Surgical Scar Recurrence of Bone Metastases to the Femur: A Case Report.

We report the case of a woman who presented with breast cancer metastases to the femur causing pathologic fracture of the femoral neck requiring surgery. She received adjuvant radiotherapy to the femur at that time that did not include the surgical scar tract. Almost four years after her surgery she presented with biopsy proven skin recurrence of breast cancer on the skin overlying her incision from her femoral surgery. Further imaging confirmed significant soft-tissue disease involving the underlying surgical scar tract. This case provides important information about the possibility of surgical scar recurrence after surgery for bone metastases which could indicate the need to include the area of the surgical scar tract and the entire prosthetic material in the post-operative radiotherapy volume.


Introduction
Bone metastases are present in up to two-thirds of patients with metastatic cancer [1]. The primary elements of treatment of symptomatic bone metastases include adequate analgesia and palliative radiotherapy. Nonetheless, certain clinical scenarios including pathological fracture, impending fracture or neurological compromise require consideration of surgical intervention. Post-operative radiotherapy is indicated in the majority of these cases as it treats residual disease, likely improves functional status and decreases the need for further orthopedic procedures [2,3]. Nonetheless, there is a paucity of information regarding the anatomical patterns of relapse and progression of bone metastases other than those in the spine to help guide treatment planning of radiotherapy [4,5]. One lingering question regarding target volumes for palliative radiotherapy is whether the operative bed and surgical scar should be included in radiotherapy volumes in addition to areas of bone that were involved preoperatively. We present the interesting case of an 81-year-old woman who presented with relapse of breast cancer in her femur both in her surgical scar and at the margin of her previous radiotherapy field.

Case Presentation
The patient was diagnosed in 2004 at age 67 with a pT2 (4.8 cm) N1 (1/15 axillary nodes) grade two lobular carcinoma of the breast and was treated with modified radical mastectomy. Her initial tumor was estrogen receptor positive and progesterone receptor negative. She was then 1 2 3 1 subsequently treated with adjuvant FAC (5-Fluorouracil, Adriamycin, Cyclophosphamide) chemotherapy followed by adjuvant radiotherapy to the chest wall and supraclavicular lymph node region. She then received Tamoxifen for two and a half years, then received Exemestane for one year which she tolerated poorly and was put back on Tamoxifen to complete the balance of a five-year course of hormonal therapy.
She showed no evidence of disease until 2014 when she presented with a pathological fracture of her left femoral neck. Figure 1A shows imaging of her plain X-rays at time of pathological fracture. This was treated surgically with a left bipolar hip hemiarthroplasty through a lateral Hardinge approach ( Figure 1B). Pathology from this initial surgery confirmed the presence of metastatic adenocarcinoma consistent with her initial breast primary. Unfortunately, three days post-operatively, she suffered a fall and a periprosthetic fracture that required revision surgery with cerclage which used the same lateral Hardinge incision ( Figure 1C). Chest, abdominal and whole-body bone imaging confirmed no other sites of metastases. She then received radiotherapy to the left proximal femur to a dose of 30 Gy in 10 fractions with an AP-PA technique as shown in Figure 2. This did not include the entirety of the prosthetic hardware, nor did it include the surgical scar tract within the soft tissues of the hip (as shown by arrow in Figure 2). There was no documented severe toxicity from her radiotherapy treatments. She was started on pamidronate which she continued until 2018. No other systemic treatment was given at that time because of the fact she had no other evidence of disease and patient preference.

Discussion
Surgical tract and procedure site recurrences have been reported in many different cancers [6][7][8]. It has also been shown that relatively low dose radiation could prevent recurrence in these sites [7]. However, there is very little in the literature with regards to surgical site recurrence in cases of orthopedic surgery for bone metastases. Although surgical scar recurrences have been anecdotally reported by many oncologists, we believe this is the first formally reported case of surgical scar recurrence after surgery for bone metastases. There are many peculiarities to this patient's case that could explain an increased risk of this type of recurrence; she did require two surgical interventions at a very short time interval which did not include any formal debulking of tumor; she also has a very prolonged history of metastatic breast cancer with this recurrence happening almost four years after her initial femur surgery and post-operative radiotherapy. Furthermore, this area was not included in her post-operative radiotherapy volume when she received adjuvant radiation to the femur.
The major learning point from her case is related to the natural history of bone metastases to long bones post-operatively. Many reports have shown the fact that adjuvant radiotherapy in these cases can reduce progressive disease, improve quality of life and decrease the need for further orthopedic procedures to the same area [2,3]. One could hypothesize that if the area of this patient's surgical scar tract had been included in her initial radiation field, she might not have recurred in this fashion. Guidelines for the treatment of bone metastases with conventional radiotherapy mention very little with regards to target volumes for palliative radiotherapy in general; even less guidance is provided as to post-operative volumes other than for spine radiotherapy [5,9,10]. Classic dogma would state that one should include the entire operative bed and prosthetic material, but this is not always the case in daily practice. More recent evidence from stereotactic body radiotherapy (SBRT) for bone metastases in the pelvis provides some evidence for wider treatment fields, as most areas of progressive disease in pelvic bones can appear 15-55 mm out of field [11]. Our current approach in our institutional dedicated rapid palliative radiotherapy service involves treating at minimum involved area of bone, plus the entirety of prosthetic material (if not the entire involved bone) as well as the surgical scar tract out to the skin ( Figure 6). With palliative radiotherapy, one must be mindful to treat only volume deemed necessary not to increase toxicity in an unneeded fashion; however, in cases of bone metastases treated surgically, we do not feel that including a wider margin of soft tissue out to the skin would substantially increase toxicity with doses used for bone metastases treatment. Despite low incidence of scar recurrences, we believe these notions should be considered for incorporation into further iterations of international guidelines on radiotherapy for bone metastases.

Conclusions
This case illustrates a previously underreported phenomenon of surgical scar recurrence of breast cancer metastases after surgical intervention to the femur. We believe this information can be useful in guiding radiation oncologists in the determination of treatment volumes in cases of post-operative radiotherapy for non-spinal bone metastases.

Additional Information Disclosures
Human subjects: Consent was obtained by all participants in this study.

Conflicts of interest:
In compliance with the ICMJE uniform disclosure form, all authors declare the following: Payment/services info: All authors have declared that no financial support was received from any organization for the submitted work. Financial relationships: All authors have declared that they have no financial relationships at present or within the previous three years with any organizations that might have an interest in the submitted work. Other relationships: All authors have declared that there are no other relationships or activities that could appear to have influenced the submitted work.