Radiation therapy slows return of head/neck cancer

Sep 14, 2009

A large, long-term outcomes study conducted in Norway revealed that radiation therapy may actually inhibit premalignant lesions in the upper aerodigestive tract from becoming cancerous for many years.

Radiation therapy treatments may cure patients of head and neck cancer, but the treatment includes the risk of unavoidable radiation exposure to the surrounding mucosa. A portion of these patients develop second primary cancer tumors, and it has been unclear whether the new cancer is a result of the treatment.

Norwegian researchers found that in a cohort of approximately 350 patients who received treatment for small localized cancer of the oral cavity, the length of time for a second primary tumor to develop was significantly longer for patients treated with radiation therapy than with surgery alone -- and their risk was actually lower. However, five years or more after treatment, the risk level switched between the two groups. The findings were published online in Radiotherapy and Oncology (September 11, 2009).

Between May 1983 and December 1997, 346 patients diagnosed with T1 and T2 localized primary tumors of the oral cavity received treatment at the Rikshospitalet and the Norwegian Radium Hospital, both located in Oslo. Ninety-nine patients (29%) had tumors surgically removed with no pre- or postsurgical radiation treatment. The remaining 247 patients had radiation therapy as the only treatment (11%) or in conjunction with surgery (60%).

When radiation was given alone, the mucosal dose ranged from 11 to 75 Gy (median, 65 Gy). When it was combined with surgery, the mucosal dose ranged from 8 to 54 Gy (median, 49 Gy).

The patients were followed for a minimum of 9.3 years, up to a maximum of 20.9 years. A total of 13%, or 45 patients, developed anatomically distinct, nonmetastatic tumors. Of these, 62.5% of the surgery-only group developed a tumor within five years, compared with 10.3% of the radiation therapy group.

This changed after five years. Seventy-three patients, or 29.5% of the original group who received radiotherapy, and 21 patients, or 21.2% of the surgery-only group, continued to be followed. Fourteen patients of the radiotherapy group and two of the surgery group were subsequently diagnosed with second primary tumors. Overall, the median time for the surgery group to develop a tumor was 3.9 years, compared with 8.6 for the radiotherapy group.

Principal investigator Dr. Erlend Rennemo of Oslo University Hospital - Rikshospitalet suggested that subclinical premalignant lesions were eradicated by the radiation, and new tumors subsequently developed or the treatment may have brought existing premalignant lesions into accelerated senescence.

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