Pathologic Fractures From Cancer

A pathologic fracture is a break through bone that was already weakened by disease. In cancer care, the weakness usually comes from a tumor deposit that has eaten into the bone from the inside. The bone gives way under a load it used to carry without trouble.

That is the part people find hard to believe. A healthy thigh bone needs a car crash to snap. A thigh bone hollowed out by cancer can break while you turn over in bed, step off a kerb, or lift a kettle. The force was normal. The bone was not.

Call emergency services or go to the emergency department if any of these happen.

A bone may have broken if:

• Sudden severe pain starts in a limb, hip, or the back, with little or no injury behind it.
• You cannot stand on a leg, or you cannot lift an arm you could lift yesterday.
• A limb looks bent, twisted, or shorter than the other side.
• You heard or felt a crack, snap, or pop.
• Pain that had been building suddenly changes character and becomes far worse.

The spinal cord may be under pressure if:

• New or changed back or neck pain that is constant and aching, worse at night, or worse when you cough, sneeze or strain.
• Your legs feel weak, heavy, or clumsy, or you are tripping and catching your feet.
• You have numbness or pins and needles in both legs, or numbness in the saddle area. That means the inner thighs, buttocks and groin.
• Bladder or bowel control has changed in any way. Trouble starting, dribbling, leaking, or not feeling the urge.

Say plainly: "I have cancer and I think this may be spinal cord compression." Ask for an urgent MRI scan. The UK national guideline from NICE says the scan should be offered "as soon as possible (and always within 24 hours)." Nerve function that has already been lost by the time treatment starts often never comes back. In the audit NICE cites, of people walking unaided at diagnosis, 81 percent could walk a month later, alone or with an aid. Of those unable to walk at diagnosis, 67 percent had recovered no function at one month.

Blood calcium may be dangerously high if you have:

• New confusion, drowsiness, or behavior that is not like you.
• Strong thirst and passing large amounts of urine.
• New constipation, nausea, vomiting, or belly pain.
• Weakness and heavy tiredness that came on over a few days.

Also seek urgent care for a temperature of 38.0 °C / 100.4 °F or higher. The CDC uses 100.4 °F and the NCI uses 100.5 °F. Use the lower number.

Five cancers account for most spread to bone: lung, breast, thyroid, kidney and prostate. The spine, the top of the thigh bone and the pelvis are the sites most often affected. The upper arm bone is another common one.

Deposits that dissolve bone leave a hole where solid bone used to be. Once enough of the hard outer shell is gone, the bone cannot handle twisting or weight. Radiotherapy, steroids and some cancer drugs can thin bone further, and so can long spells of inactivity.

Many pathologic fractures announce themselves. Doctors call it prodromal pain: an ache in one exact spot that grows over days or weeks, hurts more when you put weight through it, and often nags at night. Some people have no warning at all and the fracture is the first sign.

If you have a spot like that, do not test it. Do not push through it to see how bad it is. Get it imaged first. A bone that is about to break can be fixed on a planned operating list, in daylight, with the cancer team involved. A bone that has already broken is fixed as an emergency, with a longer stay and a harder recovery.

Surgeons score the risk rather than guess it. The Mirels system gives points for four things: how big the deposit is, which bone it sits in, whether the pain comes on with weight, and whether the deposit is the type that dissolves bone. Each scores up to 3 points, so 12 is the maximum. The higher the total, the more likely a surgeon is to fix the bone before it breaks. Ask whether your bone has been scored, what the score was, and what it means for you.

Other red flags on a scan are a deposit wider than 5 centimetres, a break in the outer shell of the bone, and disease taking up more than half of that shell.

Surgery aims for a bone you can use straight away, not a bone that must be protected for months. For the thigh or upper arm bone, that often means an intramedullary nail: a metal rod passed down the hollow center of the bone and locked with screws. A badly destroyed hip may need a replacement joint instead. In the spine, screws and rods hold the column while pressure is taken off the cord.

Healing cannot be assumed. Fracture healing rates differ sharply by cancer type, from about 67 percent in myeloma and 44 percent in kidney cancer down to 37 percent in breast cancer and close to zero in lung cancer. That is why surgeons often choose fixation that works even if the bone never knits.

Radiotherapy usually follows surgery to control the deposit and settle pain. For pain alone, a single 8 Gy dose gives the same relief as 20 Gy in 5 sessions, 24 Gy in 6, or 30 Gy in 10, and ASTRO recommends the single fraction. Around 60 percent of people get relief, usually over 2 to 3 weeks. About 35 percent get a pain flare in the first week, which normally settles within 3 days. A short course of the steroid dexamethasone, around the days of treatment, can blunt that flare. Ask whether that is planned for you. Up to 40 percent get no pain relief from the first course, and pain relapses within a year in 50 percent. The same site can often be treated again, though no formal reirradiation schedule is defined.

Bone-modifying drugs, such as zoledronic acid or denosumab, are usually added to lower the chance of the next fracture.

• Get weight-bearing instructions in writing. "Take it easy" is not an instruction. Ask: full weight, partial weight, or none at all?
• Use the walking aid you were given every time, including at 3am on the way to the toilet.
• Clear rugs, cables and clutter. Put a light within reach of the bed.
• Avoid twisting movements: getting out of a car, reaching behind you, opening a stiff window.
• Do not lift, carry or push anything heavy with an affected arm.
• Ask about a raised toilet seat, a shower stool, and grab rails before you need them.
• Keep taking pain medicine on schedule. Pain that is controlled means fewer sudden, jerky movements.

• StatPearls (NCBI Bookshelf) — Pathologic Fractures
• StatPearls (NCBI Bookshelf) — Palliative Radiation Therapy for Bone Metastases
• StatPearls (NCBI Bookshelf) — Spinal Cord Compression
• NICE (NCBI Bookshelf) — Spinal Metastases and Metastatic Spinal Cord Compression (NG234)
• NICE (NCBI Bookshelf) — Metastatic Spinal Cord Compression (CG75)
• StatPearls (NCBI Bookshelf) — Malignancy-Related Hypercalcemia
• StatPearls (NCBI Bookshelf) — Bone Metastasis
• CDC — Watch Out for Fever (Preventing Infections in Cancer Patients)