Comparison of acute toxicities between contemporary forward-planned 3D conformal radiotherapy and inverse-planned intensity-modulated radiotherapy for whole breast radiation

Is repeat breast conservation possible for small ipsilateral breast cancer recurrence?

BACKGROUND

Most cases of ipsilateral breast tumor recurrence (IBTR) after breast-conserving surgery (BCS) involve small tumors. Although a few guidelines recommend mastectomy, several patients prefer repeat BCS (re-BCS). This study aimed to compare re-BCS and mastectomy in terms of prognosis in patients with IBTR and to identify candidates for re-BCS.

METHODS

The data of patients with small IBTR between 1999 and 2015 were obtained from the Surveillance, Epidemiology, and End Results database. The outcomes of interest were overall survival (OS) and breast cancer-specific survival (BCSS). Multivariable Cox proportional hazards regression models and propensity score matching were applied.

RESULTS

Of the 3648 patients with IBTR, 2831 (77.6%) underwent mastectomy and 817 (22.4%) underwent re-BCS. The multivariate Cox model showed that re-BCS was associated with a worse OS (hazard ratio [HR], 1.342; 95% confidence interval [CI], 1.084-1.663) and BCSS (HR, 1.454; 95% CI, 1.004-2.105) compared with mastectomy. The omission of radiation after re-BCS was associated with worse survival overall and especially in patients with estrogen receptor (ER)-negative IBTR (HR, 1.384; 95% CI, 1.110-1.724; and HR, 1.577; 95% CI, 1.075-2.314, respectively). No statistically significant differences were observed in the OS and BCSS between re-BCS with radiation and mastectomy. Subgroup analysis indicated that the surgical approach was not an independent factor for survival in the ER-positive patients with IBTR.

CONCLUSIONS

Re-BCS should be considered with caution in patients with small IBTR. However, a positive ER status can be an important factor for choosing re-BCS, and radiation therapy may improve oncological safety after re-BCS.

LAY SUMMARY

Repeat breast-conserving surgery (re-BCS) was investigated to determine if it is safe for patients with small ipsilateral breast tumor recurrence (IBTR) after breast-conserving surgery (BCS). This population-based cohort study included 2831 patients with small IBTR. Re-BCS was associated with a worse overall survival and breast cancer-specific survival compared with mastectomy. Further analysis found that the IBTR estrogen receptor status was an important basis for choosing re-BCS, and radiation may improve oncological safety after re-BCS.

Risk Factors Related to Acute Radiation Dermatitis in Breast Cancer Patients After Radiotherapy: A Systematic Review and Meta-Analysis

Background

Acute radiation dermatitis (ARD) is the most common acute response after adjuvant radiotherapy in breast cancer patients and negatively affects patients’ quality of life. Some studies have reported several risk factors that can predict breast cancer patients who are at a high risk of ARD. This study aimed to identify patient- and treatment-related risk factors associated with ARD.

Methods

PubMed, Embase, Cochrane Library, China National Knowledge Infrastructure, and WanFang literature databases were searched for studies exploring the risk factors in breast cancer patients. The pooled effect sizes, relative risks (RRs), and 95% CIs were calculated using the random-effects model. Potential heterogeneity and sensitivity analyses by study design, ARD evaluation scale, and regions were also performed.

Results

A total of 38 studies composed of 15,623 breast cancer patients were included in the analysis. Of the seven available patient-related risk factors, four factors were significantly associated with ARD: body mass index (BMI) ≥25 kg/m² (RR = 1.11, 95% CI = 1.06–1.16, I² = 57.1%), large breast volume (RR = 1.02, 95% CI = 1.01–1.03, I² = 93.2%), smoking habits (RR = 1.70, 95% CI = 1.24–2.34, I² = 50.7%), and diabetes (RR = 2.24, 95% CI = 1.53–3.27, I² = 0%). Of the seven treatment-related risk factors, we found that hypofractionated radiotherapy reduced the risk of ARD in patients with breast cancer compared with that in conventional fractionated radiotherapy (RR = 0.28, 95% CI = 0.19–0.43, I² = 84.5%). Sequential boost and bolus use was significantly associated with ARD (boost, RR = 1.91, 95% CI = 1.34–2.72, I² = 92.5%; bolus, RR = 1.94, 95% CI = 1.82–4.76, I² = 23.8%). However, chemotherapy regimen (RR = 1.17, 95% CI = 0.95–1.45, I² = 57.2%), hormone therapy (RR = 1.35, 95% CI = 0.94–1.93, I² = 77.1%), trastuzumab therapy (RR = 1.56, 95% CI = 0.18–1.76, I² = 91.9%), and nodal irradiation (RR = 1.57, 95% CI = 0.98–2.53, I² = 72.5%) were not correlated with ARD. Sensitivity analysis results showed that BMI was consistently associated with ARD, while smoking, breast volume, and boost administration were associated with ARD depending on study design, country of study, and toxicity evaluation scale used. Hypofractionation was consistently shown as protective. The differences between study design, toxicity evaluation scale, and regions might explain a little of the sources of heterogeneity.

Conclusion

The results of this systematic review and meta-analysis indicated that BMI ≥ 25 kg/m² was a significant predictor of ARD and that hypofractionation was consistently protective. Depending on country of study, study design, and toxicity scale used, breast volume, smoking habit, diabetes, and sequential boost and bolus use were also predictive of ARD.

Repeat breast-conserving treatment of ipsilateral breast cancer recurrence: a nationwide survey amongst breast surgeons and radiation oncologists in the Netherlands

Background

In line with the paradigm to minimize surgical morbidity in patients with primary breast cancer, there is increasing evidence for the safety of a repeat breast-conserving treatment (BCT) of an ipsilateral breast tumour recurrence (IBTR) in selected patients. The conditions for the feasibility of a repeat BCT vary widely in literature. In clinical practice, many physicians have ongoing concerns about the oncological safety and possible toxicity of repeat BCT.

Aim

To investigate the attitude of Dutch breast surgeons and radiation oncologists towards repeat BCT and to report on their experiences with, objections against and perceived requirements to consider a repeat BCT in case of IBTR.

Patients and methods

An online survey consisting of a maximum of 26 open and multiple-choice questions about repeat BCT for IBTR was distributed amongst Dutch breast surgeons and radiation oncologists.

Results

Forty-nine surgeons representing 49% of Dutch hospitals and 20 radiation oncologists representing 70% of Dutch radiation oncology centres responded. A repeat BCT was considered feasible in selected cases by 28.7% of breast surgeons and 55% of radiation oncologists. The most important factors to consider a repeat BCT for both groups were the patient’s preference to preserve the breast and surgical feasibility of a second lumpectomy. Arguments against a repeat BCT were based on the perceived unacceptable toxicity and cosmesis of a second course of radiotherapy. The technique of preference for re-irradiation would be partial breast irradiation (PBI) according to all radiation oncologists. Differentiating between new primary tumours (NPT) and true recurrences (TR) was reported to be done by 57.1% of breast surgeons and 60% of radiation oncologists. The most important reason to differentiate between NPT and TR was to establish prognosis and to consider whether a repeat BCT would be feasible.

Conclusion

An increasing number of Dutch breast cancer specialists is considering a repeat BCT feasible in selected cases, at the patient’s preference and with partial breast re-irradiation.

Increase in Superficial Dose in Whole-Breast Irradiation With Halcyon Straight-Through Linac Compared With Traditional C-arm Linac With Flattening Filter: In vivo Dosimetry and Planning Study

Purpose

Superficial dose is an important parameter in breast cancer radiation therapy. When treated with conventional linacs, bolus is commonly applied to improve target coverage near the surface while also managing the risk of severe skin reactions and negative cosmesis. With the introduction of modern linacs with 6X flattening filter free (FFF) photon beams, the effect on superficial dose and the need for bolus must be evaluated.

Methods and Materials

In vivo measurements of superficial dose were made with optically stimulated luminescence dosimeters on 11 breast cancer patients treated with the Halcyon 6X FFF linac (Varian Medical Systems, Palo Alto, CA). Additionally, measurements were made with the Halycon 6X FFF beam and a 6X beam with flattening filter (FF) delivered to an anthropomorphic phantom. A planning study was carried out in which 14 patients treated on the Halcyon were replanned with a conventional linac to determine the difference in superficial dose predicted by the treatment planning system. Measures were taken to increase the accuracy of the treatment planning system superficial dose.

Results

The use of the Halcyon 6X FFF beam led to higher superficial dose compared with 6X FF beams. The in vivo measurements show an average superficial dose of 83.8% ± 0.6%, which is an increase of approximately 10% compared with published measurements for a 6X FF linac. Comparison of superficial dose for 6X FF and 6X FFF beams in the phantom measurements show an increase from 70% ± 1.3% to 84% ± 1.3%, which is consistent with the in vivo measurements. The planning comparison shows an increase in V70%Rx from 62% ± 4.4% to 81% ± 2.2% for the superficial breast tissue for the Halcyon 6X FFF beam compared with a standard C-arm linac with FF.

Conclusions

The use of the Halcyon 6X FFF beam was associated with higher superficial dose which may obviate the use of bolus.

Quantification of Acute Skin Toxicities in Patients With Breast Cancer Undergoing Adjuvant Proton versus Photon Radiation Therapy: A Single Institutional Experience

PURPOSE

Acute skin toxicity in the form of radiation dermatitis (RD) or skin hyperpigmentation (SH) is a common problem experienced by patients undergoing breast irradiation. Proton radiation has been thought to deliver higher doses to skin compared with photon radiation because of differences in the physical properties between photons and protons; however, limited literature exists directly comparing toxicity outcomes.

METHODS AND MATERIALS

The highest recorded grades of acute RD and SH were analyzed in 86 patients undergoing adjuvant radiation therapy to the breast with or without regional lymph nodes after lumpectomy (breast-conserving surgery) or mastectomy with either proton pencil-beam scanning (n = 39) or photon (n = 47) radiation therapy within a single institution to analyze differences in severity of acute skin reactions. For 34 of 47 photon and 33 of 39 proton patients, a "skin" contour was retroactively created in our treatment planning systems, and multiple dosimetric parameters were calculated to quantify objective radiation doses received by skin.

RESULTS

On χ² analysis, the highest reported grade of RD was significantly higher in women undergoing proton radiation compared with photon radiation; grade ≥2 RD was present in 69.2% versus 29.8% of patients receiving proton and photon therapy, respectively (P = .002). Rates of grade 3 RD were 5.1% versus 4.3% for proton versus photon radiation, respectively (P = .848). Overall, there were no significant differences in rates of SH between modalities. There were no grade 4 to 5 toxicities in either cohort.

CONCLUSIONS

In a comparison with patients receiving photon radiation, a significantly higher rate of grade ≥2 RD was observed in patients undergoing proton radiation, with very low rates of grade 3 toxicity in both groups. Rates of SH did not differ significantly between modalities. Women should be counseled regarding the possibility of increased grade 2 toxicities, although this might present a dosimetric advantage for physicians when treating patients in the postmastectomy setting or when skin was involved on presentation.