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When Rebecca Robinson showed up at the hospital expecting to receive her infusion of Doxil, a chemotherapy drug, last July, her doctors delivered the shocking news that they didn’t have any more of the drug.

Supplies of Doxil, a cornerstone for treating cancers known as sarcomas, had fallen short nationwide, along with methotrexate, a drug for treating childhood cancer, after one of the largest domestic suppliers of the drug shut down its plant over quality-control issues. What happened to Robinson, 37, as a result of the shortages is just one case study in how disruptive the shortfalls continue to be for hundreds, perhaps thousands of patients.

Robinson was diagnosed with angiosarcoma, a rare form of the cancer that often starts in the blood before spreading to other organs. Her cancer had infiltrated her liver, but the five rounds of Doxil she received before stores ran out had kept the growth in check. Her doctors were hoping to stall the cancer and make Robinson eligible for surgery to remove the biggest masses. And the strategy was working; she had not experienced too many side effects and felt strong enough during her chemo regimen to continue working full time as a historical interpreter in Massachusetts’ Old Sturbridge Village.

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But with no Doxil left for her sixth session, Robinson’s doctor decided to put her on Taxol. The drug is also effective against angiosarcoma — but it wasn’t for Robinson. She not only had to give up a day of work a week for the treatments (instead of one day a month for Doxil therapy), but she also developed nausea, pain in her hands and feet and extreme fatigue. She lost her hair.

All of that would have been worth it if the drug had continued to shrink her cancer. But after a month, a CAT scan showed that her existing tumors had grown and that new ones had sprouted in both her liver and pelvis.

Robinson then moved onto doxorubicin, an older form of Doxil that isn’t as gentle on the body and often triggers nasty side effects. The drug left her nauseous and exhausted and forced her to come in for injections of a white-blood-cell booster the day after each infusion in order to keep her immune system running. But a scan several months later showed that the chemotherapy was at least keeping her tumors in check; they didn’t appear to be expanding or venturing out to seed new growths.

Because of her combined Doxil and doxorubicin sessions, however, Robinson has reached her lifetime limit for the toxic medications. Too much exposure to the drugs, while good for incapacitating tumors, can also damage the heart, so her doctor decided to stop her treatments before she started experiencing cardiac problems.

Now Robinson is on another drug called Nexovar, which gave her such a severe skin reaction that she had to stop using it for a month. The entire ordeal has left her too spent to work much anymore. “Lately I’ve been going in four to five hours a day and leaving when I get exhausted,” she says. “And how many days a week I work really depends on the week. This week I went in five days, but last week it was four days.”

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And Robinson isn’t the only cancer patient who is anxious about what would happen if she can’t continue on her chemotherapy medication and possibly becomes too sick to go work or to school or is confined to a hospital bed, too weak to rise or visit with her family. “I tend not to be terribly volatile,” Robinson says of her reluctance to think about where she might be had she been able to continue her Doxil therapy. But, she says, “in my mind, there is no reason I should have to be on a version of a drug that makes me miserable when there’s another drug on which I was very comfortable. That just doesn’t make sense to me.”

It baffles her physician as well and has doctors increasingly worried. “The shortages clearly impact the way we care for patients,” says Dr. James Butrynski, Robinson’s cancer doctor at Dana Farber and an instructor of medicine at Harvard Medical School. “For the majority of patients we are treating with Doxil, we are achieving some clinical benefit, and for us to change treatment, that’s a challenge because we have a winning situation and when we change, there’s a risk that another medication won’t be as successful.”