques and fractionation schedules in BCT for early-stage breast cancer.

Analysis of a large number of clinical studies for breast cancer radiotherapy: estimation of radiobiological parameters for treatment planning

Numerous studies of early-stage breast cancer treated with breast conserving surgery (BCS) and radiotherapy (RT) have been published in recent years. Both external beam radiotherapy (EBRT) and/or brachytherapy (BT) with different fractionation schemes are currently used. The present RT practice is largely based on empirical experience and it lacks a reliable modelling tool to compare different RT modalities or to design new treatment strategies. The purpose of this work is to derive a plausible set of radiobiological parameters that can be used for RT treatment planning. The derivation is based on existing clinical data and is consistent with the analysis of a large number of published clinical studies on early-stage breast cancer. A large number of published clinical studies on the treatment of early breast cancer with BCS plus RT (including whole breast EBRT with or without a boost to the tumour bed, whole breast EBRT alone, brachytherapy alone) and RT alone are compiled and analysed. The linear quadratic (LQ) model is used in the analysis. Three of these clinical studies are selected to derive a plausible set of LQ parameters. The potential doubling time is set a priori in the derivation according to in vitro measurements from the literature. The impact of considering lower or higher T(pot) is investigated. The effects of inhomogeneous dose distributions are considered using clinically representative dose volume histograms. The derived LQ parameters are used to compare a large number of clinical studies using different regimes (e.g., RT modality and/or different fractionation schemes with different prescribed dose) in order to validate their applicability. The values of the equivalent uniform dose (EUD) and biologically effective dose (BED) are used as a common metric to compare the biological effectiveness of each treatment regime. We have obtained a plausible set of radiobiological parameters for breast cancer: alpha = 0.3 Gy(-1), alpha/beta = 10 Gy and sub-lethal damage repair time T(rep) = 1 h (mono-exponential behaviour is assumed). This set of parameters is consistent with in vitro experiments and with previously reported analyses. Using this set of parameters, we have found that most of the studies, using BCS plus whole breast RT and a boost to the tumour bed, have EUDs ranging from 60-70 Gy. No correlation is found between BED and the local recurrence rate. The treatments of BCS plus brachytherapy alone have a wide range of EUD (30-50 Gy), which is significantly lower than the treatments with whole breast EBRT plus a boost of the tumour bed. The studies with different fractionation schemes for whole breast EBRT also show a significant variation of EUD. Carefully designed clinical studies with large numbers of patients are required to determine clinically the relative effectiveness of these treatment variations. The derived LQ parameter set based on clinical data is consistent with in vitro experiments and previous studies. As demonstrated in the present work, these radiobiological parameters can be potentially useful in radiotherapy treatment planning for early breast cancer, e.g., in comparing biological effectiveness of different radiotherapy modalities, different fractionation schemes and in designing new treatment strategies.

T1 stage breast cancer: adjuvant hypofractionated conformal radiation therapy to tumor bed in selected postmenopausal breast cancer patients--pilot feasibility study

PURPOSE

To explore the feasibility of a short course of hypofractionated conformal radiation therapy to the tumor bed as part of a breast preservation protocol in postmenopausal patients with nonpalpable pT1N0 stage breast cancer.

MATERIALS AND METHODS

The tumor bed was imaged at computed tomography (CT) in the prone position on a dedicated table. The same table and position were used for treatment with a 4-MV linear accelerator. The planning target volume was the tumor bed plus a 1-2-cm margin defined at postmastectomy CT. A regimen of five fractions was tested in this pilot dose study. Cosmesis was assessed by patients and physicians before treatment and 36 months after treatment.

RESULTS

Ten consecutive patients who were eligible for the study were assigned to one of three dose-per-fraction regimens; nine were treatable with the proposed technique on the basis of CT findings. Patients received five fractions over 10 days (total dose range, 25-30 Gy): Three received 5.0 Gy per fraction; four, 5.5 Gy; and two, 6.0 Gy. At minimum follow-up of 36 months (range, 36-53 months), all patients were alive and disease free with good to excellent cosmesis.

CONCLUSION

Hypofractionated conformal breast radiation therapy is feasible. Further studies are warranted.

An update on radiation therapy in breast cancer

Radiation therapy plays an important role in the management of both invasive and noninvasive breast cancer. During the last 20 years, the availability of radiation therapy has made it possible to test the feasibility and safety of breast preservation after the diagnosis of early-stage breast cancer. This article summarizes some of the ongoing controversies concerning the use of radiation therapy in the multidisciplinary management of breast cancer.

The use of ultrasonography in the localization of the lumpectomy cavity for interstitial brachytherapy of the breast

PURPOSE

To determine the value of breast ultrasonography (US) in defining the lumpectomy cavity for patients treated with interstitial brachytherapy.

METHODS AND MATERIALS

In March 1993, a protocol of low dose rate (LDR) interstitial brachytherapy as the sole radiation modality in selected patients with early breast cancer was initiated at William Beaumont Hospital. To date, 60 patients have been entered in this protocol, and 38 have undergone US assisted placement of interstitial brachytherapy needles. The lumpectomy cavity was outlined in all dimensions and corresponding skin marks were placed for reference at time of implantation. These US dimensions were compared to the physician's clinical estimate of the location of the lumpectomy cavity, the patient's presurgical mammogram, and the position of the surgical scar. In the intraoperative setting, the dimensions of the lumpectomy cavity were also obtained and the placement of the deep plane of interstitial needles was verified by US.

RESULTS

The full extent of the lumpectomy cavity was underestimated by clinical examination (physical exam, operative report, mammographic information and location of the surgical scar) in 33 of 38 patients (87%). The depth to the chest wall was also incorrectly estimated in 34 (90%) patients when compared to US examination. Intraoperatively, US was performed in nine patients and was useful in verifying the accurate placement of the deepest plane of interstitial brachytherapy needles. In 7 of 9 patients (75%), clinical placement of needles did not ensure adequate coverage of the posterior extent of the lumpectomy cavity as visualized by intraoperative US.

CONCLUSIONS

In breast cancer patients considered for interstitial brachytherapy, US appears to be a more accurate means of identifying the full extent of the lumpectomy cavity when compared to clinical estimates. In addition, US allows real-time verification of needle placement in the intraoperative setting.