Many cancer patients hope to wait to begin their radiation treatments until after they've fully recovered from their surgery. But it hasn't been clear until now whether waiting has any unfavorable effects on the progression of the disease. Researchers from Canada, reporting in the Journal of Clinical Oncology (Vol.21, Issue 3, 2003; 555-563) now say that delaying radiation leads to a higher chance the cancer will come back.

Canadian doctors have a reason to be concerned about delays in radiation. Canada, along with several other countries, may have too few radiation oncology facilities. This means patients have to wait their turn in spite of having a life threatening disease.

To better understand the hazards of this delay, the researchers, led by William Mackillop at the Queen's Cancer Research Institute, reviewed studies in which the outcomes of early radiation therapy were compared with those of later treatment. The only cancers for which there was enough information were breast cancer that had been treated with lumpectomy, and head and neck cancer (cancers of the throat, voice box, mouth, nasal passages). In both types of diseases, radiation is commonly used to prevent the cancer from returning in the area in which it started.

Lumpectomy – removing only the cancer – is the preferred surgery for most women with breast cancer. This allows the woman to keep her breast and maintain a normal appearance. But because the cancer will often recur in the breast, radiation therapy is used as a preventive. Most of the time it is successful.

The researchers found that if radiation is delayed, the treatment is less successful. They divided breast cancer patients who had been treated with lumpectomy into 2 groups: those receiving radiation within 8 weeks of surgery and those treated after 8 weeks. They found the cancer came back in the breast 60% more often if radiation was delayed by more than 8 weeks.

Often, after surgery for breast cancer, other treatment such as tamoxifen and/or chemotherapy is recommended. These are mainly aimed at stopping the cancer from traveling to distant sites such as the bones, lungs, or liver. Because chemotherapy can increase the side effects of radiation, the radiation is often delayed until chemotherapy is complete.

So even though the patient is receiving chemotherapy, this delay still leads to a doubling of the local recurrence rate, according to the Canadian study. If the cancer does come back in the breast, it can almost always be treated with surgery. Although a mastectomy will usually be needed, the woman isn’t in any greater danger of dying from the cancer. The researcher couldn’t find any evidence that women whose radiation was delayed were more likely to die of their cancer.

The same thing held true for head and neck cancer. Delaying radiation treatment after surgery – this time by more than 6 weeks – lead to a tripling of the recurrence rate. Once again, it wasn’t clear that this delay led to a greater chance that the patient would die of their cancer.

This study by Canadian physicians was likely initiated because of their difficulty in obtaining prompt treatment for their patients. On average, most patients in the US receive treatment about 10 days after being referred for radiation. In Canada it takes more than a month to begin treatment.

Still, the problem of delay poses a dilemma for doctors and their patients in the US as well. Often, chemotherapy is recommended immediately after surgery. There is a body of literature demonstrating that it can lead to a higher cure rate. Many times, radiation is put off to avoid the side effects of the combined treatment. Now it appears that there may be a trade-off between long-term cure and the problems that can arise if the cancer comes back in the local area. Often, in women with breast cancer, this means they will lose their breast.

But in the absence of chemotherapy, there should be no dilemma, according to the study. "The longer radiotherapy is delayed, the poorer the outcome is likely to be," write the study authors. "We recommend that delays in initiating radiotherapy should be as short as reasonably achievable."