Escalating radiation dosages in 3-D conformal therapy do not correspond with increasing late toxicity in prostate cancer patients, according to a study by the Radiation Therapy Oncology Group (RTOG).
Dr. Janice Ryu from the University of California, Davis Medical Center presented the results of a multicenter study at the 2001 American Society of Clinical Oncology meeting in San Francisco this week. Other institutions that participated in this study included the Mallinckrodt Institute of Radiology in St. Louis and the University of Michigan in Ann Arbor.
For this prospective dose escalation study, patients were stratified into three risk groups:
- Group 1: Stage T1-T2 disease with a seminal vesicle invasion risk of less than 15%.
- Group 2: Stage T1-T2 disease with a seminal vesicle invasion risk of greater than or equal to 15%.
- Group 3: Stage T3 disease.
The planning target volume (PTV) was defined as 5-10 mm around the prostate alone for Group 1 and around the prostate and seminal vesicle for Group 2. PTV doses were started at 1.8 Gy/day (level I) and eventually raised to 79.2 Gy/day (level III).
Between November 1996 and October 1998, 173 patients were accrued to level III. According to the results, no patients experienced grade 3 acute toxicity or higher. With a median follow-up of 27.6 months, a total of 3 patients experienced grade 3 late toxicity. Two had gross hematuria from cystitis, and one experienced rectal bleeding from proctitis.
"Based on the excellent tolerance of 3-D CRT for stage T1 and stage T2 prostate cancer, further dose escalation has been proposed to level IV and V, 74 Gy and 78 Gy respectively, at 2 Gy/day in an attempt to reduce the total treatment duration," the group concluded.
Several other RTOG papers were presented at the meeting.
- In combination with radiation therapy, thalidomide shows promise for treating glioblastomas. Thalidomide has anti-angiogenesis properties that may inhibit the blood supply to malignant tumors, said Dr. Alfred Yung from the M.D. Anderson Cancer Center in Houston. For this investigation, 128 patients underwent a six-week course of conventional radiation (60 Gy/30 fractions). Out of that group, 89 patients were given a thalidomide dose of 200 mg daily, which was escalated to a maximum dose of 1,200 mg daily. A 12-month survival rate of 43% was achieved in the second group with no serious side effects.
- In stage 3 non-small cell lung cancer patients, the combination of Taxol (paclitaxel), Paraplatin (carboplatin for injection), and radiation therapy can improve survival rates, according to the initial result of the Locally Advanced Multimodality Protocol (LAMP) study. A group of 243 patients received one of three treatment regimens that included both drugs and radiation. For the 56 patients with survival data, the median survival time is 12.5 months reported Dr. Walter Curran, Jr., group chairman of the RTOG.
- A drug that stimulates the salivary glands, Pilocarpine, can alleviate permanent dry mouth, one of the major side effects of head and neck radiation therapy. Dr. Charles Scarantino of the Rex Healthcare Center in Raleigh, NC, reported the results of a 3-year study in which 249 patients took Pilocarpine 3-4 times a day in pill form. At 6-month follow-up, grade 2 or worse salivary gland toxicity was 30% for patients taking the drug, compared to 38% for those taking a placebo.
Finally, radiation treatment and chemotherapy together can help preserve the voices of patients with advanced cancer of the larynx. From August 1992 to May 2000, 547 patients with stage III and stage IV potentially resectable cancer of the larynx were randomized to receive either standardized chemotherapy followed by radiation, chemotherapy using one drug and radiation, or radiation alone.
According to the results, the 2-year laryngectomy-free survival rate was 58% for those who received standard chemotherapy and radiation, 66% for those who underwent one-drug chemotherapy and radiation, and 52% for those who had only radiation. At 76%, overall survival was the same for all three options after two years, said Dr. Arlene Forastiere from the Johns Hopkins Oncology Center in Baltimore.
The results suggest that if a patient chooses to preserve the voice box with combined chemotherapy and radiation treatment, the chance of survival is still very good, Forastiere said.
By Shalmali PalAuntMinnie.com staff writer
May 18, 2001
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