Impending Pathological Subtrochanteric Fracture in Metastatic Lung Cancer
A 63-year-old man with stage IV non-small-cell lung cancer (diagnosed 8 months ago, currently on pemetrexed and pembrolizumab) presents with 6 weeks of right thigh pain that is worse at night and now requires a crutch. He has no history of trauma and can weight-bear with pain. Radiographs show a 6 cm lytic lesion in the subtrochanteric region of the right femur with 40% cortical involvement, extending into the lesser trochanter; there is no fracture. He is otherwise performance status 1 and walks 2 km daily. His oncologist asks whether to refer for radiotherapy alone or for orthopaedic opinion. Bloods: calcium 2.5 mmol/L, ALP 180 U/L, platelets 210, Hb 11.4. He has a life expectancy estimated at 12-18 months.
1. How would you assess his risk of fracture and decide on prophylactic surgery versus radiotherapy alone?
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Use the Mirels score: site (peritrochanteric 3), nature (lytic 3), size (40% of diameter, about 2) and pain (functional, requiring a crutch, 3), giving a total of about 11. A score of 9 or above predicts a high risk of fracture and is an indication for prophylactic fixation, so radiotherapy alone would be inadequate. Other features supporting fixation include cortical destruction over 30 mm and involvement of the lesser trochanter, which is a de facto impending fracture.
The decision also depends on prognosis: prophylactic fixation is justified if life expectancy exceeds roughly 3 months and the patient can tolerate surgery. With performance status 1 and an estimated 12-18 months, he benefits from surgery, which relieves pain and allows weight-bearing and continued systemic therapy. If life expectancy were under 3 months, radiotherapy alone (for example a single 8 Gy fraction) would be more appropriate. Refer urgently to orthopaedic oncology and discuss in a multidisciplinary meeting.
2. Which implant would you choose and why, and what are the alternatives?
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A cephalomedullary nail spanning the whole lesion is the workhorse: a long reconstruction nail with proximal and distal locking, with at least two locking screws well below the lesion to avoid a stress riser. Because the bone is lytic and the lesser trochanter is involved, cement augmentation around the proximal screws or a cemented nail improves purchase in tumour-weakened bone. Preoperative embolisation is considered for hypervascular tumours such as renal cell or thyroid carcinoma; lung cancer usually does not need it.
The alternative is a proximal femoral endoprosthesis if the lesion extends into the femoral head or neck, because a nail cannot reliably stabilise the articular segment. Plate and screw constructs alone have a high failure rate in subtrochanteric pathological bone and should be avoided. Post-operative radiotherapy to the whole femur may be added, and the patient should be counselled about the risk of implant failure, non-union and further fracture.
3. Outline the perioperative and oncological plan, including timing of radiotherapy and considerations for his systemic therapy.
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Perioperative: correct calcium and vitamin D, treat hypercalcaemia if confirmed, give a single dose of prophylactic IV antibiotics, provide VTE prophylaxis with LMWH, and mobilise early with physiotherapy. Discuss systemic therapy with oncology: pemetrexed and pembrolizumab can usually continue around surgery, but checkpoint inhibitors may impair wound healing and should be timed with the surgeon; avoid bevacizumab if it is being considered, because of bleeding and wound complications. Post-operative radiotherapy, typically 30 Gy in 10 fractions or a single 8 Gy fraction, should start within 2-4 weeks once the wound has healed, and should not be delayed beyond that.
Add a bone-modifying agent (bisphosphonate or denosumab) if renal function allows, with a dental review first. Arrange follow-up radiographs at 6 weeks and 3 months, and involve palliative care early for pain control and goals-of-care discussion.