Capsular contracture of subcutaneous breast implant following hypofractionated stereotactic body radiotherapy for early stage lung cancer

Abstract

BACKGROUND

Development of capsular contracture around subcutaneously implanted breast prostheses, producing poor cosmetic outcome and pain, has been reported following standard fractionated external beam radiotherapy to whole implants for breast cancer. We report capsular contracture following partial implant irradiation from hypofractionated stereotactic body radiotherapy (SBRT) for lung cancer in a 64 year-old female with augmentation mammaplasty.

METHODS

The patient had biopsy-proven, T1 non-small cell lung carcinoma, adjacent to the implant. She received 50 Gy in 4 fractions to 91% of planning target volume using a 7-field, 3D-conformal plan with 6 MV photons and daily CT-guided target localization. The implant received 9.3 Gy mean dose, 51.7 Gy maximum point dose, with V₁₀ 41%, V₂₀ 15% and V₃₀ 4%.

RESULTS

At seven months, the patient reported left breast pain requiring narcotic analgesics and demonstrated modified Baker/Palmer grade 4 capsular contracture. Breast retraction assessment measurement increased from baseline 10.4 mm to 19.8 mm.

CONCLUSIONS

This represents the first reported case of capsular contracture from partial breast implant radiation following SBRT for lung cancer. Further investigation to elucidate maximum tolerated dose of radiation given to breast implants in this setting is needed.

1 INTRODUCTION

Development of capsular contracture around subcutaneously implanted breast prostheses has been documented following 45-60 Gy standard fractionated whole breast irradiation (WBI) as part of breast conservation therapy (BCT) for breast cancer [1], [2]. Capsular contracture leads to anatomic distortion and pain, requiring prosthesis revision or salvage surgery [3], [4]. Partial implant irradiation following high dose per fraction radiotherapy (RT) has not been described nor has maximum tolerated dose been defined in this setting. We report the outcome of a patient with prior cosmetic augmentation mammoplasty who received hypofractionated stereotactic body radiotherapy (SBRT) for early stage non-small cell lung cancer adjacent to a breast implant.

2 METHODS

The patient, a 64-year-old smoker who underwent cosmetic augmentation mammoplasty at age 26, was found to have a 1.5-cm left upper lobe lung tumor, adjacent to her left implant. On PET/CT, the nodule was FDG-avid with maximum SUV16.2 (Figure 1). Biopsy confirmed non-small cell carcinoma. Metastatic workup was negative. Due to poor pulmonary reserve, she was ineligible for surgery.

Figure 1.

Pretreatment PET/CT. Representative axial image from the patient’s F18-FDG PET fused to noncontrasted CT prior to SBRT shows a 1.7 x 1.2 cm nodule in the left upper lobe, adjacent to chest wall at the superior aspect of breast implant, with maximum SUV 16.2.

The patient was treated with definitive hypofractionated SBRT, receiving 50 Gy in 4 consecutive 12.5 Gy once-daily fractions to the tumor target. The target comprised an internal gross tumor volume (iGTV) contoured on all phases of a 4-dimensional planning CT [5]. The iGTV was expanded by 8 mm for clinical target volume (CTV), which was expanded by 3 mm for planning target volume (PTV), achieved by daily CT-based target localization. RT was delivered using a 7-field, 3-dimensional conformal plan with 6 MV photons prescribed to 91% of maximum isocenter dose with 97% PTV coverage by the prescription dose. Beams were arranged to limit dose to adjacent normal tissues and to spare the implant. The implant received mean dose 9.29 Gy and maximum point dose 51.72 Gy. The volume of the implant receiving 10 Gy (V₁₀) was 41%, 20 Gy (V₂₀) was 15%, and 30 Gy (V₃₀) was 4%. Dose-volume histogram and representative axial image showing dose distribution are shown in Figure 2.

Figure 2.

Isodose distribution and dose-volume histogram of 3D-conformal hypofractionated stereotactic plan. A representative axial image (top) shows planned isodose coverage of GTV (red colorwash), CTV (khaki colorwash) and PTV (aqua colorwash) using a 7-beam 3D-conformal plan. Corresponding dose-volume histogram for this plan is shown (bottom).

3 RESULTS

The patient tolerated SBRT well. At 6 weeks post-SBRT, she complained of brief episodes of sharp pain over the left chest region, not requiring intervention. Physical examination revealed small foci of increased pigmentation and dry desquamation along left midaxillary line and left paramedial posterior chest wall. Breast implants were symmetric.

At 4.5 months, she reported worsening pain, radiating to left arm and subscapular region, for which she required low-dose narcotic analgesia for relief. She denied focal weakness or paresethesias, and symptoms to suggest cardiac etiology. Examination revealed full, active range of motion of upper extremities and good strength except for 4/5 strength of proximal left upper extremity due to pain. There was focal tenderness along the left posterolateral chest wall, in the region of increased pigmentation. Implants were unchanged. The patient’s analgesic medication was increased and short-course steroid therapy initiated.

At 7-month follow-up, her narcotic analgesic was again increased, and she reported that her implants were asymmetric. Physical examination revealed the left breast implant to be superolaterally displaced, firm, mildly fibrotic and tender to palpation. There was no increased erythema, warmth, peau d’orange or other skin change in this region. Left upper extremity abduction was limited secondary to pain. The right breast was soft, non-tender, with implant palpated. PET/CT revealed the lung tumor to measure 0.8 cm with maximum SUV 2.3. There was new FDG uptake within the left chest wall, consistent with post-treatment inflammation. Breast implants were grossly intact (Figure 3).

Figure 3.

Post-treatment PET/CT. Representative axial image from the patient’s F18-FDG PET fused to noncontrasted CT seven months following SBRT shows left upper lobe nodule decreased to 0.8 cm and maximum SUV 2.3. Note low level FDG uptake in soft tissues posterior to left breast implant (arrows).

Implant capsule formation, classified by Baker [6], modified by Palmer [7], is based on subjective and objective endpoints (Table 1). According to the Baker/Palmer classification, this patient demonstrated grade 4 capsular contracture her ipsilateral implant seven months following SBRT. Objectively, she was found to have ~1 cm retraction of the irradiated breast (Figure 4), calculated using breast retraction assessment (BRA) [8].

Table 1.

Classification of implant capsule formation. Modified from Palmer et al. [7].

Modified Baker/Palmer Classification
Class	Description	Outcome
1A	Soft, looks natural, implant not detectable	GOOD
1B	Implant palpable, visible when supine, no distortion	GOOD
2	Obvious but not firm capsule, no complaints or distortion	SATISFACTORY
3	Firm to hard capsule, minimal distortion, uncomfortable	INFERIOR
4	Hard capsule, obvious distortion, painful	POOR

Figure 4.

Breast Retraction Assessment (BRA) measurement and Modified Baker/Palmer classification of patient before and after SBRT. Measurement of nipple retraction (BRA) and capsule contracture (Class) were determined at baseline (left) and seven months following completion of 50 Gy SBRT (right). Note the cranial implant displacement following SBRT, which is even more striking given expected caudal movement with arms adducted (superior edge = triangle arrow, inferior edge = diamond arrow).

4 DISCUSSION

Capsular contracture requiring re-operation is the most common mid-to-long term complication following breast implantation, occurring in as many as 15-38% of cases, with rate significantly higher following mastectomy [9]. Incidence of capsule formation in breast cancer patients depended upon implant location, with 9/47 (19%) patients with subcutaneous implants developing severe (Baker/Palmer grade 3-4) contracture compared with 7/64 (11%) with subpectoral implants [7]. RT impact on breast prosthesis capsule formation has been studied in the setting of WBI following mastectomy with recontruction and in previously augmented patients undergoing BCT.

The largest retrospective analysis of RT following breast reconstruction analyzed the outcomes of 66 patients [10]. Of these, 44 received adjuvant RT, and 15 received treatment after local recurrence. Five patients were irradiated following breast cancer diagnosed in previously augmented breasts. All received 50.4 Gy in 28 fractions WBI plus 10-Gy tumor bed boost. Bolus, wedge or compensating filter use varied. Fairto-poor cosmetic outcomes were reported in 25 (52%) with permanent implants, and 22 (46%) had grade 2-3 complications. Capsule formation incidence was not reported. Breast reconstruction within 6 weeks of RT initiation had worse associated cosmesis and complication rates than if reconstruction was later. Another retrospective study of 20 patients with prior augmentation mammoplasty reported good-to-excellent cosmesis in 17/20 (85%) receiving 64-71 Gy postoperative RT to whole breast plus boost [11]. Of the remaining three patients with fair-to-poor cosmesis, all had subcutaneous implants and one required surgical removal. All six patients with retromuscular implants and 5/6 receiving adjuvant chemotherapy had good-to-excellent cosmesis. Similar results were observed in another study of 21 previously augmented women requiring BCT [2]. In this group, the whole breast received median dose 50.2 Gy, with an additional 10-20 Gy surgical bed boost in 16 cases. Capsular contracture with fair-to-poor cosmesis was reported in 12 (57%) women. Seven of these had retromuscular implants. No association was found between capsule formation and radiation dose, interval between implantation and RT, chemotherapy, location or implant type. Other reports of cosmetic outcomes following BCT after augmentation mammoplasty in small patient series (n<20 patients) describe a range of good-to-excellent cosmetic results, but due to low patient numbers (summarized in [2]), meaningful conclusions cannot be drawn.

Behranwala [3] prospectively analyzed aesthetic outcome of 136 breast reconstructions in 114 patients undergoing immediate post-mastectomy reconstruction. Of the 136 implants, 62 were submuscular, 74 had latissimus dorsi myocutaneous flap, and 44 received a median dose of 50.4 Gy (range 50-60 Gy) to the reconstructed breast/chest wall. At median follow-up of 4 years, 38.6% of irradiated reconstructed breasts had capsule formation compared with only 14.1% in the non-irradiated group (P<0.001 on univariate analysis). No capsule formation was reported at one year. Chemotherapy, hormonal therapy, reconstruction type, axillary surgery or patient age was not associated with increased risk of capsule formation. Difference in sternal notch-to-nipple distance and absolute midclavicular line-to-nipple distance were greater in patients with capsule formation receiving RT versus the non-irradiated subgroup, with median difference of 1 cm in irradiated patients versus 0.5 cm in the no-RT group.

A prospective analysis of capsular contracture in 107 patients with subcutaneous implants was conducted [12]. Twenty-four reconstructed patients received 46 Gy in 23 fractions to the whole breast without boost. All patients were followed for a median of 5 years. Frequency of grade 3-4 Baker/Palmer contracture was 41.7% in irradiated patients compared with 14.5% of the non-irradiated group (P=0.012). The majority (7/11, 63.6%) of irradiated patients with grade 3-4 capsular contracture in this study, unlike the prior one, occurred within the first year post-RT.

In another prospective analysis, 19 of 81 patients undergoing expander/implant reconstruction after mastectomy received a median dose of 60.4 Gy (range, 50-66 Gy) WBI plus tumor bed boost [13]. All complications, including contracture, were scored. At a median post-operative follow-up of 31 months, 68% (13/19) irradiated patients had complications compared with 31% (19/62) in the non-irradiated group on univariate analysis (P=0.006). Neither RT timing (before v. after reconstruction), total dose (≤60 Gy v. >60 Gy), number of fields (2 v. 3 v. 4) nor use of bolus, boost, or tamoxifen was associated with increased complication rate among those irradiated.

In the above analyses, RT was delivered to the entire breast, and thus implant, using standard fractionation. Although numerous papers describe adverse effect of hypofractionated regimens used for breast cancer treatment (reviewed in [14]), impact of larger radiation dose per fraction on breast prosthesis capsule formation has not been reported. Further, effect of fraction size and partial breast implant irradiation on capsular contracture has not been described. Toxicity of hypofractionated partial breast radiotherapy is a secondary endpoint of the on-going NSABP B-39/RTOG 0413 protocol, but effect of large dose-per-fraction partial implant radiotherapy on capsule formation will not be ascertained, since presence of breast prostheses is a study exclusion criterion.

Here we observed Baker/Palmer class 4 breast implant contracture with a 1-cm change in BRA seven months following delivery of 50 Gy in 4 fractions SBRT for definitive management of early stage lung cancer (Figure 4). It should be noted that the patient was unable to abduct her left upper extremity in the post-SBRT setting due to resultant pain from the implant contracture. While the difference in arm position in the pre- versus post-SBRT photographs may alter the final BRA determination, we contend that the different arm positioning only highlights the extent of contracture, since a normal implant would be expected to have more caudal displacement with adducted upper extremities. Ultimately, although the radiation dose delivered to the entire implant was less than that reported in the WBI studies, the high dose-per-fraction radiation administered to partial prosthesis was sufficient to produce a clinically and cosmetically adverse outcome.

This case report illustrates that fraction size may be a determinant of capsule contracture following irradiation of a breast implant, and, perhaps more strikingly, that partial implant irradiation is sufficient to produce the inflammatory response necessary to produce such contracture. These observations have implications for partial breast radiation and SBRT. Further investigation to elucidate the dose constraints for breast implants is warranted.